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"Within range of our sensors, there is no life [...]. At least, no life as we know it."

— Spock, Star Trek: The Original Series, "The Devil in the Dark"

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These are really alien aliens. They may have:

• Non-vertebrate or at least radically non-humanlike biology.
• Nonhuman psychology, as opposed to Planet of Hats.
• Either unable to survive in Earth-like conditions, or able to survive nearly anywhere.
• Vastly different motor, sensory, or communication abilities.
• Completely nonhuman reproduction, such as budding, virtual immortality, unfertilized reproduction, three or more sexes, or a specialized queen.

If the aliens in question have two or more of the above traits, you're usually dealing with a Starfish Alien. However they are still "people" in the sense of having:

• Some kind of language, not necessarily verbal, we can learn to interpret (or maybe not, but we can at least recognize it as a language).
• Culture
• Their own belief systems, however unusual.
• A mind-set that admits to things like logic and intuition; not necessarily those things by our definitions, but things like them.
• At least some resemblance to living things with which we are familiar. They eat, sleep, reproduce, etc.; they are clearly organic beings, or else Mechanical Lifeforms.

Sometimes, however, they are too alien and their language, mind-set and culture remain incomprehensible to humans. Often (particularly if the beings can't communicate easily with humans) they will be presumed to be evil by the human protagonists without any actual proof. But in accordance with We Come in Peace — Shoot to Kill, starfish aliens who run across innocent, open-minded humans are themselves known to do beyond-horrible things to them, then excuse themselves later with an explanation that they were only trying to communicate with or greet us in the way they know how. Usually, their language and communication are so different from ours that if there is to be any communication between our species and theirs, it must be done by technological means of translation or them taking on a form humans can interact with.

Given the long, strange history of life on Earth (a given house includes such a bewildering variety of life as humans, houseplants, pets, spiders, molds, bacteria, etc.), it's likely if we ever actually encounter alien life it might fit in this category. Species that evolve naturally would have adapted to solve similar basic problems: obtaining food/necessities, negotiating natural disaster, adapting to new circumstances, avoiding contamination by pathogens and parasites, competing with other species, competing with themselves, and so forth. So we would expect to find at least a few familiar aspects to their psychology as opposed to sheer indecipherable mystery... if they evolved in similar conditions as us.

These are much more common in animation, video games, and literature than they are in live-action media, due to the likelihood of Special Effects Failure. They are typically located towards the "hard" end of the Sci-Fi Hardness Scale, though when their biology becomes sufficiently improbable, they may soften it instead. When a story is told from the point of view of Starfish Aliens, and other decidedly non human creatures, it's Xenofiction.

Super Trope to Octopoid Aliens. The inverse of Human Aliens or Rubber-Forehead Aliens. Aliens that don't look like humans, but still have basically the same body type are Humanoid Aliens, or Intelligent Gerbils, if they're obviously based off a particular Earth animal. Insectoid Aliens effectively split the difference.

Prone to enter Grotesque Gallery. May speak a Starfish Language. See also Bizarre Alien Biology, Starfish Robots, and Our Monsters Are Weird. Compare Eldritch Abomination (both tropes have some overlap). The Trope Namer is H.P. Lovecraft's At the Mountains of Madness, written in 1931, where the Old Ones are described as "starfish aliens."

TV Trope page for list of examples)

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The Elder Things (also known as the Old Ones and Elder Ones) are fictional extraterrestrials in the Cthulhu Mythos. The beings first appeared in H. P. Lovecraft's novella, "At the Mountains of Madness" (published in 1936, but written in 1931), and later appeared, although not named, in the short story "The Dreams in the Witch-House" (1933). Additional references to the Elder Things appear in Lovecraft's short story "The Shadow Out of Time" (1936).

Summary

Description of a partial headless body:

Six feet end to end, three and five-tenths feet central diameter, tapering to one foot at each end. Like a barrel with five bulging ridges in place of staves. Lateral breakages, as of thinnish stalks, are at equator in middle of these ridges. In furrows between ridges are curious growths – combs or wings that fold up and spread out like fans. . . which gives almost seven-foot wing spread. Arrangement reminds one of certain monsters of primal myth, especially fabled Elder Things in the Necronomicon.
—H.P. Lovecraft, At the Mountains of Madness

In the Mythos canon, the Elder Things were the first extraterrestrial species to come to the Earth, colonizing the planet about one billion years ago. They stood roughly eight feet tall and had the appearance of a huge, oval-shaped barrel with starfish-like appendages at both ends. The top appendage was a head adorned with five eyes, five eating tubes, and a set of cilia for "seeing" without light. The bottom appendage was five-limbed and was used for walking and other forms of locomotion. The beings also had five leathery, fan-like retractable wings and five sets of branching tentacles that sprouted from their torsos. Both their tentacles and the slits housing their folded wings were spaced at regular intervals about their bodies.

Lovecraft described the Elder Things as vegetable-like or echinoderm-like in shape, having radial symmetry instead of the bilateral symmetry of bipeds. They also differed in that they had a five-lobed brain. The Elder Things exhibited vegetable as well as animal characteristics, and in terms of reproduction, multiplied using spores, although they discouraged increasing their numbers except when colonizing new regions. Though they could make use of both organic and inorganic substances, the Elder Things were carnivorous by preference. They were also amphibious.

The bodies of the Elder Things were incredibly tough, capable of withstanding the pressures of the deepest ocean. Few died except by accident or violence. The beings were also capable of hibernating for vast epochs of time. Nonetheless, unlike many other beings of the Mythos, the Elder Things were made of normal, terrestrial matter.

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     Starfish Aliens: Most of them.

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     Digisapiences, of course, have no bodies at all.
     The galari are sophont crystal-virus hybrids with inbuilt techlepathy and mechanical psychokinesis.
     The codramaju are pseudo-fungoids which can merge, exchange, and separate bodies and minds at will.
     The kaeth are vaguely draconic pseudosaurians with a metal-rich biology.
     The hydrogen-breathing sssc!haaaouú are fragile collections of membranes that dwell in the upper layers of gas giants.
     The myneni are crystal-based carbohydrosilicate amoeboids with built-in chemosynthetic talents.
     The mezuar are a network of collectively sophont purplish-blue trees. (Yes, as sessile as that implies, although the selyéva are green-blue plantimals – non-sessile photosynthetics – who probably most closely resemble walking broccoli.)
     The esseli have engineered themselves into brains with manipulating tentacles and customized personal auxiliary organs, and don’t even remember what they used to look like. (And the link!n-Rechesh are heading that way.)
     The qucequql are ammonia-metabolising octopi from a world of nitrogenous oceans.
     The múrast would be simple multiheaded snakes, except that they breathe methane, live in oceans of hydrocarbons, and their primary body structures are constructed of ice.
     The ulakha are metal-plated, fast-moving lizardoids who think Venerian conditions are just about right for a planet.
     The linobir resemble furless, leathery-skinned, hexapedal, hermaphrodite bears.
     The shan kari resemble larger versions of Terran mustelids fairly closely, actually, except they prefer to breathe warm methane.
     The mirilasté are legged-serpents with skin we would recognize as essentially plastic, who breathe the most astonishingly noxious fluorine-hydrocarbon soup.
     The ktelaki are furry arachnids with trilateral symmetry and multi-branched legs.
     The seb!nt!at are star-dwelling creatures of plasma and electromagnetic force.
     The celsesh are quadrilaterally-symmetric with a fused-barrel body plan, and sensory organs on stalks in lieu of a head.
     The embatil are worm/tentacle creatures whose life cycle begins with individuals, but which merge into single creatures as they mature – while transforming a ganglionic into a collegiate intelligence.
     The tennoa are chlorine-breathing radial-crabs blessed/cursed with obligate utilitarianism…

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     And that’s all before we get to uplifts, neogens, and exotic neomorphic bioshells.

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The horror Third WatchMaster found while inspecting passenger compartments was on the manifest. He had been warned by Timmerbach that Glorious Spent carried two aliens who had boarded on the Atlantean Rim. But…

It (a Godspeaker) looked like a group-grope involving giant hydras and starfish atop a heap of exposed intestines. It was some sort of colonial, symbiotic intelligence. It was a methane breather, which explained why it had not turned out for the passenger muster.

It was revolting.

What the hell excuse was there for letting something that hideous run loose? What was Canon coming to?

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The Godspeakers had plenty of warning, though WarAvocat used Hellspinners liberally to burrow a channel so he could reach his objective more quickly. He sent a rider force ahead to strike at two incomplete habitats Seeker feared would flee before they could be destroyed.

Strate told Klass, “Tell him to concentrate on tracking those things.” Minutes after VII Gemina’s breakaway Seeker had announced that each habitat contained a “brood mass,” a mindless superGodspeaker colony serving a reproductive function resembling that of a queen ant and the data storage function of a Starbase Core—though the brood mass could not manipulate that data itself.

“It’s a repository for genes and knowledge,” Klass said. “Without one there could be no more Godspeakers.”

“Why hasn’t he mentioned it before? He’s been holding out.”

“We destroyed the original when we hit their homeworld. He says he didn’t think they could put another one together. They’ve never had two at once, ever.”

WarAvocat knew little about the biology of the methane breathers. He did not care. They were the enemy. Their biology signified only when it could be used against them.

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Nowhere in space will we rest our eyes upon the familiar shapes of trees and plants, or any of the animals that share our world. Whatsoever life we meet will be as strange and alien as the nightmare creatures of the ocean abyss, or of the insect empire whose horrors are normally hidden from us by their microscopic scale.

...you know how there are creatures that dwell in the most inaccessible, inhospitable places above, on and under the Earth and in her oceans? I am talking about life-forms you can find in any handbook of zoology, as opposed to those fearsome beings of the Cthulhu Cycle which which we are now so familiar. Well, there are also creatures which exist in the most obscure and random corridors and corners of time, in lost and unthinkable abysses of space, and in certain other twilight places which are most easily explained by referring to them as junctions of forces neither temporal nor spacial, places which by all rights should only exist in the wildest imaginings of theoreticians and mathematicians...

...Suffice to say, then that there are extreme forms of life within and without this universe of ours. And I know it to be so for I have seen or learned of many such forms.

for instance:

...intelligent energies in the heart of a giant alien sun who measure time in ratios of nuclear fission and space in unimaginable degrees of pressure! There are wraithlike biological gasses which issue at the dark of their moon from the fissures of a fungoid world in Hydra, to dance away their brief lives until, exhausted, they die at dawn, scattering the sentient seeds of mushroom minds which will sprout and take root, and whose crevice-deep roots will in turn emit at the dark of the moon euphoric, spore-bearing mists of genesis.

There is a dying purple sun on Andromeda's rim whose rays support life on all seven of its planets. On the fourth planet there are exactly seventeen forms of life, or so it would appear. On closer inspection, however, a zoologist could tell you that these forms are all different phases of only one life-form! Consider the batrachian and lepidopterous cycles of Earth life and this might not seem too astonishing, until I tell you that of these seventeen phases two are as apparently inanimate mineral deposits, six are aquatic, two others amphibious, three land-dwelling cannibals, three more are aerial and the last is to all intents and purposes a plant while all of its preliminary stages (excluding the mineral phases) were animal...

The starcraft gathered the fabric of time and space. Chayn passed stars and groupings of stars, dense clusters of young stars and swirling clouds of dust and gas giving birth to new light in their depths. Black holes tunneled through the space-time structure into elsewhere, glowing ominously as matter spiraled down to annihilation. Chayn could perceive it all, but he focused his attention on the mind fields.

Uncountable multitudes of worlds circles perhaps a third of the stars in his view. Most were lifeless, barren worlds of rock and snow, but even the tiny fraction that had given birth to life emanated a broad mind field that he could sense everywhere. There were worlds of microscopic life and paradises of forests and jungles teaming with dramas of life and death. There were worlds ancient and wise in the ways of evolution, but what Chayn watched for were the sparks of intense awareness, life on levels near his own. Intelligence too far in advance of him were incomprehensible, aware of his passage, but apathetic. Most life forms on his own level were alien, different in inexplicable ways. He felt he could adapt to some of those strange and beautiful worlds if necessary, but he staved his hunger and waited for the worlds of man.

The Watcher told him that man had lived for eons, evolving to the greatness of the stargods, but that man in this galaxy had recently arrived in fleets of starships after sleeps of many millennia. The worlds of man were new here while Earth recycled its continents and evolved new species of life...

...Danger lay immediately ahead, a gulf of darkness between two arms of the galaxy. Chayn approached the starless void with caution. In that incredible abyss four hundred light years across, he could sense another kind of life -- the star travelers. He could sense such small concentrations of explorers only where they stood out like specks of brightness, even the blank minds of those who slept in the frozen oblivion of suspended animation...

One of the star travelers in view piloted a starcraft similar to his own. Two others were primitive vehicles of metal driven by fusion or antimatter-propulsion units to velocities below that of the speed of light ... At first Chayn thought the pilot of the starcraft like his own would seek communication with him, but the entity was highly evolved and looked upon him as a curiosity. Chayn knew himself to be a primitive, more typical of the life forms frozen in their crude ships of metal...

...Chayn's fear intensified as he neared the abyss. Mindspiders lurked in the darkness, many species of them littering the void with invisible webs. Some dangled thin and scraggly. Others spread magnificently, a light year in diameter. Even in that moment, he felt the shock, the utterly brilliant flare of terror of alien minds encountering the web in the far distance. Particles rose to lethal intensities of radiation. Bodies died and the ship heated to incandescence. The mindspiders fed upon disembodied consciousness. Few of the primitives could perceive such danger lurking in the abyss...

...Ahead, he sensed an old, torn web. Even the mindspiders had their predators in their own realm. This one was gone, the web deteriorating.

Hammond's head spun with their tales of spaceman's life, tales of the vast glooms of cosmic clouds that ships rarely dared enter, of wrecks and castaways in the unexplored fringes of the galaxy, of strange races like the thinking rocks of Rigel and the fish-cities of Arcturus' watery worlds and the unearthly tree-wizards of dark Algol.

Aliens will not resemble anything we've seen. Considering that octopi, sea cucumbers, and oak trees are all very closely related to us, an alien visitor would look less like us than does a squid. Some fossils in the ancient Burgess shale are so alien that we can't determine which end of the creature is up, and yet these monsters evolved right here on Earth from the same origins as we did.

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      They halted before a massive door and the Engineer sounded a high-pitched thought-wave that beat fantastically against their minds. The great door slid back into the wall and they walked into a room that swept away in lofty reaches of vast distances, with a high-vaulted ceiling that formed a sky-like cup above them.
     The room was utterly empty of any sort of furniture. Just empty space that stretched away to the dim, far walls of soaring white. But in its center was a circular elevation of that same white stone, a dais-like structure that reared ten feet or more above the white-paved floor.
     Upon the dais stood several of the Engineers and around them were grouped queer, misshapen things, nightmares snatched from some book of olden horrors, monstrosities that made Gary's blood run cold as be gazed upon them.
     He felt Caroline's fingers closing on his arm. "Gary," her whisper was thin and weak, "what are they?"
     "Those are the ones that we have called," said the Engineer. "The ones who have come so far to help us in our fight."
     "They look like something a man would want to step on," said Herb, and there was a horrible loathing in his words.

     Gary stared at them, fascinated by their very repulsiveness. Lords of the universe, he thought. These are the things that represent the cream of the universe's intelligence. These things that looked, as Herb had said, like something you would want to step on.
     Gary looked around. They were the only ones who had chairs. The Engineers, apparently tireless, remained standing. Some of the other things stood, too. One of them stood on a single leg with his second leg tucked tight against his body — like a dreaming stork — except that he didn't look like a stork. Gary tried to classify him. He wasn't a bird or a reptile or a mammal. He wasn't anything a human being had ever imagined. Long, skinny legs, great bloated belly, head with unkempt hair falling over brooding, dead-fish eyes.
     One of the Engineers began to speak.
     "We have gathered here," said the thought-waves, "to consider ways and means of meeting one of the greatest dangers..."

     Gary studied the other things about them, the loathsome, unnatural things that had been brought here from the unguessed depths of the universe. He shuddered and felt cold beads of sweat break out upon his body as he looked at them.
     Several of them were immersed in tanks filled with liquids. One tank boiled and steamed as if with violent chemical action; another was cloudy and dirty-looking; another was clear as water and in it lurked a thing that struck stark terror into Gary's soul. Another was confined in a huge glass sphere through which shifted and swirled a poisonous-appearing atmosphere. Gary felt cold fingers touch his spine as he watched the sphere and suddenly was thankful for the shifting mists within it, for through them he had caught sight of something that he was certain would have shattered one's mind to look upon without the shielding swirl of fog within the glass.
     In a small glass cage set upon a pedestal of stone were several writhing, grub-like things that palpitated disgustingly. Squatting on its haunches directly across from Gary was a monstrosity with mottled skin and drooling mouth, with narrow, slitted eyes and slimy features. He fastened his pinpoint gaze upon the Earthman and Gary quickly looked away.

     Nothing resembled mankind, nothing except the Engineers. Here were things that were terrible caricatures of the loathsome forms of Earth life, other beings that bore not even the most remote resemblance to anything that mankind had ever seen or imagined.
     Was this a fair sample of the intelligence the universe contained? Did he and Kingsley and Caroline appear as disgusting, as fearsome in the eyes as these other denizens of the universe as they appeared to his?
     Gary looked at the mottled, droopy-eyed creature that squatted opposite him. It raised its head and in the beady eyes he imagined that he caught a glimmer of amusement.
     "By the Lord," he said to himself, "he thinks it's funny, too."
     This arguing of hideous entities! The piping thoughts of slimy things that should be wriggling through some stagnant roadside ditch back on the planet Earth. The cold thought of the brain-blasting thing that lived on a planet covered by miles of swirling gases. The pinpoint eyes of the being with the mottled skin.

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(ed note: This is about an outlandish theory in the Star Trek universe, explaining why all the alien species not only look similar but are close enough to interbreed. I'm looking at You, Sarek and Amanda. While the theory has major holes in it, the nice part is it neatly explains why the Star Trek universe does not suffer from the "Ain't Gonna Look LIke Mr. Spock" problem AND explains why it does not suffer from the "Apes or Angels" problem.

So while the theory won't work in the real world, it has the next best thing. In the Trek science fiction universe it has the sterling quality of being internally self-consistent.)

Science fiction has a problem: everyone looks the same. I know there are a few series that have aliens that look unimaginably different from human beings. But those are the exception, not the rule. Most major sci-fi series – Star Wars, Babylon 5, Mass Effect, Star Trek, Farscape, Stargate – have alien species that are hominid (note that the author is talking about TV and Movie media science fiction, not written or graphic novel science fiction. This is related to media budget constraints.).

Consider the above image. Of the twenty visible species, only five are visibly not hominid. That’s right, I count the prawn, xenomorph, predator, Cthulhu and A.L.F. as being hominid. I grant that it’s a bit of a stretch. A more conservative evaluation would be that only two of the twenty are truly hominid. The others, which we’ll call pseudo-hominids, still share the following with humans: bipedal locomotion; bilateral symmetry; a morphology of head, trunk, two arms, and two legs; upright posture; and forward-facing, stereoscopic eyes. I grant they don’t look precisely human, but the similarities are too striking to be swept into the nearest black hole.

Even the most strident supporter of parallel evolution would laugh in the face of anyone who claimed that the most intelligent species on nearly every planet in the universe just happened to evolve the exact same physiology. In series like Star Trek and Mass Effect, where interspecies relationships are possible, this cross-species compatibility is made even more preposterous. We all suspend our scientific disbelief to enjoy the story and the characters. No one believes for a second that the first species we meet in the cosmos is going to look just like us save for some pointy ears and a bowl haircut.

But what if many species in the universe do look like humans? How in Carl Sagan’s cosmos could we explain parallel evolution of that magnitude? Star Trek: The Next Generation, manages to give a scientifically plausible answer to the question of hominid and biologically compatible alien species in an episode entitled “The Chase.” Which lead me to develop the Hominid Panspermia Theory of Science Fiction Aliens.

My guess is that the writers of ST:TNG didn’t intend to plug a genre-spanning plot hole in “The Chase” given that it is, on its own, a pretty goofy episode. But, intentional or not, they gave me enough fuel to come up with a theory that would explain away a lot of sci-fi alien species similarity without resorting to a “that’s just how it is” answer. That said, I’m going to ignore the plot and jump right to the meaty conclusion. At the end of a string of clues, the crew of the Enterprise, along with a begrudging team of Klingons, Cardassians, and Romulans, activate a message from a past species. Star Trek lore is mixed as to what the nature of this species actually is, so I’m going to leverage some creative license and summarize it as I see fit. In short, an ancient hominid species sends a message to all future hominid species. That message is as follows:

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Intelligent life evolved in the universe – once. The First Intelligent Species became spacefaring but, unlike the adventures depicted in most science fiction, they found an uninhabited universe. Non-intelligent species were too rudimentary or too far away to be detected. Thus, as both a memorial to themselves and to enliven the universe, the First Intelligent Species seeded the necessary DNA for the eventual evolution of intelligent life in the primordial oceans of every planet that could support life. The First Intelligent Species did not only design the DNA to evolve intelligently, but to parallel their own evolution. An application of the idea that “ontogeny recapitulates phylogeny” on the scale of life itself. Our corner of the universe thereby became the home of Vulcans, Romulans, Cardassians, Humans, Betazoids, and other hominid species which are all decedents of the First Intelligent Species. Therefore, in the eyes of the universe, the many hominid species are closely related despite their disparate home planets.

The Hominid Panspermia Theory, as I call it, explains a lot. Why are most hominid species variations only cosmetic and cultural? Because their genetics are designed to prevent significant deviation from the First Intelligent Species’ mold. How can species interbreed? They share a distant ancestor the way lions and tigers do. How are there so many species at nearly the same level of technological development? Life was seeded on many planets at approximately the same time. These nagging, infuriating questions that take me out of the story can be set aside because I have a plausible scientific explanation. The Hominid Panspermia Theory also titillates my need to believe we are neither the only nor the first intelligent species in the universe.

The Hominid Panspermia Theory also helps explain how there are so many bizarre life-forms throughout the universe without invoking near-deity races like the Q. One could argue that in the time that it took the seeded planets to evolve spacefaring hominid species, many other forms of life, intelligent and otherwise, evolved as well. The result is a near-universe that is largely populated by hominid alien species and a far-universe populated by inconceivably strange alien species. Furthermore, unintentional forward-contamination from the First Intelligent Species would have allowed unguided panspermia to trigger life in unexpected and unanticipated ways. Thus, many alien first contacts with Humanity were with hominid aliens. As exploration continued outward from the seeded galaxies, stranger and more truly alien species were encountered.

Finally, the Hominid Panspermia Theory still requires abiogenesis at some point and allows for multiple occurrences. That is, human beings could theoretically be the First Intelligent Species. Or among some of the only life in the universe. You don’t have to presume humanity is the product of some previous species to believe the Hominid Panspermia Theory is a scientific possibility, nor does Hominid Panspermia Theory fall prey to the “well who seeded the seeders?” reductio.

I apply the Hominid Panspermia Theory theory to pretty much every sci-fi series I encounter that involves multiple alien species that are hominid. For series in which the species are distinctly hominid but not mammalian, such as Mass Effect, I just modify the theory so that the First Intelligent Species was arbitrarily dumping seed genetic code into every splash of primordial soup they could find with no intent to reproduce themselves and/or that their explorations recklessly forward-contaminated the universe. Life with a very similar genetic base still gets scattered about, but less planning leads to much less parallel evolution.

Thanks to the Hominid Panspermia Theory of Science Fiction Aliens, my neurotic need to explain the similarity among spacefaring species is sated and I can go back to enjoying the photon blasts and spaceship explosions.

Follow Kyle on his personal blog, Pop Bioethics, and on facebook and twitter.

Image of diverse aliens via alien species wiki. Image of ancient hominid via memory alpha.

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(ed note: Cunningham is on the innermost planet of the star Deneb. There is no atmosphere, the temperature during the day is hot enough to melt lead, but there is wierd alien life. With weird alien senses.)

      For the rest of the day he divided his attention between the working men and the equally busy life forms that scuttled here and there in front of his cave ; and he would have been the first to admit that he found the latter more interesting.

     He still hoped that one would approach the cave closely enough to permit a really good examination, but for a long time he remained upsatisfied. Once, one of the creatures came within a dozen yards and stood “on tiptoe”—rising more than a foot from the ground on its slender legs, while a pair of antennae terminating in knobs the size of human eyeballs extended themselves several inches from the black carapace and waved slowly in all directions. Cunningham thought that the knobs probably did serve as eyes, though from his distance he could see only a featureless black sphere. The antennae eventually waved in his direction, and after a few seconds spent, apparently in assimilating the presence of the cave mouth, the creature settled back to its former low-swung carriage and scuttled away. Cunningham wondered if it had been frightened at his presence; but he felt reasonably sure that no eye adapted to Denebian daylight could see past the darkness of his threshold, and he had remained motionless while the creature was conducting its inspection. More probably it had some reason to fear caves, or merely darkness.

     A few minutes’ excavation in the deeper layers of dust produced the complete exoskeleton of one of the smaller crablike creatures ; and Cunningham carried the remains over to the cave mouth, so as to examine them and watch the ship at the same time.

     The knobs he had taken for eyes were his first concern. A close examination of their surfaces revealed nothing, so he carefully tried to detach one from its stem. It finally cracked raggedly away, and proved, as he had expected, to be hollow. There was no trace of a retina inside, but there was no flesh in any of the other pieces of shell, so that proved nothing. As a sudden thought struck him, Cunningham held the front part of the delicate black bit of shell in front of his eyes; and sure enough, when he looked in the direction of the brightly gleaming hull of the spaceship, a spark of light showed through an almost microscopic hole. The sphere was an eye, constructed on the pinhole principle—quite an adequate design on a world furnished with such an overwhelming luminary. It would be useless at night, of course, but so would most other visual organs here; and Cunningham was once again faced with the problem of how any of the creatures had detected his presence in the cave—his original belief, that no eye adjusted to meet Deneb’s glare could look into its relatively total darkness, seemed to be sound.

     He pondered the question, as he examined the rest of the skeleton in a half-hearted fashion. Sight seemed to be out, as a result of his examination; smell and hearing were ruled out by the lack of atmosphere; taste and touch could not even be considered under the circumstances. He hated to fall back on such a time-honored refuge for ignorance as “extrasensory perception”, but he was unable to see any way around it.

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     The centipede had not seen, or at least had not pursued, the plant-eater that had escaped from Cunningham and run from the cave. Looking back, he realized that the only times he had seen the creature attack was after “blood” had been already shed —twice by one of the carnivorous animals, the third time by Cunningham himself.

     On any planet that had a respectable atmosphere, Cunningham would have taken one answer for granted—scent. In his mind, however, organs of smell were associated with breathing apparatus, which these creatures obviously lacked.

     Don’t ask why he took so long. You may think that the terrific adaptability evidenced by those strange eyes would be clue enough or perhaps you may be in a mood to excuse him. Columbus probably excused those of "his friends who failed to solve the egg problem.

     Of course, he got it at last, and was properly annoyed with himself for taking so long about it. An eye, to us, is an organ for forming images of the source of such radiation as may fall on it; and a nose is a gadget that tells its owner of the presence of molecules. He needs his imagination to picture the source of the latter. But what would you call an organ that forms a picture of the source of smell? For that was just what those “eyes” did. In the nearly perfect vacuum of this little world’s surface, gases diffused at high speed —and their molecules traveled in practically straight lines. There was nothing wrong with the idea of a pinhole camera eye, whose retina was composed of olfactory nerve endings rather than the rods and cones of photosensitive organs.

     That seemed to account for everything. Of course the creatures were indifferent to the amount of light reflected from the object they examined. The glare of the open spaces under Deneb’s rays, and the relative blackness of a cave, were all one to them—provided something were diffusing molecules in the neighborhood. And what doesn’t? Every substance, solid or liquid, has its vapor pressure ; under Deneb’s rays even some rather unlikely materials probably evaporated enough to affect the organs of these life forms—metals, particularly. The life fluid of the creatures was obviously metal—probably lead, tin, bismuth, or some similar metals, or still more probably, several of them in a mixture that carried the substances vital to the life of their body cells. Probably much of the makeup of those cells was in the form of colloidal metals.

     But that was the business of the biochemists. Cunningham amused himself for a time by imagining the analogy between smell and color which must exist here; light gases, such as oxygen and nitrogen, must be rare, and the tiny quantities that leaked from his suit would be absolutely new to the creatures that intercepted them. He must have affected their nervous systems the way fire did those of terrestrial wild animals. No wonder even the centipede had thought discretion the better part of valor!

Scent seems to have all the disadvantages and none of the advantages, as a long-range sense. However, under special circumstances even a modified nose may fill the need. In a story of my own some years ago (“Uncommon Sense,” Astounding Science Fiction, September 1945), I assumed an airless planet, so that molecules could ditfuse in nearly straight lines. The local sense organs were basically pinhole cameras, with the retinal mosaic formed of olfactory cells. Since the beings in question were not intelligent, the question of what sort of universe they believed in did not arise.

Granting the intelligence, it would have been—would still be, indeed—interesting to work out their cosmology. Naturally, the first few hours are spent wondering whether and how they could fill the intellectual gaps imposed by their lack of sight and hearing. Then, of course, the intelligent speculator starts wondering what essential details are missing from our concept of the universe, because of our lack of the sense of (you name it). This, for what my opinion is worth, is one of the best philosophical excuses for the practice of science fiction—if an excuse is needed. The molecule-seers presumably lack all astronomical data; what are we missing? This question, I hope I needn’t add, is not an excuse to go off on a mystical kick, though it is one which the mystics are quite reasonably fond of asking (and then answering with their own version of Truth). The human species has, as a matter of fact, done a rather impressive job of overcoming its sensory limitations, though I see no way of ever being sure when the job is done.

• 

      I must begin by speaking of the biological equipment of the Other Men. Their animal nature was at bottom much like ours. They responded with anger, fear, hate, tenderness, curiosity, and so on, much as we respond. In sensory equipment they were not unlike ourselves, save that in vision they were less sensitive to color and more to form than is common with us. The violent colors of the Other Earth appeared to me through the eyes of its natives very subdued. In hearing also they were rather ill-equipped. Though their auditory organs were as sensitive as ours to faint sounds, they were poor discriminators. Music, such as we know, never developed in this world.

     In compensation, scent and taste developed amazingly. These beings tasted not only with their mouths, but with then-moist black hands and with their feet. They were thus afforded an extraordinarily rich and intimate experience of their planet. Tastes of metals and woods, of sour and sweet earths, of the many rocks, and of the innumerable shy or bold flavors of plants crushed beneath the bare running feet, made up a whole world unknown to terrestrial man.

     The genitals also were equipped with taste organs. There were several distinctive male and female patterns of chemical characteristics, each powerfully attractive to the opposite sex. These were savored faintly by contact of hands or feet with any part of the body, and with exquisite intensity in copulation.

     This surprising richness of gustatory experience made it very difficult for me to enter fully into the thoughts of the Other Men. Taste played as important a part in their imagery and conception as sight in our own. Many ideas which terrestrial man has reached by way of sight, and which even in their most abstract form still bear traces of their visual origin, the Other Men conceived in terms of taste. For example, our "brilliant," as applied to persons or ideas, they would translate by a word whose literal meaning was "tasty." For "lucid" they would use a term which in primitive times was employed by hunters to signify an easily runnable taste-trail. To have "religious illumination" was to "taste the meadows of heaven." Many of our non-visual concepts also were rendered by means of taste. "Complexity" was "many flavored," a word applied originally to the confusion of tastes round a drinking pool frequented by many kinds of beasts. "Incompatibility" was derived from a word meaning the disgust which certain human types felt for one another on account of their flavors.

     Differences of race, which in our world are chiefly conceived in terms of bodily appearance, were for the Other Men almost entirely differences of taste and smell. And as the races of the Other Men were much less sharply localized than our own races, the strife between groups whose flavors were repugnant to one another played a great part in history. Each race tended to believe that its own flavor was characteristic of all the finer mental qualities, was indeed an absolutely reliable label of spiritual worth. In former ages the gustatory and olfactory differences had, no doubt, been true signs of racial differences; but in modern times, and in the more developed lands, there had been great changes. Not only had the races ceased to be clearly localized, but also industrial civilization had produced a crop of genetic changes which rendered the old racial distinctions meaningless. The ancient flavors, however, though they had by now no racial significance at all, and indeed members of one family might have mutually repugnant flavors, continued to have the traditional emotional effects. In each country some particular flavor was considered the true hall-mark of the race of that country, and all other flavors were despised, if not actually condemned.

     In the country which I came to know best the orthodox racial flavor was a kind of saltness inconceivable to terrestrial man. My hosts regarded themselves as the very salt of the earth. But as a matter of fact the peasant whom I first "inhabited" was the only genuine pure salt man of orthodox variety whom I ever encountered. The great majority of that country's citizens attained their correct taste and smell by artificial means. Those who were at least approximately salt, with some variety of saltness, though not the ideal variety, were forever exposing the deceit of their sour, sweet, or bitter neighbors. Unfortunately, though the taste of the limbs could be fairly well disguised, no effective means had been found for changing the flavor of copulation. Consequently newly married couples were apt to make the most shattering discoveries about one another on the wedding night. Since in the great majority of unions neither party had the orthodox flavor, both were willing to pretend to the world that all was well. But often there would turn out to be a nauseating incompatibility between the two gustatory types. The whole population was rotten with neuroses bred of these secret tragedies of marriage. Occasionally, when one party was more or less of the orthodox flavor, this genuinely salt partner would indignantly denounce the impostor. The courts, the news bulletins, and the public would then join in self-righteous protests.

     Some "racial" flavors were too obtrusive to be disguised. One in particular, a kind of bitter-sweet, exposed its possessor to extravagant persecution in all but the most tolerant countries. In past times the bitter-sweet race had earned a reputation of cunning and self-seeking, and had been periodically massacred by its less intelligent neighbors. But in the general biological ferment of modern times the bitter-sweet flavor might crop up in any family. Woe, then, to the accursed infant, and to all its relatives! Persecution was inevitable; unless indeed the family was wealthy enough to purchase from the state "an honorary salting" (or in the neighboring land, "an honorary sweetening"), which removed the stigma.

     In the more enlightened countries the whole racial superstition was becoming suspect. There was a movement among the intelligentsia for conditioning infants to tolerate every kind of human flavor, and for discarding the deodorants and degustatants, and even the boots and gloves, which civilized convention imposed. Unfortunately this movement of toleration was hampered by one of the consequences of industrialism. In the congested and unhealthy industrial centers a new gustatory and olfactory type had appeared, apparently as a biological mutation. In a couple of generations this sour, astringent, and undisguisable flavor dominated in all the most disreputable working-class quarters. To the fastidious palates of the well-to-do it was overwhelmingly nauseating and terrifying. In fact it became for them an unconscious symbol, tapping all the secret guilt and fear and hate which the oppressors felt for the oppressed.

Bizarre Alien Senses: Well, hell, who doesn’t have some sort of bizarre senses? Especially since it gets very tricky if you count the whole electromagnetic spectrum as one – i.e., “ultravision” and “infravision” are both strict subsets of “vision”. As, for that matter, is sensing gamma rays – and other similar elisions. It’s not like anyone gets to claim the canonical radiation range for “sight”, now is it?

But we’ve got people sensing everything from low infrared to high UV, with bioradio senses, with the ability to detect electromagnetic fields both static and changing, with the ability to feel the curvature of space-time (that would be those bionano vector-control effectors again), with echolocation and/or sonar, the ability to read plasmids by tasting them, and pretty much any other physical effect that you can measure somehow on the macroscale.

(The current eldrae alpha baseline clocks in at 24 recognized senses, by the way, counting the synthetic and transcendent ones, and that’s after considering smell and taste as one: photoception, audition, chemoception/olfaction, static mechanoception, dynamic mechanoception, thermoception, nociception, static electroception, dynamic electroception, proprioception, chronoception, farspeech, spatioception, secondary gestalt, secondary linear, mesh, metadata, worth, mnemonesis, nature, utility, entelechy, obligation, and autosentience.)

      On the northern continent, Area Commander Folve stared moodily from the narrow slit which served as a window and locked his six fingered hands behind his back. Had there been room he might have paced moodily up and down but since there was none, the thought did not occur to him. He was used to cramped quarters; in fact, after the claustrophobic overcrowding of his parent planet, this office was almost spacious. Here he could move his arms, even turn with moderate quickness; it was one of the very few compensations of promotion.

     At intervals of approximately three seconds, Folve blinked. That is to say, a transparent membrane descended from the top of his orange-coloured eye to be met, halfway, by a similar membrane rising from the bottom. As the operation, from beginning to end, took five seconds and was involuntary, Folve’s eyesight was by human standards severely restricted.

     There were, however, compensations. His hearing was frighteningly acute and could, by controlled variations of his hearing organs, be adjusted to immediacy or a considerable distance. Nerne specialists could, and often did, pinpoint and identify small insects in long grass by the normal use of their hearing faculties.

• 

      Then, without any warning, they were on a gallery high above a large circular chamber, perhaps a hundred metres across. As usual, there was no protective parapet, and for a moment Jan hesitated to go near the edge. But Vindarten was standing on the very brink, looking calmly downwards, so Jan moved cautiously forward to join him.

     The floor was only twenty metres below—far, far too close. Afterwards, Jan was sure that his guide had not intended to surprise him, and was completely taken aback by his reaction. For he had given one tremendous yell and jumped backwards from the gallery's edge, in an involuntary effort to hide what lay below. It was not until the muffled echoes of his shout had died away in the thick atmosphere that he steeled himself to go forward again.

     It was lifeless, of course—not, as he had thought in that first moment of panic, consciously staring up at him. It filled almost all that great circular space, and the ruby light gleamed and shifted in its crystal depths.

     It was a single giant eye.

     His heart was still pounding violently as he stared down once more at that monstrous eye. Of course, it might have been a model, enormously enlarged as were microbes and insects in terrestrial museums. Yet even as he asked the question, Jan knew, with a sickening certainty, that it was no larger than life.

     Vindarten could tell him little; this was not his field of knowledge, and he was not particularly curious. From the Overlord's description, Jan built up a picture of a cyclopean beast living among the asteroidal rubble of some distant sun, its growth uninhibited by gravity, depending for food and life upon the range and resolving power of its single eye.

• 

     They were near the door when a shadow fell over them. They whirled and stared upward. Yukiko's indrawn breath hissed from their receivers.
     Aloft hovered one of the great ornithoids. Sunlight struck through its outermost pinions, turning them golden. Otherwise it showed stormcloud-dark. Down the wind stooped a second.
     The sight was terrifying. Only later did the humans realize it was magnificent. Those wings spanned six meters. A muzzle full of sharp white fangs gaped before them. Two legs the length and well-nigh the thickness of a man's arms reached crooked talons between them. At their angles grew claws. In thrust after thrust, they hurled the creature at torpedo speed. Air whistled and thundered.
     Their guns leaped into the men's hands. "Don't shoot!" Yukiko's cry came as if from very far away.
     The splendid monster was almost upon them. Fire speared from Webner's weapon. At the same instant, the animal braked—a turning of quills, a crack and gust in their faces—and rushed back upward, two meters short of impact.
     Turekian's gaze stamped a picture on his brain which he would study over and over and over. The unknown was feathered, surely warm-blooded, but no bird. A keelbone like a ship's prow jutted beneath a strong neck. The head was blunt-nosed, lacked external ears; fantastically, Turekian saw that the predator mouth had lips. Tongue and palate were purple. Two big golden eyes stabbed at him, burned at him. A crest of black-tipped white plumage rose stiffly above, a control surface and protection for the backward-bulging skull. The fan-shaped tail bore the same colors. The body was mahogany, the naked legs and claws yellow.
     Webner's shot hit amidst the left-side quills. Smoke streamed after the flameburst. The creature uttered a high-pitched yell, lurched, and threshed in retreat. The damage wasn't permanent, had likely caused no pain, but now that wing was only half-useful.
     Turekian thus had time to see three slits in parallel on the body. He had time to think there must be three more on the other side. They weirdly resembled gills. As the wings lifted, he saw them drawn wide, a triple yawn; as the downstroke began, he glimpsed them being forced shut.

---

     "I shot at a dangerous animal. Didn't you see those talons, those fangs? And a buffet from a wing that big—ignoring the claws on it—could break your neck."
     Webner's gaze sought Yukiko's. He mainly addressed her: "Granted, they must be domesticated. I suspect they're used in the hunt, flown at game like hawks though working in packs like hounds. Conceivably the pair we encountered were, ah, sicced onto us from afar. But that they themselves are sophonts—out of the question."
     Her murmur was uneven. "How can you be sure?"
     Webner leaned back, bridged his fingers, and grew calmer while he lectured: "You realize the basic principle. All organisms make biological sense in their particular environments, or they become extinct. Reasoners are no exception—and are, furthermore, descended from nonreasoners which adapted to environments that had never been artificially modified.
     "On nonterrestroid worlds, they can be quite outré by our standards, since they developed under unearthly conditions. On an essentially terrestroid planet, evolution basically parallels our own because it must. True, you get considerable variation. Like, say, hexapodal vertebrates liberating the forelimbs to grow hands and becoming centauroids, as on Woden. That's because the ancestral chordates were hexapods. On this world, you can see for yourself the higher animals are four-limbed.
     "A brain capable of designing artifacts such as we observe here is useless without some equivalent of hands. Nature would never produce it. Therefore the inhabitants are bound to be bipeds, however different from us in detail. A foot which must double as a hand, and vice versa, would be too grossly inefficient in either function. Natural selection would weed out any mutants of that tendency, fast, long before intelligence could evolve.
     "What do those ornithoids have in the way of hands?" He smiled his tight little smile.
     "The claws on their wings?" Yukiko asked shyly.
     "'Fraid not," Turekian said. "I got a fair look. They can grasp, sort of, but aren't built for manipulation."
     "You saw how the fledgling uses them to cling to the parent," Webner stated. "Perhaps it climbs trees also. Earth has a bird with similar structures, the hoactzin. It loses them in adulthood. Here they may become extra weapons for the mature animal."
     "The feet." Turekian scowled. "Two opposable digits flanking three straight ones. Could serve as hands."
     "Then how does the creature get about on the ground?" Webner retorted. "Can't forge a tool in midair, you know, let alone dig ore and erect stone houses."
     He wagged a finger. "Another, more fundamental point," he went on. "Flyers are too limited in mass. True, the gravity's weaker than on Earth, but air pressure's lower. Thus admissible wing loadings are about the same. The biggest birds that ever lumbered into Terrestrial skies weighed some fifteen kilos. Nothing larger could get aloft. Metabolism simply can't supply the power required. We established aboard ship, from specimens, that local biochemistry is close kin to our type. Hence it is not possible for those ornithoids to outweigh a maximal vulture. They're big, yes, and formidable. Nevertheless, that size has to be mostly feathers, hollow bones—spidery, kitelike skeletons anchoring thin flesh.
     "Aram, you hefted several items today, such as a stone pot. Or consider one of the buckets, presumably used to bring water up from the river. What would you say the greatest weight is?"
     Turekian scratched in his beard. "Maybe twenty kilos," he answered reluctantly.
     "There! No flyer could lift that. It was always superstition about eagles stealing lambs or babies. They weren't able to. The ornithoids are similarly handicapped. Who'd make utensils he can't carry?"
     "M-m-m," Turekian growled rather than hummed. Webner pressed the attack:
     "The mass of any flyer on a terrestroid planet is insufficient to include a big enough brain for true intelligence. The purely animal functions require virtually all those cells. Birds have at least lightened their burden, permitting a little more brain, by changing jaws to beaks. So have those ornithoids you called 'watchfalcons.' The big fellows have not."
     He hesitated. "In fact," he said slowly, "I doubt if they can even be considered bright animals. They're likely stupid . . . and vicious. If we're set on again, we need have no compunctions about destroying them."

---

• 

     Maybe his irritation with the pilot spoke for Webner: "How often must I explain there is no such risk, yet? Instead, here's a chance to learn. What happens next could give us invaluable clues to understanding the whole ethos. We stay." To Turekian: "Forget about that alleged metal. Could be protective collars, I suppose. But take the supercharger off your imagination."
     The other man froze where he stood.
     "Aram." Yukiko seized his arm. He stared beyond her. "What's wrong?"
     He shook himself. "Supercharger," he mumbled. "By God, yes."
     Abruptly, in a bellow: "We're leaving! This second! They are the dwellers, and they've gathered the whole countryside against us!"

---

     When you know what to expect, a little, you can lay plans. We next sought the folk of Ythri, as the planet is called by its most advanced culture, a thousand kilometers from the triumph which surely prevailed in the mountains. Approached with patience, caution, and symbolisms appropriate to their psyches, they welcomed us rapturously. Before we left, they'd thought of sufficient inducements to trade that I'm sure they'll have spacecraft of their own in a few generations.
     Still, they are as fundamentally territorial as man is fundamentally sexual, and we'd better bear that in mind.
     The reason lies in their evolution. It does for every drive in every animal everywhere. The Ythrian is carnivorous, aside from various sweet fruits. Carnivores require larger regions per individual than herbivores or omnivores do, in spite of the fact that meat has more calories per kilo than most vegetable matter. Consider how each antelope needs a certain amount of space, and how many antelope are needed to maintain a pride of lions. Xenologists have written thousands of papers on the correlations between diet and genotypical personality in sophonts.
     I have my doubts about the value of those papers. At least, they missed the possibility of a race like the Ythrians, whose extreme territoriality and individualism—with the consequences to governments, mores, arts, faiths, and souls—come from the extreme appetite of the body.
     They mass as high as thirty kilos; yet they can lift an equal weight into the air or, unhampered, fly like demons. Hence they maintain civilization without the need to crowd together in cities. Their townspeople are mostly wing-clipped criminals and slaves. Today their wiser heads hope robots will end the need for that.
     Hands? The original talons, modified for manipulating. Feet? Those claws on the wings, a juvenile feature which persisted and developed, just as man's large head and sparse hair derive from the juvenile or fetal ape. The forepart of the wing skeleton consists of humerus, radius, and ulnar, much as in true birds. These lock together in flight. Aground, when the wing is folded downward, they produce a "knee" joint. Bones grow from their base to make the claw-foot. Three fused digits, immensely lengthened, sweep backward to be the alatan which braces the rest of that tremendous wing and can, when desired, give additional support on the surface. To rise, the Ythrians usually do a handstand during the initial upstroke. It takes less than a second.
     Oh, yes, they are slow and awkward afoot. They manage, though. Big and beweaponed, instantly ready to mount the wind, they need fear no beast of prey.
     You ask where the power comes from to swing this hugeness through the sky. The oxidation of food, what else? Hence the demand of each household for a great hunting or ranching demesne. The limiting factor is the oxygen supply. A molecule in the blood can carry more than hemoglobin does, but the gas must be furnished. Turekian first realized how that happens. The Ythrian has lungs, a passive system resembling ours. In addition he has his supercharger, evolved from the gills of an amphibianlike ancestor. Worked in bellows fashion by the flight muscles, connecting directly with the bloodstream, those air-intake organs let him burn his fuel as fast as necessary.

• 

A shape blotted out the sun. They bounded to their feet.

That which was descending passed the disc, and light blazed off the gold-bronze pinions of a six-meter wingspan. Air whistled and thundered. Fraina cried out. Mikkal poised his javelin. "Don't!" Ivar shouted. "Ya-lawa! He's Ythrian!"

"O-o-oh, ye-e-es," Mikkal said softly. He lowered the spear though he kept it ready. Fraina gripped Ivar's arm and leaned hard against him.

The being landed. Ivar had met Ythrians before, at the University and elsewhere. But his astonishment at this arrival was such that he gaped as if he were seeing one for the first time.

Grounded, the newcomer used those tremendous wings, folded downward, for legs, claws at the bend of them spreading out to serve as feet, the long rear-directed bones lending extra support when at rest. That brought his height to some 135 centimeters, mid-breast on Ivar, farther up on the tinerans; for his mass was a good 25 kilos. Beneath a prowlike keelbone were lean yellow-skinned arms whose hands, evolved from talons, each bore three sharp-clawed fingers flanked by two thumbs, and a dewclaw on the inner wrist. Above were a strong neck and a large head proudly held. The skull bulged backward to contain the brain, for there was scant brow, the face curving down in a ridged muzzle to a mouth whose sensitive lips contrasted curiously with the carnivore fangs behind. A stiff feather-crest rose over head and neck, white edged with black like the fan-shaped tail. Otherwise, apart from feet, arms, and huge eyes which burned gold and never seemed to waver or blink, the body was covered with plumage of lustrous brown.

He wore an apron whose pockets, loops, and straps supported what little equipment he needed. Knife, canteen, and pistol were the only conspicuous items. He could live off the country better than any human…

…The Anglic which replied was sufficiently fluent that one couldn't be sure how much of the humming accent and sibilant overtones were due to Ythrian vocal organs, how much simply to this being an offplanet dialect the speaker had learned. "Thanks, greetings, and fair winds wished for you. I hight Erannath, of the Stormgate choth upon Avalon. Let me quench thirst and we can talk if you desire."

As awkward on the ground as he was graceful aloft, he stumped to the pool. When he bent over to drink, Ivar glimpsed the gill-like antlibranchs, three on either side of his body. They were closed now, but in flight the muscles would work them like bellows, forcing extra oxygen into the bloodstream to power the lifting of the great weight. That meant high fuel consumption too, he remembered. No wonder Erannath traveled alone, if he had no vehicle. This land couldn't support two of him inside a practical radius of operations…

…Mikkal settled himself back in the shade where he had been. "Might I ask what brings you, stranger?"

"Circumstances," Erannath replied. His race tended to be curt. A large part of their own communication lay in nuances indicated by the play of marvelously controllable quills…

…Expressions they could not read rippled across the feathers…

…"A sophont," Mikkal said redundantly. He proceeded: "More bright and tough than most. Maybe more than us. Could be we're stronger, we humans, simply because we outnumber them, and that simply because of having gotten the jump on them in space travel and, hm, needing less room per person to live in."

"A bird?"

"No," Ivar told her. "They're feathered, yes, warm-blooded, two sexes. However, you noticed he doesn't have a beak, and females give live birth. No lactation—no milk, I mean; the lips're for getting the blood out of prey."

• 

• 

• 

A canned lecture was barely under way. A human xenologist stood in the screen and intoned:

"Warm-blooded, feathered, and flying, the Ythrians are not birds; they bring their young forth viviparously after a gestation of four and a half months; they do not have beaks, but lips and teeth. Nor are they mammals; they grow no hair and secrete no milk; those lips have developed for parents to feed infants by regurgitation. And while the antlibranchs might suggest fish gills, they are not meant for water but for—"…

…He reactivated the screen. It showed an Ythrian walking on the feet that grew from his wings: a comparatively slow, jerky gait, no good for real distances. The being stopped, lowered hands to ground, and stood on them. He lifted his wings, and suddenly he was splendid.

Beneath, on either side, were slits in column. As the wings rose, the feathery operculum-like flaps which protected them were drawn back. The slits widened until, at full extension, they gaped like purple mouths. The view became a closeup. Thin-skinned tissues, intricately wrinkled, lay behind a curtain of cilia which must be for screening out dust.

When the wings lowered, the slits were forced shut again, bellows fashion. The lecturer's voice said: "This is what allows so heavy a body, under Terra-type weight and gas density, to fly. Ythrians attain more than twice the mass of the largest possible airborne creature on similar planets elsewhere. The antlibranchs, pumped by the wing-strokes, take in oxygen under pressure to feed it directly to the bloodstream. Thus they supplement lungs which themselves more or less resemble those of ordinary land animals. The Ythrian acquires the power needed to get aloft and, indeed, fly with rapidity and grace."

The view drew back. The creature in the holograph flapped strongly and rocketed upward.

"Of course," the dry voice said, "this energy must come from a correspondingly accelerated metabolism. Unless prevented from flying, the Ythrian is a voracious eater. Aside from certain sweet fruits, he is strictly carnivorous. His appetite has doubtless reinforced the usual carnivore tendency to live in small, well-separated groups, each occupying a wide territory which instinct makes it defend against all intruders.

"In fact, the Ythrian can best be understood in terms of what we know or conjecture about the evolution of his race."…

…"We believe that homeothermic—roughly speaking, warm-blooded—life on Ythri did not come from a reptilian or reptiloid form, but directly from an amphibian, conceivably even from something corresponding to a lungfish. At any rate, it retained a kind of gill. Those species which were most successful on land eventually lost this feature. More primitive animals kept it. Among these was that small, probably swamp-dwelling thing which became the ancestor of the sophont. Taking to the treetops, it may have developed a membrane on which to glide from bough to bough. This finally turned into a wing. Meanwhile the gills were modified for aerial use, into superchargers."

"As usual," Wa Chaou observed. "The failures at one stage beget the successes of the next."

"Of course, the Ythrian can soar and even hover," the speaker said, "but it is the tremendous wing area which makes this possible, and the antlibranchs are what make it possible to operate those wings.

"Otherwise the pre-Ythrian must have appeared fairly similar to Terran birds." Pictures of various hypothetical extinct creatures went by. "It developed an analogous water-hoarding system—no separate urination—which saved weight as well as compensating for evaporative losses from the antlibranchs. It likewise developed light bones, though these are more intricate than avian bones, built of a marvelously strong two-phase material whose organic component is not collagen but a substance carrying out the functions of Terra-mammalian marrow. The animal did not, however, further ease its burdens by trading teeth for a beak. Many Ythrian ornithoids have done so, for example the uhoth, hawklike in appearance, doglike in service. But the pre-sophont remained an unspecialized dweller in wet jungles.

"The fact that the young were born tiny and helpless—since the female could not fly long distances while carrying a heavy fetus—is probably responsible for the retention and elaboration of the digits on the wings. The cub could cling to either parent in turn while these cruised after food; before it was able to fly, it could save itself from enemies by clambering up a tree. Meanwhile the feet acquired more and more ability to seize prey and manipulate objects.

"Incidentally, the short gestation period does not mean that the Ythrian is born with a poorly developed nervous system. The rapid metabolism of flight affects the rate of fetal cell division. This process concentrates on laying down a body pattern rather than on increasing the size. Nevertheless, an infant Ythrian needs more care, and more food, than an infant human. The parents must cooperate in providing this as well as in carrying their young about. Here we may have the root cause of the sexual equality or near equality found in all Ythrian cultures.

"Likewise, a rapid succession of infants would be impossible to keep alive under primitive conditions. This may be a reason why the female only ovulates at intervals of a year—Ythri's is about half of Terra's—and not for about two years after giving birth. Sexuality does not come overtly into play except at these times. Then it is almost uncontrollably strong in male and female alike. This may well have given the territorial instinct a cultural reinforcement after intelligence evolved. Parents wish to keep their nubile daughters isolated from chance-met males while in heat. Furthermore, husband and wife do not wish to waste a rich, rare experience on any outsider.

"The sexual cycle is not totally rigid. In particular, grief often brings on estrus. Doubtless this was originally a provision of nature for rapid replacement of losses. It seems to have brought about a partial fusion of Eros and Thanatos (sex+death motif. In Freudian psychology these are opposed, apparently in Ythrian psychology they are fused) in the Ythrian psyche which makes much of the race's art, and doubtless thought, incomprehensible to man. An occasional female can ovulate at will, though this is considered an abnormality; in olden days she would be killed, now she is generally shunned, out of dread of her power. A favorite villain in Ythrian story is the male who, by hypnosis or otherwise, can induce the state. Of course, the most important manifestation of a degree of flexibility is the fact that Ythrians have successfully adapted their reproductive pattern, like everything else, to a variety of colonized planets."…

…"But to return to evolution," the lecturer was saying. "It seems that a major part of Ythri underwent something like the great Pliocene drought in Terra's Africa. The ornithoids were forced out of dwindling forests onto growing savannahs. There they evolved from carrion eaters to big-game hunters in a manner analogous to pre-man. The original feet became hands, which eventually started making tools. To support the body and provide locomotion on the ground, the original elbow claws turned into feet, the wings that bore them became convertible to legs of a sort.

"Still, the intelligent Ythrian remained a pure carnivore, and one which was awkward on land. Typically, primitive hunters struck from above, with spears, arrows, axes. Thus only a few were needed to bring down the largest beasts. There was no necessity to cooperate in digging pits for elephants or standing shoulder to shoulder against a charging lion. Society remained divided into families or clans, which seldom fought wars but which, on the other hand, did not have much contact of any sort.

"The revolution which ended the Stone Age did not involve agriculture from the beginning, as in the case of man. It came from the systematic herding, at last the domestication, of big ground animals like the maukh, smaller ones like the long-haired mayaw. This stimulated the invention of skids, wheels, and the like, enabling the Ythrian to get about more readily on the surface. Agriculture was invented as an ancillary to ranching, an efficient means of providing fodder. The food surplus allowed leisure for travel, trade, and widespread cultural intercourse. Hence larger, complex social units arose.

"They cannot be called civilizations in a strict sense, because Ythri has never known true cities. The mobility of being winged left no necessity for crowding together in order to maintain close relationships. Granted, sedentary centers did appear—for mining, metallurgy, and other industry; for trade and religion; for defense in case the group was defeated by another in aerial battle. But these have always been small and their populations mostly floating. Apart from their barons and garrisons, their permanent inhabitants were formerly, for the main part, wing-clipped slaves—today, automated machines. Clipping was an easy method of making a person controllable; yet since the feathers could grow back, the common practice of promising manumission after a certain period of diligent service tended to make prisoners docile. Hence slavery became so basic to pre-industrial Ythrian society that to this day it has not entirely disappeared."

Between these investigations, he caught momentary glimpses of the city, and realized how difficult—and dangerous—it would be for him to travel around in it. Streets were practically non-existent, and there seemed to be no surface transport. This was the home of creatures who could fly, and who had no fear of gravity. It was nothing to come without warning upon a vertiginous drop of several hundred metres, or to find that the only entrance into a room was an opening high up in the wall. In a hundred ways, Jan began to realize that the psychology of a race with wings must be fundamentally different from that of earthbound creatures.

It was strange to see the Overlords flying like great birds among the towers of their city, their pinions moving with slow, powerful beats. And there was a scientific problem here.

This was a large planet—larger than Earth. Yet its gravity was low, and Jan wondered why it had so dense an atmosphere. He questioned Vindarten on this, and discovered, as he had half expected, that this was not the original planet of the Overlords. They had evolved on a much smaller world and then conquered this one, changing not only its atmosphere but even its gravity.

The architecture of the Overlords was bleakly functional; Jan saw no ornaments, nothing that did not serve a purpose, even though that purpose was often beyond his understanding. If a man from mediaval times could have seen this red-lit city, and the beings moving through it, he would certainly have believed himself in Hell. Even Jan, for all his curiosity and scientific detachment, sometimes found himself on the verge of unreasoning terror. The absence of a single familiar reference point can be utterly unnerving even to the coolest and clearest minds.

• 

The city marched up out of the crimson haze, ever more awful, the bulk of it swelling to blot out half the red sky with gleaming black metal, the titanic machines that crowned it frowning down with the threat of unknown death. A palpable atmosphere of dread and horror hung over that unearthly metropolis, a sense of evil power and hostile strength, of ancient wisdom and monstrous science, for it had endured since the Earth was new.

The four ragged creatures on the raft gazed on those marching walls with a hopeless horror. Their minds sank prostrate with realization that unless their puny efforts could free the girl imprisoned there, the makers of this pile of black metal had also shaped the doom of mankind.

The city seemed dead at first, a somber necropolis, too old for any life. But presently they saw movement along the walls. A black spider-ship spread titanic vanes, and rose silently from a high platform to vanish in the red sky eastward.

"We must cover ourselves," said Jay Kalam. "They might be watching."

He had them screen the raft with broken branches, to look like driftwood. And the river carried them on toward the mighty wall. They were gazing upward in awe­struck silence when Hal Samdu cried: "See them moving! Above the wall!"

And the others could presently distinguish the creatures that moved—still tiny with many miles of distance—the ancient masters of this aged planet!

John Star had glimpsed one of the Medusas on Mars, that thing in the gondola swung from the black flier, whose weapon had struck him down. A swollen, greenish surface, wetly heaving; a huge, ovoid eye, luminous and purple. But these were the first he had fully seen.

They drifted above the wall like little green balloons. Their eyes were tiny dark points in their bulging sides—each had four eyes, spaced at equal distances about its circumference. From the lower, circular edge, like the ropes that would have suspended the car of a balloon, hung a fringe of black and whiplike tentacles.

John Star could see the superficial likeness, the dome shape, the fringing tentacles, that had earned them the name Medusae.

In the distance they did not look impressive. There was about them a certain grotesq«eness, a slow awkwardness. They didn't look intelligent. Yet in the way they moved, floating apparently at will above the black wall, was a power and mystery that made for respect. And in the knowledge that they were the builders of this black metropolis was room for awe and terror.

---

Scrambling over the immense bearing of the shaft, they found a little circular hole in the roof of the tank—it must have been left for attention to the bearings. They climbed through it, Giles Habibula sticking until the others pulled him out, and so at last, on top of the reservoir, they were fairly within the city.

They stood on the lower edge of a conical black metal roof, a dizzy drop of two thousand feet below them, and the slope too steep for comfort.

Standing there on that perilous brink, John Star felt a staggering impact of nightmare strangeness and bewildering confusion. Buildings, towers, stacks, tanks, machines, all loomed up about him, a black fantastic forest against the lurid sky, appallingly colossal. The tallest structures reached, he soberly estimated, two miles high.

If this black metropolis of the monstrous Medusae had order or plan, he did not grasp it. The black wall had seemed to enclose a regular polygon. But within all was strange, astounding, incomprehensible, to the point of stunning dismay.

There were no streets, but merely yawning cavernous abysms between mountainous black structures. The Medusae had no need of streets. They didn't walk, they floated! Doors opened upon sheer space, at any level from the surface to ten thousand feet.

The stupendous ebon buildings had no regular height or plan, some were square, some cylindrical or domed, some terraced, some—like the reservoir upon which they stood—sheerly vertical. All among them were bewildering machines of unguessable function—save that a few were apparently aerial or interstellar fliers, moored on landing stages—but all black, ugly, colossal; dread instrumentalities of a science older than the life of Earth.

     "Ah, a bit more than nothing," Turekian said. "A tiny bit. I just wish you were less convinced your science has the last word on all the possibilities. Things I've seen—"
     "I've heard your song before," Webner scoffed. "In a jungle on some exotic world you met animals with wheels."
     "Never said that. Hm-m-m … make a good yarn, wouldn't it?"
     "No. Because it's an absurdity. Simply ask yourself how nourishment would pass from the axle bone to the cells of the disc. In like manner—"

• 

     The boy slowed. An alien was squatting in the path. A Polarian.
     They drew up before the strange creature. It was a teardrop-shaped thing with a massive spherical wheel on the bottom and a limber tentacle or trunk at the top. When that tentacle reached straight up, it would be as high as Flint, and the body's mass was similar to his. But the Polarian had no eyes, ears, nose, or other appendages.
     The Shaman claimed they were similar to human beings because they liked similar gravity, breathed the same air—though they had no lungs—and had a similar body chemistry. Their brains were as massive and versatile as man's, and they were normally inoffensive. But they looked quite different, and such details as how they ate, reproduced, and eliminated were mysteries.
     But Flint had promised himself to treat the next alien he met with special courtesy. He and the boy halted politely. "Greetings, explorer," Flint said.
     The creature's body glowed with simulated pleasure. It put its stalk down to the ground. In this position it looked more than ever like a dinosaur dropping. Flint stifled a laugh.
     A little ball in the tip of the trunk spun rapidly. "Greetings, native," the ground said.
     Flint was not surprised. He had been familiar with the mechanism from infancy. The little ball vibrated against the ground—or any available surface—to produce intelligible sounds. As the Polarian had no mouth, it could not talk as humans did.

---

     Now he had done it! He had never suspected the creature would accept! Well, it couldn't be helped. "It is an emergency. We shall be hurrying."
     "I shall not impede you," the Polarian replied.
     Fat chance! But Flint smiled graciously. He gestured to the boy. "Show the way."
     The runner was off, sensing a race. This was firm, level ground, excellent for making time. Flint followed, stretching his legs.
     But Tsopi followed right along, rolling smoothly on her ball-wheel. She was at no disadvantage. Polarians could move rapidly and effortlessly when the terrain was right; their wheel was efficient. Flint had not before appreciated how efficient. On occasion he had wondered how the aliens kept themselves upright. The Shaman had remarked that a man on a unicycle performed the same feat. But there were no unicycles on Outworld.

---

     How did no-handed creatures manage to build such edifices? Again his memory provided the answer: Polarians were adept at circular manipulation of objects and concepts. They did not carry building blocks into place, they rolled building spheres into place. Where men laid bricks, Polarians rolled stones. Where men hammered nails, Polarians squeezed glue. The end result was rather similar, as though civilization shaped itself into certain configurations regardless of the sapient species invoking it. Here there were no square skyscrapers, but domed dunes serving the same purpose.
     They passed down a smooth ramp, where on Earth there would have been stairs. Of course; ramps were better for wheels, stairs for legs. Ramps were everywhere, contributing to the fluidity of the architectural design.
     They had to roll single file, for efficient progress through the throng. Tsopi's trail just ahead of him was sweet; she had a tantalizingly feminine taste.
     Taste? Flint concentrated, and it came: Polarians laid down taste trails with their wheels, much as humans laid down scent. No, more than that: These were actual, conscious signatures of passage, like the trails of Earthly snails. He remembered the first snail he had seen, beside the huge water of the ocean inlet, under the odd blue sky of Earth. Today he didn't even notice the color of the sky of a given planet; sky was sky color, right for its world. But this taste; every Polarian was really a super-bloodhound, sniffing out every other, all the time. It was the natural way. In fact, it was already difficult to imagine how it could be otherwise.

• 

     The monster charged, when Herald was off-balanced from his effort. And suddenly he realized another point of affinity: the monster was like a Slash, his own kind! A Slash was a tubular creature with disks around its girth that it used for slicing out pathways, cutting up food, and dismembering enemies. It also had laser lenses for longer-range action. In his natural body, Herald could have met this creature on even terms, perhaps more than even terms. A Slash was smaller, but the lasers could score with devastating effect before the disks struck. But this Solarian host was a poor excuse for a combat creature.

Once upon a time animals were shaped like sticks (worms), and couldn't manipulate or even locomote very well. Then the sticks grew smaller sticks (arms and legs) and locomotion was much improved, and manipulation a little. Then the smaller sticks grew yet smaller sticks (fingers), and hands were invented, and manipulation got better.

Generalize the concept. I visualize a robot that looks like a tree, with a big stem, repeatedly branching into thinner, shorter and more numerous twigs, finally ending up in jillions of near-microscopic cilia. Each intermediate branch would have three or four degrees of freedom, an azimuth-elevation mount at its base, and an axial rotation joint at the top, where it connects to the next level of smaller twigs, and possibly also a length altering telescoping joint. To a large extent fewer degrees of freedom per level can be traded off for more levels. Each branch would also incorporate force sensing. Though each branch would be a rigid "mechanical" object, the overall structure would have an "organic" flexibility because of the great multitude of degrees of freedom.

• 

HIVE ENTITY. A type of REALLY ALIEN intelligent species - one of the most Really Alien of all - organized along lines rather like the social insects. In a Hive Entity, individuals members of the community count for nothing, and indeed most of them have no individual intelligence to speak of. They are specialized for various functions (particularly warriors), and exist entirely to serve the Hive Entity as a whole.

A Hive Entity's intelligence may reside in specialized "brain" individuals, which have only vestigial legs and even digestive systems, and are themselves entirely dependent on various kinds of "slave" individuals. Or the intelligence may somehow be spread out collectively though the whole Hive Entity, each individually-mindless inhabitant in effect contributing a few neurons to the whole. (Or some combination of these.) Some Hive Entities may not really be intelligent at all, but have evolved the ability to blow up other people's spacecraft the same way that some ants have evolved the ability to keep aphids as cattle.

When encountered in the KNOWN GALAXY, Hive Entities are almost invariably hostile. They apparently have nothing to offer in trade, much less arts or ideas, and you can't even negotiate a peace treaty with them, because there isn't really anyone to negotiate with. In WARFARE they are at once mindlessly ruthless - attacking in endless waves like giant army ants, which they also tend to look like - and malevolently intelligent. Putting no value on their own automaton lives, they obviously have no concept of valuing anyone else's.

In fact, Hive Entities are basically the ultimate totalitarians. It is no surprise that they appeared in written SF, so far as I know, around the mid 20th century CE, the same time that giant ants showed up in HOLLYWOOD SCIFI. Hive Entities were, and are, Nazis, Stalinists, and ChiComs, magnified to the Nth degree and let loose to give better races a harsh lesson in the precious value of individualism.

Which is really too bad. Taken in themselves, Hive Entities are a fascinating concept, precisely because they really are Really Alien. Yet if in fact they are intelligent, they must have ideas of some sort, however hard for them to express in a way we can understand. If the intelligence is spread through the hive community, the time scale of its thinking might be drastically slower than our own, maybe taking weeks to form the equivalent of a sentence. This indeed could make them tricky to deal with at first, since on our time scale they would necessarily act on reflex.

But if we EARTH HUMANS, and similar species, really want to demonstrate individual intelligence, we might actually try figuring the Hive Entities out, and see if we and they might have something to contribute to each other, instead of fighting pretty mindless wars with them. Don't hold your breath, though. It hasn't happened in fifty years, so far as I know.

But maybe the Hive Entities' mental time scale is longer than that.

I love social insects. Whether they’re ants, bees, termites, wasps, aphids, thrips, or ambrosia beetles, I find them fascinating to learn about. But if the sci-fi books I read as a kid had had their way, I should have run screaming from every ant colony I saw.

From the buggers in Ender’s Game to the Borg in Star Trek to the Vord in Codex Alera to ants and termites themselves from a morph’s-eye view in Animorphs, social insects, and the aliens or artificial intelligences that closely resemble them, are portrayed as “hive minds” with an emotional tone of existential terror. And I’m here to tell you that these portrayals are totally unfair.

What they get right

Here are some features that most portrayals of social insects and their analogues in sci-fi get right. Yes, social insect colonies have queens that are primarily responsible for reproduction. Yes, social insects have very different sensory modalities from ours. We primarily use sight and sound to communicate and navigate the world, while social insects use taste and smell and vibration. Yes, social insects have specialized division of labor to particular tasks, and yes, they are willing to sacrifice themselves in droves to protect the colony. And sometimes, they will enslave social insects from other colonies or even species to serve their own ends (x).

Thus ends what sci-fi portrayals get right.

What they get wrong: Queens

Almost universally in sci-fi, when you kill the queen, the hive disintegrates into chaos. You’ve cut off the head! The central intelligence of the hive is gone! They’re just mindless borg-units with no idea what to do!

Indeed, in some social insects, such as leafcutter ants, if you kill the queen, the whole colony will die – but probably not for the reasons you think. However, it’s more common for social insects to be able to carry on just fine regardless. In most ants and bees, there are “backup” queens that are reared up by the workers in case the current queen should die. And in many social insects, a worker can step up and become a queen in her place.

But here is the most important problem with the sci-fi trope of killing the queen to kill the hive. The queen is not the brain of the hive. She is the ovary.

If you think of a social insect colony as a superorganism, which it’s useful to do in many cases, different groups of insects within the colony act like organs. One caste protects the colony from invaders, which is like an immune system. One caste scouts for new places to forage, which is like a sensory system. Generally, science fiction has a good grip on this idea. Where sci-fi authors fail is that they think the queen is the brain of this superorganism. She is not. She is the reproductive system. The queen does not control what happens in the hive any more than your reproductive system controls what happens in your body. (Which is to say, she has some influence, but she is not the brains of the operation.)

The reason why leafcutter ant colonies die when the queen dies is because the colony has been castrated, not beheaded. Most animals die when they are no longer able to reproduce, even if their brains are still perfectly functional. For castrated colonies with no backup queen or gamergate and no hope of getting one, there is no point in carrying on. Their evolutionary line has ended.

What they get wrong: Swarm intelligence

Here is how social insect hive minds work in science fiction: the queen does the thinking, and the rest of the hive goes along with whatever she thinks.

Now, I’ve already told you that the queen is not the brain of the hive. So where is the brain? Well, that is exactly the point of swarm intelligence. The brain does not reside in one particular animal. It’s an emergent property of many animals working together. A colony is not like your body, where your brain sends an impulse to your mouth telling it to move, and it moves. It’s more like when two big groups of people are walking toward each other, and they spontaneously organize themselves into lanes so no one has a collision (x). There’s no leader telling them to do that, but they do it anyway.

Much of the efficiency of social insect colonies comes from very simple behavioral rules (x). Hymenopterans, the group of insects that includes ants, bees, and wasps, have a behavioral rule: work on a task until it is completed, and when it is done, switch to a different task. If you force solitary bees (yes, most bee species are solitary) to live together, they will automatically arrange themselves into castes, because when one bee sees another bee doing a task like building the nest, its behavioral rule tells it that the task is completed and it needs to switch to a different task, like looking for food.

Individually, a social insect isn’t all that smart, whether it’s a queen, worker, soldier, or drone. But collectively, social insects can do incredibly smart things, like find the most efficient route from the colony to some food (x), or choose the perfect spot to build their hive (x).

What they get wrong: Individuality

The existential terror of the hive mind in science fiction comes from the loss of the self. The idea is that in a social insect colony, there is no individual, but one whole, united to one purpose. No dissent, disagreement, or conflicting interests occur, just total lockstep. I totally get why that’s scary.

The thing is, it’s just not true of real social insects. There is conflict within colonies all the time, up to and including civil war.

A common source of conflict within colonies is worker reproduction. Yes, in most social insects, workers can in fact reproduce, though usually they can only produce males. So why don’t they? Because it’s not in the interest of their fellow workers. Workers are more closely related to their siblings and half-siblings produced by the queen than they are to their nephews, so they pass on more of their genes if they spend resources on raising the queen’s eggs. So, if a worker catches its fellow laying an egg, it will eat the egg. Not exactly “all for one and one for all,” is it?

Worker insects may also fight in wars of succession. If there is more than one queen in a species where queens do not tolerate each other (yes, there are species where multiple queens get along together just fine), such as monogynous fire ants, the workers will ally themselves with one queen or another and engage in very deadly civil war.

Finally, in some species, the queen needs to bully the workers into doing their jobs, and the dominant workers need to bully subordinate workers into doing their jobs (x). Yes, sometimes workers try to laze around and mooch.

Surprisingly human

Here’s what I find weird about depictions of social insects in science fiction. They are portrayed as utterly alien, Other, and horrifying. Yet humans and social insects are very, very similar. The famous sociobiologists E.O. Wilson and Bernard Crespi have both described humans as chimpanzees that took on the lifestyle of ants.

I think what fascinates people, including me, about ants, bees, and their ilk is that you watch, say, a hundred ants working together to tear up a leaf into tiny bits and carry it back to their colony, or a hundred bees all appearing out of seemingly nowhere to sacrifice themselves en masse to stop a bear from eating their hive, and it looks like magic. It really does look like some kind of overmind is controlling their collective actions.

But imagine you’re an alien who comes to Earth, and you know nothing about humans or the way we communicate. Wouldn’t we look exactly the same to them as ants and bees look to us? Wouldn’t they look at us sacrificing our lives by the thousands in wars, or working together to build cities from nothing, and think, Wow, how do they coordinate themselves in such huge numbers, why do they give up their lives to defend their borderlines, I guess there must be some kind of mega-brain they all share that tells them what to do, and they just march in lockstep and do it.

If there’s anything I’ve learned from the study of both social insects and humans, it’s that any system that looks monolithic and simple from a distance is in fact fractured, messy, and complicated when you look at it up close.

Social insects aren’t scary mindless robot-aliens. They’re a lot like you and me. As much as I was terrified as a kid by the Animorphs book where an ant morphs into Cassie and screams in pure existential horror at its sudden individuality, I actually think an ant would adjust very easily to being a human, and that a human would adjust very easily to being an ant — much more easily, in fact, than humans adjusted to morphing, say, sharks, in the very same book series.

• 

      “I know you have all been wondering,” began Alveron, “why we were ordered to abandon our survey and to proceed at such an acceleration to this region of space. Some of you may realize what this acceleration means. Our ship is on its last voyage: the generators have already been running for sixty hours at Ultimate Overload. We will be very lucky if we return to Base under our own power.
     “We are approaching a sun which is about to become a Nova (yes, I know sun-like stars cannot go nova. Story was written in 1946). Detonation will occur in seven hours, with an uncertainty of one hour, leaving us a maximum of only four hours for exploration. There are ten planets in the system about to be destroyed — and there is a civilization on the third (Terra, of course). That fact was discovered only a few days ago. It is our tragic mission to contact that doomed race and if possible to save some of its members. I know that there is little we can do in so short a time with this single ship. No other machine can possibly reach the system before detonation occurs.”

---

     Torkalee’s three companions lost no time in leaving the machine. Leader of the party, by seniority of rank and race was T’sinadree, who like Alveron himself had been born on one of the ancient planets of the Central Suns. Next came Alarkane, from a race which was one of the youngest in the Universe and took a perverse pride in the fact. Last came one of the strange beings from the system of Palador. It was nameless, like all its kind, for it possessed no identity of its own, being merely a mobile but still dependent cell in the consciousness of its race. Though it and its fellows had long been scattered over the galaxy in the exploration of countless worlds, some unknown link still bound them together as inexorably as the living cells in a human body.
     When a creature of Palador spoke, the pronoun it used was always “We.” There was not, nor could there ever be, any first person singular in the language of Palador.

---

     The party stopped dead and looked down the passageway with a single thought. A tunnel, leading down into the depths of Earth! At its end, they might yet find the people of this world and rescue some of them from their fate. For there was still time to call the mother ship if the need arose.
     T’sinadree signaled to his commander and Torkalee brought the little machine immediately overhead. There might not be time for the party to retrace its footsteps through the maze of passages, so meticulously recorded in the Paladorian mind that there was no possibility of going astray. If speed was necessary, Torkalee could blast his way through the dozen floors above their head. In any case, it should not take long to find what lay at the end of the passage.
     It took only thirty seconds. The tunnel ended quite abruptly in a very curious cylindrical room with magnificently padded seats along the walls. There was no way out save that by which they had come and it was several seconds before the purpose of the chamber dawned on Alarkane’s mind. It was a pity, he thought, that they would never have time to use this. The thought was suddenly interrupted by a cry from T’sinadree. Alarkane wheeled around, and saw that the entrance had closed silently behind them.

     Even in that first moment of panic, Alarkane found himself thinking with some admiration: Whoever they were, they knew how to build automatic machinery!
     The Paladorian was the first to speak. It waved one of its tentacles toward the seats.
     “We think it would be best to be seated,” it said. The multiplex mind of Palador had already analyzed the situation and knew what was coming.
     They did not have long to wait before a low-pitched hum came from a grill overhead, and for the very last time in history a human, even if lifeless, voice was heard on Earth. The words were meaningless, though the trapped explorers could guess their message clearly enough. “Choose your stations, please, and be seated.” Simultaneously, a wall panel at one end of the compartment glowed with light. On it was a simple map, consisting of a series of a dozen circles connected by a line. Each of the circles had writing alongside it, and beside the writing were two buttons of different colors. Alarkane looked questioningly at his leader. “Don’t touch them,” said T’sinadree. “If we leave the controls alone, the doors may open again.” He was wrong. The engineers who had designed the assumed that anvone who entered it would naturally wish to go somewhere. If they selected no intermediate station, their destination could only be the end of the line.
     There was another pause while the relays and thyratrons (the controlling computer) waited for their orders. In those thirty seconds, if they had known what to do, the party could have opened the doors and left the subway. But they did not know, and the machines geared to a human psychology acted for them.

     The surge of acceleration was not very great; the lavish upholstery was a luxury, not a necessity. Only an almost imperceptible vibration told of the speed at which they were traveling through the bowels of the earth, on a journey the duration of which they could not even guess. And in thirty minutes, the S9000 would be leaving the Solar System.
     There was a long silence in the speeding machine. T’sinadree and Alarkane were thinking rapidly. So was the Paladorian, though in a different fashion. The conception of personal death was meaningless to it, for the destruction of a single unit meant no more to the group mind than the loss of a nail-paring to a man. But it could, though with great difficulty, appreciate the plight of individual intelligences such as Alarkane and T’sinadree, and it was anxious to help them if it could.
     Alarkane had managed to contact Torkalee with his personal transmitter, though the signal was very weak and seemed to be fading quickly. Rapidly he explained the situation, and almost at once the signals became clearer. Torkalee was following the path of the machine, flying above the ground under which they were speeding to their unknown destination. That was the first indication they had of the fact that they were traveling at nearly a thousand miles an hour, and very soon after that Torkalee was able to give the still more disturbing news that they were rapidly approaching the sea. While they were beneath the land, there was a hope, though a slender one, that they might stop the machine and escape. But under the ocean — not all the brains and the machinery in the great mother ship could save them. No one could have devised a more perfect trap.
     The little light on the map crawled slowly through the illuminated circle without checking its speed. And at the same time Torkalee called from the ship overhead. “You have just passed underneath a city and are heading out to sea. There cannot be another stop for nearly a thousand miles.”

---

     Alveron had given up all hope of finding life on this world. The S9000 had roamed over half the planet, never staying long in one place, descending ever and again in an effort to attract attention. There had been no response; Earth seemed utterly dead. If any of its inhabitants were still alive, thought Alveron, they must have hidden themselves in its depths where no help could reach them, though their doom would be nonetheless certain.
     Rugon brought news of the disaster. The great ship ceased its fruitless searching and fled back through the storm to the ocean above which Torkalee’s little tender was still following the track of the buried machine.
     Fortunately, there had been no serious earthquakes yet. Far beneath the bed of the ocean, the wonderful piece of engineering which had been the World President’s private vacuum-subway was still working perfectly, unaffected by the tumult and destruction above. It would continue to work until the last minute of the Earth’s existence, which, if the astronomers were right, was not much more than fifteen minutes away — though precisely how much more Alveron would have given a great deal to know. It would be nearly an hour before the trapped party could reach land and even the slightest hope of rescue.

     Meanwhile, a mile below the bed of the ocean Alarkane and T’sinadree were very busy indeed with their private communicators. Fifteen minutes is not a long time in which to wind up the affairs of a lifetime. It is indeed, scarcely long enough to dictate more than a few of those farewell messages which at such moments are so much more important than all other matters.
     All the while the Paladorian had remained silent and motionless, saying not a word. The other two, resigned to their fate and engrossed in their personal affairs, had given it no thought. They were startled when suddenly it began to address them in its peculiarly passionless voice. “We perceive that you are making certain arrangements concerning your anticipated destruction. That will probably be unnecessary. Captain Alveron hopes to rescue us if we can stop this machine when we reach land again.”
     Both T’sinadree and Alarkane were too surprised to say anything for a moment. Then the latter gasped, “How do you know?”
     It was a foolish question, for he remembered at once that there were several Paladorians — if one could use the phrase — in the S9000, and consequently their companion knew everything that was happening in the mother ship. So he did not wait for an answer but continued, “Alveron can’t do that! He daren’t take such a risk!”
     “There will be no risk,” said the Paladorian. “We have told him what to do. It is really very simple.”

     Alarkane and T’sinadree looked at their companion with something approaching awe, realizing now what must have happened. In moments of crisis, the single units comprising the Paladorian mind could link together in an organization no less close than that of any physical brain. At such moments they formed an intellect more powerful than any other in the Universe. All ordinary problems could be solved by a few hundred or thousand units. Very rarely, millions would be needed, and on two historic occasions the billions of cells of the entire Paladorian consciousness had been welded together to deal with emergencies that threatened the race. The mind of Palador was one of the greatest mental resources of the Universe; its full force was seldom required, but the knowledge that it was available was supremely comforting to other races. Alarkane wondered how many cells had co-ordinated to deal with this particular emergency. He also wondered how so trivial an incident had ever come to its attention.
     To that question he was never to know the answer, though he might have guessed it had he known that the chillingly remote Paladorian mind possessed an almost human streak of vanity. Long ago, Alarkane had written a book trying to prove that eventually all intelligent races would sacrifice individual consciousness and that one day only group-minds would remain in the Universe. Palador, he had said, was the first of those ultimate intellects, and the vast, dispersed mind had not been displeased.

• 

     They had no time to ask any further questions before Alveron himself began to speak through their communicators.
     “Alveron calling! We’re staying on this planet until the detonation waves reach it, so we may be able to rescue you. You’re heading toward a city on the coast which you’ll reach in forty minutes at your present speed. If you cannot stop yourselves then, we’re going to blast the tunnel behind and ahead of you to cut off your power. Then we’ll sink a shaft to get you out — the chief engineer says he can do it in five minutes with the main projectors. So you should be safe within an hour, unless the sun blows up before.”
     “And if that happens, you’ll be destroyed as well! You mustn’t take such a risk!”
     “Don’t let that worry you; we’re perfectly safe. When the sun detonates, the explosion wave will take several minutes to rise to its maximum. But apart from that, we’re on the night side of the planet, behind an eight-thousand-mile screen of rock. When the first warning of the explosion comes, we will accelerate out of the Solar System, keeping in the shadow of the planet. Under our maximum drive, we will reach the velocity of light before leaving the cone of shadow, and the sun cannot harm us then.”

     T’sinadree was still afraid to hope. Another objection came at once into his mind. “Yes, but how will you get any warning, here on the night side of the planet?”
     “Very easily,” replied Alveron. “This world has a moon which is now visible from this hemisphere. We have telescopes trained on it. If it shows any sudden increase in brilliance, our main drive goes on automatically and we’ll be thrown out of the system.”
     The logic was flawless. Alveron, cautious as ever, was taking no chances. It would be many minutes before the eight-thousand-mile shield of rock and metal could be destroyed by the fires of the exploding sun. In that time, the S9000 could have reached the safety of the velocity of light.

     Alarkane pressed the second button when they were still several miles from the coast. He did not expect anything to happen then, assuming that the machine could not stop between stations. It seemed too good to be true when, a few minutes later, the machine’s slight vibration died away and they came to a halt.
     The doors slid silently apart. Even before they were fully open, the three had left the compartment. They were taking no more chances. Before them a long tunnel stretched into the distance, rising slowly out of sight. They were starting along it when suddenly Alveron’s voice called from the communicators.
     “Stay where you are! We’re going to blast!”

     The ground shuddered once, and far ahead there came the rumble of falling rock. Again the earth shook — and a hundred yards ahead the passageway vanished abruptly. A tremendous vertical shaft had been cut clean through it.
     The party hurried forward again until they came to the end of the corridor and stood waiting on its lip. The shaft in which it ended was a full thousand feet across and descended into the earth as far as the torches could throw their beams. Overhead, the storm clouds fled beneath a moon that no man would have recognized, so luridly brilliant was its disk. And, most glorious of all sights, the S9000 floated high above, the great projectors that had drilled this enormous pit still glowing cherry red.
     A dark shape detached itself from the mother ship and dropped swiftly toward the ground. Torkalee was returning to collect his friends. A little later, Alveron greeted them in the control room. He waved to the great vision screen and said quietly, “See, we were barely in time.”

• 

• 

      The historians can't seem to settle whether to call this one "The Third Space War" (or the "Fourth"), or whether "The First Interstellar War" fits it better. We just call it "The Bug War" if we call it anything, which we usually don't.

     I do have one comment to make to any armchair strategist who has never made a drop. Yes, I agree that the Bugs' planet possibly could have been plastered with H-bombs until it was surfaced with radioactive glass. But would that have won the war? The Bugs are not like us. The Pseudo-Arachnids aren't even like spiders. They are arthropods who happen to look like a madman's conception of a giant, intelligent spider, but their organization, psychological and economic, is more like that of ants or termites; they are communal entities, the ultimate dictatorship of the hive. Blasting the surface of their planet would have killed soldiers and workers; it would not have killed the brain caste and the queens—I doubt if anybody can be certain that even a direct hit with a burrowing H-rocket would kill a queen; we don't know how far down they are. Nor am I anxious to find out; none of the boys who went down those holes came up again.

     So suppose we did ruin the productive surface of Klendathu? They still would have ships and colonies and other planets, same as we have, and their HQ is still intact—so unless they surrender, the war isn't over. We didn't have nova bombs at that time; we couldn't crack Klendathu open. If they absorbed the punishment and didn't surrender, the war was still on.

     If they can surrender—

     Their soldiers can't. Their workers can't fight (and you can waste a lot of time and ammo shooting up workers who wouldn't say boo!) and their soldier caste can't surrender. But don't make the mistake of thinking that the Bugs are just stupid insects because they look the way they do and don't know how to surrender. Their warriors are smart, skilled, and aggressive—smarter than you are, by the only universal rule, if the Bug shoots first. You can burn off one leg, two legs, three legs, and he just keeps on coming; burn off four on one side and he topples over—but keeps on shooting. You have to spot the nerve case and get it … whereupon he will trot right on past you, shooting at nothing, until he crashes into a wall or something.

---

     The next eighteen hours were nightmare. I shan't tell much about it because I don't remember much, just snatches, stop-motion scenes of horror. I have never liked spiders, poisonous or otherwise; a common house spider in my bed can give me the creeps. Tarantulas are simply unthinkable, and I can't eat lobster, crab, or anything of that sort. When I got my first sight of a Bug, my mind jumped right out of my skull and started to yammer. It was seconds later that I realized that I had killed it and could stop shooting. I suppose it was a worker; I doubt if I was in any shape to tackle a warrior and win.

     Presently I got so that I could kill a Bug without wasting ammo or juice, although I did not learn to distinguish between those that were harmless and those that were not. Only about one in fifty is a warrior but he makes up for the other forty-nine. Their personal weapons aren't as heavy as ours but they are lethal just the same—they've got a beam that will penetrate armor and slice flesh like cutting a hard-boiled egg, and they cooperate even better than we do … because the brain that is doing the heavy thinking for a "squad" isn't where you can reach it; it's down one of the holes.

---

     We certainly didn't know that we were losing.

     Those Bugs lay eggs. They not only lay them, they hold them in reserve, hatch them as needed. If we killed a warrior—or a thousand, or ten thousand—his or their replacements were hatched and on duty almost before we could get back to base. You can imagine, if you like, some Bug supervisor of population flashing a phone to somewhere down inside and saying, "Joe, warm up ten thousand warriors and have 'em ready by Wednesday … and tell engineering to activate reserve incubators N, O, P, Q, and R; the demand is picking up."

     I don't say they did exactly that, but those were the results. But don't make the mistake of thinking that they acted purely from instinct, like termites or ants; their actions were as intelligent as ours (stupid races don't build spaceships!) and were much better coordinated. It takes a minimum of a year to train a private to fight and to mesh his fighting in with his mates; a Bug warrior is hatched able to do this.

     Every time we killed a thousand Bugs at a cost of one M.I. it was a net victory for the Bugs. We were learning, expensively, just how efficient a total communism can be when used by a people actually adapted to it by evolution; the Bug commissars didn't care any more about expending soldiers than we cared about expending ammo. Perhaps we could have figured this out about the Bugs by noting the grief the Chinese Hegemony gave the Russo-Anglo-American Alliance; however the trouble with "lessons from history" is that we usually read them best after falling flat on our chins.

     But we were learning. Technical instructions and tactical doctrine orders resulted from every brush with them, spread through the Fleet. We learned to tell the workers from the warriors—if you had time, you could tell from the shape of the carapace, but the quick rule of thumb was: If he comes at you, he's a warrior; if he runs, you can turn your back on him. We learned not to waste ammo even on warriors except in self-protection; instead we went after their lairs. Find a hole, drop down it first a gas bomb which explodes gently a few seconds later, releasing an oily liquid which evaporates as a nerve gas tailored to Bugs (it is harmless to us) and which is heavier than air and keeps on going down—then you use a second grenade of H. E. to seal the hole.

     We still didn't know whether we were getting deep enough to kill the queens—but we did know that the Bugs didn't like these tactics; our intelligence through the Skinnies and on back into the Bugs themselves was definite on this point. Besides, we cleaned their colony off Sheol completely this way. Maybe they managed to evacuate the queens and the brains … but at least we were learning to hurt them.

---

• 

     The described real estate didn't seem worth the price. Planet P is smaller than Terra, with a surface gravity of 0.7, is mostly arctic-cold ocean and rock, with lichenous flora and no fauna of interest. Its air is not breathable for long, being contaminated with nitrous oxide and too much ozone. Its one continent is about half the size of Australia, plus many worthless islands; it would probably require as much terra-forming as Venus before we could use it.

     However we were not buying real estate to live on; we went there because Bugs were there—and they were there on our account, so Staff thought. Staff told us that Planet P was an uncompleted advance base (prob. 87±6 percent) to be used against us.

     Since the planet was no prize, the routine way to get rid of this Bug base would be for the Navy to stand off at a safe distance and render this ugly spheroid uninhabitable by Man or Bug. But the C-in-C had other ideas.

     The operation was a raid. It sounds incredible to call a battle involving hundreds of ships and thousands of casualties a "raid," especially as, in the meantime, the Navy and a lot of other cap troopers were keeping things stirred up many light-years into Bug space in order to divert them from reinforcing Planet P.

But the C-in-C was not wasting men; this giant raid could determine who won the war, whether next year or thirty years hence. We needed to learn more about Bug psychology. Must we wipe out every Bug in the Galaxy? Or was it possible to trounce them and impose a peace? We did not know; we understood them as little as we understand termites. To learn their psychology we had to communicate with them, learn their motivations, find out why they fought and under what conditions they would stop; for these, the Psychological Warfare Corps needed prisoners.

     Workers are easy to capture. But a Bug worker is hardly more than animate machinery. Warriors can be captured by burning off enough limbs to make them helpless—but they are almost as stupid without a director as workers. From such prisoners our own professor types had learned important matters—the development of that oily gas that killed them but not us came from analyzing the biochemistries of workers and warriors, and we had had other new weapons from such research even in the short time I had been a cap trooper. But to discover why Bugs fight we needed to study members of their brain caste. Also, we hoped to exchange prisoners.

     So far, we had never taken a brain Bug alive. We had either cleaned out colonies from the surface, as on Sheol, or (as had too often been the case) raiders had gone down their holes and not come back. A lot of brave men had been lost this way.

     Still more had been lost through retrieval failure. Sometimes a team on the ground had its ship or ships knocked out of the sky. What happens to such a team? Possibly it dies to the last man. More probably it fights until power and ammo are gone, then survivors are captured as easily as so many beetles on their backs.

     From our co-belligerents the Skinnies we knew that many missing troopers were alive as prisoners—thousands we hoped, hundreds we were sure. Intelligence believed that prisoners were always taken to Klendathu; the Bugs are as curious about us as we are about them—a race of individuals able to build cities, starships, armies, may be even more mysterious to a hive entity than a hive entity is to us.

     But in a hive polyarchy, some castes are valuable or so our Psych Warfare people hoped. If we could capture brain Bugs, alive and undamaged, we might be able to trade on good terms.

     And suppose we captured a queen!

     What is a queen's trading value? A regiment of troopers? Nobody knew, but Battle Plan ordered us to capture Bug "royalty," brains and queens, at any cost, on the gamble that we could trade them for human beings.

     The strategy was simple, and, I guess, logical … if we could afford the losses. Let the Bugs come up. Meet them and kill them on the surface. Let them keep on coming up. Don't bomb their holes, don't gas their holes—let them out. After a while—a day, two days, a week if we really did have overwhelming force, they would stop coming up. Planning Staff estimated (don't ask me how!) that the Bugs would expend 70 percent to 90 percent of their warriors before they stopped trying to drive us off the surface.

     Then we would start the unpeeling, killing surviving warriors as we went down and trying to capture "royalty" alive. We knew what the brain caste looked like; we had seen them dead (in photographs) and we knew they could not run—barely functional legs, bloated bodies that were mostly nervous system. Queens no human had ever seen, but Bio War Corps had prepared sketches of what they should look like—obscene monsters larger than a horse and utterly immobile.

     Besides brains and queens there might be other "royalty" castes. As might be—encourage their warriors to come out and die, then capture alive anything but warriors and workers.

---

     A tremendous shock wave slammed me just as I bounced again, slapped me sideways. Three minutes thirty-seven seconds—call it thirty miles. Was that our sappers "putting down their corks"? "First section! Brace yourselves for another shock wave!" I landed sloppily, almost on top of a group of three or four Bugs. They weren't dead but they weren't fighting; they just twitched. I donated them a grenade and bounced again. "Hit 'em now!" I called out. "They're groggy. And mind that next—"

     The second blast hit as I was saying it. It wasn't as violent. "Cunha! Call off your section. And everybody stay on the bounce and mop up."

     The call-off was ragged and slow—too many missing files as I could see from my physicals display. But the mop-up was precise and fast. I ranged around the edge and got half a dozen Bugs myself—the last of them suddenly became active just before I flamed it. Why did concussion daze them more than it did us? Because they were unarmored? Or was it their brain Bug, somewhere down below, that was dazed?

---

     In one long stretch of tunnel I lost touch with Brumby—some oddity in reflection of radio waves, I guess, for I picked him up at the next intersection. But there he could not tell me which way to turn. This was the place, or near the place, where the Bugs had hit them.
     And here the Bugs hit us.
     I don't know where they came from. One instant everything was quiet. Then I heard the cry of "Bugs! Bugs!" from back of me in the column, I turned—and suddenly Bugs were everywhere. I suspect that those smooth walls are not as solid as they look; that's the only way I can account for the way they were suddenly all around us and among us.
     We couldn't use flamers, we couldn't use bombs; we were too likely to hit each other. But the Bugs didn't have any such compunctions among themselves if they could get one of us. But we had hands and we had feet—
     It couldn't have lasted more than a minute, then there were no more Bugs, just broken pieces of them on the door … and four cap troopers down.
     One was Sergeant Brumby, dead. During the ruckus the second section had rejoined. They had been not far away, sticking together to keep from getting further lost in that maze, and had heard the fight. Hearing it, they had been able to trace it by sound, where they had not been able to locate us by radio.
     Cunha and I made certain that our casualties were actually dead, then consolidated the two sections into one of four squads and down we went—and found the Bugs that had our platoon sergeant besieged.
     That fight didn't last any time at all, because he had warned me what to expect. He had captured a brain Bug and was using its bloated body as a shield. He could not get out, but they could not attack him without (quite literally) committing suicide by hitting their own brain.
     We were under no such handicap; we hit them from behind.

• 

• 

(ed note: This is not the extreme hive type where every hive creature is telepathically linked. It is the more mundane "ant-hill" type of hive.)

      Let’s get cracking. If we don’t hit the next touchdown precisely, we’ll have dry throats for a long time thereafter. Posts!’

     Dry throats, however, did not turn out to be the problem. There was indeed water where they were going — plenty of water.
     In fact, over the whole surface of the planet, they could see nothing else.
     Even a close approach, in orbit about the planet, did not modify this impression more than slightly. The world was Earth-like in size, atmosphere, and distance from its sun, which, in turn, was very like Sol, but it had no continents at all, nor did it have polar ice caps. The universal ocean which covered it was so heat-conservative that its climate was uniformly subtropical. Even the closest observation — not an easy matter, since about 80 per cent of the surface was always obscured by masses of clouds — disclosed no breaks in the rolling sea except for a number of what looked to be coral atolls. They were big ones by earthly standards, but not even the biggest could properly be dignified with the name of island. And anyhow, they were deserted and bare.
     All the same, from the planet to the Argo poured a steady stream of information and directions, in machine-translated and hence readily understandable English. There was a civilization here, a civilization with an advanced technology, and one with access to the knowledge and resources of the Heart Stars. But where was it?

     Obviously it was under water. Jack had immediately suspected a dominant creature something like Earth’s dolphins but with flukes sufficiently modified to handle and make tools, and with a civilization centred, most probably, around underwater cities built inside the lagoons formed by the atolls. But the picture that gradually emerged contradicted his idea at almost every point.
     There were whale-like mammals here, all right, but they were not the planet’s rulers, were not, in fact, as far advanced as their parallels on Earth. The dominant creature was actually not even a vertebrate. It was a mollusk or something very like one.

     The closest resemblance to an earthly animal Jack could think of was the octopus, which has marvellously developed eyes rivalling those of any mammal and is capable in a crude way of learning from experience. There was nothing crude about the decapod squids of this planet, however. They were vastly intelligent in a quite inhuman way — garrulous, solemn, self-important, seemingly quite without humour or any sense of beauty.
     ‘That’s not an unknown combination of character traits among human beings,’ Dr Langer said when Jack reported this impression, for it was to Jack that the task of talking to the decapods had been assigned. ‘But I agree that among humans it’s never been wide-spread. All the same it’s common elsewhere. All hive cultures are like that.’
     This is a hive culture?’ Sandbag said in astonishment ‘How could such a thing evolve among free-swimming animals?’
     ‘Bees are free-flying,’ Dr Langer pointed out.
     ‘Yes, but they go through the whatyoumaycallum insects go through — the metamorphosis. They’re born as grubs that have to be protected.’
     ‘Well, something like that is going on here,’ Dr Langer said. ‘What do you make of those big hydra-like things, like animated trees or giant sea anemones, that build the coral reefs?’
     ‘Just what you just said,’ Jack said promptly. ‘They’re hydroids; they belong to the coelenterates, not to the mollusks. They’re as far away from the decapods on the evolutionary line as the decapods are from us.’
     ‘Jerry, do you agree? No connection between the atoll creatures and the decapods?’

• 

     ‘I can’t see any,’ Sandbag said. These atolls sure aren’t the squid cities we first guessed they were.’
     ‘But they are,’ Dr Langer said calmly. ‘We were just using the wrong definition of a city.’

     There’s nothing in them, sir,’ Jack objected. ‘Nothing in the lagoons but fish, and nothing on the reefs but the hydroids. The decapods have their machinery scattered all over the ocean floor; they ignore the reefs entirely.’
     True,’ Dr Langer said. ‘Because the reefs are hives, not centres of commerce or thought. A hive is a breeding machine. You see, gentlemen — to put a complicated matter as simply as it allows — we were guilty of thinking too rigidly in terms of what we know on Earth, where there’s a long distance between the mollusk and the coelenterate. But evolution didn’t follow the same course here as it did on Earth, and here there’s no such firm distinction. Here the decapods and the hydras are both the same creature.’
     ‘But, sir,’ Jack said. The hydras are just vegetables! I don’t mean that they’re plants. But they’re rooted to the spot; they don’t do anything but catch fish; they don’t even have a brain!’
     ‘And they reproduce by budding,’ Dr Langer added, ‘all true enough. They are a little like the bee grubs Jerry mentioned. The life-cycle of these creatures is what we call “alternation of generation”. The hydras reproduce without sex, by budding. But they also produce sexual buds, male on one individual, female on another. Out of the fertilized egg comes a free-swimming form, the medusoid stage. This swims around for the balance of its lifetime, then settles down, roots itself, turns into a hydroid — and starts a new colony, a new atoll. Thus far, what I’ve said would apply equally well to Earth’s coral polyps … but here the medusoid stage is not a jellyfish but a squid — a molluskoid, if you like. They do the thinking and the organizing. The hydroid forms are the breeders.’
     ‘And the reefs are the hives,’ Jack said. ‘It fits, all right. But what about the central lagoons of the atolls? They can’t have been formed by Darwin’s system, because this planet never had any low volcanic islands to sink into the sea. Still, these atolls look as if they were built up on the run of a crater. How come?’

     ‘That’s the clue that got me started thinking about this in the first place,’ Dr Langer said. ‘Why the similarity of shape when the mechanism couldn’t be the same? But the crucial difference turns out to be one of size. The reefs we have here are very large and built on drowned plateaus of what’s essentially a rather shallow sea. They have plenty of room to expand, and they do. But coral isn’t a strong structural material; it’s just a loose network of glassy splinters that won’t bear a lot of weight. As the atoll here spreads out, its centre gets crushed down by the weight of trapped water, silt, and additional coral, and there you have your lagoon.
     ‘Notice, by the way, that this process very much favoured the way evolution has gone here. The polyps are sessile — fixed to one spot — so they can’t hunt fish; the fish have to come to them, something that even fish would have better sense than to do. On the other hand, if the molluskoid forms had to herd fish for the benefit of their sessile parents, they’d have no time to develop a civilization, especially since herding fish is by no means so easy as herding sheep. The lagoon solves that problem: fish get trapped in there by storms, by tides, by sheer blundering, and in an emergency, schools of fish can be herded in there. Thus, the hydroid stage of the creature can largely feed itself from the warehouse, so to speak, and the free-swimming form can prosecute other concerns. One of those concerns, I would guess, is protecting the defenceless hydroids from being picked off by natural enemies — sharks or whatever the local equivalent is.’

     ‘One thing still bothers me, sir,’ Sandbag said. ‘The whole set-up sounds to me like it would last for ever. The creatures don’t have nations, they don’t have wars. In a word, they’ve got it made. Why do they need to belong to the Hegemony? What good does it do them? I don’t think any other planet would bother trying to conquer a thawed-out snowball like this.’
     ‘No. Water-breathing races don’t develop space flight in the first place, because they never see the sky,’ Dr Langer agreed. ‘So these people don’t need military protection from possible predators. But, Jerry, highly stable cultures are just what the Heart Stars are interested in most of all. It’s not only that they won’t admit unstable cultures; they can’t afford not to take in the stable ones for the sake of the overall stability of the Hegemony. I suspect that this planet joined the Heart Stars because it had to, not to protect itself from some single rival but in self-protection against the Hegemony itself.’

(ed note: The immortal Howard Families are immortal due to centuries of covert selective breeding. One fine day the ephemeral normal humans become aware of the Howard's existence, and immediately start hunting them down. Captured Howards are tortured to get them to reveal the secret of immortality. Trouble is, there is no secret, just genetics. Normal humans think the Howards are lying, and redouble their torturing.

To escape this no-win situation, the Howards steal a protype generation starship, outfit it with a prototype FTL drive, and flee the solar system to escape persecution.

Eventually they find a second human-habitable planet. "Second" because the first planet they found had problems: a native species called the Jockaira.)

• 

      The flight to star PK3722 took seventeen months and three days, ship’s time.
     The ship’s officers had as little choice about the journey’s end as about its beginning. A few hours before their arrival star images flashed back into being in the stellarium screens and the ship rapidly decelerated to interplanetary speeds. No feeling of slowing down was experienced; whatever mysterious forces were acting on them acted on all masses alike. The New Frontiers slipped into an orbit around a live green planet some hundred million miles from its sun; shortly Libby reported to Captain King that they were in a stable parking orbit.
     Neither King nor Lazarus had time to give the matter much thought. Barstow’s face appeared on an interstation viewscreen. “Captain!” he called out. “Can you come aft to lock seven? We have visitors!”
     Barstow had exaggerated; there was only one. The creature reminded Lazarus of a child in fancy dress, masqueraded as a rabbit. The little thing was more android than were the Jockaira, though possibly not mammalian. It was unclothed but not naked, for its childlike body was beautifully clothed in short sleek golden fur. Its eyes were bright and seemed both merry and intelligent.
     But King was too bemused to note such detail. A voice, a thought, was ringing in his head: “ … so you are the group leader” it said. “ … welcome to our world … we have been expecting you … the (blank) told us of your coming …”
     Controlled telepathy—
     A creature, a race, so gentle, so civilized, so free from enemies, from all danger and strife that they could afford to share their thoughts with others—to share more than their thoughts; these creatures were so gentle and so generous that they were offering the humans a homestead on their planet. This was why this messenger had come: to make that offer.
     To King’s mind this seemed remarkably like the prize package that had been offered by the Jockaira; he wondered what the boobytrap might be in this proposition (The Jockaira were nice enough. It is just that they were also basically domesticated animals owned by the Star Gods who lived on the planet. The humans were welcome to stay, as long as they became domesticated as well).
     The messenger seemed to read his thought. “ … look into our hearts … we hold no malice toward you … we share your love of life and we love the life in you …”
     “We thank you,” King answered formally and aloud. “We will have to confer.” He turned to speak to Barstow, glanced back. The messenger was gone (it used psionic teleportation).

---

     They indicated to the Earth people where they were to land, a wide sandy stretch of beach running down to the sea. Back of the low break of the bank lay mile on mile of lush meadowland, broken by irregular clumps of bushes and trees. The landscape had a careless neatness, as if it were a planned park, although there was no evidence of cultivation.
     It was here, a messenger told the first scouting party, that they were welcome to live.
     There seemed always to be one of the Little People present when his help might be useful—not with the jostling inescapable overhelpfulness of the Jockaira, but with the unobtrusive readiness to hand of a phone or a pouch knife. The one who accompanied the first party of explorers confused Lazarus and Barstow by assuming casually that he had met them before, that he had visited them in the ship. Since his fur was rich mahogany rather than golden, Barstow attributed the error to misunderstanding, with a mental reservation that these people might possibly be capable of chameleonlike changes in color. Lazarus reserved his judgment.

---

     However the Little People differed from Earthmen only in degree with respect to scientific attainments. In an utterly basic sense they differed from humans in kind.
     They were not individuals. No single body of a native housed a discrete individual. Their individuals were multi-bodied; they had group “souls.” The basic unit of their society was a telepathic rapport group of many parts. The number of bodies and brains housing one individual ran as high as ninety or more and was never less than thirty-odd.
     The colonists began to understand much that had been utterly puzzling about the Little People only after they learned this fact. There is much reason to believe that the Little People found the Earthmen equally puzzling, that they, too, had assumed that their pattern of existence must be mirrored in others. The eventual discovery of the true facts on each side, brought about by mutual misunderstandings over identity, seemed to arouse horror in the minds of the Little People. They withdrew themselves from the neighborhood of the Families’ settlement and remained away for several days.
     At length a messenger entered the camp site and sought out Barstow. “ … we are sorry we shunned you … in our haste we mistook your fortune for your fault … we wish to help you … we offer to teach you that you may become like ourselves …”
     Barstow pondered how to answer this generous overture. “We thank you for your wish to help us,” he said at last, “but what you call our misfortune seems to be a necessary part of our makeup. Our ways are not your ways. I do not think we could understand your ways.”
     The thought that came back to him was very troubled. “ … we have aided the beasts of the air and of the ground to cease their strife … but if you do not wish our help we will not thrust it on you …”
     The messenger went away, leaving Zaccur Barstow troubled in his mind. Perhaps, he thought, he had been hasty in answering without taking time to consult the elders. Telepathy was certainly not a gift to be scorned; perhaps the Little People could train them in telepathy without any loss of human individualism. But what he knew of the sensitives among the Families did not encourage such hope; there was not a one of them who was emotionally healthy, many of them were mentally deficient as well—it did not seem like a safe path for humans.
     One thing he did learn, and its implications opened up whole new fields of thought: the Little People had, in one sense, conquered death.
     Since each of their egos was shared among many bodies, the death of one body involved no death for the ego. All memory experiences of that body remained intact, the personality associated with it was not lost, and the physical loss could be made up by letting a young native “marry” into the group. But a group ego, one of the personalities which spoke to the Earthmen, could not die, save possibly by the destruction of every body it lived in. They simply went on, apparently forever.
     Their young, up to the time of “marriage” or group assimilation, seemed to have little personality and only rudimentary or possibly instinctive mental processes. Their elders expected no more of them in the way of intelligent behavior than a human expects of a child still in the womb. There were always many such uncompleted persons attached to any ego group; they were cared for like dearly beloved pets or helpless babies, although they were often as large and as apparently mature to Earth eyes as were their elders.

---

     Lazarus hurried to the ship’s boat parked on the beach in which Captain King shared with Barstow a semblance of community headquarters. “You sent for me, Skipper. What’s up?”
     King’s austere face was grave. “It’s about Mary Sperling.” 
     Lazarus felt a sudden cold tug at his heart. “Dead?” 
     “No. Not exactly. She’s gone over to the Little People. ‘Married’ into one of their groups.” 
     “What? But that’s impossible!” 
     Lazarus was wrong. There was no faint possibility of interbreeding between Earthmen and natives but there was no barrier, if sympathy existed, to a human merging into one of their rapport groups, drowning his personality in the ego of the many.
     Mary Sperling, moved by conviction of her own impending death, saw in the deathless group egos a way out. Faced with the eternal problem of life and death, she had escaped the problem by choosing neither … selflessness. She had found a group willing to receive her, she had crossed over.
     “It raises a lot of new problems,” concluded King. “Slayton and Zaccur and I all felt that you had better be here.”
     “Yes, yes, sure—but where is Mary?” Lazarus demanded and then ran out of the room without waiting for an answer. He charged through the settlement ignoring both greetings and attempts to stop him. A short distance outside the camp he ran across a native. He skidded to a stop. “Where is Mary Sperling?”
     “ … I am Mary Sperling …” 
     “For the love of—You can’t be.” 
     “ … I am Mary Sperling and Mary Sperling is myself … do you not know me, Lazarus? … I know you …” 
     Lazarus waved his hands. “No! I want to see Mary Sperling who looks like an Earthman—like me!” 
     The native hesitated. “ … follow me, then …” 
     Lazarus found her a long way from the camp; it was obvious that she had been avoiding the other colonists. “Mary!” 
     She answered him mind to mind: “ … I am sorry to see you troubled … Mary Sperling is gone except in that she is part of us …”
     “Oh, come off it, Mary! Don’t give me that stuff! Don’t you know me?”
     “ … of course I know you, Lazarus … it is you who do not know me … do not trouble your soul or grieve your heart with the sight of this body in front of you … I am not one of your kind … I am native to this planet …”
     “Mary,” he insisted, “you’ve got to undo this. You’ve got to come out of there!”
     She shook her head, an oddly human gesture, for the face no longer held any trace of human expression; it was a mask of otherness. “ … that is impossible … Mary Sperling is gone … the one who speaks with you is inextricably myself and not of your kind …” The creature who had been Mary Sperling turned and walked away.
     “Mary!” he cried. His heart leapt across the span of centuries to the night his mother had died. He covered his face with his hands and wept the unconsolable grief of a child.

• 

• 

The Borg are an alien group that appear as recurring antagonists in the Star Trek franchise. The Borg are cybernetic organisms linked in a hive mind called "the Collective". The Borg co-opt the technology and knowledge of other alien species to the Collective through the process of "assimilation": forcibly transforming individual beings into "drones" by injecting nanoprobes into their bodies and surgically augmenting them with cybernetic components. The Borg's ultimate goal is "achieving perfection".

Aside from being recurring antagonists in the Next Generation television series, they are depicted as the main threat in the film Star Trek: First Contact. In addition, they played major roles in the Voyager series, and serve as the way home to the Alpha Quadrant for the isolated Federation starship USS Voyager.

The Borg have become a symbol in popular culture for any juggernaut against which "resistance is futile", a common phrase uttered by the Borg.

Depiction

The Borg are cyborgs, having outward appearances showing both mechanical and biological body parts. Individual Borg are referred to as drones and move in a robotic, purposeful style ignoring most of their environment, including beings they do not consider an immediate threat. Borg commonly have one eye replaced with a sophisticated ocular implant. Borg usually have one arm replaced with a prosthesis, bearing one of a variety of multipurpose tools in place of a humanoid hand. Since different drones have different roles, the arm may be specialized for myriad purposes such as medical devices, scanners, and weapons. Borg have flat, white skin, giving them an almost zombie-like appearance.

Some Borg have been shown to be far stronger than humans, able to easily overpower most humans and similar species. Typical Borg have never been seen to run, instead moving in a deliberate fashion, never retreating. Borg are highly resistant to energy-based weapons, having personal shielding that quickly adapts to them. In various episodes, phasers and other directed energy weapons tend to quickly become ineffective as the Borg are able to adapt to the specific frequencies on which these weapons are projected once a ship or an individual drone is struck down by them. Later attempts to modulate phaser and other weapon frequencies have had limited success. Borg shields are ineffective protection against projectile or melee weapons, and several have been defeated in this way, or through hand-to-hand combat.

Borg possess a "cortical node" that controls other implanted cybernetic devices within a Borg's body; it is most often implanted in the forehead above the organic eye. If the cortical node fails, the Borg eventually dies. Successful replacement of the node can be carried out on a Borg vessel.

Borg Collective

Borg civilization is based on a hive or group mind known as the Collective. Each Borg drone is linked to the collective by a sophisticated subspace network that ensures each member is given constant supervision and guidance. The mental energy of the group consciousness can help an injured or damaged drone heal or regenerate damaged body parts or technology. The collective consciousness gives them the ability not only to "share the same thoughts", but also to adapt quickly to new tactics. Drones in the Collective are never seen speaking, but a collective "voice" is sometimes transmitted to ships.

"Resistance is futile"

Individual Borg rarely speak, though they do send a collective audio message to their targets, stating that "resistance is futile", generally followed by a declaration that the target in question will be assimilated and its "biological and technological distinctiveness" will be added to their own. The exact phrasing varies and evolves over the various series episodes and film.

The complete phrase used in Star Trek: First Contact is:

We are the Borg. Lower your shields and surrender your ships. We will add your biological and technological distinctiveness to our own. Your culture will adapt to service us. Resistance is futile.

Nanoprobes

Nanoprobes are microscopic machines that inhabit a Borg's body, bloodstream, and many cybernetic implants. The probes maintain the Borg cybernetic systems and repair damage to the organic parts of a Borg. They generate new technology inside a Borg when needed and protect them from many forms of disease. Borg nanoprobes, each about the size of a human red blood cell, travel through the victim's bloodstream and attach to individual cells. The nanoprobes rewrite the cellular DNA, altering the victim's biochemistry, and eventually form larger, more complicated structures and networks within the body, like electrical pathways, processing and data-storage nodes, and ultimately prosthetic devices that spring forth from the skin. In "Mortal Coil", Seven of Nine says the Borg assimilated the nanoprobe technology from "Species 149". In addition, the nanoprobes maintain and repair their host's mechanical and biological components on a microscopic level, imparting regenerative capabilities.

Though used by the Borg to exert control over another being, reprogrammed nanoprobes were used by the crew of the starship Voyager in many instances as medical aids.

The capability of nanoprobes to absorb improved technologies they find into the Borg collective is shown in the Voyager episode "Drone", where Seven of Nine's nanoprobes are fused with the Doctor's mobile emitter which uses technology from the 29th century, creating a 29th-century drone existing outside the Collective, with capabilities far surpassing that of the 24th-century drones.

The Borg do not try to immediately assimilate any being with which they come into contact; Borg drones tend to completely ignore individuals that are identified as too weak to be an imminent threat or too inferior to be worth assimilating. Captain Picard and his team walk safely past a group of Borg drones in a scene from the film Star Trek: First Contact while the drones fulfill a programmed mission. In the Star Trek: Voyager episode "Mortal Coil", Seven of Nine told Neelix the Kazon were "unworthy" of assimilation and would serve only to detract from the Borg's quest for perceived perfection.

Travel

The Borg are a spacefaring race, and their primary interstellar transport is known as a "Borg Cube" due to its shape. A cube was first seen in the Next Generation episode "Q Who?" set in 2365. Common capabilities of cubes include high speed warp and transwarp drives, self-regeneration and multiple-redundant systems, adaptability in combat, and various energy weapons as well as tractor beams and cutting beams. Additionally, different types and size of Cubes have been observed as well as Borg Spheres and some smaller craft.

As with most other Star Trek races, the Borg also have transporter capability.

Assimilation

Assimilation is the process by which the Borg integrate beings, cultures, and technology into the Collective. "You will be assimilated" is one of the few on-screen phrases employed by the Borg when communicating with other species. The Borg are portrayed as having found and assimilated thousands of species and billions to trillions of individual life-forms throughout the galaxy. The Borg designate each species with a number assigned to them upon first contact, humanity being "Species 5618".

When first introduced, the Borg are said to be more interested in assimilating technology than people, roaming the universe as single-minded marauders assimilating starships, planets, and entire societies to collect new technology. They are discriminating in this area, finding certain races, for example the Kazon, to be technologically inferior and unworthy of assimilation. A Borg infant found aboard a Borg Cube in "Q Who?" shows that the Borg will assimilate even children. The Borg then place the assimilated children into maturation chambers to quickly and fully grow them into mature drones.

In their second appearance, "The Best of Both Worlds", they capture and assimilate Captain Jean-Luc Picard into the Collective, creating Locutus of Borg (meaning "he who has spoken", in Latin).

The method of assimilating individual life-forms into the Collective has been represented differently over time. When we see the Borg in Star Trek: The Next Generation, assimilation is through abduction and then surgical procedure. In Star Trek: First Contact and Star Trek: Voyager, assimilation is through injection of nanoprobes into an individual's bloodstream via a pair of tubules that spring forth from a drone's hand. Assimilation by tubules is depicted on-screen as being a fast-acting process, with the victim's skin pigmentation turning gray and mottled with visible dark tracks forming within moments of contact. After assimilation, a drone's race and gender become "irrelevant". After initial assimilation through injection, Borg are surgically fitted with cybernetic devices. In Star Trek: First Contact an assimilated crew member is shown to have a forearm and an eye physically removed and replaced with cybernetic implants.

The Borg also assimilate, interface, and reconfigure technology using these tubules and nanoprobes. However, in Q Who? we see a Borg apparently trying to assimilate, probe, or reconfigure a control panel in engineering using an energy interface instead of nanoprobes.

Some species, for various stated reasons, are able to resist assimilation by nanoprobes. Species 8472 is the only race shown to be capable of completely rejecting assimilation attempts. Other species, such as the Hirogen, have demonstrated resistance to assimilation as well as Dr Phlox, who was able to partially resist the assimilation process in the Star Trek: Enterprise episode "Regeneration".

Concept

The Borg represented a new antagonist and regular enemy which had been lacking during the first season of TNG; the Klingons were allies and the Romulans mostly absent. The Ferengi were originally intended as the new enemy for the United Federation of Planets, but their comical appearance and devotion to capitalist accumulation by free enterprise failed to portray them as a convincing threat. The Borg, however, with their frightening appearance, their immense power, and their sinister motive, became the signature villains for the TNG and Voyager eras of Star Trek. In Voyager episode "Q2", even Q tells his son, "Don't provoke the Borg."

Star Trek: The Next Generation (TNG) writers began to develop the idea of the Borg as early as the Season 1 episode, "Conspiracy", which introduced a coercive, symbiotic life form that took over key Federation personnel. Plans to feature the Borg as an increasingly menacing threat were subsequently scrapped in favor of a more subtle introduction, beginning with the mystery of missing colonies on both sides of the Neutral Zone in "The Neutral Zone" and culminating in the encounter between Borg and the Enterprise crew in "Q Who?".

• 

(ed note: the aliens known as "Tinker Composites" are actually hive entities. The "Angels" are composite creatures)

The Angel acknowledged the reference with a wave of blue-green fronds. It was itself a symbiotic life-form, discovered a century and a half earlier when the expanding wave-front of the Perimeter had reached the star Capella and the planets around it. The visible part of the Angel was the Chassel-Rose, slow-moving, mindless, and wholly vegetable. Shielded within the bulbous central section lived the sentient crystalline Singer, relying upon the Chassel-Rose for habitat, transportation, and communication with the external world.

The screen first showed the quivering mass of a Tinker Composite, men the enlarged view of individual components from which the Tinker was made. They were fast-flying legless creatures about the size of a humming-bird. Each of them possessed just enough nerve tissue for independent locomotion, sensation, feeding, breeding, and clustering. Each had a ring of eyes on its blunt head, and long antennae to permit coupling into the Composite. The bodies were purple and black, shiny, sticky-looking.

"I do not ask any. I would suggest that you decide for Dougal MacDougal what his line ought to be when he discusses this with the Stellar Group Ambassadors. And you ought to know what I am doing with your pseudo-Construct. We have the first Pursuit Team assembled and waiting, out on Dembricot: one human woman, one Tinker ten-thousand Composite, one sterile female Pipe-Rilla, and their preferred form of Angel—an experienced Singer carried by a new-grown Chassel-Rose."

Telepathy? Even as the thought came, Chan rejected it. He remembered what Flammarion had told him during a Ceres briefing: "An Angel doesn't normally think like a human, but not because it can't. When an Angel wants to, it can put part of its brain into what we call 'emulator mode.' Then that piece can be instructed by the Angel to think like a human, or a Pipe-Rilla, or a Tinker of any number of components, or maybe like all three at once. And probably any other creature you care to name, maybe even like a Morgan Construct. And while all that's going on, the Angel still performs logical analysis in its own way. Whatever that might be."

Skrynol extended a tough and whiskery palp behind her for Mondrian to hold on to, and led the way up a thirty-degree slope. "As for the Tinkers, at the level of individual components they know aggression, and they fight over food, living space, and mates. But a Tinker Composite has no such needs. It does not eat, drink, or mate in the Composite form. It is in some sense immortal, and in another sense it has no permanent existence at all. It has no sense of danger at the Composite level, because at the first sign of danger its instinct is simply to disperse. And resolved to elements, the Composite no longer exists to feel fear or danger. Mercantor is a cold world, and to a Tinker 'intelligence' is a synonym for 'closeness and warmth.'

"As for the Angels, their form of intelligence remains as much of a mystery to us as I suspect it does to you. The Chassel-Rose will live and bud and die, and know little more than a yearning for light and fertile soil. But the Singers live a long, long time, and no one knows how they came to be intelligent, or what purpose that intelligence evolved to serve. Perhaps some day, after another few hundred years of interaction and mutual effort ..."

---

The Tinker had increased noticeably in size as the sun set and the air was less scorchingly hot. The central mass contained almost twice as many components as when Chan had first met it, and its response time was painfully slow.

The Angel at least would not run away. It could not. No matter how intelligent the crystalline Singer might be, it was bound within the vegetable body of the Chassel-Rose and suffered that plant's extreme slowness of movement. When the Angel wanted to move, the bulbous green body first lifted the root-borers up close underneath it. When they were stowed safely away it could creep along on the down-pointing adventitious stems at the edge of the body base. Chan guessed that if it was in a real hurry it might manage up to a hundred steps an hour.

• 

(ed note: Firstname Lastname is a young human woman who is the only human being for many tens of light-years. She is living in an interstellar community of hundreds of different aliens. Her name is due to an input error, which defies correction due to interstellar bureaucracy. She is currently employed by an alien named Loritt.)

      The alien (Loritt) was roughly humanoid in body layout—torso, two backward-bending legs, two big and two little arms, a head, and a plump, stubby tail that looked better suited to storing fat than correcting balance. After that, things got weird. They didn’t have any skin, for one thing, and the various exposed pieces seemed to be held together by nothing more than collective agreement.
     “What are you?” First asked, trying hard to promote the morbid curiosity she felt over the fear.
     “My dear, I’m a Nelihexu. One of the six Assembly Council races.”

---

     Hashin shook his head reproachfully. “I have to stay here and keep an eye on the floor. Could you go find the boss for me? He’s supposed to give a little speech before introducing the candidate.”
     (First said) “Sure. Where’d you see him last?”
     “Hallway by his bedroom.”
     First nodded and headed for the sleeping quarters, glad to leave the noise and push of the crowd behind for a few minutes. Loritt’s bedroom was the farthest down the hall and to the right, although First wasn’t sure what he needed a bedroom for, as it wasn’t clear his race slept in the first place. First rapped her knuckles on the rich, deep-lavender grain of the door.
     “Loritt?” she asked. When no answer came, she knocked harder and turned the old-fashioned knob in the middle of the door. It wasn’t locked, so she pushed it open. “Loritt, Hashin is looking for—”

     The shock at what she saw scattered around the bed and floor froze the air in First’s lungs. Loritt’s body had been dismembered—no, ripped apart, and tossed around the room like seventy kilos of shredded pork. Some parts of him still twitched, the violence was so fresh.
     The instant First’s diaphragm thawed from the initial trauma, she screamed like a horror movie queen.
     Jrill came charging down the hallway like an avenging vulture, Hashin close behind her.
     “What’s wrong, girl?” Jrill demanded of her.
     “He’s dead!” First said through heaving sobs. “Someone murdered Loritt!”

     Jrill pushed past her and threw the door open, only to stop dead, a quizzical look on her face. Then she motioned to Hashin to come and look.
     Hashin surveyed the scene from the door before closing it again. “Ah. I see.”
     “You handle this, Hashin,” Jrill said. “I have to return to my post.” Without another word, Jrill swept back down the hallway in the direction of the party.
     “Where the hell is she going?” First demanded.

     “First,” Hashin beckoned her to follow a short way down the hall. “What do you know about Nelihexu?”
     “I don’t know.” First fought against hyperventilating just to talk. “They look like somebody skinned a big cat and taught it to walk upright. I just know Loritt was nice to me and now he’s dead.”
     Hashin nodded. “Okay, I see the problem. Nelihexu are communal organisms. Just like my body and yours have specialized tissue that make up our organs, they have specialized individual multicellular species that make up their bodies. All these animals live in a community. You know this particular community as Loritt Chessel.”
     “Yeah? So?”

     “So,” Hashin said, trying to be delicate, “when it’s time for, ah, mating, these communities have to…” Hashin made a coming apart gesture with his hands.
     “Oh,” First said one second before the full implication of what he’d said hit here. “Ooh. Uuuuuugh! You mean I just saw Loritt and Kula having sex?!”
     “That is exactly what I mean.”
     First stuck her fingers in her ears. “Lalalalala!”

     The bedroom door flung open, and a visibly agitated Loritt in a hastily tied robe stared out at the two of them. “What in the name of Supol is going on out here?”
     First stared at him slack-jawed.
     Hashin spoke first. “Nothing, boss. Just a little biology tutorial. But you and Kula should get dressed. You have to introduce our honored guest shortly.”
     “Fine.” Loritt’s gaze turned over to First. “And what about you, young lady?”
     First swallowed. “I’ll be in the bathroom, washing my brain out with ammonia.”

---

     “Good. I’m glad.” Loritt sat down in an open deck chair next to her. He was wearing floral-patterned swimming trunks and a wide-brimmed hat.
     “Going for a swim?” First asked.
     “Thinking about it. How’s the water?”
     “Crisp and refreshing. But, er, how do you keep all of your parts from drowning?”
     Loritt smiled. It was still a strange thing to see on a skinless face, but First had adapted.
     “My ‘parts,’ as you say, share a circulatory system through a series of collared sphincter attachment points when joined. Two of my components act as self-constricting air bellows, much like your lungs. As long as my mouth is above water, the rest of my communal body gets all the oxygen it needs through the shared blood supply.”

     “And your brain? Is it, um, ‘communal,’ too?”
     “I have a trio of components whose main function is to process sensory input, but yes, my ‘brain’ is more akin to a distributed nodal network.”
     “So is it like a hundred voices in your head arguing all the time?”
     Loritt laughed. “I can see why you might think that, but no. No individual node has the processing power for sentience. My consciousness is an emergent property of the total system. There’s just me in here.”
     “Still, it must be weird to be made up of a herd of different animals. Like if Noah’s ark made one of those combining robots.”
     “Like Voltron?”
     “Er, afraid I don’t know that one,” First said sheepishly.
     “It just reached us. Great show. Anyway, it’s the only existence I’ve ever known, so it seems perfectly normal to me. Besides, is it really any stranger than your body? You’re made up of billions of individual cells, each completely unaware that it’s part of something bigger than itself. Making up tissues, then organs, then all of you.”

---

(ed note: Loritt and First are covertly infiltrating a group of ultra-rich aliens. )

     First heard the acid behind Loritt’s sarcasm, and something in her perspective on the man shifted ever so slightly.
     “You really hate them, don’t you?”
     “I wasn’t always … myself. I haven’t told many people this. Not sure why I’m telling you, honestly, but I’m assembled from cast-off parts. Pieces of factory workers and miners who either had to sell off bits of themselves to pay the rent or couldn’t afford to continue and chose to disincorporate entirely. That’s where I came from, once, long ago. Factories and mines in my colony closed or automated by their off-world owners without thought or regard for what it would do to the people who relied on those for their livelihoods. So yes, I really hate them.”
     First laughed, then stared at Loritt with wide eyes and a warm smile.
     “What’s funny?”
     “Not funny,” First said. “Not exactly. Look at you. A community of castoffs and misfits who made it big by nurturing castoffs and misfits into a community. Now, our whole team is kinda its own superorganism.”
     “I, um, I hadn’t thought of it like that before,” Loritt said, choking up on both his throat and the throttle.

• 

      Vindarten took him out of the museum by a different route. Once again they floated effortlessly through great vaulted corridors, but this time they were moving past the creations of nature, not of conscious mind. Sullivan, thought Jan, would have given his life to be here, to see what wonders evolution had wrought on a hundred worlds. But Sullivan, he remembered, was probably already dead.

     Then, without any warning, they were on a galleiy high above a large circular chamber, perhaps a hundred metres across. As usual, there was no protective parapet, and for a moment Jan hesitated to go near the edge. But Vindarten was standing on the very brink, looking calmly downwards, so Jan moved cautiously forward to join him.

     The floor was only twenty metres below—far, far too close. Afterwards, Jan was sure that his guide had not intended to surprise him, and was completely taken aback by his reaction. For he had given one tremendous yell and jumped backwards from the gallery's edge, in an involuntary effort to hide what lay below. It was not until the muffled echoes of his shout had died away in the thick atmosphere that he steeled himself to go forward again.

     It was lifeless, of course—not, as he had thought in that first moment of panic, consciously staring up at him. It filled almost all that great circular space, and the ruby light gleamed and shifted in its crystal depths.

     It was a single giant eye.

     "Why did you make that noise?" asked Vindarten.
     "I was frightened," Jan confessed sheepishly.
     "But why? Surely you did not imagine that there could be any danger here?"
     Jan wondered if he could explain what a reflex action was, but decided not to attempt it.
     "Anything completely unexpected is frightening. Until a novel situation is analysed, it is safest to assume the worst."

     His heart was still pounding violently as he stared down once more at that monstrous eye. Of course, it might have been a model, enormously enlarged as were microbes and insects in terrestrial museums. Yet even as he asked the question, Jan knew, with a sickening certainty, that it was no larger than life.

     Vindarten could tell him little; this was not his field of knowledge, and he was not particularly curious. From the Overlord's description, Jan built up a picture of a cyclopean beast living among the asteroidal rubble of some distant sun, its growth uninhibited by gravity, depending for food and life upon the range and resolving power of its single eye.

     There seemed no limit to what Nature could do if she was pressed, and Jan felt an irrational pleasure at discovering something which the Overlords would not attempt. They had brought a full-sized whale from Earth—but they had drawn the line at this.

• 

      There were four cartridges in the clip. Ryeland checked them, blessed Quiveras for having left the gun and started down the passages. He didn't say anything to Donna Creery; he didn't know what to say.

     Then there was a pyropod on their Reef …

     Ryeland's throat was raw and dry. Pyropods. "Flame-feet." Outer-space animals which, Ryeland thought, sounded vaguely like Earthly squids. Ryeland tried to picture one, and failed; but Quiveras had said there was a possibility that the caverns in their Reef might house one. And Chiquita's terrible wounds had converted that possibility into something far stronger.

     Ryeland paused at the end of the passages they had explored, and picked up the discarded crystal sword Quiveras had left there. It was still bright; it was all the light he had. Then he drove into the first of the great convoluted burrows.
     In five minutes he was at an end; the tunnel narrowed sharply, so that he could hardly move, and poised bits of rubble showed that nothing of any size had passed that way in finite time.
     He went back again. Another tunnel, a much longer one this time, but again a dead end. It was difficult to maneuver; in no-gravity, he could not walk, and the shape and constriction of the tunnel made it hard to leap.
     He came to another branch and stopped.
     There were two tunnels, both enormous, both dark and soundless. The air was the air the spaceling had brought, but it had a sharp strange odor, like burning gunpowder. (the spaceling animal has the ability to surround the asteroid with a breathable atmosphere. Don't ask.)
     And one of the tunnels was scarred with the enormous claws that had left their sign near the surface.
     Ryeland plunged in without giving himself time to think.

     He came almost at once to a chamber. He paused and hung in its entrance, peering about in the faint light his crystal sword gave. It was roughly spherical, so vast that its farther walls were dim; and in a niche at one side of it was a clutter of tangled objects.
     Warily he approached.
     It seemed to be a sort of midden, and the blood began to pulse in his ears. It contained odd-shaped objects that might have resembled the bones and fangs and carapaces of animals like no animals that had ever lived on. earth. He stood staring at it, every sense poised. Then, with infinite pain, he approached. There was no sound. There was no motion. Gently he poked the crystalline light into a gap in the tangle. But nothing moved and there was nothing revealed.
     Ryeland moved back. and considered.
     Space had its own scale of time. The discarded bones and the clawmarks in the rock might look just as fresh after another hundred million years. Undoubtedly the cave had been abandoned.

     He turned.

     Something screamed behind him. He had only time to halt his turn, to start to move his head back.
     And the heap of bones exploded.

---

     What kept Ryeland from dying at once was the tiny scope of the cavern, compared to the scale of interplanetary distances. The pyropod, rocket driven, enormously strong, hadn't the room to maneuver or even to build up speed. But it blasted up at him with frightening speed. It was huge — as Earth animals go — larger than a horse, and armored with mirror-bright scales. It had a solitary eye, a wide mirror on a stalked central organ. It had a single, enormous claw at the end of a writhing, flexible trunk. It roared like a rocket at takeoff — which it was — and the great heavy-metal claw snapped violently.
     But the trash in its way screened Ryeland for a moment; he was thrust back and out of the way, and the pyropod flew past to gouge great chips qut of the wall of the cavern.

     Ryeland took quick aim and fired.

     Even in the roar of the pyropod's drive, he could hear his bullet scream away, and knew that it had hit that armor and ricocheted off The pyropod did not turn to strike toward him again; it turned away, in fact, and its thin bright tail whipped toward him. White fire jetted out furiously. The tail! The tail was a more fearsome weapon than the claw — the mighty drive that could hurl it through space could char him in a second! But Ryeland was already moving, and the blast missed him entirely, though a backwash of flame from the wall caught his leg and (he discovered later) raised great angry blisters on his skin. Ryeland crashed into the wall, spun like a racing swimmer in a pool, raised the gun again and fired —rapidly —one, two, three!

     And then his cartridges were gone …

     But one of those bullets had struck a target. The stalk that held its eye was hit. The bulb exploded; the creature was blinded. It blundered about the chamber like a rocket gone mad, colliding with the walls, recoiling, plunging wildly again. The blazing jet licked perilously close —
     And then the jet was screaming away, bouncing and roaring through the tunnel, out, out and away …

• 

(ed note: Claire is an asteroid miner prospecting iceteroids {asteroids with lots of volatiles} in the Kuiper Belt. She has a little accident and wrecks her spacecraft. The ship's AI, which goes by the name of "Erma", can give Claire advice but little else. Claire goes out exploring, hoping to find something that will save her before the oxygen runs out.)

      She (Claire) didn’t want to clamber down, not when she could rip this suit on a sharp edge. So she took a long look down for a level spot and—with a sharp sudden breath—jumped.
     The first hit was off balance but she used that to tilt forward, springing high. She watched the ragged rocks below, and dropped with lazy slowness to another flat place—and sprang again. And again. She hit the plain and turned her momentum forward, striding in long lopes. From here though the bright lights were—gone.
     “What the hell? What’re you seeing, Erma?”
     (Erma the AI said) While you descended I watched the bright points here dim and go out.
     “Huh. Mica reflecting the sunlight? But there would be more at every angle . . . Gotta go see.”
     She took long steps, semiflying in the low grav as sunlight played across the plain. She struck hard black rock, slabs of pocked ice, and shallow pools of gray dust. The horizon was close here. She watched nearby and—
     Suddenly a strong light struck her, illuminating her suit. “Damn! A . . . flower.”
     Perhaps your low oxy levels have induced illusions. I—
     “Shut it!”
     Fronds . . . beautiful emerald leaves spread up, tilted toward her from the crusty soil. She walked carefully toward the shining leaves. They curved upward to shape a graceful parabola, almost like glossy, polished wings. In the direct focus the reflected sunlight was spotlight bright. She counted seven petals standing a meter high. In the cup of the parabola their glassy skins looked tight, stretched. They let the sunlight through to an intricate pattern of lacy veins.
     Please send an image.
     “Emerald colored, mostly . . .” Claire was enchanted.
     Chloroplasts make plants green,Erma said. This is a plant living in deep cold.
     “No one ever reported anything like this.”
     Few come out this far. Seldom do prospectors land; they interrogate at a distance with lasers. The bots who then follow to mine these orbiting rocks have little curiosity.
     “This is . . . astonishing. A biosphere in vacuum.”
     I agree, using my pathways that simulate curiosity. These have a new upgrade, which you have not exercised yet. These are generating cross-correlations with known biological phenomena. I may be of help.
     “Y’know, this is a ‘resource’ as you put it, but”—she sucked in air that was getting chilly, looked around at the sun-struck plain—“how do we use it?”
     I cannot immediately see any—
     “Wait—it’s moving.” The petals balanced on a grainy dark stalk that slowly tilted upward. “Following the sun.”
     Surely no life can evolve in vacuum.
     With a stab of pain her knee gave way. She gasped and nearly lurched into the plant. She righted herself gingerly and made herself ignore the pain. Quickly she had her suit inject a pain killer, then added a stimulant. She would need meds to get through this . . .
     I register your distress.
     Her voice croaked when she could speak. “Look, forget that. I’m hurt but I’ll be dead, and so will you, if we don’t get out of here. And this thing . . . this isn’t a machine, Erma. It’s a flower, a parabolic bowl that tracks the sun. Concentrates weak sunlight on the bottom. There’s an oval football-like thing there. I can see fluids moving through it. Into veins that fan out into the petals. Those’ll be nutrients, I’ll bet, circulating—all warmed by sunlight.”
     This is beyond my competence. I know the machine world.
     She looked around, dazed, forgetting her aches and the cold. “I can see others. There’s one about fifty meters away. More beyond, too. Pretty evenly spaced across the rock and ice field. And they’re all staring straight up at the sun.”
     A memory of her Earthside childhood came. “Calla lilies, these are like that . . . parabolic . . . but green, with this big oval center stalk getting heated. Doing its chemistry while the sun shines.”
     Phototropic, yes; I found the term.
     She shook her head to clear it, gazed at the—“Vacflowers, let’s call them.”—stretching away.
     I cannot calculate how these could be a resource for us.
     “Me either. Any hail from Lugger?”
     No. I was hoping for a laser-beam scan, which protocol requires the Luggerto sweep when our carrying wave is not on. That should be in operation now.
     “Lugger’s got a big solid angle to scan.” She loped over to the other vacflower, favoring her knee. It was the same but larger, a big ball of roots securing it in gray, dusty, ice-laced soil. “And even so, Lugger prob’ly can’t get a back-response from us strong enough to pull the signal out from this iceteroid.”
     These creatures are living in sunlight that is three thousand times weaker than at Earth. They must have evolved below the surface somehow, or moved here. From below they broke somehow to the surface, and developed optical concentrators. This still does not require high-precision optics. Their parabolas are still about fifty times less precise than the optics of your human eye, I calculate. A roughly parabolic reflecting surface is good enough to do the job. Then they can live with Earthly levels of warmth and chemistry.
     “But only when the sun shines on them.” She shook herself. “Look, we have bigger problems—”
     My point is this is perhaps useful optical technology.
     Sometimes Erma could be irritating and they would trade jibes, having fun on the long voyages out here. This was not such a time. “How . . .” Claire made herself stop and eat warmed soup from her helmet suck. Mushroom with a tad of garlic, yum. Erma was a fine personality sim, top of the market, though detaching her from Lugger meant she didn’t have her shipwiring along. That made her a tad less intuitive. In this reduced mode she was like a useful bureaucrat—if that wasn’t a contradiction, out here. So . . .
     An old pilot’s lesson: in trouble, stop, look, think.
     She stepped back from the vacflower, fingered its leathery petals. She jumped straight up a bit, rising five meters, allowing her to peer down into the throat. Coasting down, she saw the shiny emerald sheets focus sunlight on the translucent football at the core of the parabolic flower. The filmy football in turn frothed with activity—bubbles streaming, glinting flashes tracing out veins of flowing fluids. No doubt there were ovaries and seeds somewhere in there to make more vacflowers. Evolution finds ways quite similar in strange new places.
     She landed and her knee held, did not even send her a flash of pain. The meds were working; she even felt more energetic. Wheeee!
     She saw that the veins fed up into the petals. She hit, then crouched. The stalk below the paraboloid was flexing, tilting the whole flower to track as the hard bright dot of the sun crept across a black sky. Its glare made the stars dim, until her helmet compensated.
     She stood, thinking, letting her body relax a moment. Some intuition was tugging at her . . .
     Most probably, life evolved in some larger asteroid, probably in the dark waters below the ice when it was warmed by a core. Then by chance some living creatures were carried upward through cracks in the ice. Or evolved long shoots pushing up like kelp through the cracks, and so reached the surface where energy from sunlight was available. To survive on the surface, the creatures would have to evolve little optical mirrors concentrating sunlight on to their vital parts. Quite simple. I found such notions in my library of science journals—
     “Erma, shut up. I’m thinking.”
     Something about the reflection . . .
     She recalled a teenage vacation in New Zealand, going out on a “night hunt.” The farmers exterminated rabbits, who competed with sheep for grazing land. She rode with one farmer, excited, humming and jolting over the long rolling hills under the Southern Cross, in quiet electric Land Rovers with headlights on. The farmer had used a rifle, shooting at anything that stared into the headlights and didn’t look like a sheep. Rabbit eyes staring into the beam were efficient reflectors. Most light focused on their retina, but some focused into a narrow beam pointing back to the headlight. She saw their eyes as two bright red points. A crack of the rifle and the points vanished. She had even potted a few herself.
     “Vacflowers are bright!”
     Well, yes. I can calculate how much so.
     “Uh, do that.” She looked around. How many . . .
     She groped at her waist and found the laser cutter. Charged? Yes, its butt light glowed.
     She crouched and turned the laser beam on the stem. The thin bright amber line sliced through the tough, sinewy stuff. The entire flower came off cleanly in a spray of vapor. The petals folded inward easily, too.
     “I guess they close up at night,” she said to Erma. “To conserve heat. Plants on Earth do that.” The AI said nothing in reply.
     Claire slung it over her shoulder. “Sorry, fella. Gotta use you.” Though she felt odd, apologizing to a plant, even if an alien one.
     She loped to the next, which was even larger. Crouch, slice, gather up. She took her microline coil off its belt slot and spooled it out. Wrapped together, the two bundles of vacflower were easier to carry. Mass meant little in low grav, but bulk did.
     I calculate that a sunflower on the surface will then appear at least twenty-five times brighter than its surroundings, from the backscatter of the parabolic shape.
     “Good girl. Can you estimate how often Lugger’s laser squirt might pass by?”
     I can access its probable search pattern. There are several, and it did know our approximate vicinity.
     “Get to it.”
     She was gathering the vacflowers quickly now, thinking as she went. The Lugger laser pulse would be narrow. It would be a matter of luck if the ship was in the visible sky of this asteroid.
     She kept working as Erma rattled on over her comm.
     For these flowers shining by reflected sunlight, thebrightness varies with the inverse fourth power of distance. There are two powers of distance for the sunlight going out and another two powers for the reflected light coming back. For flowers evolving with parabolic optical concentrators, the concentration factor increases with the square of distance to compensate for the decrease in sunlight. Then the angle of the reflected beam varies inversely with distance, and the intensity of the reflected beam varies with the inverse square instead of the inverse fourth power of distance—
     “Shut up! I don’t need a lecture, I need help.”
     She was now over the horizon from Sniffer and had gathered in about as many of the long petal clusters as she could. Partway through she realized abruptly that she didn’t need the ovaloid focus bodies at the flower bottom. But they were hard to disconnect from the petals, so she left them in place.
     The sun was high up in the sky. Maybe half an hour till it set? Not much time . . .
     Claire was turning back when she saw something just a bit beyond the vacflower she had harvested.
     It was more like a cobweb than a plant, but it was green. The thing sprouted from an ice field, on four sturdy arms of interlaced strands. It climbed up into the inky sky, narrowing, with cross struts and branches. Along each of these grew larger vacflowers, all facing the sun. She almost dropped the bundled flowers as she looked farther and farther up into the sky—because it stretched away, tapering as it went.
     “Can you see this on my suit cam?”
     I assume it is appropriate that I speak now? Yes, I can see it. This fits with my thinking.
     “It’s a tower, a plant skyscraper—what thinking?”
     A plant community living on the surface of a small object far from the Sun has two tools. It can grow optical concentrators to focus sunlight. It can also spread out into the space around its ’roid, increasing the area of sunlight it can collect.
     “Low grav, it can send out leaves and branches.”
     Apparently so. This thing seems to be at least a kilometer long, perhaps more.
     “How come we didn’t see it coming in?”
     Its flowers look always toward the sun. We did not approach from that direction, so it was just a dark background.
     “Can you figure out what I’m doing?” Huffing and puffing while she worked, she hadn’t taken time to talk.
     You will arrange a reflector, so the laser finder gets a backscatter signal to alert the ship.
     “Bright girl. This rock is what, maybe two-eighty klicks across? Barely enough to let me skip-walk. If I get up this bean stalk, I can improve our odds of not getting blocked by the ’roid.”

• 

Life on a Virgin Comet

     The barren, icy world of the comet is the only known home of the therm-trap, a meter-sized living greenhouse that houses a community of organisms living in ecological balance. They are sustained by the comet’s main ingredient, water.

     Called a virgin comet because it has never passed close to a star, Comet Stubbs is a permanent traveler in the vast dark regions of interstellar space. This comet is named for its discoverer, Dr. Harold Stubbs, who has studied over 200,000 comets using detection gear of his own design.

     Interest in therm-traps is not based solely on scientific curiosity. They produce a waste product that stays fluid in space, an ideal lubricant for machines used in supercool environments.

     Science has learned that the therm-trap is a delicate system of animals centered on a creature supporting a lenslike organ. It keeps this moving “eye” focused on the brightest light in the sky, absorbing all the energy it can. It has a tenuous grasp on life, slipping easily into long periods of dormancy triggered by loss of light — a natural defense. But it is sensitive, too. Should too much lubricant be removed from its base, it will lose heat and perish. Thus, the therm-traps remain a mystery to frustrated biologists, who study them only from safe distances.

     Sadly, with its waste oil so popular on the black market, and no substitute thus far invented, the survival of this unique species remains in question.

• 

(ed note: this is science fiction)

These were pavements of the commonest vacuum organism, mosaics made of hundreds of different strains of the same species. Here and there bright red whips stuck out from the pavement; a commensal species that deposited iron sulphate crystals within its integument. The pavement seemed to stretch endlessly below her. No probe or proxy had yet reached the bottom of Tigris Rift, still more than thirty kilometers away. Microscopic flecks of sulfur-iron complexes, sloughed cells and excreted globules of carbon compounds and other volatiles formed a kind of smog or snow, and the vacuum organisms deposited nodes and intricate lattices of reduced metals that, by some trick of superconductivity, produced a broad-band electromagnetic resonance that pulsed like a giant's slow heartbeat.

---

Eighty years ago, an experiment in accelerated evolution of chemoautotrophic vacuum organisms had been set up on a planetoid in the outer edge of the Kuiper Belt. The experiment had been run by a shell company registered on Ganymede but covertly owned by the Democratic Union of China. In those days, companies and governments of Earth had not been allowed to operate in the Kuiper Belt, which had been claimed and ferociously defended by outer system cartels. That hegemony had ended in the Quiet War, but the Quiet War had also destroyed all records of the experiment; even the Democratic Union of China had disappeared, absorbed into the Pacific Community.

---

Margaret's crew had discovered that the vacuum organisms had proliferated wildly in the deepest part of the Rift, deriving energy by oxidation of elemental sul­fur and ferrous iron, converting carbonaceous material into useful organic chemicals. There were crusts and sheets, things like thin scarves folded into fragile vases and chimneys, organ pipe clusters, whips, delicate fretted laces. Some fed on others, one crust slowly overgrowing and devouring another. Others appeared to he para­sites, sending complex veins ramifying through the thalli of their victims. Water-mining organisms recruited sulfur oxidizers, trading precious water for energy and forming warty outgrowths like stromatolites. Some were more than a hundred meters across, surely the largest prokaryotic colonies in the known Solar System.

All this variety, and after only eighty years of accelerated evolution! Wild beauty won from the cold and the dark. The potential to feed billions. The science crews would get their bonuses, all right; the citizens would become billionaires.

---

Clearly, the experiment had far exceeded its parameters, but no one knew why. The AI that had overseen the experiment had shut down thirty years ago. There was still heat in its crude proton beam fission pile, hut it had been overgrown by the very organisms it had manipulated.

Its task had been simple. Colonies of a dozen species of slow growing chemo-autotrophs had been introduced into a part of the Rift rich with sulfur and ferrous iron. Thousands of random mutations had been induced. Most colonies had died, and those few which had thrived had been sampled, mutated, and reintroduced in a cycle repeated every hundred days.

But the Al had selected only for fast growth, not for adaptive radiation, and the science crews held heated seminars about the possible cause of the unexpected rich­ness of the reef's biota.

---

The reef could make the Ganapati the richest habitat in the Outer System, where expansion was limited by the availability of fixed carbon. Even a modest-sized comet nucleus, ten kilometers in diameter, say, and salted with only one hundredth of one percent carbonaceous material, contained fifty million tons of carbon, mostly as methane and carbon monoxide ice, with a surface dusting of tarry long chain hydrocarbons. The problem was that most vacuum organisms converted simple carbon compounds into organic matter using the energy of sunlight captured by a variety of photosynthetic pigments, and so could only grow on the surfaces of planetoids. No one had yet developed vacuum organisms that, using other sources of energy, could efficiently mine planetoid interiors, but that was what accelerated evolution appeared to have produced in the reef. It could enable exploitation of the entire volume of objects in the Kuiper Belt, and beyond, in the distant Oort Cloud. It was a discovery of incalculable worth.

• 

(ed note: one fine day astronomers notice that a gigantic Bok Globule is entering the solar system and maneuvering to engulf the sun. After a while they come to the uneasy conclusion that the entire cloud is a living organism.)

      Marlowe shook his head. "This comes of reading science fiction."
     "No bloody fiction about Cloud coming straight for dam' Sun. No bloody fiction about Cloud stopping. No bloody fiction about ionisation," growled Alexandrov. McNeil, the physician, was intrigued. The new development was more in his line than transmitters and aerials.
     "I'd like to know, Chris, what you mean in this context by the word 'alive'."
     "Well, John, you know better than I do that the distinction between animate and inanimate is more a matter of verbal convenience than anything else. By and large, inanimate matter has a simple structure and comparatively simple properties. Animate or living matter on the other hand has a highly complicated structure and is capable of very involved behaviour. When I said the Cloud may be alive I meant that the material inside it may be organised in an intricate fashion, so that its behaviour and consequently the behaviour of the whole Cloud is far more complex than we previously supposed."
     "Isn't there an element of tautology there?" — from Weichart.
     "I said that words such as 'animate' and 'inanimate' are only verbal conveniences. If they're pushed too far they do appear tautological. In more scientific terms I expect the chemistry of the interior of the Cloud to be extremely complicated — complicated molecules, complicated structures built out of molecules, complicated nervous activity. In short I think the Cloud has a brain."
     "A dam' straightforward conclusion," nodded Alexandrov. When the laugh had subsided, Marlowe turned to Kingsley.
     "Well, Chris, we know what you mean, at any rate we know near enough. Now let's have your argument. Take your time. Let's have it point by point, and it'd better be good."
     "Very well then, here goes. Point number one, the temperature inside the Cloud is suited to the formation of highly complicated molecules."
     "Right! First point to you. In fact, the temperature is perhaps a little more favourable than it is here on the Earth."
     "Second point, conditions are favourable to the formation of extensive structures built out of complicated molecules."
     "Why should that be so?" asked Yvette Hedelfort.
     "Adhesion on the surface of solid particles. The density inside the Cloud is so high that quite large lumps of solid material — probably mostly ordinary ice — are almost certainly to be found inside it. I suggest that the complicated molecules get together when they happen to stick to the surfaces of these lumps."
     "A very good point, Chris," agreed Marlowe.
     "Sorry, I don't pass this round." McNeil was shaking his head. "You talk of complicated molecules being built up by sticking together on the surface of solid bodies. Well, it won't do. The molecules out of which living material is made contain large stores of internal energy. Indeed the processes of life depend on this internal energy. The trouble with your sticking together is that you don't get energy into the molecules that way."
     Kingsley seemed unperturbed.
     "And from what source do the molecules of living creatures here on the Earth get their internal supplies of energy?" he asked McNeil.
     "Plants get it from sunlight, and animals get it from plants, or from other animals of course. So in the last analysis the energy always comes from the Sun."
     "And where is the Cloud getting energy from now?" The tables were turned. And as neither McNeil nor anyone else seemed disposed to argue, Kingsley went on:
     "Let's accept John's argument. Let's suppose that my beast in the Cloud is built out of the same sort of molecules that we are. Then the light from some star is required in order that the molecules be formed. Well, of course starlight is available far out in the space between the stars, but it's very feeble. So to get a really strong supply of light the beast would need to approach close to some star. And that's just what the beast has done!"
     Marlowe became excited.
     "My God, that ties three things together, straight away. The need for sunlight, number one. The Cloud making a beeline for the Sun, number two. The Cloud stopping when it reached the Sun, number three. Very good, Chris."
     "It is a very good beginning, yes, but it leaves some things obscure," Yvette Hedelfort remarked. "I do not see," she went on, "how it was that the Cloud came to be out in space. If it has need of sunlight or starlight, surely it would stay always around one star. Do you suppose that this beast of yours has just been born somewhere out in space and has now come to attach itself to our Sun?"
     "And while you're about it, Chris, will you explain how your friend the beast controls its supplies of energy? How did it manage to fire off those blobs of gas with such fantastic speed when it was slowing down?" asked Leicester.
     "One question at a time! I'll take Harry's first, because it's probably easier. We tried to explain the expulsion of those blobs of gas in terms of magnetic fields, and the explanation simply didn't work. The trouble was that the required fields would be so intense that they'd simply burst the whole Cloud apart. Stated somewhat differently, we couldn't find any way in which large quantities of energy could be localised through a magnetic agency in comparatively small regions. But let's now look at the problem from this new point of view. Let's begin by asking what method we ourselves would use to produce intense local concentrations of energy."
     "Explosions!" gasped Barnett.
     "That's right, explosions, either by nuclear fission, or more probably by nuclear fusion. There's no shortage of hydrogen in this Cloud."
     "Are you being serious, Chris?"
     "Of course I'm being serious. If I'm right in supposing that some beast inhabits the Cloud, then why shouldn't he be at least as intelligent as we are?"
     "There's the slight difficulty of radioactive products. Wouldn't these be extremely deleterious to living material?" asked McNeil.
     "If they could get at the living material, certainly they would. But although it isn't possible to produce explosions with magnetic fields, it is possible to prevent two samples of material mixing with each other. I imagine that the beast orders the material of the Cloud magnetically, that by means of magnetic fields he can move samples of material wherever he wants inside the Cloud. I imagine that he takes very good care to keep the radioactive gas well separated from the living material — remember I'm using the term 'living' for verbal convenience. I'm not going to be drawn into a philosophical argument about it."
     "You know, Kingsley," said Weichart, "this is going far better than I thought it would. What I suppose you would say is that whereas basically we assemble materials with our hands, or with the aid of machines that we have made with our hands, the beast assembles materials with the aid of magnetic energy."
     "That's the general idea. And I must add that the beast seems to me to have far the better of it. For one thing he's got vastly more energy to play with than we have."
     "My God, I should think so, billions of times more, at the very least," said Marlowe. "It's beginning to look, Chris, as if you're winning this argument. But we objectors over here in this corner are pinning our faith to Yvette's question. It seems to me a very good one. What can you offer in answer to it?"
     "It is a very good question, Geoff, and I don't know that I can give a really convincing answer. The sort of idea I've got is that perhaps the beast can't stay for very long in the close proximity of a star. Perhaps he comes in periodically to some star or other, builds his molecules, which form his food supply as it were, and then pushes off again. Perhaps he does this time and time again."
     "But why shouldn't the beast be able to stay permanently near a star?"
     "Well, an ordinary common or garden cloud, a beastless cloud, if it were permanently near a star would gradually condense into a compact body, or into a number of compact, bodies. Indeed, as we all know, our Earth probably condensed at one time from just such a cloud. Obviously our friend the beast would find it extremely embarrassing to have his protective Cloud condense into a planet. So equally obviously he'll decide to push off before there's any danger of that happening. And when he pushes off he'll take his Cloud with him."
     "Have you any idea of how long that will be?" asked Parkinson.
     "None at all. I suggest that the beast will push off when he's finished recharging his food supply. That might be a matter of weeks, months, years, millennia for all I know."
     "Don't I detect a slight smell of rat in all this?" Barnett remarked.
     "Possibly. I don't know how keen your sense of smell is, Bill. What's your trouble?"
     "I've got lots of troubles. I should have thought that your remarks about condensing into a planet apply only to an inanimate cloud. If we grant that the Cloud is able to control the distribution of material within itself, then it could easily prevent condensation from taking place. After all, condensation must be a sort of stability process and I would have thought that quite a moderate degree of control on the part of your beast could prevent any condensation at all."
     "There are two replies to that. One is that I believe the beast will lose his control if he stays too long near the Sun. If he stays too long, the magnetic field of the Sun will penetrate into the Cloud. Then the rotation of the Cloud round the Sun will twist up the magnetic field to blazes. All control would then be lost."
     "My God, that's an excellent point."
     "It is, isn't it? And here's another one. However different our beast is to life here on Earth, one point he must have in common with us. We must both obey the simple biological rules of selection and development. By that I mean that we can't suppose that the Cloud started off by containing a fully-fledged beast. It must have started with small beginnings, just as life here on Earth started with small beginnings. So to start with there would be no intricate control over the distribution of material in the Cloud. Hence if the Cloud had originally been situated close to a star, it could not have prevented condensation into a planet or into a number of planets."

• 

     "Then how do you visualise the early beginnings?"
"As something that happened far out in interstellar space. To begin with, life in the Cloud must have depended on the general radiation field of the stars. Even that would give it more radiation for molecule-building purposes than life on the Earth gets. Then I imagine that as intelligence developed it would be discovered that food supplies — i.e. molecule-building — could be enormously increased by moving in close to a star for a comparatively brief period. As I see it, the beast must be essentially a denizen of interstellar space. Now, Bill, have you any more troubles?"      "Well, yes, I've got another problem. Why can't the Cloud manufacture it's own radiation? Why bother to come in close to a star? If it understands nuclear fusion to the point of producing gigantic explosions, why not use nuclear fusion for producing its supply of radiation?"
     "To produce radiation in a controlled fashion requires a slow reactor, and of course that's just what a star is. The Sun is just a gigantic slow nuclear fusion reactor. To produce radiation on any real scale comparable with the Sun, the Cloud would have to make itself into a star. Then the beast would get roasted. It'd be much too hot inside."
     "Even then I doubt whether a cloud of this mass could produce very much radiation," remarked Marlowe. "It's mass is much too small. According to the mass-luminosity relation it'd be down as compared with the Sun by a fantastic amount. No, you're barking up a wrong tree there, Bill."
     "I've a question that I'd like to ask," said Parkinson. "Why do you always refer to your beast in the singular? Why shouldn't there be lots of little beasts in the Cloud?"
     "I have a reason for that. but it'll take quite a while to explain."
     "Well, it looks as if we're not going to get much sleep tonight, so you'd better carry on."
     "Then let's start by supposing that the Cloud contains lots of little beasts instead of one big beast. I think you'll grant me that communication must have developed between the different individuals."
     "Certainly."
     "Then what form will the communication take?"
     "You're supposed to be telling us, Chris."
     "My question was purely rhetorical. I suggest that communication would be impossible by our methods. We communicate acoustically."
     "You mean by talking. That's certainly your method all right, Chris," said Ann Halsey.
     But the point was lost on Kingsley. He went on.
     "Any attempt to use sound would be drowned by the enormous amount of background noise that must exist inside the Cloud. It would be far worse than trying to talk in a roaring gale. I think we can be pretty sure that communication would have to take place electrically."
     "That seems fair enough."
     "Good. Well the next point is that by our standards the distances between the individuals would be very large, since the Cloud by our standards is enormously large. It would obviously be intolerable to rely on essentially D.C. methods over such distances."
     "D.C. methods? Chris, will you please try to avoid jargon."
     "Direct current."
     "That explains it, I suppose!"
     "Oh, the sort of thing we get on the telephone. Roughly speaking the difference between D.C. communication and A.C. communication is the difference between the telephone and radio."
     Marlowe grinned at Ann Halsey.
     "What Chris is trying to say in his inimitable manner is that communication must occur by radiative propagation."
     "If you think that makes it clearer ... "
     "Of course it's clear. Stop being obstructive, Ann. Radiative propagation occurs when we emit a light signal or a radio signal. It travels across space through a vacuum at a speed of 186,000 miles per second. Even at this speed it would still take about ten minutes for a signal to travel across the Cloud.
     "My next point is that the volume of information that can be transmitted radiatively is enormously greater than the amount that we communicate by ordinary sound. We've seen that with our pulsed radio transmitters. So if this Cloud contains separate individuals, the individuals must be able to communicate on a vastly more detailed scale than we can. What we can get across in an hour of talk they might get across in a hundredth of a second."
     "Ah, I begin to see light," broke in McNeil. "If communication occurs on such a scale then it becomes somewhat doubtful whether we should talk any more of separate individuals!"
     "You're home, John!"
     "But I'm not home," said Parkinson.
     "In vulgar parlance," said McNeil amiably, "what Chris is saying is that individuals in the Cloud, if there are any, must be highly telepathic, so telepathic that it becomes rather meaningless to regard them as being really separate from each other."
     "Then why didn't he say so in the first place?" — from Ann Halsey.
     "Because like most vulgar parlance, the word 'telepathy' doesn't really mean very much."
     "Well, it certainly means a great deal more to me."
     "And what does it mean to you, Ann?"
     "It means conveying one's thoughts without talking, or of course without writing or winking or anything like that."
     "In other words it means — if it means anything at all — communication by a non-acoustic medium."
     "And that means using radiative propagation," chipped in Leicester.
     "And radiative propagation means the use of alternating currents, not the direct currents and voltages we use in our brains."
     "Kingsley's ideas have many very interesting neurological implications," McNeil remarked. "Communication for us is a matter of extreme difficulty. We ourselves have to make a translation of the electrical activity — essentially D.C. activity — in our brains. To do this quite a bit of the brain is given over to the control of the lip muscles and of the vocal chords. Even so our translation is very incomplete. We don't do too badly perhaps in conveying simple ideas, but the conveying of emotions is very difficult. Kingsley's little beasts could, I suppose, convey emotions too, and that's another reason why it's rather meaningless to talk of separate individuals. It's rather terrifying to realise that everything we've been talking about tonight and conveying so inadequately from one to another could be communicated with vastly greater precision and understanding among Kingsley's little beasts in about a hundredth of a second."
     "I'd like to follow the idea of separate individuals a little further," said Barnett, turning to Kingsley. "Would you think of each individual in the Cloud as building a radiative transmitter of some sort?"
     "Not as building a transmitter. Let me describe how I see biological evolution taking place within the Cloud. At an early stage I think there would be a whole lot of more or less separate disconnected individuals. Then communication would develop, not by a deliberate inorganic building of a means of radiative transmission, but through a slow biological development. The individuals would develop a means of radiative transmission as a biological organ, rather as we have developed a mouth, tongue, lips, and vocal chords. Communication would improve to a degree that we can scarcely contemplate. A thought would no sooner be thought than it would be communicated. An emotion would no sooner be experienced than it would be shared. With this would come a submergence of the individual and an evolution into a coherent whole. The beast, as I visualize it, need not be located in a particular place in the Cloud. Its different parts may be spread through the Cloud, but I regard it as a neurological unity, interlocked by a communication system in which signals are transmitted back and forth at a speed of 186,000 miles a second."
     "We ought to get down to considering those signals more closely. I suppose they'd have to have a longish wave-length. Ordinary light presumably would be useless since the Cloud is opaque to it," said Leicester.
     "My guess is that the signals are radio waves," went on Kingsley. "There's a good reason why it should be so. To be really efficient one must have complete phase control in a communication system. This can be done with radio waves, but not so far as we know with shorter wave-lengths."
     McNeil was excited.
     "Our radio transmissions!" he exclaimed. "They'd have interfered with the beast's neurological control."
     "They would if they'd been allowed to."
     "What d'you mean, Chris?"
     "Well, the beast hasn't only to contend with our transmissions, but with the whole welter of cosmic radio waves. From all quarters of the Universe there'd be radio waves interfering with its neurological activity unless it had developed some form of protection."
     "What sort of protection have you in mind?"
     "Electrical discharges in the outer part of the Cloud causing sufficient ionisation to prevent the entry of external radio waves. Such a protection would be as essential as the skull is to the human brain."
     Aniseed smoke was rapidly filling the room. Marlowe suddenly found his pipe too hot to hold and put it down gingerly.
     "My God, you think this explains the rise of ionisation in the atmosphere, when we switch on our transmitters?"
     "That's the general idea. We were talking earlier on about a feedback mechanism. That I imagine is just what the beast has got. If any external waves get in too deeply, then up go the voltages and away go the discharges until the waves can get in no farther."
     "But the ionisation takes place in our own atmosphere."
     "For this purpose I think we can regard our atmosphere as a part of the Cloud. We know from the shimmering of the night sky that gas extends all the way from the Earth to the denser parts of the Cloud, the disk-like parts. In short we're inside the Cloud, electronically speaking. That, I think, explains our communication troubles. At an earlier stage, when we were outside the Cloud, the beast didn't protect itself by ionising our atmosphere, but through its outer electronic shield. But once we got inside the shield the discharges began to occur in our own atmosphere. The beast has been boxing-in our transmissions."
     "Very fine reasoning, Chris," said Marlowe.
     "Hellish fine," nodded Alexandrov.
     "How about the one centimetre transmissions? They went through all right," Weichart objected.
     "Although the chain of reasoning is getting rather long there's a suggestion that one can make on that. I think it's worth making because it suggests the next action we might take. It seems to me most unlikely that this Cloud is unique. Nature doesn't work in unique examples. So let's suppose there are lots of these beasts inhabiting the Galaxy. Then I would expect communication to occur between one cloud and another. This would imply that some wavelengths would be required for external communication purposes, wave-lengths that could penetrate into the Cloud and would do no neurological harm."
     "And you think one centimetre may be such a wavelength?"
     "That's the general idea."
     "But then why was there no reply to our one centimetre transmission?" asked Parkinson.
     "Perhaps because we sent no message. There'd be no point in replying to a perfectly blank transmission."
     "Then we ought to start sending pulsed messages on the one centimetre," exclaimed Leicester. "But how can we expect the Cloud to decipher them?"
     "That's not an urgent problem to begin with. It will be obvious that our transmissions contain information - that will be clear from the frequent repetition of various patterns. As soon as the Cloud realises that our transmissions have intelligent control behind them I think we can expect some sort of reply. How long will it take to get started, Harry? You're not in a position to modulate the one centimetre yet, are you."
     "No, but we can be in a couple of days, if we work night shifts. I had a sort of presentiment that I wasn't going to see my bed tonight. Come on, chaps, let's get started."

---

• 

     "How on earth did you come on such an idea, Chris?"
     "Well, it's pretty obvious really. The trouble is that we're all inhibited against such thinking. The idea that the Earth is the only possible abode of life runs pretty deep in spite of all the science fiction and kid's comics. If we had been able to look at the business with an impartial eye we should have spotted it long ago. Right from the first, things have gone wrong and they've gone wrong according to a systematic sort of pattern. Once I overcame the psychological block, I saw all the difficulties could be removed by one simple and entirely plausible step. One by one the bits of the puzzle fitted into place. I think Alexandrov probably had the same idea, only his English is a bit on the terse side."
     "On the bloody terse side, you mean. But seriously, do you think this communication business will work?"
     "I very much hope so. It's quite crucial that it should."
     "Why do you say that?"
     "Think of the disasters the Earth has suffered so far, without the Cloud taking any purposive steps against us. A bit of reflection from its surface nearly roasted us. A short obscuration of the Sun nearly froze us. If the merest tiny fraction of the energy controlled by the Cloud should be directed against us we should be wiped out, every plant and animal."
     "But why should that happen?"
     "How can one tell? Do you think of the tiny beetle or the ant that you crush under your foot on an afternoon's walk? One of those gas bullets that hit the Moon three months ago would finish us. Sooner or later the Cloud will probably let fly with some more of 'em. Or we might be electrocuted in some monstrous discharge."
     "Could the Cloud really do that?"
     "Easily. The energy that it controls is simply monstrous. If we can get some sort of a message across, then perhaps the Cloud will take the trouble to avoid crushing us under its foot."
     "But why should it bother?"
     "Well, if a beetle were to say to you, 'Please, Miss Halsey, will you avoid treading here, otherwise I shall be crushed,' wouldn't you be willing to move your foot a trifle?"

---

(ed note: communication with the cloud is established. After a long period of time, a mathematical language is created as the basis of communication. It helps that the cloud is far more intelligent than any human.)

     (the Cloud said) "Your first transmission came as a surprise, for it is most unusual to find animals with technical skills inhabiting planets, which are in the nature of extreme outposts of life."
     Joe was asked why this should be so.
     "For two quite simple reasons. Living on the surface of a solid body you are exposed to a strong gravitational force. This greatly limits the size to which your animals can grow and hence limits the scope of your neurological activity. It forces you to possess muscular structures to promote movement, and it also forces you to carry protective armour against sharp blows — as for instance your skulls are a necessary protection for your brains. The extra weight of muscle and armour still further reduces the scope of your neurological activities. Indeed your very largest animals have been mostly bone and muscle with very little brain. As I have already said, the strong gravitational field in which you live is the cause of this difficulty. By and large, one only expects intelligent life to exist in a diffuse gaseous medium, not on planets at all.
     "The second unfavourable factor is your extreme lack of basic chemical foods. For the building of chemical foods on a large scale starlight is necessary. Your planet, however, absorbs only a very minute fraction of the light from the Sun. At the moment I myself am building basic chemicals at about 10,000,000,000 times the rate at which building is occurring on the whole entire surface of your planet.
     "This shortage of food chemicals leads to a tooth and claw existence in which it is difficult for the first glimmerings of intellect to gain a foothold in competition with bone and muscle. Of course once intelligence becomes firmly established, competition with sheer bone and muscle becomes easy, but the first steps along the road are excessively difficult — so much so that your own case is a rarity among planetary life forms."
     "And so much for the space travel enthusiasts," said Marlowe. "Ask him, Harry, to what we owe the emergence of intelligence here on the Earth." The question was put, and after a time the answer came:
     "Probably to the combination of several circumstances, among which I would rate as most important the development about fifty million years ago of an entirely new type of plant: the plant that you call grass. The emergence of this plant caused a drastic re-organisation of the whole animal world, due to the peculiarity that grass can be cropped to ground level, in distinction from all other plants. As the grasslands spread over the Earth those animals that could take advantage of this peculiarity survived and developed. Other animals declined or became extinct. It seems to have been in this major reshuffle that intelligence was able to gain its first footing on your planet.
     "Do we have anything neurological in common? Do you, for instance, have anything that corresponds to our 'headache'?" asked McNeil. The reply came:
     "In a broad sense we share the emotions of pleasure and pain. But this is only to be expected of any creature that possesses a neurological complex. Painful emotions correspond to a sharp disruption of neurological patterns, and this can happen with me as well as with you. Happiness is a dynamic state in which neurological patterns are being extended, not disrupted, and this too can happen with me as well as with you. Although there are these similarities, I imagine that my subjective experiences are very different from yours, except in one particular — like you I regard painful emotions as emotions that I wish to avoid, and vice versa for happy emotions.
     "More specffically, your headaches arise from a faulty blood supply that destroy the precision of the electrical firing sequences in your brains. I experience something very akin to a headache if radio-active material gets into my nervous system. It causes electrical discharges in much the way that happens in your Geiger counters. These discharges interfere with my timing sequences and produce an extremely unpleasant subjective experience.

---

     McNeil put his question to the Cloud:
     "It would be of interest to us to know how our reproductive system compares with your own case."
     "Reproduction in the sense of giving rise to a new individual proceeds in our case along entirely different lines. Barring accidents, or an overwhelming desire for self-destruction — which happens sometimes with us as with you — I can live indefinitely, you see. Therefore I am not under the necessity, as you are, of generating some new individual to take over at my death."
     "How old in fact are you?"
     "Rather more than five hundred million years."
     "And was your birth, your origin, that is to say, a consequence of spontaneous chemical action, as we believe life here on the Earth to have been?"
     "No, it was not. As we travel around the Galaxy we keep a look-out for suitable aggregation of material, suitable clouds in which we can plant life. We do this in rather the way that you might grow saplings from a tree. If I, for instance, were to find a suitable cloud not already endowed with life I would plant a comparatively simple neurological structure within it. This would be a structure that I myself had built, a part of myself.
     "The multitude of hazards with which the spontaneous origin of intelligent life is faced is overcome by this practice. Let me take an example. Radio-active materials must be rigorously excluded from my nervous system for a reason that I explained in an earlier conversation. To ensure that this is so I possess an elaborate electromagnetic screen that serves to prevent the ingress of any radio-active gas into my neurological regions — into my brain in other words. Should this screen fail to operate, I would experience great pain and would soon die. A screen-failure is one of the possible accidents I mentioned a little while ago. The point of this example is that we can provide our 'infants' both with screens and with the intelligence to operate them, whereas it would be most improbable that such screens would develop in the course of a spontaneous origin of life."
     "Apart from providing such protective devices," the Cloud went on, "we leave our 'infants' free to develop as they think best. Here I must explain an important difference between us and you. The number of cells in your brain is more or less fixed at birth. Your development then consists of learning to use a brain of fixed capacity in the best possible way. With us the case is quite different. We are free to increase the capacity of our brains as we find best. And of course worn or defective parts can be removed or replaced. Thus development with us consists in extending the brain in the best way, as well as in learning to use it in the best way — by the best way I mean of course in the way best suited to the solution of problems as they arise. You will realise therefore that as 'infants' we start with comparatively simple brains and as we grow older our brains become very much larger and more complicated."
     "Could you describe, in a way we could understand, how you would go about building a new part to your brain?" asked McNeil.
     "That I think I can do. First, I build chemical foods into complicated molecules of the required types. A supply of these is always kept on hand. Then the molecules are carefully laid down in an appropriate neurological structure on the surface of a solid body. The material of the body is adjusted so that its melting point is not too low — ice for instance would have a dangerously low melting point — and so that it is electrically a very good insulator. The outer part of the solid has also to be carefully prepared so that it will anchor the neurological material — the brain stuff as you might say — firmly in position.
     "The design of the neurological structure is of course the really difficult part of the business. This is arranged so that the new brain acts as a unit for attaining some specffied purpose. It is also arranged that the new unit does not come spontaneously into operation, but only when signals are received from the previously existing part of my brain. These signals have a variety of points of entry into the new structure. Likewise the output of the new unit has a host of connections to the older part of my brain. In this way its activity can be controlled and integrated into the whole of my neurological activity."
     "There are two other points," said McNeil. "How do you recharge your neurological material with energy? This is done in the human case by the blood supply. Do you have an equivalent to our blood supply? Secondly, what would be the rough size of the units that you build?"
     The answer came:
     "The size is variable according to what particular end the unit is designed for. The underlying solid may measure anything from a yard or two up to several hundred yards.
     "Yes, I do have an equivalent to a blood supply. A supply of appropriate substances is maintained by a flow of gas that streams constantly past the units of which I am composed. The flow is maintained by an electromagnetic pump instead of by a 'heart', however. That is to say, the pump is of an inorganic nature. This is another facility that we always provide when we plant new life. The gas flows from the pump to a supply of chemical foods, then past my neurological structure, which absorbs the sundry materials that are required for my brain operation. These materials also deposit their waste products in the gas. The gas then makes its way back to the pump, but before it does so it passes through a filter that removes the waste products - a filter that is rather akin to your kidneys.
     "There is an important advantage in my having heart, kidneys and blood that are essentially inorganic in their mode of operation. Failure of operation can readily be allowed for. If my 'heart' goes wrong I simply switch over to a spare 'heart' which I always keep in readiness. If my 'kidneys' go wrong I do not die as your musician Mozart did. I again switch over to spare 'kidneys'. And I can make new 'blood' in vast quantities."
     Shortly afterwards the cloud went off the air.
     "The thing which staggers me is the astonishing similarity in the principles on which life is maintained," remarked McNeil. "The details are of course wildly different: gas instead of blood, electromagnetic heart and kidneys, and so on. But the logic of the lay-out is the same."
     "And the logic of brain-building seems to have some relation to our programming of a computer," said Leicester.
     "Did you notice that, Chris? It sounded almost like designing some new subroutine."

• 

(ed note: Mr. Miller apparently got a good bargain on a crate of exclamation points.)

It wakened a lustrous opalescence in the two great spheres (alien spaceships) that nestled like mighty twin pearls against the dark rock, to create beings of the rock and of the shadow, gliding wraithlike among the shattered boulders!

Painfully I crept through the dense growth of the brink, nearer to those great spheres and their dreadful cargo. Within me my brain whirled and throbbed, my throat froze against the cry of shocked incredulity that rushed to my lips, cold, clammy sweat oozed from gaping pores ! It was beyond all reason — all possibility ! And yet — it was! Now I could see them clearly, rank on rank of them in orderly file, some hundred of them, strewn in great concentric rings about the softly glowing spheres — harsh as the black rock itself, hard, and glittering, and angular — a man’s height and more from summit to base — great, glittering tetrahedra — tetrahedra of terror!

They were tetrahedra, and they were alive — living even as you and I! They stirred restlessly in their great circles, uneasy in the dim light. Here and there little groups formed, and sometimes they clicked together in still other monstrous geometric shapes, yet always they moved with an uncanny stillness, darting with utter sureness among the scattered rocks. And now from the nearer of the twin spheres came another of their kind, yet twice their size, the pearly walls opening and closing as by thought-magic for his passing! He swept forward a little, into the full light of the moon, and the rings followed him, centered about him, until the spheres lay beyond the outermost and the giant tetrahedron faced alone the hosts of his lesser fellows!

Then came their speech — of all things the most mind-wracking! I felt it deep within my brain, before I sensed it externally, a dull, heavy rhythm of insistent throbbing, beating at my temples and throwing up a dull red haze before my staring eyes!

---

“Yes, I’m Hawkins. The plane is somewhere over there, if it didn’t burn, with all your supplies in it. I was held up crossing the mountains. But tell me, first — those things, there — are they alive?”

“You've wondered that? I suppose anyone would. The Indians make them gods of a kind — realize they’re beyond all experience and tradition. But I'm a biologist. I have had some experience in strange forms of life. They are as much alive as we — perhaps even more than we. After all, if life is energy, why should it not rest where it will? Need we — soft, puny things of carbon and water and a few unstable elements — be the only things to harbor life? But this is no place to moralize — come on!”

---

• 

And through the curtain where fire of heavens and fire of Earth met in that terrible holocaust, those three saw the curving flames of the twin spheres gape wide, saw huge angular shapes file from the darkness within — shapes never yet associated in the Mind of Man with the meaning of life! Careless of the flame that seethed about them, they glided out over the fusing rock of the valley floor, score on score of them, showing in the fierce glare as mighty, eight-foot tetrahedra of dark, glistening crystal. They were of a purple that seemed to be of the essence of the things themselves, rather than a pigmentation of their surface; and near one apex each had two green-yellow unstaring, unseeing eyes!

Within them one glimpsed a spherical body — purple too — from which ran hundreds of curious filaments to the smooth surfaces. Tetrahedra they were — living tetrahedra of chilling terror that feared neither flame nor lightning and spread destruction on every side!

Sick at heart the three men watched, while the flames died and the winds came and stripped the blanket of dust and ash from the blasted rock. The tetrahedra meanwhile glided about their endless affairs, forming and reforming in geometric pattern. Or they clicked swiftly into many-faceted forms that in turn mounted into monolithic, crystalline monstrosities, then melted with startling suddenness into their original components. These were idle, pointless maneuverings from the human viewpoint, yet fraught with some hidden meaning and purpose as alien to Earth as the things themselves. They suggested the terrible energies that were under their control — energies such as our little science has never hinted at.

---

Now, in the full light of day, I could see that it was as Professor Hornby had said. The tetrahedra were formed from some hard, crystalline mineral, black almost to invisibility, with a faint wash of rich purple running through it. As they moved, the sun sent up glittering flashes of brilliance from their polished flanks, dancing like little searchlight rays along the shadowed face of the forest. For the tetrahedra were restless, were weaving aimlessly in and out among the boulders in weird arabesques as of some unearthly dance of the crystal folk, were condensing in little groups of half a dozen or less that formed and broke again even as do restless humans, waiting impatiently for some anticipated event.

Apart from the rest, motionless in a sort of circular clearing among the rocks, squatted the giant leader of the tetrahedra. In him the deep violet of the crystal became a rich, plum-like hue, purple flushed with warm red, and the underlying black seemed less harsh. It was warmer and more like the calm velvet of the tropic night. But these are impressions, qualitative terms with which to distinguish him in some way other than by mere size from his fellows. To an observer, the distinction was apparent, but it is not easy to express in everyday terms. It must suffice that he was indefinably different from the others, that he seemed to have character and personality, where the rest were but pyramidal crystals, albeit terribly alive.

And now the giant leader was dinning out his mighty call in long, slow billows of beating sound that seemed to thrust me back, press me into the dark of the forest, away from the alien monsters of the valley! In response came thirty of the lesser tetrahedra, chosen seemingly at random from the scattered ranks, to range themselves at equal intervals about their master, forming a single great circle a dozen yards in diameter.

Again the throbbing call shattered against the cliffs about me, and now all the hordes of the tetrahedra broke into flowing motion, converging in a torrent of glittering purple crystal upon the natural amphitheater, clustering in threes at the spots that their fellows had marked — all but ten, who glided into place before every third group, forming a giant toothed wheel with hub and rim and spokes of living, sentient crystal — crystal with a purpose!

There under that blazing sun they lay, gleaming like giant purple gems against the jetty rock. I thought of the great stone wheel of Stonehenge, and of the other monolithic circles that men have found in England and on the Continent. Strange resemblance, between the pattern of living monsters of another world and the ancient temples of a prehistoric race! And yet, is it too far-fetched to suggest that the superstitious savages should pattern their greatest temples after the unearthly gods of their worship — gods of purple crystal that came and smote and vanished again into the skies, leaving the memory of their inevitable circling, and the thunder of their language in the great drums of worship? May it not be that they have come before, and found Earth unfitted for their usage, and passed on to other worlds? And if they have so come, and found us wanting, what lies beyond that has prevented them from bearing back the tale of their findings, marking Earth as useless for their tetrahedral purposes ? Why have they had to come again and again ?

I COULD see that the groups of three that formed the toothed rim of the giant crystal wheel were tipping inward, bringing their peaks together in a narrow focus, and more, that the ten that were the spokes, the binding members of the wheel, were of the same rich hue as their master. The shadows of the myriad tetrahedra squatted short and black about their shining bases, against the shining rock.

As the sun soared higher, pouring its blazing rays straight down upon the sweltering world, I sensed the beginning of a vague roseate glow at the foci of the circling trios, a glow as of energy, light, focussed by the tetrahedra themselves, yet not of themselves, but sucked from the flood of light that poured upon them from above. For the light that was reflected from their sides gleamed ever bluer, ever colder, as they drank in the warm red rays and spewed them forth again into the seething globes of leashed energy that were forming just beyond their pointing tips!

The rose-glow had deepened to angry vermillion, seemingly caged within the spheres defined by the tips of the tilted tetrahedra. Thirty glowing coals against the black, ninety great angular forms gleaming ghastly blue in the pillaged sunlight, forms that were slowly closing in upon the center, upon their mighty master, bearing him food, energy of the sun for his feasting!

Now the scarlet flame of the prisoned light was mounting swiftly in an awful pinnacle of outrageous color — pure fire torn from the warm rays of the sun — raw energy for the glutting of these tetrahedral demons of another world! It seemed to me that it must needs burst its bounding spheres and fuse all that crystal horde with its unleashed fury of living flame, must win free of the unimaginable forces that held it there between the eager, glittering facets, must burst its unnatural bonds and sweep the valley with a tempest of awful fire that would consign the furnace of the tetrahedra to pitiful insignificance! It did none of these, for the power that had reft it from the golden sunbeams could mould it to the use and will of the tetrahedra, as clay before the potter!

Slowly the great ring contracted, slowly the tetrahedra tipped toward their common center, bearing at their foci the globes of angry flame. Now they stopped, hung for a long moment in preparation. Then in an instant they loosed the cradled energy of the spheres in one mighty blaze of blinding crimson that swept out in a single huge sheet of flame, blanketing all the giant wheel with its glory, then rushing into the blazing vortex of its center. Here, all the freed energy of the flame was flowing into the body of the mighty ruler of the tetrahedra, bathing him in a fury of crimson light that sank into his glowing facets as water into parched sand of the desert, bringing a fresh, new glow of renewed life to his giant frame!

And now, as in recoil, there spouted from his towering peak a fine, thin fountain of pale blue fire, soundless, like the blaze of man-made lightning between two mightily energized electrodes — the blue of electric fire — the seepage of the giant’s feast! Like slaves snatching at the crumbs from their master’s board, the ten lesser tetrahedra crowded close. As their fierce hunger voiced itself in awful, yearning force, the fountain of blue flame split into ten thin tongues, barely visible against the black rock, that bent down into the pinnacles of the ten and poured through them into the crowding rim of the giant wheel, a rim where again the spheres of crimson fire were mounting to their climactic burst!

Again the crimson orbs shattered and swept over the horde in a titanic canopy of flame, and again the giant master drank in its fiery glory! Now the fountain of seepage had become a mighty geyser of sparkling sapphire light that hurtled a hundred feet into the shimmering atmosphere, and, bent by the fierce hungering of the lesser creatures, curved in a glorious parabola above the crystal wheel, down over them and into them, renewing their substance and their life!

For as I watched, each tetrahedron began to swell, visibly, creeping in horrid slow growth to a magnitude very little less than that of their giant leader. And as they mounted in size, the torrent of blue fire paled and died, leaving them glutted and expectant of the final stage!

• 

It came, with startling suddenness! In an instant each of the hundred clustering monsters budded, burst, shattered into four of half its size that cleaved from each corner of the parent tetrahedron. They left an octahedral shape of transparent crystal, colorless and fragile, whence every evidence of life had been withdrawn into the new-born things — a shell that crumpled and fell in fine, sparkling crystal dust to the valley floor. Only the giant ruler lay unchanged beneath the downward slanting rays of the sun. The hundred had become four hundred! The tetrahedra had spawned!

Four hundred of the monstrous things where a hundred had lain the moment before! Drinking in the light of the noonday sun, sucking up its energy to give them substance, these tetrahedral beings from an alien world held it in their power to smother out the slightest opposition by sheer force of ever-mounting numbers! Against a hundred, or four hundred, the armies and the science of mankind might have waged war with some possibility of success, but when each creature of these invulnerable hosts might become four, with the passing of each noon’s sun, surely hope lay dead ! Man was doomed!

---

“Do you realize that this spawning means that they’re ready to go ahead and burn their way right through everything — make this whole planet a safer and better place for tetrahedra? Doc has figured they’re from Mercury — overcrowded, probably, by this wholesale system of reproduction in job-lots, and hunting for new stamping-grounds. I don’t know what our chances are of bucking them — about a quarter of what they were an hour ago — but they’re mighty slim, armed as we are. You’ve got the other machine-gun?”

---

I HAD no trouble in finding the Professor. In truth, he found me. He was all but boiling over with excitement, for he had seen something we had not. “Hawkins,” he exclaimed, grabbing my shoulder fiercely, “did you see them spawn? It is remarkable — absolutely unequalled! The speed of it all — and, Hawkins, they do not have to grow before cleaving. I saw two that divided and redivided into three-inch tetrahedra — over a thousand of them ! Think of it — Hawkins, they can overrun our little planet in a few days, once they start! We’re done for!”

---

Now, their army of destruction assembled, the tetrahedra began their conquest of Earth! In vast waves of horrid destruction with rays of angry yellow flame darting from apexes their flaming floods of energy swept over the jungle, and now not even its damp dark could resist. Mighty forest-giants toppled headlong, by the cleaving yellow flame, to melt into powdery ash before they touched the ground. Giant lianas writhed like tortured serpents as their juices were vaporized by the awful heat, then dropped away in death to lie in long grey coils along the stripped rock of the forest floor — rock that was fast taking on the glassy glare of the little valley, rock fused by heat such as Earth had never known.

Now we could watch their plan of campaign, and our hearts sank in fear for our race, for while half of the tetrahedral army engaged in its holocaust of destruction, the remaining half fed and spawned in the full blaze of the sun. With every day dozens of square miles were added to their hellish domain and thousands of tetrahedra to their unnatural army. For now we could see that more and more of them were taking the second course, were splitting into hosts of tiny, three-inch creatures which, within a few days’ time, had swelled to full size and on the following day could spawn anew!

---

The yelling circle was thinning fast, yet they had not realized the futility of their attack when suddenly the tetrahedra deserted quiet defense for active combat!

The cause was evident. Five Indians on the upslope had shoved over the cliff a huge rounded boulder that bounded like a live thing among the rocks and crashed fufl into the side of a great eight-foot tetrahedron, splintering its flinty flank and freeing the pent-up energy in a blinding torrent of blue flame that cascaded over the nearby ledges, fusing them into a white-hot, smoking pool of molten lava that glowed evilly in the ill-lit gloom! It was the last straw! The mad attack had become a thing of real menace to the tetrahedra, and they sprang into swift retribution. From their apexes they flashed out the flaming yellow streaks of destruction.

---

Ever since Marston had first mentioned Professor Hornby’s theory that the things were Mercutians, I had been trying to find some way of verifying it. Now that we were in semi-intimate terms with the tetrahedra, I wondered if I might not get them, somehow, to supply this evidence. I thought of stories I had read of interplanetary communication — of telepathy, of word-association, of sign-language. They had all seemed far-fetched to me, impossible of attainment, but I resolved to try my hand at the last.

There was some rather soft rock in the structure of the watch-tower, and as Valdez had rescued my tool kit from the plane, I had a hammer and chisel. With these, and a faulty memory, I set out to make a rough scale diagram of the inner planets, leaning a bit on the Professor’s theory. I cut circular grooves for the orbits of the four minor planets — Mercury, Venus, Earth, Mars — and dug a deep central pit. In this I set a large nugget of gold, found in the ruins of the fortress, for the Sun, and in the grooves a tiny black pebble for Mercury, a large white one for Venus, and a jade bead from the ruins for Earth. Earth had a very small white moon, in its own deep-cut spiral orbit. Mars was a small chunk of rusty iron with two grains of sand for moons. I had a fair-sized scale, and there was no room for more.

Now I was prepared to attempt communication with the tetrahedra, but I wanted more than one diagram to work with. Consequently I attempted a map of Earth, with hollowed oceans and low mountain-ridges.

---

A cloud-burst, it would be called in the United States. The heavens opened in the night, and water fell in torrents, streaming from every angle of the rock, standing in pools wherever a hollow offered itself, drenching us and the world through and through. Day came, but there was no sun for the tetrahedra to feed on. Nor were they thinking of feeding, for very definite peril threatened them. To the tetrahedra, water was death!

As I have said, their fires had flaked huge slabs of rock from the walls of the ravine leading from the high-walled valley where they slept, choking its narrow throat with shattered stone. And now that the mountain slopes, shorn of soil and vegetation, were pouring water into its bed, the stream that had carved that ravine found its course dammed — rose against it, poured over it, but not until the valley had become a lake, a lake where only the two pearly spheres floated against the rocky wall, the thousands of tetrahedra gone forever — dissolved!

Water was death to them — dissolution! Only in the shelter of the spheres was there safety, and they were long since crowded. The hordes of the tetrahedral monsters perished miserably in the night, before they could summon the forces that might have spun them a fiery canopy of arching lightnings that would drive the water back in vapor and keep them safely dry beneath. A hundred had come in the twin spheres. A hundred thousand had been born. A bare hundred remained.

(ed note: Our heroes use the the map of the solar system to explain to the tetrahedrons that [a] water is death to tetrahedrons, [b] Earth is 75% water, [c] right now Earth is in the dry season. Implication is that if the cloud-burst that killed 99.9% of their invasion force happens in the dry season, the wet season will be utterly deadly. Perhaps it would make more sense to go invade Mars?)

• 

• 

Jack: You're a motorcycle, Arcee. Shouldn't you know how to build a motorcycle engine?
Arcee: You're a human, Jack. Can you build me a small intestine?
—Transformers Prime, "Masters and Students"

Mechanical Lifeforms are a race of robots or robot-like creatures that are also considered a honest-to-goodness species of living things. They're just like your everyday living organisms, except they happen to have metal for skin, wires for nerves, and so on. They're often silicon-based as well.

These may be robotic animals, plants, micro-organisms, or sapient creatures. If they are sapient, they would never wish to Become a Real Boy because, as far as they can see, they are as real as that boy. May also form a Robot Republic.

The origin of such creatures is best left unexplained - they were never built by another race (well, that anyone knows of), and if they were, it would be treated as a very shocking revelation, due to the audience accepting their mechanical nature as-is. And should any creators arrive to cart them back, expect them to react just the same as humans would (i.e. much anger, denial, violence, and maybe a speech or two about free will).

Contrast Organic Technology, which are machines that happen to be organic in nature. Also see Mechanical Monster and Mechanical Evolution.

TV Trope page for list of examples)

• 

"The Cylons were created by man.
They rebelled.
They evolved.
There are many copies.
And they have a plan."
— Battlestar Galactica

Mechanical Evolution is the tendency in speculative fiction to apply the idea of biological evolution to mechanical devices, wherein later versions of the devices become progressively more suited to their niche (or more likely just progressively better at everything). This is frequently used to explain the presence of Mechanical Lifeforms or Ridiculously Human Robots.

It is seldom shown as the equivalent of the biological process; rather, the mechanical species will be shown to actively design their own successors, or even "evolve" within their current generation through self-modification. This is similar to real-life design, which is in a sense an evolutionary process; success is defined by market factors, testing and other pressures; successive designs build on those before them and attempt to improve or refine them to better fit the given application. With mechanical creatures the "market" becomes society; a common result is a rigid caste system where various machines are built to specialise in particular applications. The most important caste is likely to also be the most humanoid, or be a Master Computer.

This trope often appears in A.I. Is a Crapshoot and/or Robot War story arcs, as a justification for why the machines want to Kill All Humans. More serious authors will try to justify the Mechanical Evolution with Applied Phlebotinum like Nanomachines or self-learning algorithms; less serious authors will simply toss out the words "Mechanical Evolution" and leave it at that.

If the setting also features a Robot Religion (especially of a Thank the Maker variety), expect jokes about them not believing in Mechanical Evolution (or perhaps the other way around).

No one ever seems to compare the advancement of machines to the theory of Lamarckian evolution, which says that traits acquired by an organism over its life will be passed on to the child. Though wrong when talking about organic evolution, this makes perfect sense for mechanical evolution. If an upgrade to an existing model of robot is developed it can be incorporated as standard into future robots of that model when they are created. The Lamarck comparison is probably taken out because the writers assume the viewers don't know who Lamarck is.

A subtrope of Hollywood Evolution. See also Mechanical Lifeforms, Ridiculously Human Robots, and Artificial Human. Compare Grew Beyond Their Programming.

TV Trope page for list of examples)

• 

Theory

In theory, a self-replicating spacecraft could be sent to a neighbouring planetary system, where it would seek out raw materials (extracted from asteroids, moons, gas giants, etc.) to create replicas of itself. These replicas would then be sent out to other planetary systems. The original "parent" probe could then pursue its primary purpose within the star system. This mission varies widely depending on the variant of self-replicating starship proposed.

Given this pattern, and its similarity to the reproduction patterns of bacteria, it has been pointed out that von Neumann machines might be considered a form of life. In his short story, "Lungfish", David Brin touches on this idea, pointing out that self-replicating machines launched by different species might actually compete with one another (in a Darwinistic fashion) for raw material, or even have conflicting missions. Given enough variety of "species" they might even form a type of ecology, or – should they also have a form of artificial intelligence – a society. They may even mutate with untold thousands of "generations".

The first quantitative engineering analysis of such a spacecraft was published in 1980 by Robert Freitas, in which the non-replicating Project Daedalus design was modified to include all subsystems necessary for self-replication. The design's strategy was to use the probe to deliver a "seed" factory with a mass of about 443 tons to a distant site, have the seed factory replicate many copies of itself there to increase its total manufacturing capacity, over a 500-year period, and then use the resulting automated industrial complex to construct more probes with a single seed factory on board each.

It has been theorized that a self-replicating starship utilizing relatively conventional theoretical methods of interstellar travel (i.e., no exotic faster-than-light propulsion, and speeds limited to an "average cruising speed" of 0.1c.) could spread throughout a galaxy the size of the Milky Way in as little as half a million years.

Implications for Fermi's paradox

In 1981, Frank Tipler put forth an argument that extraterrestrial intelligences do not exist, based on the absence of von Neumann probes. Given even a moderate rate of replication and the history of the galaxy, such probes should already be common throughout space and thus, we should have already encountered them. Because we have not, this shows that extraterrestrial intelligences do not exist. This is thus a resolution to the Fermi paradox – that is, the question of why we have not already encountered extraterrestrial intelligence if it is common throughout the universe.

A response came from Carl Sagan and William Newman. Now known as Sagan's Response, it pointed out that in fact Tipler had underestimated the rate of replication, and that von Neumann probes should have already started to consume most of the mass in the galaxy. Any intelligent race would therefore, Sagan and Newman reasoned, not design von Neumann probes in the first place, and would try to destroy any von Neumann probes found as soon as they were detected. As Robert Freitas has pointed out, the assumed capacity of von Neumann probes described by both sides of the debate are unlikely in reality, and more modestly reproducing systems are unlikely to be observable in their effects on our Solar System or the Galaxy as a whole.

Another objection to the prevalence of von Neumann probes is that civilizations of the type that could potentially create such devices may have inherently short lifetimes, and self-destruct before so advanced a stage is reached, through such events as biological or nuclear warfare, nanoterrorism, resource exhaustion, ecological catastrophe, or pandemics.

Simple workarounds exist to avoid the over-replication scenario. Radio transmitters, or other means of wireless communication, could be used by probes programmed not to replicate beyond a certain density (such as five probes per cubic parsec) or arbitrary limit (such as ten million within one century), analogous to the Hayflick limit in cell reproduction. One problem with this defence against uncontrolled replication is that it would only require a single probe to malfunction and begin unrestricted reproduction for the entire approach to fail – essentially a technological cancer – unless each probe also has the ability to detect such malfunction in its neighbours and implements a seek and destroy protocol (which in turn could lead to probe-on-probe space wars if faulty probes first managed to multiply to high numbers before they were found by sound ones, which could then well have programming to replicate to matching numbers so as to manage the infestation). Another workaround is based on the need for spacecraft heating during long interstellar travel. The use of plutonium as a thermal source would limit the ability to self-replicate. The spacecraft would have no programming to make more plutonium even if it found the required raw materials. Another is to program the spacecraft with a clear understanding of the dangers of uncontrolled replication.

Applications for self-replicating spacecraft

The details of the mission of self-replicating starships can vary widely from proposal to proposal, and the only common trait is the self-replicating nature.

Von Neumann probes

A von Neumann probe is a spacecraft capable of replicating itself. The concept is named after Hungarian American mathematician and physicist John von Neumann, who rigorously studied the concept of self-replicating machines that he called "Universal Assemblers" and which are often referred to as "von Neumann machines". While von Neumann never applied his work to the idea of spacecraft, theoreticians since then have done so.

If a self-replicating probe finds evidence of primitive life (or a primitive, low level culture) it might be programmed to lie dormant, silently observe, attempt to make contact (this variant is known as a Bracewell probe), or even interfere with or guide the evolution of life in some way.

Physicist Paul Davies of Arizona State University has even raised the possibility of a probe resting on our own Moon, having arrived at some point in Earth's ancient prehistory and remained to monitor Earth (see Bracewell probe), which is very reminiscent of Arthur C. Clarke's The Sentinel.

A variant idea on the interstellar von Neumann probe idea is that of the "Astrochicken", proposed by Freeman Dyson. While it has the common traits of self-replication, exploration, and communication with its "home base", Dyson conceived the Astrochicken to explore and operate within our own planetary system, and not explore interstellar space.

Oxford-based philosopher Nick Bostrom discusses the idea that future powerful superintelligences will create efficient cost-effective space travel and interstellar Von Neumann probes.

Berserkers

A variant of the self-replicating starship is the Berserker. Unlike the benign probe concept, Berserkers are programmed to seek out and exterminate lifeforms and life-bearing exoplanets whenever they are encountered.

The name is derived from the Berserker series of novels by Fred Saberhagen which describe a war between humanity and such machines. Saberhagen points out (through one of his characters) that the Berserker warships in his novels are not von Neumann machines themselves, but the larger complex of Berserker machines – including automated shipyards – do constitute a von Neumann machine. This again brings up the concept of an ecology of von Neumann machines, or even a von Neumann hive entity.

It is speculated in fiction that Berserkers could be created and launched by a xenophobic civilization (see Anvil of Stars, by Greg Bear or could theoretically "mutate" from a more benign probe. For instance, a von Neumann ship designed for terraforming processes – mining a planet's surface and adjusting its atmosphere to more human-friendly conditions – might malfunction and attack inhabited planets, killing their inhabitants in the process of changing the planetary environment, and then self-replicate and dispatch more ships to attack other planets.

Replicating seeder ships

Yet another variant on the idea of the self-replicating starship is that of the seeder ship. Such starships might store the genetic patterns of lifeforms from their home world, perhaps even of the species which created it. Upon finding a habitable exoplanet, or even one that might be terraformed, it would try to replicate such lifeforms – either from stored embryos or from stored information using molecular nanotechnology to build zygotes with varying genetic information from local raw materials.

Such ships might be terraforming vessels, preparing colony worlds for later colonization by other vessels, or – should they be programmed to recreate, raise, and educate individuals of the species that created it – self-replicating colonizers themselves. Seeder ships would be a suitable alternative to Generation ships as a way to colonize worlds too distant to travel to in one lifetime.

• 

gosh but like we spent hundreds of years looking up at the stars and wondering “is there anybody out there” and hoping and guessing and imagining

because we as a species were so lonely and we wanted friends so bad, we wanted to meet other species and we wanted to talk to them and we wanted to learn from them and to stop being the only people in the universe

and we started realizing that things were maybe not going so good for us— we got scared that we were going to blow each other up, we got scared that we were going to break our planet permanently, we got scared that in a hundred years we were all going to be dead and gone and even if there were other people out there, we’d never get to meet them

and then

we built robots?

and we gave them names and we gave them brains made out of silicon and we pretended they were people and we told them hey you wanna go exploring, and of course they did, because we had made them in our own image

and maybe in a hundred years we won’t be around any more, maybe yeah the planet will be a mess and we’ll all be dead, and if other people come from the stars we won’t be around to meet them and say hi! how are you! we’re people, too! you’re not alone any more!, maybe we’ll be gone

but we built robots, who have beat-up hulls and metal brains, and who have names; and if the other people come and say, who were these people? what were they like?

the robots can say, when they made us, they called us discovery; they called us curiosity; they called us explorer; they called us spirit. they must have thought that was important.

and they told us to tell you hello.

• 

The guide waved at the next display, "And this... this is a special piece. You're lucky! We're only allowed to show you this at one solar position of one particular planet. Silence now, here it comes..."

A soft, tinny music filled the suddenly silent space by the display. It was awkward, almost hesitant, as if it wasn't quite sure it was meant to be music at all. And yet, the crowd stared, straining for the notes, silent and still until silence again filled the hall. With the sound gone, the audience again focused on their guide and personal translators.

"Ah. That never gets old. This piece is more than a nine-hundred year-old relic, it is a symbol. The young often ask why there are so few requirements to enter the Galactic Union. This is why. This is piece of a culture so impatient to see the stars it hurled devices out into them. Not so different than many of our cultures, yes? Ah, but see, this planet was still in its infancy, at war with itself, a candle still at risk of snuffing itself out. And yet, they sent this to a nearby, uninhabitable planet. Just to see." The guide paused, "But that is not the most wondrous thing."

"The device you see here, is not autonomous. A simple, 'robot' that took commands directly from the home planet and relayed back information. A machine, nothing more." Again a pause, "And yet. This culture programmed this simple, data gathering machine, to make music. And not just any music, but a song played when the solar position approximated that of an individual's genesis."

"The humans have been members of the Galactic Union for over eight-hundred years. They bear little resemblance to the ones who built this device, which they named — NAMED, Opportunity. But they still have that unique trait they brought to the Union, as all species bring something unique. Though the humans had not realized it yet themselves, as they gave their machines names of hope and flung them into the stars, programmed them to play music, and mourned them when they went cold, the Union saw their potential."

The guide waved an arm to encompass the room, "Yes. Humans. Our great peacemakers, were once at risk of destroying themselves. Yet even then, their empathy was so great they mourned not only for a species not their own, but for an inanimate machine that 'survived' more than sixty times longer than expected. They listened, long after it had passed into silence, waiting to make sure it did not pass alone, as they would a living family member."

The guide turned back to the machine, now silent again, "And the humans returned to recover this simple machine and still, nine-HUNDRED years later, allow us only to send the command to play this music, 'happy birthday' when the sun of their homeworld approximates the position it did then. They are... a special race to be sure. And this 'Opportunity' is a symbol of that. Antiquated and clumsy technology, but a symbol of an empathy deep enough to unite the Galactic Union, and keep it strong, peaceful, and expanding."

The crowd paused, considering, then moved on to the next museum exhibit, leaving one lone figure staring at the display.

Softly, even softer than the music, it spoke. "Of course we came back. Good job, Oppy. Who's the best little rover?" The figure smiled, waved as if at the silent machine, and turned to follow the group.

---

     The above is an unedited first-draft written as I watched messages spread across the web of Opportunity's last message, "My battery is low and it's getting dark." and a universal mourning.
     But it struck me as people were sad that Oppy passed, "alone" that it was the opposite. Like a beloved pet, we sat with Oppy as it went to sleep for the final time. We listened, long after, to be sure that it didn't wake up alone.
     And it struck me that that is a truly AMAZING thing, to invest so much, to care SO much about something inanimate. And so, I wrote this. Because I see a lot of hope in this. If we can just get past all the other stuff, humans are AMAZING.
     And yeah, if we get to the stars? You know we're totally gonna go back for Oppy. 'Cause humans are big emotional saps. And maybe that's our strength.

• 

(ed note: The hexagonals are mechanical aliens)

The hostility radiating from the second expedition soon drove the hexagonals back into their ship and away. The fresh humans from Earth felt something gut-level and instinctive, a reaction beyond words. The hexagonals retreated without showing a coherent reaction. They simply turned and walked away, holding to the four centimeter spacing. The 1.27 second flicker stopped and they returned to a bland expression, alert but giving nothing away.

The vision these hexagonals conveyed was austere, jarring… and yet, plainly intended to be inviting.

The magnitude of their failure was a measure of the abyss that separated the two parties. The hexagonals were now both more and less than human.

The hexagonals left recurrent patterns that told much, though only in retrospect. Behind the second expedition’s revulsion lay a revelation: of a galaxy spanned by intelligences formal and remote, far developed beyond the organic stage. Such intelligences had been born variously, of early organic forms, or of later machine civilizations which had arisen upon the ashes of extinct organic societies. The gleam of the stars was in fact a metallic glitter. This vision was daunting enough: of minds so distant and strange, hosted in bodies free of sinew and skin. But there was something more, an inexpressible repulsion.

A nineteenth-century philosopher, Goethe, had once remarked that if one stared into the abyss long enough, it stared back. This proved true. A mere moment’s lingering look, quiet and almost casual, was enough. The second expedition panicked. It is not good to stare into a pit that has no bottom.

• 

      Any intelligent aliens that humans manage to contact probably won't look much like you or me, or the squid-like creatures in the new film "Arrival."
     If an extraterrestrial species becomes advanced enough to send signals Earthlings can pick up, it will likely shed its traditional biological trappings and become a form of machine intelligence in rather short order, said veteran alien hunter Seth Shostak.
     To make his case, Shostak pointed to the path that humanity appears to be on. The human species invented the radio around 1900 and the computer in 1945, and it's already manufacturing relatively cheap devices with greater computing power than the human brain.
      The development of true, strong artificial intelligence (AI) is therefore not too far off, experts have said. The famous futurist Ray Kurzweil, for example, has pegged 2045 as the year this world-changing "singularity" will hit.
      "But maybe it takes to 2100, or 2150, or 2250. It doesn't matter," Shostak said in September during a presentation at the Dent:Space conference in San Francisco. "The point is, any society that invents radio, so we can hear them, within a few centuries, they've invented their successors. And I think that's important, because the successors are machines."
      AI will interface with people's bodies for a while, but eventually humans will abandon the wetware and go fully digital, Shostak predicted.
      "It'll be like — you build a four-cylinder engine. You put it in a horse to get a faster horse. And pretty soon you say, 'Look, let's get rid of the horse part and just build a Maserati,'" said Shostak, an astronomer at the Search for Extraterrestrial Intelligence (SETI) Institute in Mountain View, California. "So that's probably what's going to happen."
      Humans' machine selves will get smarter and more capable incredibly quickly, he added. Humanity's present intelligence is the result of 4 billion years of Darwinian evolution, which uses random variation as its raw material and is not directed toward any particular goal. But the evolution of machine intelligence will be engineered and efficient, Shostak said.
      "Once you invent a thinking machine, you say, 'Invent something better than you are,' and you build that. 'Design something better than you are,' and you build that, and so forth," he said.
      This idea has serious implications for the search for intelligent alien life. Unlike Earth organisms, super-advanced extraterrestrial machines would not require water or other chemicals to survive, so they would not be tied to their ancestors' home worlds tightly at all, Shostak said. And journeying tremendous distances would not be a big deal to these machines, provided they could access enough energy and raw materials to keep repairing themselves over the millennia, he said.
      "We continue to look in the directions of star systems that we think have habitable words, that have planets where biology could cook up and eventually turn into something clever like you guys," he told the Dent:Space audience. "But I don't think it's going to be that way."
      Shostak said he isn't counseling his fellow SETI astronomers to stop investigating potentially Earth-like planets such as Proxima b, a recently discovered world that lies just 4.2 light-years away. (And simple life-forms could still inhabit such worlds even if their most intelligent inhabitants went digital and departed long ago, Shostak said.) But it may be a good idea to expand the search to regions of space that would seemingly be attractive to digital life-forms, he said — for example, places with lots of available energy, such as the centers of galaxies.
      "That may be where the really clever beings are," Shostak said.
      "Maybe what we ought to do is look at places on the sky that connect two places where there is a lot of energy," in an attempt to intercept communications between alien machines, Shostak added.
      "This is my message to you: We're looking for analogues of ourselves, but I don't know that that's the majority of the intelligence in the universe," Shostak concluded. "I'm willing to bet it's not."

• 

      Ursula Fleming stared as the asteroid's slow rotation brought ancient, shattered ruins into view below. “Lord, what a mess," she said, sighing.
     She had been five years in the Belt, exploring and salvaging huge alien works, but never had she beheld such devastation as this.
     Only four kilometers away, the hulking asteroid lay nearly black against the starry band of the Milky Way, glistening here and there in the light of the distant sun. The rock stretched more than two thousand meters along its greatest axis. Collisions had dented, cracked, and cratered it severely since it had broken from its parent body, more than a billion years ago.
     On one side it seemed a fairly typical carbonaceous planetoid, like millions of others orbiting out here at the edge of the Belt. But this changed as the survey ship Hairy Thunderer orbited around the nameless hunk of rock and frozen gases. Then the sun's vacuum brilliance cast lonely, sharp shadows across ruined replication yards jagged, twisted remnants of a catastrophe that had taken place back when dinosaurs still roamed the Earth.
     “Gavin!” she called over her shoulder. “Come down here! You've got to see this!"
     In a minute her partner floated through the overhead hatch, flipping in midair. There was a faint click as his feet contacted the magnetized floor.
     “All right, Urs. What's to see? More murdered babies to dissect and salvage? Or have we finally found a clue to who their killers were?"
     Ursula only gestured toward the viewing port. Her partner moved closer and stared. Highlights reflected from Gavin's glossy features as the ship's searchlight swept the shattered scene below.
     "Yep." Gavin nodded at last. “Dead babies again. Fleming Salvage and Exploration ought to make a good price off each little corpse."
     Ursula frowned. “Don't be morbid, Gavin. Those are unfinished interstellar probes, destroyed ages ago before they could be launched. We have no idea whether they were sentient machines like you, or just tools, like this ship. You of all people should know better than to go around anthropomorphizing alien artifacts." Gavin's grimace was an android's equivalent of a sarcastic shrug. “If I use ‘morbid' imagery, whose fault is it?"

---

     After centuries of wondering, mankind has at last realized an ancient dream. We have discovered proof of civilizations other than our own.
     In the decade we have been exploring the Outer Belt in earnest, humanity has uncovered artifacts from more than forty difierent cultures … all represented by robot starships … all apparently long dead.
     What happened here?
     And why were all those long-ago visitors robots?
     Back in the late twentieth century, some scholars had begun to doubt that biological beings could ever adapt well enough to space travel to colonize more than a little corner of the Milky Way. But even if that were so, it would not prevent exploration of the galaxy. Advanced intelligences could send out mechanical representatives, robots better suited to the tedium and dangers of interstellar spaceflight than living beings.
     Alter all, a mature, long-lived culture could afford to wait thousands of years for data to return from distant star systems.
     Even so, the galaxy is a big place. To send a probe to every site of interest could impoverish a civilization.
     The most efficient way would be to dispatch only a few deluxe robot ships, instead of a giant fleet of cheaper models. Those first probes would investigate nearby stars and planets. Then, after their exploration was done, they would use local resources to make copies of themselves.
     The legendary John Von Neumann first described the concept. Sophisticated machines, programmed to replicate themselves from raw materials, could launch their "daughters" toward still farther stellar systems. There, each probe would make still more duplicates, and so on.
     Exploration could proceed far faster than if carried out by living beings. And after the first wave there would be no further cost to the home system. From then on information would pour back, year alter year, century after century.
     It sounded so logical. Those twentieth-century scholars calculated that the technique could deliver an exploration probe to every star in our galaxy a mere three million years after the first was launched — an eyeblink compared to the age of the galaxy.
     But there was a rub! When we humans discovered radio and then spaceflight, no extra-solar probes announced themselves to say hello. There were no messages welcoming us into the civilized sky.
     At first those twentieth-century philosophers thought there could only be one explanation …
     Let us re-create the logic of those philosophers of the last century, in an imagined conversation.

     “We will certainly build robot scouts someday. Colonization aside, any truly curious race could hardly resist the temptation to send out mechanical emissaries, to say ‘hello’ to strangers out there and report back what they find. The first crude probes to leave our solar system — the Voyagers and Pioneers — demonstrated this basic desire. They carried simple messages meant to be deciphered by other beings long after the authors were dust.
     “Anyone out there enough like us to be interesting would certainly do the same.
     “And yet, if self-reproducing probes are the most efficient way to explore, why haven't any already said hello to us? It must mean that nobody before us ever attained the capability to send them!
     “ We can only conclude that we are the first curious, gregarious, technically competent species in the history of the Milky Way. "

     The logic was so compelling that most people gave up on the idea of contact, especially when radio searches turned up nothing but star static.
     Then humanity spread out beyond Mans and the Inner Belt, and we stumbled onto the Devastation.
     The story is still sketchy, but we can already begin to guess some of what happened out here, long before mankind was a glimmer on the horizon.
     Long ago the first " Von Neumann type" interstellar probe arrived in our solar system. It came to explore and perhaps report back across the empty light-years. That earliest emissary found no intelligent life here, so it proceeded to its second task.
     It mined an asteroid and sent newly made duplicates of itself onward to other stars. The original then remained behind to watch and wait, patient against the day when something interesting might happen in this little corner of space.
     As the epochs passed, new probes arrived, representatives of other civilizations. Once their own replicas had been launched, the newcomers joined a small but growing community of mechanical ambassadors to this backwater system — waiting for it to evolve somebody to say hello to.
     We have found a few of these early probes, remnants of a lost age of innocence in the galaxy.
     More precisely, we have found their blasted remains.
     Perhaps one day the innocent star emissaries sensed some new entity enter the solar system. Did they move to greet it, eager for gossip to share? Like those twentieth-century thinkers, perhaps they believed that replicant probes would have to be benign.
     But things had changed. The age of innocence was over. The galaxy had grown up; it had become nasty.
     The wreckage we are finding now — whose salvage drives our new industrial revolution — was left by an unfathomable war that stretched across vast times, and was fought by entities to whom biological life was a nearly forgotten oddity.

---

Seeder type probe. Those carry DNA encoded in their computer banks and upon arrival at a solar system with habitable planets they genetically engineer biological creatures suitable for the planets. Ursula is looking at a wall of carved pictographs made by the Seeder for the benefit of the biologicals it created. Said biologicals sad mummified bodies litter the floor. Apparently another probe arrived and bombed the place.)

     In the feeble gravity Ursula's arms hung out in front of her, like frames encompassing the picture she was trying to understand.
     The creatures must have had a lot of time while the battles raged outside their deep catacombs, for the wall carvings were extensive and intricate, arrayed in neat rows and columns. Separated by narrow lines of peculiar chiseled text were depictions of suns and planets and great machines.
     Most of all, pictographs of great machines covered the wall.
     They had agreed that the first sequence appeared to begin at the lower left, where a two-dimensional image of a starprobe could be seen entering a solar system — presumably this one — its planets’ orbits sketched out in thin lines upon the wall. Next to that initial frame was a portrayal of the same probe, now deploying subdrones, taking hold of a likely planetoid, and beginning the process of making replicas of itself.
     Eight replicas departed the system in the following frame. There were four symbols below the set of stylized child probes … Ursula could read the binary symbol for eight, and there were eight dots, as well. It didn't take much imagination to tell that the remaining two symbols also stood for the same numeral.
     Ursula made a note of the discovery. Translation had begun already. Apparently this type of probe was programmed to make eight copies of itself, and no more. That settled a nagging question that had bothered Ursula for years.
     If sophisticated self-replicating probes had been roaming the galaxy for aeons, why was there any dead matter left at all? It was theoretically possible for an advanced enough technology to dismantle not only asteroids but planets and stars, as well. If the replicant probes had been as simplemindedly voracious as viruses, they would by now have gobbled the entire galaxy! There would be nothing left in the sky but a cloud of innumerable starprobes … reduced to preying on each other for raw materials until the entire pathological system fell apart in entropy death.
     But that fate had been avoided. This type of mother probe showed how it could be done. It was programmed to make a strictly limited number of copies of itself.
     This type of probe was so programmed, Ursula reminded herself.
     In the final frame of the first sequence, after the daughter probes had been dispatched to their destinations, the mother probe was shown moving next to a round globe — a planet. A thin line linked probe and planet. A vaguely humanoid figure, resembling in caricature the mummies on the floor, stepped across the bridge to its new home.
     The first story ended there. Perhaps this was a depiction of the way things were supposed to have gone. But there were other sequences. Other versions of reality. In several, the mother probe arrived at the solar system to find others already there before it.
     Ursula realized that one of these other depictions must represent what had really happened here, so long ago. She breathed quickly, shallowly, as she traced out the tale told by the first of these.
     On the second row the mother probe arrived to find others already present. All the predecessors had little circular symbols next to them. In this case everything proceeded as before. The mother probe made and cast out its replicas, and went on to seed a planet with duplicates of the ancient race that had sent out the first version so long ago.
     “The little circle means those other probes are benign," Ursula muttered to herself.
     Gavin stepped back and looked at the scene she pointed to. “What are the little symbols beside these machines?"
     “They mean that those types won't interfere with this probe's mission."
     Gavin was thoughtful for a moment. Then he reached up and touched the next row above.
     “Then this crosslike symbol…?" He paused, examining the scene. “It means that there were other types that would object," he said, answering his own question.
     Ursula nodded. The third row showed the mother probe arriving once again, but this time amid a crowd of quite different machines, each accompanied by a glyph faintly like a crisscross tong sign. In that sequence the mother probe did not make replicates. She did not seed a planet. Her fuel used up, unable to flee the system, she found a place to hide, behind the star, as far from the others as possible.
     “She's afraid of them," Ursula announced. She expected Gavin to accuse her of anthropomorphizing, but her partner was silent, thoughtful. Finally, he nodded. “I think you're right."
     He pointed. “Look how each of the little cross or circle symbols are subtly different."
     "Yeah." She nodded, sitting forward on the gently humming drone. “Let's assume there were two basic types of Von Neumann probes loose in the galaxy when this drawing was made. Two different philosophies, perhaps. And within each camp there were differences, as well."
     She gestured to the far right end of the wall. That side featured a column of sketches, each depicting a different variety of machine, every one with its own cross or circle symbol. Next to each was a pictograph.
     Some of the scenes were chilling.
     Gavin shook his head, obviously wishing he could disbelieve. “But why? Von Neumann probes are supposed to … to …"
     "To what?" Ursula asked softly, thoughtfully. “For years men assumed that other races would think like us. We figured they would send out probes to gather knowledge, or maybe say hello. There were even a few who suggested that we might someday send out machines like this mother probe, to seed planets with humans, without forcing biologicals to actually travel interstellar space.
     "Those were the extrapolations we thought of, once we saw the possibilities in self-replicating probes. We expected the aliens who preceded us in the galaxy would do the same.
     “But that doesn't exhaust even the list of human motivations, Gavin. And there may be concepts other creatures invented which to us would be unimaginable!"
     She stood up suddenly and drifted above the dusty floor before the feeble gravity finally pulled her down in front of the chiseled wall. Her gloved hand touched the outlines of a stone sun.
     “Let's say a lot of planetary races evolve like we did on Earth, and discover how to make smart, durable machines capable of interstellar flight and replication. Would all such species be content just to send out emissaries?"
     Gavin looked around at the silent, still mummies. “Apparently not," he said.
Ursula turned and smiled. "In recent years we've given up on sending our biological selves to the stars. Oh, it'd be possible, marginally, but why not go instead as creatures better suited to the environment? That's a major reason we developed types of humans like yourself, Gavin."     Still looking downward, her partner shook his head. “But other races might not give up the old dream so easily."
     “No. They would use the new technology to seed far planets with duplicates of their biological selves. As I said, it's been thought of by Earthmen. I've checked the old databases. It was discussed even in the twentieth century."
     Gavin stared at the pictograms. “All right. That I can understand. But these others The violence! What thinking entity would do such things!"
     Poor Gavin, Ursula thought. This is a shock for him.
     “You know how irrational we biologicals can be sometimes. Humanity is trying to convert over to partly silico-cryo life in a smooth, sane way, but other races might not choose that path. They could program their probes with rigid commandments, based on logic that made sense in the jungles or swamps where they evolved, but which are insane in intergalactic space. Their emissaries would follow their orders, nevertheless, long after their makers were ashes and the homeworld dust."
     “Craziness! " Gavin shook his head.
     Ursula sympathized, she also felt a faint satisfaction. For all his ability to tap directly into computer memory banks, Gavin could never share her expertise in this area. He had been brought up to be human, but he would never hear within his own mind the faint, lingering echoes of the savannah, or see flickering shadows of the Old Forest … remnants of tooth and claw that reminded all biological men and women that the Universe owed nobody any favors. Or even explanations.
     “Some makers thought differently, obviously," she told him. “Some sent their probes out to be emissaries, or sowers of seeds and others, perhaps, to be doctors, lawyers, policemen."
     She once more touched an aeons-old pictograph, tracing the outlines of an exploding planet.
     “Still others," she said, “may have been sent forth to commit murder."

---

     In the article, she had laid out the story of the rock wall — carved in brave desperation by little biological creatures so very much like men. Many readers, probably, would sympathize with the alien colonists, slaughtered helplessly so many millions of years ago. And yet, without their destruction, mankind would never have come about. For even if the colonists were environmentalists who cared for their adopted world, evolution on Earth would have been changed forever if the colony had succeeded. Certainly human beings would not have evolved.
     Simple archaeological dating experiments had brought forth a chilling conclusion.
     Apparently, the mother probe and her replicas died at almost precisely the same moment as the dinosaurs on Earth went extinct — when a huge piece of debris from the probe war struck the planet, wreaking havoc on the Earth's biosphere.
     All those magnificent creatures, killed as innocent bystanders in a battle between great machines … a war which incidentally gave Earth's mammals their big chance.
     The wall carvings filled her mind — their depictions of violence and mayhem on a stellar scale. Ursula dimmed the remaining lights in the control room and looked out on the starfield.
     She found herself wondering how the war was going, out there.
     We're like ants, she thought, building our tiny castles under the tread of rampaging giants. And, like ants, we've spent our lives unaware of the battles going on overhead.
     Depicted on the rock wall had been almost every type of interstellar probe imaginable … and some whose purposes Ursula might never fathom.
     There were Berserkers, for instance — a variant thought of even in Twentieth-century science fiction. Thankfully, those wreckers of worlds were rare, according to the wall chart. And there were what appeared to be Policeman probes, as well, who hunted the berserkers down wherever they could be found.
     The motivations behind the two types were opposite. And yet Ursula was capable of understanding both. After all, there had always been those humans who were destroyer types … and those who were rescuers.
     Apparently both berserkers and police probes were already obsolete by the time the stone sketches had been hurriedly carved. Both types were relegated to the corners — as if they were creatures of an earlier, more uncomplicated day. And they were not the only ones. Probes Ursula had nicknamed Gobbler, Emissary, and Howdy also were depicted as simple, crude, archaic.
     But there had been others.
     One she had called Harm, seemed like a more sophisticated version of Berserker. It did not seek out life-bearing worlds in order to destroy them. Rather it spread innumerable copies of itself and looked for other types of probes to kill. Anything intelligent. Whenever it detected modulated radio waves, it would hunt down the source and destroy it.
     Ursula could understand even the warped logic of the makers of the Harm probes. Paranoid creatures who apparently wanted the stars only for themselves, and sent out their robot killers ahead to make sure there would be no competition awaiting them among the stars.
     Probes like that could explain the emptiness of the airwaves, which naive twentieth-century scientists had expected to be filled with interstellar conversation. They could explain why the Earth was never colonized by some starfaring race.
     At first Ursula had thought that Harm was responsible for the devastation here too, in the solar system's asteroid belt. But even Harm, she had come to realize, seemed relegated to one side of the rock carving, as if history had passed it by, as well.
     The main part of the frieze depicted machines whose purposes were not so simple to interpret. Perhaps the professional decipherers — archaeologists and cryptologists — would do better.
     Somehow, though, Ursula doubted they would have much luck.
     Man was late upon the scene, and a billion years was a long, long head start.
     She sat very still in the darkness of the control room, her breathing light in the faint pseudogravity of the throbbing rockets. Her own gentle pulse rocked her body to a regular rhythm, seeming to roll her slightly, perceptibly, with every beat of her heart.
     The ship surrounded her and yet, in a sense, it did not. She felt awash, as if the stars were flickering dots of plankton in a great sea … the sea that was the birthplace of all life.
     What happened here? she wondered. What really went by so many, many years ago?
     What is going on out there, in the galaxy, right now?
     The central part of the rock mural had eluded understanding. Ursula suspected that there were pieces of the puzzle which none of the archaeologists and psychologists, biological or cybernetic, would ever be able to decipher.
     We are like lunglish, trying to climb out of the sea long after the land has already been claimed by others, she realized. We've arrived late in the game.
     The time when the rules were simple had passed long ago. Out there, the probes had changed. They had evolved.
     In changing, would they remain true to the fundamental programming they had begun with? The missions originally given them? As we biologicals still obey instincts imprinted in the jungle and the sea?
     Soon, very soon, humans would begin sending out probes of their own. And if the radio noise of the last few centuries had not brought the attention of the galaxy down upon Sol, that would surely do it.
     We'll learn a lot from studying the wrecks we find here, but we had better remember that these were the losers! And a lot may have changed since the little skirmish ended here, millions of years ago.
     An image came to her, of Gavin's descendants — and hers — heading out bravely into a dangerous galaxy whose very rules were a mystery. It was inevitable, whatever was deciphered from the ruins here in the asteroid belt. Mankind would not stay crouched next to the fire, whatever shadows lurked in the darkness beyond. The explorers would go forth, machines who had been programmed to be human, or humans who had turned themselves into starprobes.
     It was a pattern she had not seen among the sad depictions on the rock wall. Was that because it was doomed from the start?
     Should we try something else, instead?
     Try what? What options has a fish who chose to leave the sea a billion years too late?
     Ursula blinked, and as her eyes opened again the stars diffracted through a thin film of tears. The million pinpoint lights broke up into rays, spreading in all directions.

• 

The Mechanical Heirs of Man

Nebogipfel reconstructed something of the history of Humanity, across fifty million years. Much of this picture was tentative, he warned me—an edifice of speculation, founded on the few unambiguous facts he had been able to retrieve from the Information Sea.
     There had probably been several waves of star colonization by man and his descendants, said Nebogipfel. During our journey through time in the car, we had seen the launch of one generation of such ships, from the Orbital City.
     "It is not difficult to build an interstellar craft," he said, "if one is patient. I imagine your 1944 friends in the Palaeocene could have devised such a vessel a mere century or two after we left them. One would need a propulsion unit, of course — a chemical, ion or laser rocket; or perhaps a solar sail of the type we have observed. And there are strategies to use the resources of the solar system to escape from the sun. You could, for instance, swing past Jupiter, and use that planet's bulk to hurl your star-ship in towards the sun. With a boost at perihelion, you could very easily reach solar escape velocity."
     "And then one would be free of the solar system?"
     "At the other end a reverse of the process, the exploitation of the gravity wells of stars and planets, would be necessary, to settle into the new system. It might take ten, a hundred thousand years to complete such a journey, so great are the gulfs between the stars…"
     "A thousand centuries? But who could survive so long? What ship—the supply question alone—"
     "You miss the point," he said. "One would not send humans. The ship would be an automaton. A machine, with manipulative skills, and intelligence at least equivalent to a human's. The task of the machine would be to exploit the resources of the destination stellar system—using planets, comets, asteroids, dust, whatever it could find—to construct a colony."
     "Your automatons,"' I remarked, "sound rather like our friends, the Universal Constructors." He did not reply.
     "I can see the use of sending a machine to gather information. But other than that—what is the point? What is the meaning of a colony without humans?"
     "But such a machine could construct anything, given the resources and sufficient time," the Morlock said. "With cell synthesis and artificial womb technology, it could even construct humans, to inhabit the new colony. Do you see?"
     I protested at this—for the prospect seemed unnatural and abhorrent to me—until I remembered, with reluctance, that I had once watched the "construction" of a Morlock, in just such a fashion!
     Nebogipfel went on, "But the probe's most important task would be to construct more copies of itself. These would be fueled up—for example, with gases mined from the stars—and sent on, to further star systems.
     "And so, slow but steady, the colonization of the Galaxy would proceed."
     "But," I protested, "even so, it would take so much time. Ten thousand years to reach the nearest star, which is some light years away—"
     "Four."
     "And the Galaxy itself—"
     "Is a hundred thousand light years across. It would be slow," he said. "At least at first. But then the colonies would begin to interact with each other. Do you see? Empires could form, straddling the stars. Other groups would oppose the empires. The diffusion would slow further… but it would proceed, inexorably. By such techniques as I have described, it would take tens of millions of years to complete the colonization of the Galaxy — but it could he done. And, since it would be impossible to recall or redirect the mechanical probes, once launched, it would be done. It must have been done by now, fifty million years after the founding of First London." He went on, "The first few generations of Constructors were, I think, built with anthropocentric constraints incorporated into their awareness. They were built to serve man. But these Constructors were not simple mechanical devices—these were conscious entities. And when they went out into the Galaxy, exploring worlds undreamed of by man and redesigning themselves, they soon passed far beyond the understanding of Humanity, and broke the constraints of their authors… The machines broke free."
     "Great Scott," I said. "I can't imagine the military chaps of that remote Age taking to that idea very kindly."
     "Yes. There were wars… The data is fragmented. In any event, there could be only one victor in such a conflict."
     "And what of men? How did they take to all this?"
     "Some well, some badly." Nebogipfel twisted his face a little and swiveled his eyes. "What do you think? Humans are a diverse species, with multiple and fragmented goals—even in your day; imagine how much more diverse things became when people were spread across a hundred, a thousand star systems. The Constructors, too, rapidly fragmented. They are more unified as a species than man has ever been, by reason of their physical nature, but because of the much greater Information pool to which they have access—their goals are far more complex and varied."
     But, through all this conflict, Nebogipfel said, the slow Conquest of the stars had proceeded. The launching of the first star-ships, Nebogipfel said, had marked the greatest deviation we had yet witnessed from my original, unperturbed History. "Men—your friends, the New Humans—have changed everything about the world, even on a geological—a cosmic scale. I wonder if you can understand—"
     "What?"
     "I wonder if you understand, really, the meaning of a million years—or ten million—or fifty."
     "Well, I ought to. I've traversed through such intervals, with you, on the way to the Palaeocene and back."
     "But then we traveled through a History free of intelligence. Look—I have told you of interstellar migration. If Mind is given the chance to work on such scales—"
     "I've seen what can be done to the earth."
     "More than that—more than a single planet! The patient, termite-burrowing of Mind can undermine even the fabric of the universe," he whispered, "if given enough time... Even we only had a half-million years since the plains of Africa, and we captured a sun...
     "Look at the sky," he said. " Where are the stars? There is hardly a naked star in the sky. This is 1891, or thereabouts, remember: here can be no cosmological reason for the extinction of the stars, as compared to the sky of your own Richmond.
     "With my dark-evolved eyes, I can see a little more than you. And I tell you there is an array of dull-red pinpoints up there: it is infra-red radiation—heat."
     Then it struck me, with almost a physical force. "It is true," I said. " It is true... Your hypothesis of Galactic conquest. The proof of it is visible, in the sky itself! The stars must be cloaked about almost all of them—by artificial shells, like your Morlock Sphere." I stared out at the empty sky. "Dear God, Nebogipfel; human beings—and their machines—have changed Heaven itself!"
     "It was inevitable that it would come to this, once the first Constructor was launched—do you see?" I stared into that darkened sky, oppressed by awe. It was not so much the changed nature of the sky that astonished me so, but the notion that all this — all of it, to the furthest end of the Galaxy had been brought about by my shattering of History with the Time Machine!
     "I can see that men have gone from the earth," I said. "The climatic instability has done for us here. But somewhere"—I waved a hand—"somewhere out there must be men and women, in those scattered homes!"
     "No," he said. "The Constructors see everywhere, remember; they know everything. And I have seen no evidence of men like you. Oh, here and there you may find biological creatures descended from man—but as diverse, in their way, from your form of human as I am. And would you count me a man? And the biological forms are, besides, mostly degenerated…"
     "There are no true men? "
     "There are descendants of man everywhere. But nowhere will you find a creature who is more closely related to you than say—a whale or an elephant…"
     I quoted to him what I remembered of Charles Darwin: "Judging by the past, we may safely infer that not one living species will transmit its unaltered likeness to a distant futurity…"
     "Darwin was right," Nebogipfel said gently.
     That idea—that, of your type, you are alone in the Galaxy!—is hard to accept, and I fell silent, gazing up at the blanked-out stars. Was each of those great globes as densely populated as Nebogipfel's Sphere? My fertile mind began to inhabit those immense world-buildings with the descendants of true men—with fish-men, and bird-men, men of fire and ice—and I wondered what a tale might be brought back if some immortal Gulliver were able to travel from world to world, visiting all the diverse offspring of Humanity.
     "Men may have become extinct," Nebogipfel said. "Any biological species will, on a long enough time-scale, become extinct. But the Constructors cannot become extinct. Do you see that? With the Constructors, the essence of the race is not the form, biological or otherwise—it is the Information the race has gathered, and stored. And that is immortal. Once a race has committed itself to such Children, of Metal and Machines and Information, it cannot die out. Do you see that?"
     I turned to the prospect of White Earth beyond our window.
     I saw it, all right — I saw it all, only too well!
     Men had launched off these mechanical workers to the stars, to find new worlds, build colonies. I imagined that great argosy of light reaching out from an earth which had grown too small, going glittering up into the sky, smaller and smaller until the blue had swallowed them up… There were a million lost stories, I thought, of how men had come to know how to bear the strange gravitations, the attenuated and unfamiliar gases and all the stresses of space. It was an epochal migration—it changed the nature of the cosmos—but its launch was, perhaps, a last effort, a spasm before the collapse of civilization on the Mother World. In the face of the disintegration of the atmosphere, men on earth weakened, dwindled—we had the evidence of the pathetic mirror on the moon to show us that—and, at last, died. But then, much later, to the deserted earth, back came the colony machines man had sent out—or their descendants, the Universal Constructors, enormously sophisticated. The Constructors were descended from men, in a way and yet they had gone far beyond the boundaries of what men could achieve; for they had discarded old Adam, and all the vestiges of brutes and reptiles that had lurked in his body and spirit.
     I saw it all! The earth had been repopulated; and—not by man—but by the Mechanical Heirs of Man, who had returned, changed, from the stars.
     And all of this— all of it—had propagated out of the little colony which had been founded in the Palaeocene. Hilary had foreseen something of this, I thought: the re-engineering of the cosmos had unfolded from that little, fragile huddle of twelve people, that unremarkable seed planted fifty million years deep.
     

Abstract

     The concept of a rapid spread of self-replicating interstellar probes (SRPs) throughout the Milky Way adds considerable strength to Fermi’s Paradox. A single civilisation creating a single SRP is sufficient for a fleet of SRPs to grow and explore the entire Galaxy on timescales much shorter than the age of the Earth — so why do we see no signs of such probes? One solution to this Paradox suggests that self-replicating probes eventually undergo replication errors and evolve into predator-prey populations, reducing the total number of probes and removing them from our view.

     I apply Lotka-Volterra models of predator-prey competition to interstellar probes navigating a network of stars in the Galactic Habitable Zone to investigate this scenario. I find that depending on the local growth mode of both populations and the flow of predators/prey between stars, there are many stable solutions with relatively large numbers of prey probes inhabiting the Milky Way. The solutions can exhibit the classic oscillatory pattern of Lotka-Volterra systems, but this depends sensitively on the input parameters. Typically, local and global equilibria are established, with prey sometimes outnumbering the predators. Accordingly, we find this solution to Fermi’s Paradox does not reduce the probe population sufficiently to be viable.

1 Introduction

     Why have we detected no sign of intelligent life beyond the Earth? This fundamental question continues to challenge our deepest-held beliefs about humanity and our place in the Universe. Fermi’s Paradox forces us to confront our Copernican assumptions about our lack of uniqueness with the lack of extraterrestrial intelligences. Its strongest formulation can be given as follows:

     Imagine a civilisation constructs an interstellar probe that is self-replicating. Such a probe would be able to produce a copy every time it visits a new star system. As each copy makes copies, the number of self-replicating probes (SRPs) grows exponentially, and every star in the Milky Way is explored on a timescale much, much shorter than its age. Estimates for this exploration timescale vary, but are as short as ten million years, and perhaps shorter still.

     Given that this timescale is much shorter than the age of the Earth, and only one ETI constructing SRPs is sufficient to produce this scenario, on balance we should expect to see an interstellar probe orbiting the Sun. And yet, we do not. How can this be resolved?

     Among many possibilities, we can include solutions that require civilisations to be rare. However, as a single civilisation is sufficient to swamp the galaxy in SRPs, we are effectively asking for humanity to be alone in the Universe.

     It may well be the case that other intelligent beings exist, and that their probes are en route, and may not arrive for several thousand or several million years. This demands that the biological timescale of most of the Milky Way is somehow correlated. Perhaps this is due to global regulation mechanisms, large scale destructive events that reset the biological clocks of many civilisations simultaneously. However, there are no known astrophysical regulation mechanisms that are truly global. For example, when the Milky Way’s central supermassive black hole enters an active accreting phase, the subsequent radiation output results in a regulation mechanism with a correlation length of order ten thousand light years. The Milky Way is much larger than this correlation length, and even a small handful of uncorrelated biospheres is fit to make this type of solution untenable.

     Of course, it may well be the case that an interstellar probe is in the outer solar system, and we have not yet found it. While this is indeed plausible, the possible places for an interstellar probe to hide continues to decrease.

     Other solutions suggest that SRPs themselves are rare. There have been several arguments put forth regarding the safety of SRPs as a technology. Sagan & Newman suggest that civilisations will voluntarily refrain from building SRPs, for a host of reasons. For example, self-replication could result in encoding errors. These “mutations” will propagate from generation to generation with unforeseen, unintended consequences. The consequences of this could be severe, e.g. a genocidal conversion of a species and its technology into probes. It has been argued that these risks would persuade intelligent beings to place a moratorium on SRPs. Such arguments are notorious for their anthropological assumptions, and the larger assumption that “civilisations” are unified in purpose and execution — an assumption humanity repeatedly invalidates. This heterogeneity crucially undermines the likelihood of a Galactic moratorium. Once technology achieves a certain threshold, a very small number of individuals in a single civilisation become capable of building illegal technology and producing a species-ending moment, or indeed an SRP fleet.

     We will explore a variant of the unintended consequences of SRPs, the “Predator-Prey” hypothesis. In this scenario, a subset of SRPs mutate into predators of other SRPs. For an SRP to make a copy of itself, it is likely that cannibalising another SRP will be the most energy-efficient solution. In the standard description of this scenario, predators reduce the prey population until the available prey are exhausted, reducing the visibility of SRPs in the Milky Way.

     However, we should also expect in this scenario that the spread of SRPs across interstellar space will be modulated by the non-trivial population dynamics of predator-prey systems, which are among the most well-studied fundaments of mathematical biology. The full implications of these population dynamics in SRPs are largely unstudied.

     In this work, we apply the classic Lotka-Volterra formalism for predator-prey systems to an interstellar network. In the network, each star plays host to a predator-prey population, which transmits and receives both predator and prey from neighbouring star systems. We will consider under what circumstances predators can reduce the population significantly, as well as what circumstances permit stable, significant populations of prey to remain in existence.

2 Method

We model the Galactic Habitable Zone (GHZ) as a graph of N_* stars. The stars are distributed in space, with their locations fixed. The semimajor axes of the stars a_i around the Galactic Centre are exponentially distributed to simulate the Milky Way’s surface density profile:

with the scale radius r_S = 3.5 kpc. The minimum and maximum permitted radius of the stars is [7; 10] kpc respectively, following the Gowanlock model of the GHZ. We assume a uniform eccentricity distribution, provided that the star’s orbit prevents its closest approach to the Galactic Centre being smaller than the inner radius of the GHZ.We also restrict the inclination of the orbits so that they do not exceed 0.5 radians. The longitude of the ascending node, the argument of periapsis and the true anomaly are uniformly sampled in the range [0; 2π] radians. Note that once the stellar orbital parameters are determined, we fix the stellar positions throughout the calculation.

     Each star provides a vertex to our graph, and we construct the graph G such that for a star i, any star j within a minimum distance R_min of i is connected by an edge. We then define the minimum spanning tree T of this graph, and use this for computing predator/prey evolution (see Figure 1).

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     For each star i in the network, we solve the Lotka-Volterra equations for the local numbers of prey R_i, and number of predators P_i, with inflow and outflow rates of prey determined by the edges that connect each star to its neighbours. For logistic growth, the equations for star i are:

(ed note: I don't know what happened to equation (4), it seems to be missing)

To model exponential growth, we can simply set the carrying capacity K to very large values (10³⁰). We give a list of all variables with their definition in Table 1. The outflow of prey from star i to star j, O_R,ij is calculated assuming a fixed outflow rate o_R,i, a fixed probe speed v_probe, and the distance between i and j, D_ij :

As we begin our simulations with many stars containing zero prey initially, we demand that O_R,ij be zero until a sufficient time has elapsed for the first prey to arrive at i to complete the journey to j. The total outflow is then

Inflows are computed similarly:

where all outflow/inflow terms are pairwise, i.e.

and an identical set of equations are used for predator outflow and inflow (O_P,i, I_P,i).

3 Results

3.1 Tests

3.1.1 Single Star, Exponential Growth

We test the code by considering a single star with no inflow or outflow, to ensure that we retrieve the solution to the classic or “vanilla” Lotka-Volterra equations for exponential growth (i.e. infinite carrying capacity), where we now drop the i subscript for clarity:

(ed note: I don't know what happened to equation (11), it seems to be missing)

Table 2 shows the parameter values for this run,

and Figure 2 shows the resulting behaviour. We see that the predator/prey populations are oscillatory, both with period 8.6 Myr, and out of phase. This represents a fixed locus in predator-prey space (bottom panel of Figure 2).

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This locus can be determined by condensing the coupled equations into a single equation:

If we define the above as a Hamiltonian:

We can use standard Hamiltonian analysis to obtain a single solution for the predator/ prey population:

This defines an initial point on the R — P locus, with all other points on the locus defining a surface of constant H.

3.1.2 Single Star, Logistic Growth

We repeat the calculation of section 3.1.1, where we now impose a prey carrying capacity K_R = 20 (see Table 3). We recover the standard result, that the stabilising effect of carrying capacity damps the oscillations in predator/prey populations, until an equilibrium is eventually found at late times (Figure 3). This is represented in R — P space by a spiral with end point given by the equilibrium solution. Note that the equilibrium prey value is much less than the carrying capacity, which is a common outcome in models of this type. Depending on the input parameters, steady state solutions are possible where either the prey or predators dominate the combined population.

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3.2 Logistic Growth, Globally Constant Parameters

3.2.1 Moderate, Constant Outflow Rate

We now consider a full stellar network, where each star possesses the same fixed values for all parameters (see Table 4). We place an initial population (R₁, P₁) on star 1, with all other stars hosting zero prey/predators initially. The global picture is similar to the single star case (section 3.1.2) — the initial oscillatory phase is quickly damped towards equilibrium values. Again, we find that the total prey population is lower than the maximum permitted by carrying capacity (N_*K_R,i = 10⁴), but the predator population is also constrained, and hence we find the prey population can be sustained at relatively high levels (provided they do not exhaust local resources for self-replication).

     Interrogating individual stars reveals that all systems assume damped oscillatory states similar to the previous section, all with equal oscillation periods for both the prey and predator populations (now 9.17 Myr). This is made possible by the relatively large outflow rate (o_R,i = 10^-3), which seeds a system with sensible initial quantities of prey/predators, while remaining sufficiently small that the internal predatorprey dynamics dominates the population’s evolution.

     As the initial prey population requires time to traverse the stellar network, each predator-prey system begins operating at a slightly different initial time. The oscillations seen in the global population have a slightly increased wavelength compared to individual systems, due to the constructive interference of many oscillatory curves, each slightly out of phase with each other, “smearing” the curve over a longer period range.

3.2.2 Low, Constant Outflow Rate

We consider the effect of outflow rate by repeating the previous experiment, with the outflow parameter reduced to very low values (o_R,i = 10^-9). We find that this significantly alters both the global behaviour and the behaviour of individual systems (Figures 5 and 6).

     The reduced outflow rate ensures that a greater time interval is required for all stars to host predator prey systems with sufficient quantities of each population. As a result, the initial evolution of all systems depends strongly on their local environment — the number of directly connected neighbours, and the quantities of prey/predators arriving from each neighbour. Once each star in the entire Galaxy is sufficiently populated, the individual systems are able to attain an equilibrium state, resulting in a global equilibrium with total predator/prey counts very similar to the previous example (where o_R,i = 10^-3). Note that while the behaviour of each individual system is markedly different (Figure 6), the periodic behaviour of prey and predators in any given system remains tightly coupled.

     This run demonstrates the highly time dependent nature of this solution to Fermi’s Paradox. Two quite distinct phases of evolution can be characterised — a relaxation phase which persists for the first 200-400 Myr, followed by an equilibrium phase that endures beyond 400 Myr. Given that human SETI searches span a time interval of less than 10⁼⁴ Myr, any constraint we can place on the total number of probes in a given star system will only be a brief snapshot. As a result, our ability to use observations of any kind to constrain any of the parameters of our model will be extremely limited indeed, even with a bona fide detection of alien SRPs.

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3.3 Spatially Varying Prey Growth Rates

It is quite likely that the prey growth rate around individual stars will vary, perhaps due to the quality of resources available for self-replication. This is likely to be a function of system chemical composition (i.e. stellar metallicity), but also the degree of element differentiation and chemical processing experienced by asteroids and minor bodies orbiting said star. The location of the debris may also limit its usefulness to self-replicating probes — if most of the “desirable” raw material resides inside a deep gravitational potential well, this places energy constraints on the probe’s manouevrability, further restricting its maximum replication rate.

     We consider this possibility by rerunning the previous calculation (section 3.2.1), but now randomly sampling b_R,i in the range [0.5; 2.0]. The resulting total population can be seen in Figure 7. The steady equilibrium of the previous section has disappeared. Periodogram analysis shows oscillatory behaviour over a range of periods, with principal period 8.77 Myr. However, there is significant amplitude spread around this principal period, as the oscillation period of an individual system (equivalently, the velocity of the system’s trajectory around its constant H surface in R — P surface) will depend on its individual Lotka-Volterra parameters (b_R,i, d_R,i, b_P,i, d_P,i). The combination of a range of oscillation periods results in a “smearing” of the total oscillatory period.

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3.4 Spatially Varying Prey Carrying Capacity

In a similar vein to the previous section, the resources provided by local asteroid belts may support varying levels of prey populations. We might therefore expect that the prey carrying capacity will vary between individual stars. We investigate this possibility by resetting b_R,i = 0.6 and randomly sampling K_R,i from a uniform distribution in the range [5, 30]. The resulting total populations again assume an oscillatory state, but with no clear principal period, and reduced variations in the value of R and P (Figure 8). The total prey population tends to remain at larger values than the previous case, mostly because the prey growth rates can now be set at a relatively large value.

     When we consider individual star systems (Figure 9), we can see that the individual predator populations are difficult to distinguish from the total predator population. However, we can see that the prey populations show a variety of periodicities, defined not only by the local K_R,i but also the carrying capacity of its neighbouring stars. For example, the prey population in the top right panel of Figure 8 exhibits a visible periodicity of around 100 Myr, whereas the bottom right panel shows no obvious evidence of periodicity.

     Notably, in contrast to every other simulation conducted so far, computing periodograms for individual systems reveals that predator and prey populations no longer share the same overall periodicity. This decoupling is a direct consequence of the predator populations practising exponential growth, while the prey populations exercise logistic growth with varying K.

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3.5 Spatially Varying Outflow Rates

Finally, we consider the effect of varying outflow rates between star systems by running the model with o_R,i uniformly sampled in the range (10^-4, 10^-3) (Figures 10 and 11). As with the previous section, this variation forces the predator and prey populations of individual stars to oscillate on differing periods, with the oscillation period being sensitive to the local o and the value of o for connected neighbours. However, Figure 10 shows that this decoupling at local scales is not evident at global scales. Periodogram analysis confirms that the predator and prey populations on Galaxy-wide scales oscillate with identical periodicity!

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4 Discussion

4.1 Comparison with other studies of Predator-Prey Dynamics

Predator-prey dynamics has a rich history of study in mathematical biology. The Lotka-Volterra equations have been applied to a variety of cases, in particular considering how the system is generalised to more than two species, as an attempt to model the food chain of an ecosystem.

At a basic level, one can incorporate spatial effects into the vanilla Lotka-Volterra system by recasting it as a set of reaction-diffusion equations, where one can think of predators and prey as two reactants combining to form a product, and both entities diffuse spatially with a diffusion constant D, e.g.:

(ed note: I don't know what happened to equation (17), it seems to be missing)

Such systems can be stable in the absence of diffusion (D = 0), only to become unstable when diffusion is added (Turing, 1952). Of course, these models are inherently symmetric, and cannot account for spatial heterogeneities.

     Most modern attempts to incorporate geography into calculations of this sort assume a lattice configuration, upon which either analytic or probabilistic solutions can be obtained. For example, Frachebourg considered the behaviour of predator-prey systems on a 1D lattice. For a two-species system, one can model the entire evolution in terms of interfaces separating species. Over time, species tend to organise into a mosaic of alternating domains, with the size of each domain increasing linearly with time. If the number of species exceeds 5, these domains can become “frozen-in” (although this depends on whether the species chain is symmetric, i.e. can species 1 eat species 2 and species 5?).

     Tom´e & de Carvalho construct a probabilistic cellular automaton, inspired by the Lotka-Volterra equations, on a 2D lattice. They are able to show that self-sustained stable oscillations can be set up in the system, just as in the “vanilla” Lotka-Volterra case. However, these oscillations are stable against changes in the initial conditions1. A more generalised version of this result was obtained by Rozhnova & Nunes, who considered random networks with k neighbours per node.

As far as the author is aware, there are no examples of a coupled Lotka-Volterra system computed on spatial graphs/networks. Lotka-Volterra systems usually model spatially continuous environments, although deliberately inserting heterogeneity into a continuous environment has been shown to remove the sustained oscillations, as we have found in our analysis.

4.2 Limitations of the Analysis

The flow of predators/prey between star systems depends heavily on the distance between them. In our model, we have kept stellar positions fixed. If we allowed the stars to move, we can expect that this will result in quasi-periodic forcing of the flow rates. The periodicity of both predator and prey populations for a given star would be further modified, to accommodate both the star’s motion and that of its neighbours.

     We also assume that each star system has an unending supply of resources. While the growth of prey is generally limited by the local carrying capacity K, we have not considered the possibility that replication eventually exhausts the local supply of raw materials. One could model this rather simply as a non-constant K that decays with time. If resources could be exhausted sufficiently quickly, that might limit the number of probes overall, and provide a resolution to Fermi’s Paradox. However, if one considers the number of probes that can be produced from the available debris mass in the Solar system, the exhaustion timescale of a typical star system is likely to be much too long to be of concern to this analysis.

     That being said, we might note that the quality of raw material can vary from system to system, as a function of local metallicity. We have attempted to model this by allowing K to vary between stars. However, our models allowed K to be effectively random. In practice, K should vary according to the metallicity gradient of the Galaxy. This uniform variation may result in similar spatial variations in system periodicities.

     It is also worth noting that predator probes can also scavenge other predators for resources to selfreplicate. Adding such “omnivorous” probes to a star system could have important consequences — reducing the predator population in this way could allow prey populations to grow to larger values.

     In any case, the above additions to the analysis will not affect the final result — the predator/prey solution to the SRP formulation of Fermi’s Paradox does not significantly reduce the SRP population, and is therefore not a viable solution.

5 Conclusions

In this paper, we have considered a proposed solution to Fermi’s Paradox regarding the growth and spread of self-replicating interstellar probes. It has been proposed that if some self-replicating probes were to “mutate” and begin predating other probes, this would reduce the total population of probes, ensuring that humanity would not see them.

     We conduct simulations of predator-prey probe evolution using the Lotka-Volterra equations, amongst a connected network of stars in the Galactic Habitable Zone. We find that traditional competition can result in oscillating behaviour for the predator/prey populations at a given star, as well as equilibrium solutions where both local and global populations tend to fixed values. The nature of the system behaviour depends sensitively on the birth and death rates of each species, as well as the local carrying capacity and the flow of species between star systems. In any case, we find that significant quantities of prey probes can persist throughout the Galaxy — admittedly less than the maximum permitted by carrying capacity, but still sufficiently large that this solution to Fermi’s Paradox is weak at best, and in effect not a solution at all.

     In summary, the self-replicating probe formulation of Fermi’s Paradox remains, in our view, one of the strongest and most testing formulations, and an important check on our assumptions regarding the number of intelligent species in the Milky Way.

Galactic North by Alastair Reynolds )

Greenfly was a human-designed terraforming machine programmed to break apart terrestrial planets and transform them into self-sufficient habitats filled with atmosphere, water and vegetation. Composed of swarms of Von Neumann robots, it was fully capable of self-replication and autonomous action. First seen aboard the lighthugger Hirondelle in 2303, it was taken by the pirate Run Seven in 2309, and unleashed some time after in the Ross 128 system.

Greenfly was programmed to adapt to the external challenges it encountered. Because of this, potential threats were assimilated, and used to improve and evolve greenfly. By 2931, the Nestbuilders, or rather their Slug overlords, were convinced that greenfly had been deliberately exposed to the Melding Plague to circumvent any limitations placed on its self-replication, and that they had assimilated a sample of Inhibitor machinery, as well. They were concerned that even their advanced military technology would be unable to counteract them.

Sometime after they encountered active resistance, greenfly began to categorize any intelligent life as a potential threat to its endless terraforming, and made destroying that life a priority. (i.e., greenfly had evolved into a paperclip maximizer)

By 40,000, greenfly had transformed vast swathes of the Milky Way galaxy.

The shadows, ostensibly alien entities claiming to originate from a parallel brane, came from a universe in which machines remarkably similar to greenfly had restructured multiple galaxies. This may be a coincidence, or may suggest that the shadows in fact exist in a future version of the "native" universe of humanity overtaken by greenfly.

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GALACTIC NORTH

This story starts in the year 2303, when Captain Irravel Veda of the lighthugger Hirondelle, her second-in-command Markarian, and some fraction of their Ultranaut crew are ambushed by pirates while engaged in an unexpected repair stopover in a cloud of rocks and cometary matter in the charted but uninhabited star system Luyten 726-8. She briefly considers activating the "Greenfly" terraforming Von Neumann machines being transported onboard, which she believes would easily be able to swarm and dismantle the pirate vessel and probably aid in repair as well. She rejects this option, however, and their ship is captured by the infamous terroristic pirate Run Seven. She is tortured to reveal the codes to the security protecting her ship's cargo – twenty thousand colonists' cryopreserved bodies – but refuses due to intense psychological conditioning that makes her view the cargo as her children and do anything to protect them.

She awakens aboard the mostly abandoned Hirondelle some time later, having no memory of the interrogation. She discovers that almost all of the colonists have been taken, while the handful that were left behind have been cut to pieces in order to acquire their tissues and implants; the valuable Greenfly machines they were transporting have also been stolen by Seven. …

By 2658, Irravel has acquired a cloned body of herself. Markarian has disappeared with the remaining colonists and is fleeing aboard the pirates' ship Hideyoshi. Still under the influence of her Ultranaut conditioning, Irravel gives chase, interested in exacting revenge, rescuing the colonists, and learning why Markarian gave up the codes to their security. By 2931 she has followed him to a refuge among the "Nestbuilder" race, from whom she attempts to purchase advanced weapons technology in order to have the advantage against the Hideyoshi during the next encounter. However, the Nestbuilders and their symbiotic species, the Slugs, reveal that while she was travelling at high relativistic velocities, the Greenfly terraformers were unleashed around the star Ross 128 (the same star that Diadem orbits in "Glacial"), and have since malfunctioned, destroying the planets there and turning them into trillions of orbiting bio-domes filled with vegetation. The inhabitants of the star system failed to stop them and were apparently killed in the process. Irravel says that she cannot provide any information that would help the Nestbuilders/Slugs, and leaves on the trail of Markarian again. Mirsky dies an old woman in space in 3354. In their last conversation, they discuss the Greenfly, which they observe by now has begun spreading to other systems, destroying the intelligent societies it was designed to provide for. All attempts at containing the swarm have failed.

In 4161, Irravel stops at the Pleiades cluster and meets distant descendants of the Conjoiners living amongst a race known as the Islanders, who inhabit the planets in the star cluster. Markarian is still fleeing her. She learns that the Greenflies are now consuming whole star systems at a massive rate, surging outward in a fractal pattern in massive swarming tendril-like waves made of substantial fractions of the mass orbiting each star. She also discovers that herself, Markarian, Mirsky, and Seven, their confrontation having unleashed the Greenfly upon the galaxy, have receded into the mists of prehistory and become mythologised as primordial figures.…

Eventually, she catches up with the Hideyoshi in AD 9730, by which point the Greenflies have wiped out most of human civilisation. The two ships view this under the effects of heavy time dilation from high above the Galactic Plane (Galactic North), and the two captains discuss the situation. Markarian reveals that they both were involved in a betrayal during that fateful encounter: he gave Run Seven the codes to the colonists' reefersleep caskets when Seven forced him to watch her undergo torture, while she, under the influence of torture, provided Seven and his crew with the Greenflies and their activation codes. They wonder between them if anybody could have survived within the swarm of machine-tended bio-domes. Eventually they detect a message emanating from the swarm, parsed in an ancient human format, tight-beamed directly at them. The message is from Remontoire, who has managed to survive with a small group of Conjoiners orbiting a pulsar (the Greenflies do not attack pulsars, which lack the light to sustain vegetation and usually the mass to build domes).…

The novel Absolution Gap contains a reference to entities in a parallel universe (or at least claiming to be from one) facing attack from an agent very similar to the Greenfly. In their world, the Greenfly gradually consume the entire universe, rendering it uninhabitable. There are references that may imply the alternate universe entities are actually the extreme far future of humanity.

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      One night, during their absence, and close to the front door, something grew. The scientists, after long conference, decided it was a plant but it didn't look like a plant.
     It was a triangular mirror balanced on a cable-like stem as thick as a man's wrist. The "mirror" followed the sun and, at evening or on dull days, folded itself up geometrically into a neat square black box.
     Two days later there was another growth. This was a small brass colored sphere about the size of a walnut perched on the top of a thin black rod about two feet in height.
     An intrigued expert touched it with his hand and was flung untidily to the path. He was not dead but the local hospital had some difficulty bringing him round. A diagnostician pronounced near-lethal electric shock.

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     The door of Lipscombe's house had been open and on the path was—It had looked like an oxygen cylinder some six feet in length and supported itself on thin legs like black cables. On top, near the thicker end, something spun rapidly, catching the sunlight. He'd had the curious impression that something was watching through it and the thought radar vision had occurred to him before the soldiers had bustled him out of the room.

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     After much security checking they were finally admitted to a pleasantly furnished recreation room where a group of obvious scientists were arguing fiercely.
     "But, my dear fellow, why should such a conclusion strike you as pure fantasy?"
     "Because the conception in itself is preposterous—the term natural electronic life is a sheer absurdity."
     "Why should it be? When one considers the incredible complication of normal organic life why should not a simpler, less complex life form evolve in a different environment. A planet with a highly radio-active crust, a chemical atmosphere and, possibly, rich surface metal deposits and you have the perfect incubator for electronic life to develop. Consider, an almost pure copper deposit, a few drops of acid from the chemical atmosphere, a natural vein of metallic ore and you have not only natural electricity, but the basis for a natural circuit, or, if you prefer it, an electronic nervous system. Have you read what Mayer deduced during his experiments with radio-active crystals, for example?"
     "I have, but the fact that these artificial cells developed apparent reflexes is no basis for presupposing the preposterous."
     "My God, man, you conceded yesterday that we can make organic life cells in a laboratory. You must also concede, therefore, that this same organic life has evolved naturally on this planet. Why, then, knowing also that electrical life has also been constructed in a laboratory will you not admit the possibility of electronic life evolving naturally?"
     "I still find the conception of intelligent life housed in a metallic body and based on series of circuits wildly improbable. The theory of outworld invasion by what you call an electronic life form is, in my opinion, sheer imagination and owes nothing whatever to applied science."

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"What good do they think all these troops and weapon experts will do? They're still thinking in terms of an outworld alien invader with super weapons and they're not. Why the hell can't they see that? This is a minor occupation force sitting on its presumed backside in one of the safest conquests it's possible to conceive. They've introduced their own ecology into this environment and, because it's dominant in respect of our own, we're going under. Oh yes, I know it looks horrible and alien to our own but the principle is the same. We have sparrows and they introduce hawks. We have oak trees but along comes a strangling ivy; it's as simple as that. Some of the alleged machines our troops are now reporting may be equivalent of wolves or tigers and not armored vehicles at all. Once or twice they have opened up with something new, but this, I think, is reflex. At times we may be an irritant and the aliens take a smack at us like a dozing man slapping at a fly. They can afford to doze, chuck a few seeds out of the window, let loose some hawks and nature will do the job for them. Not too far in the future they can step out of the front door into world which is seeded, prepared and ready for them. Their peculiar ecology will have removed anything alien which might once have cluttered up the place."

It was a world that had never known a sun. For more than a billion years, it had hovered midway between two galaxies, the prey of their conflicting gravitational pulls. In some future age the balance would be tilted, one way or the other, and it would start to fall across the light-centuries, down toward a warmth alien to all its experience.

Now it was cold beyond imagination; the intergalactic night had drained away such heat as it had once possessed. Yet there were seas there—seas of the only element that can exist in the liquid form at a fraction of a degree above absolute zero. In the shallow oceans of helium that bathed this strange world, electric currents once started could flow forever, with no weakening of power. Here superconductivity was the normal order of things; switching processes could take place billions of times a second, for millions of years, with negligible consumption of energy. It was a computer’s paradise. No world could have been more hostile to life, or more hospitable to intelligence.

And intelligence was there, dwelling in a planet-wide incrustation of crystals and microscopic metal threads. The feeble light of the two contending galaxies—briefly doubled every few centuries by the flicker of a supernova—fell upon a static landscape of sculptured geometrical forms. Nothing moved, for there was no need of movement in a world where thoughts flashed from one hemisphere to the other at the speed of light. Where only information was important, it was a waste of precious energy to transfer bulk matter.

Yet when it was essential, that, too, could be arranged. For some millions of years, the intelligence brooding over this lonely world had become aware of a certain lack of essential data. In a future that, though still remote, it could already foresee, one of those beckoning galaxies would capture it. What it would encounter, when it dived into those swarms of suns, was beyond its power of computation.

So it put forth its will, and myriad crystal lattices reshaped themselves. Atoms of metal flowed across the face of the planet. In the depths of the helium sea, two identical subbrains began to bud and grow…

Once it had made its decision, the mind of the planet worked swiftly; in a few thousand years, the task was done. Without a sound, with scarcely a ripple in the surface of the frictionless sea, the newly created entities lifted from their birthplace and set forth for the distant stars.

crusade to exterminate all warm-life in our galaxy. )

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(ed note: Terran civilization has become very high tech. They have lots of self-reproducing self-maintaining sun-powered gadgets. Nuclear war looms. A group of fifty scientist run away to Tau Ceti to make an interstellar colony. Years later they go back to visit Terra. Due to the weird properties of their faster-than-light starship, they arrive at Terra about three billion years after they left.)

(They are rather startled to discover that humans are extinct, and there is now an ecosystem based on cybernetic life.)

Earth rolled into sight. The planetary disc was still edged with blueness darkening toward black. Clouds still trailed fleecy above shining oceans; they gleamed upon the darkness near the terminator as they caught the first light before sunrise. Earth was forever fair.

But the continental shapes were new, speckled with hard points of reflection upon black and ocher where once they had been softly green and brown. There were no polar caps; sea level temperatures ranged from eighty to two hundred degrees Fahrenheit. No free oxygen remained: the atmosphere was nitrogen, its oxides, ammonia, hydrogen sulfide, sulfur dioxide, carbon dioxide, and steam. Spectroscopes had found no trace of chlorophyll or any other complex organic compound. The ground cover, dimly glimpsed through clouds, was metallic.

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His name was a set of radio pulses. Converted into equivalent sound waves, it would have been an ugly squawk; so because he, like any consciousness, was the center of his own coordinate system, let him be called Zero.

He was out hunting that day. Energy reserves were low in the cave. That other who may be called One—being the most important dweller in Zero's universe—had not complained. But there was no need to. He also felt a dwindling potential. Accumulators grew abundantly in their neighborhood, but an undue amount of such cells must be processed to recharge One while she was creating. Motiles had more concentrated energy. And, of course, they were more highly organized. Entire parts could be taken from the body of a motile, needing little or no reshaping for One to use. Zero himself, though the demands on his functioning were much less, wanted a more easily assimilated charge than the accumulators provided.

In short, they both needed a change of diet.

The sky was still light when he came on spoor: broken earthcrystals not yet healed, slabs cut from several boles, a trace of lubricant. Tuning his receptors to the highest sensitivity, he checked all the bands commonly made noisy by motiles. He caught a low-amplitude conversation between two persons a hundred miles distant, borne this far by some freak of atmospherics; closer by he sensed the impulses of small scuttering things, not worth chasing; a flier jetted overhead and filled his perception briefly with static. But no vibration of the big one. It must have passed this way days ago and now be out of receptor-shot.

A nearly full moon rose over the hills like a tiny cold lens. Night vapors glowed in masses and streamers against a purple-black sky where stars glittered in the optical spectrum and which hummed and sang in the radio range. The forest sheened with alloy, flashed with icy speckles of silicate. A wind blew through the radiation-absorber plates overhead, setting them to ringing against each other; a burrower whirred, a grubber crunched through lacy crystals, a river brawled chill and loud down a ravine toward the valley below.

Once he tapped lubricant from a cylinder growth and once he thinned his acids with a drink of water. Several times he felt polarization in his energy cells and stopped for a while to let it clear away: he rested.

---

Swiftly, he prepared himself. First he considered his ordinary weapons. The wire noose would never hold the monster, nor did he think the iron hammer would smash delicate moving parts (it did not seem to have any), or the steel bolts from his crossbow pierce a thin plate to short out a crucial circuit. But the clawed, spearheaded pry bar might be of use. He kept it in one hand while two others unfastened the fourth and laid it with his extra armament in the carrier rack. Thereupon they deftly hooked his cutting torch in its place. No one used this artificial device except for necessary work, or to finish off a big motile whose cells could replace the tremendous energy expended by the flame, or in cases of dire need.

---

A tree is a tree, anywhere and anywhen, no matter how intricate its branching or how oddly shaped its leaves and blossoms. But what is a—

—thick shaft of gray metal, planted in the sand, central to a labyrinthine skeleton of straight and curved girders, between which run still more enigmatic structures embodying helices and toruses and Möbius strips and less familiar geometrical elements; the entire thing some fifty feet tall; flaunting at the top several hundred thin metal plates whose black sides are turned toward the sun?

There was no soil, only sand, rusty red and yellow. But outside the circle which had been devastated by the boat's jets, Darkington found the earth carpeted with prismatic growths, a few inches high, seemingly rooted in the ground. He broke one off for closer examination and saw tiny crystals, endlessly repeated, in some transparent siliceous material: like snowflakes and spiderwebs of glass. It sparkled so brightly, making so many rainbows, that he couldn't well study the interior. He could barely make out at the center a dark clump of … wires, coils, transistors?

They walked among surrealistic rods and frames and spirals, under ringing sheet metal. The crystals crunched beneath their tread and broke sunlight into hot shards of color. But not many rays pushed through the tangle overhead; shadows were dense and restless. Darkington began to recognize unrelated types of structure. They included long, black, seemingly telescopic rods, fringed with thin plates; glassy spheres attached to intricate grids; cables that looped from girder to girder. Frequently a collapsed object was seen crumbling on the ground.

Frederika looked at several disintegrated specimens, examined others in good shape, and said: "I'd guess the most important material, the commonest, is an aluminum alloy. Though—see here—these fine threads embedded in the core must be copper. And this here is probably manganese steel with a protective coating of … um … something more inert."

Darkington peered at the end of a broken strut through a magnifying glass. "Porous," he said. "Good Lord, are these actually capillaries to transport water?"

It stirred among shadows, behind a squat cylinder topped with the usual black-and-mirror plates. Perhaps three feet long, six or eight inches high … It came out into plain view. Darkington glimpsed a slim body and six short legs of articulated dull metal. A latticework swiveled at the front end like a miniature radio-radar beamcaster. Something glinted beadily beneath, twin lenses? Two thin tentacles held a metal sliver off one of the great stationary structures. They fed it into an orifice, and sparks shot back upward—

The thing stopped in its tracks. The front-end lattice swung toward the humans. Then the thing was off, unbelievably fast. In half a second there was nothing to see.

"It was eating that strut." Frederika walked over to the piece of metal which the runner had dropped. She picked it up and came stiffly back with it. "See, the end has been ground away by a set of coarse emery wheels or something. You couldn't very well eat alloy with teeth like ours. You have to grind it."

Somehow they found themselves pushing on. Once, crossing an open spot where only the crystals stood, they spied something in the air. Through binoculars, it turned out to be a metallic object shaped vaguely like an elongated manta. Apparently it was mostly hollow, upborne by air currents around the fins and propelled at low speed by a gas jet. "Oh, sure," Frederika muttered. "Birds."

(ed note: Zero appears and charges)

Time slowed for Darkington, he had minutes or hours to tug at his gun, hear Frederika call his name, see Kuroki take aim and fire. The shape was mountainous before him. Nine feet tall, he estimated in a far-off portion of his rocking brain, three yards of biped four-armed monstrosity, head horned with radio lattice, eyes that threw back sunlight in a blank glitter, grinder orifice and— The rocket exploded. The thing lurched and half fell. One arm was in ruins.

(ed note: Zero captures the humans. He finds them puzzling.)

The units Zero had captured were making considerable sound-wave radiation. If not simply the result of malfunction in their damaged mechanism, it must be produced by some auxiliary system which they had switched on through interior controls. Zero's sound receptors were not sensitive enough to tell him whether the emission was modulated. Nor did he care. Certain low forms of motile were known to have well-developed sonic parts, but anything so limited in range was useless to him except as a warning of occurrences immediately at hand. A person needed many square miles to support himself. How could there be a community of persons without the effortless ability to talk across trans-horizon distances?

That energy drain left him ravenous. He scouted the forest in a jittery spiral until he found some accumulators of the calathiform sort (cup-shaped; concave). A quick slash with his pry bar exposed their spongy interiors, rich with energy storage cells and mineral salts. They were not very satisfying eaten unprocessed, but he was too empty to care. With urgency blunted, he could search more slowly and thoroughly. Thus he found the traces of a burrow, dug into the sand, and came upon a female digger. She was heavy with a half-completed new specimen and he caught her easily. This too would have been better if treated with heat and acid, but even raw the materials tasted good in his grinder.

• 

"You can't beat the Drej. They're pure energy!"

— Korso, Titan A.E.

Creatures that dispense with the need to have a body altogether.

Energy Beings are frequently Sufficiently Advanced or Precursors; in fact, non-physicality is a common prerequisite, though they may take on A Form You Are Comfortable With. Often times this means that when they "Touch" a corporeal being it has interesting side effects. Other times they are the result of when a species Ascend to a Higher Plane of Existence. e Even cheaper and simpler to pull off than Rubber-Forehead Aliens, which explains why Energy Beings and Human Aliens so often dominate the demographics of The Final Frontier. The Angelic Aliens and Starfish Aliens especially may appear in this form.

Never mind that being "made of energy" makes as much sense as being "made of weight". This shows that many still don't know what the word "energy" really means.

It is also considered nonsensical because "energy" beings usually act more like floating clouds of luminescent gas. So a better term to use here might be "gaseous beings". Or, they might just plain be made of stars.

They may often be used as a way to represent gods, angels, the afterlife, and similar subjects without dealing with the religious connotations normally attached to them.

Of course, Energy Beings share many characteristics usually ascribed to concepts such as spirits and souls, often making them an example of Sufficiently Analyzed Magic.

See Made of Magic for a more fantastic version.

See also: Evolutionary Levels and Hollywood Evolution, as well as Ball of Light Transformation.

TV Trope page for list of examples)

• 

• 

(ed note: Hugh Kellard was a member of the Survey. In the academy he was always spouting the glories of the conquest of space. Then something happened. A survey ship crashed on Mercury with Kellard the only survivor. He walked out on the surface and Something Happened. After being rescued, he immediately quit the Survey. At his retirement home, he is unexpectedly visited by his old buddy Halfrich, who is now the leader of Survey.

Halfrich just has one question: What happened to Kellard that made him quit? Since Halfrich has not accepted Kellard's resignation, he can and does drag Kellard back to Mercury to try and find the truth. Kellard tries to be evasive but Halfrich is not taking "no" for an answer. Especially since the radar record shows that Kellard was not alone at the crash site. Halfrich does not know it but Kellard is trying to protect him, and the Survey.

They stand on the surface of Mercury, and Something Happens)

      Morgenson’s voice chattered in their ears. “Blips showing, coming—” And then he suddenly yelled, “I see them! They—”
     Halfrich swung around with ponderous swiftness. There was nothing between them and the fire-fountain, nothing around the spouting flames.
     “Above you, coming down!” shouted Morgenson. “My God, what—?”
     Kellard slowly raised his head. Because he knew what to look for, he saw them while Halfrich was still gazing around searching.
     They came flashing down out of the sky. There were four of them this time—no, five. They were like five individual swirls of shining light, so bright that the sun-bleached heavens seemed to darken around them.
     Halfrich said bewilderedly, “I don’t see—”
     Kellard pointed upward. “There.”
     “Those flakes of flame?”
     “Not flakes of flame,” said Kellard. “They are the children of the stars.”
     Halfrich went rigid, staring upward. And now Kellard knew that there was no more hope. No hope at all.

     The five bright things had flashed down toward the great fire-fountain. They plunged into it, out of it, climbed swift as the eye could follow, racing up its mighty geyser, frolicking in it joyously. The fountain raved higher and the five sped up and whirled and danced upon its rising plume, and Kellard thought that they were laughing. In and out of the leaping fires they plunged, and then one of them veered down toward the place where Halfrich and Kellard stood. There was something so humanly purposeful in its sudden movement that Halfrich stepped back.
     “Stand still.” said Kellard.
     “But—” Halfrich protested.
     “They won’t hurt us,” said Kellard, his voice flat and dull. “They’re friendly, playful, curious. Stand still.”

     And now all five of the flashing flames were around them, darting, recoiling, then gliding forward again to touch their heat-armor with questing tendrils of living force, living light.
     Halfrich spoke, trying to keep his voice steady but forming the words in a choked fashion.
     “Something—in my mind—”
     “They’re telepathic, in a way you can’t even imagine,” said Kellard. “And they’re curious. They’re curious about us, what we are, how we think. They can merge minds with us, somehow.” And he added, with a last cruel impulse of dying anger, “You wanted to know. Now know.”

     He had time to say nothing more before the impact hit him, just as it had that other time, the full stunning shock of unearthly minds interlocking with his own, searching out his thoughts and memories.
     Curious, yes. Like children who have found strange, ungainly creatures and wish to know how they live. And as they entered his mind, Kellard’s mind entered theirs, fused with them, and there was again the dizzying whirl of memories and feelings that were not his own, that his different, more brutishly physical nature could never apprehend more than dimly.

     But that half-apprehension was staggering. He was no longer Hugh Kellard, a man with flesh and bones who had been born on an air-drowned heavy planet named Earth.
     He was one of the children of the stars.

     His memory stretched far back, for his life was almost unlimited in time. For long and long beyond human comprehension he had lived with his companions the strange and beautiful life of their kind.
     Born of the stars, of the unimaginable forces, pressures, temperatures, atomic conditions within the mighty suns. Born, as the end product of an evolutionary chain almost as old as the universe itself, a grouping of photons that grew toward consciousness, toward individuality and volition. Their bodies were force, rather than matter, their senses had nothing to do with sight or hearing, their movement was an effortless flash and glide as fast as the photons of light itself.

---

     With the other kind of life in the universe, the heavy slow-moving things of matter that grew upon the comparatively cold, dark planets, they had had nothing to do at all. They were of the suns, not the planets. and those chill worlds of fixed, solid matter so repelled them that they would not even approach most of them.
     Star-child, star-child, at home in the bursting splendors of the stellar fires, and able to move like light from star to star. And again Kellard felt the agony of that ecstasy that was his in this shared memory.

     “We things of matter, we men, who thought that space and the stars would be ours—”

     But how could the wide universe belong to solid, heavy, physical creatures who must painfully move in bubbles of air, who crawled between the petty planets encased in metal tombs, who could not even approach the glories of the great suns?
     No, the ecstasy was one that men would never know except at secondhand through this brief contact! The glorious rush together of the star-children through the vast abysses, drinking up the energy of the radiation about them. The audacious and dangerous coasting along the shores of dark nebulae, racing the lumbering comets and leaving them behind, on until you felt through all your photons the beckoning warmth of the star you approached. Ignore the cinders called planets that creep around it, speed faster, faster, brothers, the way has been long but we are almost there! And now the radiation that was so weak in the outer darks is strong and lusty-roaring, and the great prominences reach out like arms to gather us in. The shock, the joy, of the first plunge once more into the star. Dive deep, brothers, deep through the outer fires into the throbbing solar furnaces where the atoms are hammered as in forges, changing, shifting their shapes, exploding into force.
     Spin in the vortices of the great stellar tornadoes, fling off and fall headlong and then dive laughing in again. Search for the others of your kind, if there are none here there will be at the next star. Up again, out of the boiling fires, and then drift quiet, dreaming, in the pearly glow of the corona, endless afternoon of warmth and light and peace.

---

     But on the sunward side of the tiny planet nearby, a plaything beckons. Fire and light fountain up from the solid rock. There at least we can go, for that place is washed by tides of solar life, not chilled and dead. Speed down toward it, as the fire, the life it spouts higher out of the repellently fixed and solid matter. Frolic in the fountain, through and around it as it rises higher. And what are the things that move on the rock near it, the things that look grotesquely as though matter had been endowed with life? Reach out with your thought-senses and try to apprehend them. Mind, life—in matter! Try to understand how matter thinks, how matter feels, plumb the grotesque memories of them, the vistas of crawling things at the bottom of whelming air-oceans, things of clay too frail to endure, yet things that in their brief living have come here. But the mind recoils from such memories, such a life.
     Brothers, we go! First to refresh ourselves in the deepest streams of the star, and then away across the abysses to another star we know. There is nothing to hold us here—

     And the oneness was gone from Kellard’s mind, and he was no child of light and stars, he was a man of clay, standing stupid and sick and shaking by the falling fires of the fountain.
     He looked at Halfrich. But Halfrich stood, with his head bowed, and Kellard felt only pity.
     He touched his arm. “We’ll go back to the ship.”
     For a long moment. Halfrich did not respond. Then he turned and walked, plodding with head down, not looking up once at the flaring sky.

---

     In the little ship, he sat later with Kellard. He had not spoken yet, and Morgenson and the others, bewildered and awed, had still not dared ask questions. Finally Halfrich looked at Kellard, pain still in his eyes.
     “I was thinking,” he said. “I was remembering my little boy, years ago. He had just learned to walk, and he started out the door, eager to explore the whole town. He stubbed his toe, and he sat down and cried.”
     “You tried to spare me this,” said Halfrich after a little while. “Thanks for that, Kellard. It didn’t work, but thanks anyway.”

     Kellard said, "Look, no one else knows. No one else is ever likely to know. The only place where the men of matter and the children of stars could meet is a place like Sunside, and how many such meetings would ever by chance happen? We don’t have to tell everyone, to take the heart and eagerness out of them by letting them know they’ll always be second-best in space.”
     Halfrich thought about that. And then he shook his head. “No. We’ve stubbed our toe. We’ve learned we’re not and never will be the sole inheritors of the universe. All right, we’ll accept the fact and go on. The planets will be ours, just the same. And someday—” He paused, then said, “—someday, maybe, the sons of the planets and the children of stars will take hands, know each other. No, Kellard. We’ll tell them.”

• 

• 

(ed note: This charming story from those innocent days when astronomers thought Mercury was tidally braked to Sol. The scene is an observatory based in the twilight belt, observing the Sun on every conceivable frequency. One fine day there is a record-breaking solar prominence. As the astronomers frantically observe it they notice something ... odd. )

      Though this had happened half a dozen times before, it was always exciting. It meant that we could capture some of the very substance of the sun as it went hurtling past in a great cloud of electrified gas. There was no danger; by the time it reached us it would be far too tenuous to do any damage, and, indeed, it would take sensitive instruments to detect it at all.
     One of those instruments was the Observatory’s radar, which was in continual use to map the invisible ionised layers that surround the sun for millions of miles. This was my department; as soon as there was any hope of picking up the oncoming cloud against the solar background, I aimed my giant radio mirror toward it.
     It came in sharp and clear on the long-range screen—a vast, luminous island still moving outward from the sun at hundreds of miles a second. At this distance it was impossible to see its finer details, for my radar waves were taking minutes to make the round trip and to bring me back the information they were presenting on the screen. Even at its speed of not far short of a million miles an hour, it would be almost two days before the escaping prominence reached the orbit of Mercury and swept past us toward the outer planets. But neither Venus nor Earth would record its passing, for they were nowhere near its line of flight.

---

     I switched to the short-range scanner, and the image of the cloud expanded so enormously that only its central portion was on the screen. At the same time I began to change frequency, tuning across the spectrum to differentiate among the various levels. The shorter the wave length, the farther you can penetrate into a layer of ionised gas; by this technique I hoped to get a kind of X-ray picture of the cloud’s interior.
     It seemed to change before my eyes as I sliced down through the tenuous outer envelope with its trailing arms, and approached the denser core. ‘Denser’, of course, was a purely relative word; by terrestrial standards even its most closely packed regions were still a fairly good vacuum. I had almost reached the limit of my frequency band, and could shorten the wave length no farther, when I noticed the curious, tight little echo not far from the centre of the screen.
     It was oval, and much more sharp-edged than the knots of gas we had watched adrift in the cloud’s fiery streams. Even in that first glimpse, I knew that here was something very strange and outside all previous records of solar phenomena. I watched it for a dozen scans of the radar beam, then called my assistant away from the radio-spectrograph, with which he was analysing the velocities of the swirling gas as it spun toward us.

     ‘Look, Don,’ I asked him, ‘have you ever seen anything like that?’
     ‘No,’ he answered after a careful examination. ‘What holds it together? It hasn’t changed its shape for the last two minutes.’
     ‘That’s what puzzles me. Whatever it is, it should have started to break up by now, with all that disturbance going on around it. But it seems as stable as ever.’
     ‘How big would you say it is?’ I switched on the calibration grid and took a quick reading.
     ‘It’s about five hundred miles long, and half that in width.’
     ‘Is this the largest picture you can get?’
     ‘I’m afraid so. We’ll have to wait until it’s closer before we can see what makes it tick.’
     Don gave a nervous little laugh.
     ‘This is crazy,’ he said, ‘but do you know something? I feel as if I’m looking at an amoeba under a microscope.’
     I did not answer; for, with what I can only describe as a sensation of intellectual vertigo, exactly the same thought had entered my mind.

     We forgot about the rest of the cloud, but luckily the automatic cameras kept up their work and no important observations were lost. From now on we had eyes only for that sharp-edged lens of gas that was growing minute by minute as it raced towards us. When it was no farther away than is the moon from Earth, it began to show the first signs of its internal structure, revealing a curious mottled appearance that was never quite the same on two successive sweeps of the scanner.
     By now, half the Observatory staff had joined us in the radar room, yet there was complete silence as the oncoming enigma grew swiftly across the screen. It was coming straight toward us; in a few minutes it would hit Mercury somewhere in the centre of the daylight side, and that would be the end of it—whatever it was. From the moment we obtained our first really detailed view until the screen became blank again could not have been more than five minutes; for every one of us, that five minutes will haunt us all our lives.
     We were looking at what seemed to be a translucent oval, its interior laced with a network of almost invisible lines. Where the lines crossed there appeared to be tiny, pulsing nodes of light; we could never be quite sure of their existence because the radar took almost a minute to paint the complete picture on the screen—and between each sweep the object moved several thousand miles. There was no doubt, however, that the network itself existed; the cameras settled any arguments about that.

     So strong was the impression that we were looking at a solid object that I took a few moments off from the radar screen and hastily focused one of the optical telescopes on the sky. Of course, there was nothing to be seen—no sign of anything silhouetted against the sun’s pock-marked disc. This was a case where vision failed completely and only the electrical senses of the radar were of any use. The thing that was coming toward us out of the sun was as transparent as air—and far more tenuous.

     As those last moments ebbed away, I am quite sure that every one of us had reached the same conclusion—and was waiting for someone to say it first. What we were seeing was impossible, yet the evidence was there before our eyes. We were looking at life, where no life could exist…
     The eruption had hurled the thing out of its normal environment, deep down in the flaming atmosphere of the sun. It was a miracle that it had survived its journey through space; already it must be dying, as the forces that controlled its huge, invisible body lost their hold over the electrified gas which was the only substance it possessed.
     Today, now that I have run through those films a hundred times, the idea no longer seems so strange to me. For what is life but organised energy? Does it matter what form that energy takes—whether it is chemical, as we know it on Earth, or purely electrical, as it seemed to be here? Only the pattern is important; the substance itself is of no significance. But at the time I did not think of this; I was conscious only of a vast and overwhelming wonder as I watched this creature of the sun live out the final moments of its existence.
     Was it intelligent? Could it understand the strange doom that had befallen it? There are a thousand such questions that may never be answered. It is hard to see how a creature born in the fires of the sun itself could know anything of the external universe, or could even sense the existence of something as unutterably cold as rigid nongaseous matter. The living island that was falling upon us from space could never have conceived, however intelligent it might be, of the world it was so swiftly approaching.
     Now it filled our sky—and perhaps, in those last few seconds, it knew that something strange was ahead of it. It may have sensed the far-flung magnetic field of Mercury, or felt the tug of our little world’s gravitational pull. For it had begun to change; the luminous lines that must have been what passed for its nervous system were clumping together in new patterns, and I would have given much to know their meaning. It may be that I was looking into the brain of a mindless beast in its last convulsion of fear—or of a godlike being making its peace with the universe.

     Then the radar screen was empty, wiped clean during a single scan of the beam. The creature had fallen below our horizon, and was hidden from us now by the curve of the planet. Far out in the burning dayside of Mercury, in the inferno where only a dozen men have ever ventured and fewer still come back alive, it smashed silently and invisibly against the seas of molten metal, the hills of slowly moving lava. The mere impact could have meant nothing to such an entity; what it could not endure was its first contact with the inconceivable cold of solid matter.
     Yes, cold. It had descended upon the hottest spot in the solar system, where the temperature never falls below seven hundred degrees Fahrenheit and sometimes approaches a thousand. And that was far, far colder to it than the Antarctic winter would be to a naked man.
     We did not see it die, out there in the freezing fire; it was beyond the reach of our instruments now, and none of them recorded its end. Yet every one of us knew when that moment came, and that is why we are not interested when those who have seen only the films and tapes tell us that we were watching some purely natural phenomenon.
     How can one explain what we felt, in that last moment when half our little little world was enmeshed in the dissolving tendrils of that huge but immaterial brain? I can only say that it was a soundless cry of anguish, a death pang that seeped into our minds without passing through the gateways of the senses. Not one of us doubted then, or has ever doubted since, that he had witnessed the passing of a giant.

     We may have been both the first and the last of all men to see so mighty a fall. Whatever they may be, in their unimaginable world within the sun, our paths and theirs may never cross again. It is hard to see how we can ever make contact with them, even if their intelligence matches ours.
     And does it? It may be well for us if we never know the answer. Perhaps they have been living there inside the sun since the universe was born, and have climbed to peaks of wisdom that we shall never scale. The future may be theirs, not ours; already they may be talking across the light-years to their cousins in other stars.
     One day they may discover us, by whatever strange senses they possess, as we circle around their mighty, ancient home, proud of our knowledge and thinking ourselves lords of creation. They may not like what they find, for to them we should be no more than maggots, crawling upon the skins of worlds too cold to cleanse themselves from the corruption of organic life.
     And then, if they have the power, they will do what they consider necessary. The sun will put forth its strength and lick the faces of its children; and thereafter the planets will go their way once more as they were in the beginning—clean and bright… and sterile.

• 

• 

And now, out among the stars, evolution was driving toward new goals. The first explorers of Earth had long since come to the limits of flesh and blood; as soon as their machines were better than their bodies, it was time to move. First their brains, and then their thoughts alone, they transferred into shining new homes of metal and of plastic.

In these, they roamed among the stars. They no longer built spaceships. They were spaceships.

But the age of the Machine-entities swiftly passed. In their ceaseless experimenting, they had learned to store knowledge in the structure of space itself, and to preserve their thoughts for eternity in frozen lattices of light. They could become creatures of radiation, free at last from the tyranny of matter.

Into pure energy, therefore, they presently transformed themselves; and on a thousand worlds, the empty shells they had discarded twitched for a while in a mindless dance of death, then crumbled into rust.

Now they were lords of the galaxy, and beyond the reach of time. They could rove at will among the stars, and sink like a subtle mist through the very interstices of space. But despite their godlike powers, they had not wholly forgotten their origin, in the warm slime of a vanished sea.

And they still watched over the experiments their ancestors had started, so long ago.

He had quickly realized that he was a specimen in a cosmic zoo, his cage carefully recreated from the images in old television programmes. And he wondered when his keepers would appear, and in what physical form.

How foolish that expectation had been! He knew now that one might as well hope to see the wind, or speculate about the true shape of fire.

• 

(ed note: While reading this quote, the following reference links might help:

Chronology of the universe: Tabular summary

Graphical timeline of the Big Bang

Timeline of epochs in cosmology

)

      There was no place. There was no time. A human observer would have recognized nothing here: no mass, energy, or force. There was only a rolling, random froth whose fragmented geometry constantly changed. Even causality was a foolish dream.
     The orderly spacetime with which humans were familiar was suffused with vacuum energy, out of which virtual particles, electrons and quarks, would fizz into existence, and then scatter or annihilate, their brief walks upon the stage governed by quantum uncertainty. In this extraordinary place whole universes bubbled out of the froth, to expand and dissipate, or to collapse in a despairing flare.
     This chaotic cavalcade of possibilities, this place of nonbeing where whole universes clustered in reefs of foamy spindrift, was suffused by a light beyond light. But even in this cauldron of strangeness there was life. Even here there was mind.

---

     Call them monads.
     This would be the label given them by Commissary Nilis, when he deduced their existence. But the name had much deeper roots.
     In the seventeenth century the German mathematician Gottfried Leibniz had imagined that reality was constructed from pseudo-objects that owed their existence solely to their relation to each other. In his idea of the “monad,” Leibniz had intuited something of the truth of the creatures who infested this domain. They existed, they communicated, they enjoyed a richness of experience and community. And yet “they” didn’t exist in themselves; it was only their relationships to each other that defined their own abstract entities.
     No other form of life was possible in this fractured place.
     Long ago they had attended the birth of a universe.
     It had come from a similar cauldron of realities, a single bubble plucked out of the spindrift. As the baby universe had expanded and cooled, the monads had remained with it. Immanent in the new cosmos, they suffused it, surrounded it. Time to them was not as experienced by the universe’s swarming inhabitants; their perception was like the reality dust of configuration space, perhaps.
     But once its reality had congealed, once the supracosmic froth had cooled, the monads were forced into dormancy. Wrapped up in protective knots of spacetime, they dreamed away the long history of their universe, with all its empires and wars, its tragedies and triumphs. It had been the usual story—and yet it was a unique story, for no two universes were ever quite the same. And something of this long saga would always be stored in the monads’ dreaming.
     The universe aged, as all things must; within, time grew impossibly long and space stretched impossibly thin. At last the fabric of the universe sighed and broke—and a bubble of a higher reality spontaneously emerged, a recurrence of the no-place where time and distance had no meaning. Just as the universe had once been spawned from chaos, so this droplet of chaos was now born from the failing stuff of the universe. Everything was cyclic.
     And in this bubble, where the freezing of spacetime was undone, the monads awoke again; in their supracosmic froth, they were once more briefly alive.

     The monads considered the bubbling foam around them.
     They dug into a reef of spindrift, selected a tangle of possibilities, picked out one evanescent cosmic jewel. This one—yes. They closed around it, as if warmed by its glow of potentialities.
     And, embedding themselves in its structure, they prepared to shape it. The monads enriched the seedling universe with ineffable qualities whose existence few of its inhabitants would even guess at.
     The new universe, for all its beauty, was featureless, symmetrical—but unstable, like a sword standing on its point. Even the monads could not control how that primordial symmetry would be broken, which destiny, of an uncountable number of possibilities, would be selected.
     Which was, of course, the joy of it.
     For the inhabitants of this new cosmos, it began with a singularity: a moment when time began, when space was born. But for the monads, as their chaotic Ur-reality froze out once more into a rigid smoothness, the singularity was an end: for them, the story was already over. Encased in orderly, frozen spacetime, they would slumber through the long ages, until this universe in turn grew old and spawned new fragments of chaos, and they could wake again.
     But all that lay far in the future.
     There was a breathless instant. The sword toppled. Time flowed, like water gushing from a tap.
     History began.

---

     The balancing sword tipped and fell. The primordial simplicity of the new universe was lost. From the broken symmetry of a once-unified physics, two forces emerged: gravity, and a force humans would call the GUT force—“GUT” for Grand Unified Theory, a combination of electromagnetic and nuclear forces. The separating-out of the forces was a phase change, like water freezing to ice, and it released energy that immediately fed the expansion of the seedling universe.
     Gravity’s fist immediately clenched, crushing knots of energy and matter into black holes. It was in the black holes’ paradoxical hearts that the sleeping monads huddled. But the black holes were embedded in a new, unfolding spacetime: three dimensions of space and one of time, an orderly structure that congealed quickly out of the primitive chaos.
     Yet there were flaws. The freezing-out had begun spontaneously in many different places, like ice crystals growing on a cold window. Where the crystals met and merged, discontinuities formed. Because the spacetime was three-dimensional, these defects were born in two dimensions, as planes and sheets—or one dimension, as lines of concentrated energy scribbled across spacetime’s spreading face—or no dimensions at all, simple points.
     Suddenly the universe was filled with these defects; it was a box stuffed with ribbons and strings and buttons.
     And the defects were not inert. Propagating wildly, they collided, combined, and interacted. A migrating point defect could trace out a line; a shifting line could trace out a plane; where two planes crossed, a line was formed, to make more planes and lines. Feedback loops of creation and destruction were quickly established, in a kind of spacetime chemistry. There was a time of wild scribbling.
     Most of these sketches died as quickly as they were formed. But as the networks of interactions grew in complexity, another kind of phase shift was reached, a threshold beyond which certain closed loops of interactions emerged—loops which promoted the growth of other structures like themselves. This was autocatalysis, the tendency for a structure emerging from a richly connected network to encourage the growth of itself, or copies of itself. And some of these loops happened to be stable, immune to small perturbations. This was homeostasis, stability through feedback.
     Thus, through autocatalysis and homeostasis working on the flaws of the young spacetime, an increasingly complex hierarchy of self-sustaining structures emerged. All these tangled knots were machines, fundamentally, heat engines feeding off the flow of energy through the universe. And the black holes, drifting through this churning soup, provided additional points of structure, seeds around which the little cycling structures could concentrate. In the new possibilities opened up by closeness, still more complex aggregates grew: simple machines gathered into cooperative “cells,” and the cells gathered into colonial “organisms” and ultimately multicelled “creatures” …
     It was, of course, life. All this had emerged from nothing.
     In this universe it would always be this way: structures spontaneously complexified, and stability emerged from fundamental properties of the networks—any networks, even such exotica as networks of intersecting spacetime defects. Order emerging for free: it was wonderful. But it need not have been this way.
     Deep in the pinprick gravity wells of the primordial black holes, the feeding began.

---

     The universe inhabited by the spacetime-defect fauna was quite unlike that of humans. There was no light, for instance, for the electromagnetic force which governed light’s propagation had yet to decouple from the GUT superforce. But the spacetime-flaw creatures, huddled around their black holes, could “see” by the deep glow of the gravity waves that crisscrossed the growing cosmos.
     To them, of course, it had always been this way; to them the sky was beautiful.
     The basis of all life in this age was the chemistry of spacetime defects, an interconnected geometric churning of points and lines and planes. Most life-forms were built up of “cells,” tightly interconnected, and very stable. But more complex creatures, built from aggregates of these cells, were not quite so stable. They were capable of variation, one generation to the next.
     And where there is variation, selection can operate.
     On some of the black-hole “worlds,” fantastic ecologies developed: there were birds with wings of spacetime, and spiders with arms of cosmic string, even fish that swam deep in the twisted hearts of the black holes. “Plants” passively fed on energy flows, like the twisting of space at the event horizons of the black holes, and “animals,” exploiters, fed on those synthesizers in turn—and other predators fed on them. Everywhere there was coevolution, as species adapted together in conflict or cooperation: “plants” and “animals,” “flowers” and “insects,” parasites and hosts, predators and prey. Some of this—the duets of synthesizers and exploiters, for instance—had echoes in the ecologies with which humans were familiar. But there were forms like nothing in human experience.
     The creatures of one black hole “world” differed from the inhabitants of another as much as humans would differ from, say, Silver Ghosts. But just as humans and Ghosts were both creatures of baryonic matter who emerged on rocky planets, so the inhabitants of this age, dominated by its own dense physics, had certain features in common.
     All life-forms must reproduce. Every parent must store information, a genotype, to pass on to its offspring. From this data is constructed a phenotype, the child’s physical expression of that information—its “body.”
     In this crowded young universe the most obvious way to transmit such information was through extended quantum structures. Quantum mechanics allowed for the long-range correlation of particles: once particles had been in contact, they were never truly separated, and would always share information.
     Infants were budded, unformed, from parents. But each child was born without a genotype. It was unformed, a blank canvas. A mother would read off her own genotype, and send it to her newborn daughter—by touch, by gravity waves. In the process, depending on the species, the mother’s data might be mixed with that of other “parents.”
     But there was a catch. This was a quantum process. The uncertainty principle dictated that it was impossible to clone quantum information: it could be swapped around, but not copied. For the daughter to be born, the mother’s genotype had to be destroyed. Every birth required a death.
     To human eyes this would seem tragic; but humans worked on different assumptions. To the spacetime fauna, life was rich and wonderful, and the interlinking of birth and death the most wonderful thing of all.
     As consciousness arose, the first songs ever sung centered on the exquisite beauty of necrogenesis.

---

     As the young universe unfolded, some of the spacetime-chemistry races developed high technologies. They ventured from their home “worlds,” and came into contact with each other. Strange empires were spun across galaxies of black holes. Terrible wars were fought.
     Out of the debris of war, the survivors groped their way to a culture that was, if not unified, at least peaceable. A multispecies federation established itself. Under its benevolent guidance new merged cultures propagated, new symbiotic ecologies arose. The endless enrichment of life continued. The inhabitants of this golden time even studied their own origins in the brief moments of the singularity. They speculated about what might have triggered that mighty detonation, and whether any conscious intent might have lain behind it.
     Time stretched and history deepened.
     It was when the universe was very old indeed—ten billion times as old as it had been at the moment of the breaking of its primordial symmetry—that disaster struck.

     Light itself did not yet exist, and yet lightspeed was embedded in this universe.
     At any given moment, only a finite time had passed since the singularity, and an object traveling at lightspeed could have traversed only part of the span of the cosmos. Domains limited by lightspeed travel were the effective “universes” of their inhabitants, for the cosmos was too young for any signal to have been received from beyond their boundaries. But as the universe aged, so signals propagated further—and domains which had been separated since the first instant, domains which could have had no effect on each other before, were able to come into contact.
     And as they overlapped, life-forms crossed from one domain into another.
     For the federation, the creatures that suddenly came hurtling out of infinity were the stuff of nightmare. These invaders came from a place where the laws of physics were subtly different: the symmetry-breaking which had split gravity from the GUT superforce had occurred differently in different domains, for they had not been in causal contact at the time. That difference drove a divergence of culture, of values. The federation valued its hard-won prosperity, peace, and the slow accumulation of knowledge. The invaders, following their own peculiar imperatives, were intent only on destruction, and fueling their own continuing expansion. It was like an invasion from a parallel universe. Rapprochement was impossible.
     The invaders came from all around the federation’s lightspeed horizon. Reluctantly, the federation sought to defend itself, but a habit of peace had been cultivated for too long; everywhere the federation fell back. It seemed extinction was inevitable.
     But one individual found a dreadful alternative.
     Just as the cosmos had gone through a phase change when gravity had separated from the GUT force, so more phase changes were possible. The GUT force itself could be induced to dissociate further. The energy released would be catastrophic, unstoppable, universal—but, crucially, it would feed a new burst of universal expansion.
     The homelands of the invaders would be pushed back beyond the lightspeed horizon.
     But much of the federation would be scattered too. And, worse, a universe governed by a new combination of physical forces would not be the same as that in which the spacetime creatures had evolved. It would be unknowable, perhaps unsurvivable.
     It was a terrible dilemma. Even the federation was unwilling to accept the responsibility to remake the universe itself. But the invaders encroached, growing more ravenous, more destructive, as they approached the federation’s rich and ancient heart. In the end there was only one choice.
     A switch was thrown.

     A wall of devastation burned at lightspeed across the cosmos. In its wake the very laws of physics changed; everything it touched was transformed.
     The invaders were devastated.
     The primordial black holes survived—and, by huddling close to them, so did some representatives of the federation.
     But the federation’s scientists had not anticipated how long this great surge of growth would continue. With the domain war long won, the mighty cosmic expansion continued, at rates unparalleled in the universe’s history. Ultimately, it would last sixty times the age of the universe at its inception, and it would expand the federation’s corner of spacetime by a trillion, times a trillion, times a trillion, times a trillion. Human scientists, detecting the traces of this great burst of “inflation,” the single worst catastrophe in the universe’s long history, would always wonder what had triggered it. Few ever guessed it was the outcome of a runaway accident triggered by war.
     As the epochal storm continued the survivors of the federation huddled, folding their wings of spacetime flaws over themselves. When the gale at last passed, the survivors emerged into a new, chill cosmos. So much time had passed that they had changed utterly, and forgotten who they were, where they had come from. But they were heirs of a universe grown impossibly huge—a universe all of ten centimeters across.

---

• 

     The monstrous swelling of the age of inflation was over.
     The universe continued to expand, more sedately than before, but relentlessly. Still phase changes occurred, as the merged forces broke up further, and with each loss of symmetry more energy was injected into the expansion.
     The release of the electromagnetic force from its prison of symmetry was particularly spectacular, for suddenly it was possible for light to exist. The universe lit up in a tremendous flash—and space filled immediately with a bath of searing radiation. So energetically dense was this first exuberant glow that it continually coalesced into specks of matter—quarks and antiquarks, electrons and positrons—that would almost as rapidly annihilate each other. There were no atoms yet, though, no molecules. Indeed, temperatures were too high for the quarks to combine into anything as sedate as a proton.
     The primordial black holes, surviving from the age of spacetime chemistry, again provided some structure in this seething chaos; passing through the glowing soup they would gather clusters of quarks or antiquarks. Though the quarks themselves continually melted away, the structure of these clusters persisted; and in those structures were encoded information. Interactions became complex. Networks and loops of reactions formed, some were reinforced by feedback loops.
     Certain consequences inevitably followed. For this universe it was already an old story—but it was a new generation of life.
     But this was a universe of division. For every particle of matter created there was an antimatter twin. If they met they would mutually annihilate immediately. It was only chance local concentrations of matter, or antimatter, that enabled any structures to form at all.
     In these intertwined worlds of matter and antimatter, parallel societies formed. Never able to touch, able to watch each other only from afar, they nevertheless made contact, exchanging information and images, science and art, reciprocally influencing each other at every stage. Mirror-image cultures evolved, each seeking to ape the achievements of the unreachable other. There were wars too, but these were always so devastating for both sides that mutual deterrence became the only possible option. Even a few impossible, unrequitable parity-spanning love affairs were thrown up.
     The fundamental division of the world was seen as essentially tragic, and inspired many stories.
     The various matter species, meanwhile, were not the only inhabitants of this ferocious age. They shared their radiation bath with much more ancient life-forms. To the survivors of the spacetime-chemistry federation, this age of an endless radiation storm was cold, chill, empty, the spacetime defects which characterized their kind scattered and stretched to infinity. But survive they had. Slowly they moved out of their arks and sought new ways to live.

---

     Among the cultures of matter and antimatter, clinging to their evanescent quark-gluon islands in a sea of radiation, a crisis approached.
     As the universe cooled, the rate of production of quarks and antiquarks from the radiation soup inevitably slowed—but the mutual destruction of the particles continued at a constant rate. Scientists on each side of the parity (antimatter) barrier foresaw a time when no more quarks would coalesce—and then, inevitably, all particles of matter would be annihilated, as would the precisely equal number of particles of antimatter, leaving a universe filled with nothing but featureless, reddening light. It would mean extinction for their kinds of life; it was hardly a satisfactory prospect.
     Slowly but surely, plans were drawn up to fix this bug in the universe. At last an empire of matter-cluster creatures discovered that it was possible to meddle with the fundamental bookkeeping of the cosmos.
     Human scientists would express much of their physics in terms of symmetries: the conservation of energy, for instance, was really a kind of symmetry. And humans would always believe that a certain symmetry of a combination of electrical charge, left- and right-handedness, and the flow of time could never be violated. But now quark-gluon scientists dug deep into an ancient black hole, which had decayed to expose the singularity at its heart. The singularity was like a wall in the universe—and by reaching through this wall the quark scientists found a way to violate the most fundamental symmetry of all.
     The imbalance they induced was subtle: for every thirty million antimatter particles, thirty million and one matter particles would be formed—and when they annihilated, that one spare matter particle would survive.
     The immediate consequence was inevitable. When the antimatter cultures learned they were to be extinguished while their counterparts of matter would linger on, there was a final, devastating war; fleets of opposing parity annihilated each other in a bonfire of possibilities.
     Enough of the matter cultures survived to carry through their program. But it was an anguished victory; even for the victors only a fraction could survive.
     Another metaphorical switch was pulled.

     Across the cooling cosmos, the mutual annihilation continued to its conclusion. When the storm of co-destruction ceased, when all the antimatter was gone, there was a trace of matter left over. Another mystery was left for the human scientists of the future, who would always wonder at the baffling existence of an excess of matter over antimatter.
     Yet again the universe had passed through a transition; yet again a generation of life had vanished, leaving only scattered survivors, and the ruins of vanished and forgotten civilizations. For its few remaining inhabitants the universe now seemed a very old place indeed, old and bloated, cool and dark.
     Since the singularity, one millionth of a second had passed.

---

     The universe was expanding at half the speed of light. It was small and ferociously dense, still many times as dense as an atomic nucleus.
     At least quarks were stable now. But in this cannonball of a cosmos the matter familiar to humans, composed of protons and neutrons—composites of quarks, stuck together by gluons—could not yet exist. There were certainly no nuclei, no atoms. Instead, space was filled with a soup of quarks, gluons and leptons, light particles like electrons and neutrinos. It was a “quagma,” a magma of quarks, like one immense proton.
     As time wore inexorably away, new forms of life rose in the new conditions.
     The now-stable quarks were able to combine into large assemblies; and as these assemblies complexified and interacted, the usual processes of autocatalysis and feedback began. The black holes were still there to provide structure, but larger clumps of matter also served as a stratum for life’s new adventures, and there was energy for free in the radiation bath that still filled the universe.
     Among the new kinds, ancient strategies revived. There were exploiters and synthesizers. “Plants” fueled their growth with radiant energy—but there were no stars yet, no suns; rather the whole sky glowed. “Animals” evolved to feed off these synthesizers, and learned to hunt each other.
     As always the variation in life-forms across the cosmos was extraordinarily wide, but most shared certain basics of their physical design. Almost all of them stored information about themselves in their own complicated structures, rather than in an internal genetic data store, as humans one day would: for these creatures their genotype was their phenotype, as if they were made wholly of DNA.
     Their way of communicating would have seemed ferocious to a human. A speaker would modify its listener’s memories directly, by firing quagma pellets into them; it was a message carried in a spray of bullets. They even reproduced rather like DNA molecules. They opened out their structures, like flowers unfolding, and constructed a mirror-image version of themselves by attracting raw material from the surrounding soup of loose quarks. These “quagmites” were not quite like the creatures humans would one day encounter in the Galaxy’s Core, but they were their remote ancestors.
     There was little in common in the physical basis of human and quagmite; a quagmite was not much bigger than an atomic nucleus. But the largest of the quagma creatures were composed of a similar number of particles to the atoms which would comprise a human body. So humans and quagmites were comparable in internal complexity, and their inner lives shared a similar richness. Many humans would have appreciated the best quagmite poetry—if they could have survived being bombarded by it.
     Meanwhile, the quagmite creatures shared their universe with older forms of life.
     The ancient spacetime-chemistry creatures, having survived yet another cosmic transition, gradually found ways to accommodate themselves to the latest climate, even though to them it was cold and dark and dead. In their heyday there had been no “matter” in the normal sense. But now they found they could usefully form symbiotic relationships with creatures formed of condensate matter: extended structures locked into a single quantum state. A new kind of being ventured cautiously through the light-filled spaces, like insects with “bodies” of condensate and “wings” of spacetime defects. It was the formation of a new kind of ecology, emerging from fragments of the old and new. But symbiosis and the construction of composite creatures from lesser components were eternal tactics for life, eternal ways of surviving changed conditions.
     In the unimaginably far future humans would call the much-evolved descendants of these composite forms “Xeelee.”
     The proto-Xeelee were, meanwhile, aware of another species of matter born out of this turbulent broth. This would one day be called dark matter by human scientists, for it would bond with other types of matter only loosely, through gravity and the weakest nuclear force. There was a whole hierarchy of particles of this stuff, even a sort of chemistry. This faint stuff passed through the quark-cluster cities and the nests of the proto-Xeelee alike as if they didn’t exist. But it was there—and, like the Xeelee, this dark matter was going to be around for good.

     As the endless expansion continued, the quagmites swarmed through their quagma broth, fighting and loving and dying. The oldest of them told their legends of the singularity. The young scoffed, but listened in secret awe.
     It seemed to the quagmites that the ages that had preceded their own had been impossibly brief, a mere flash in the afterglow of the singularity. But it was a common error. The pace of life scaled to temperature: if you lived hot, you lived fast. The quagmites did not suspect that the creatures who had inhabited earlier, warmer ages had crammed just as many experiences—just as much “life”—into their brief instants of time. As the universe expanded, every generation, living slower than the last, saw only a flash of heat and light behind it, nothing but a cold dark tunnel ahead—and each generation thought that it was only now that a rich life was possible.
     The comfortable era of the quagmites couldn’t last forever; nothing ever did. It was when the universe was thirty times older than it was at the end of the matter-antimatter conflict that the first signs of the quagmites’ final disaster were detected.

---

     The trouble started in the most innocuous, most mundane of ways: problems with waste.
     For many quagmite kinds, eliminated waste was in the form of compressed matter, quarks and gluons wadded together into baryons—protons and neutrons. You could even find a few simple nuclei, if you dug around in there. But the universe was still too hot for such structures to be stable long, and the waste decayed quickly, returning its substance to the wider quagma bath.
     Now, as the universe cooled, things changed. The mess of sticky proton-neutron cack simply wouldn’t dissolve as readily as it once had. Great clumps of it clung together, stubbornly resistant, and had to be broken up to release their constituent quarks. But the energy expenditure was huge.
     Soon this grew to be an overwhelming burden, the primary task of civilizations. Citizens voiced concerns; autocrats issued commands; angry votes were taken on councils. There were even wars over waste dumping. But the problem only got worse.
     And, gradually, the dread truth was revealed.
     The cooling universe was approaching another transition point, another phase change. The ambient temperature, steadily falling, would soon be too low to force the baryons to break up—and the process of combination would be one way. Soon all the quarks and gluons, the fundamental building blocks of life, would be locked up inside baryons.
     The trend was inescapable, its conclusion staggering: this extraordinary implosion would wither the most bright, the most beautiful of the quagmite ecologies, and nobody would be left even to mourn.
     As the news spread across the inhabited worlds, a cosmic unity developed. Love and hate, war and peace were put aside in favor of an immense research effort to find ways of surviving the impending baryogenetic catastrophe.
     A solution was found. Arks were devised: immense artificial worlds, some as much as a meter across, their structures robust enough to withstand the collapse. It was unsatisfactory; the baryogenesis could not be prevented, and almost everything would be lost in the process. But these ships of quagma would sail beyond the end of time, as the quagmites saw it, and in their artificial minds they would store the poetry of a million worlds. It was better than nothing.
     As time ran out, as dead baryons filled up the universe and civilizations crumbled, the quagma arks sailed away. But mere survival wasn’t enough for the last quagmites. They wanted to be remembered.

---

     The universe was now about the size of Sol system, and still swelling.
     And even before baryogenesis was complete, another transition was approaching. The new baryons gathered in combinations of two, three, four, or more. These were atomic nuclei—although nothing like atoms, with their extended clouds of electrons, could yet exist; each nucleus was bare.
     These simple nuclei spontaneously formed from the soup of protons and neutrons, but the background radiation was still hot enough that such clusters were quickly broken up again. That would soon change, though: just as there had been a moment when matter could no longer evaporate back to radiant energy, and a moment when quarks no longer evaporated out of baryons, soon would come a time when atomic nuclei became stable, locking up free baryons. This was nucleosynthesis.
     For the last quagmites, huddled in their arks, it was hard to imagine any form of life that could exploit such double-dead stuff, with quarks locked inside baryons locked inside nuclei. But from a certain point on, such nuclear matter must inevitably dominate the universe, and any life that arose in the future would be constructed of it.
     The quagmites wanted to be remembered. They had determined that any creatures of the remote future, made of cold, dead, nuclear stuff, would not forget them. And they saw an opportunity.
     At last the moment of nucleosynthesis arrived.
     The universe’s prevailing temperature and pressure determined the products of this mighty nucleus-baking. Around three-quarters of the nuclei formed would be hydrogen—simple protons. Most of the rest would be helium, combinations of four baryons. Any nuclei more complex would be—ought to be—vanishingly rare; a universe of simple elements would emerge from this new transition.
     But the quagmites saw a way to change the cosmic oven’s settings.
     The fleet of arks sailed through the cosmos, gathering matter with gauzy magnetic wings. Here a knotted cloud was formed, there a rarefied patch left exposed. They worked assiduously, laboring to make the universe a good deal more clumpy than it had been before. And this clumpiness promoted the baking, not just of hydrogen and helium nuclei, but of a heavier nucleus, a form of lithium—three protons and four neutrons. There was only a trace of it compared to the hydrogen and helium; the quagmites didn’t have enough power to achieve more than that. Nevertheless there was too much lithium to be explained away by natural processes.
     The scientists of the ages to follow would indeed spot this anomalous “lithium spike,” and would recognize it for what it was: a work of intelligence. At last cold creatures would come to see, and the quagmite arks would begin to tell their story. But that lay far in the future.
     With the subatomic drama of nucleosynthesis over, the various survivors sailed resentfully on. There were the last quagmites in their arks, and much-evolved descendants of the spacetime-condensate symbiotes of earlier times yet, all huddling around the primordial black holes. To them the universe was cold and dark, a swollen monster where the temperature was a mere billion degrees, the cosmic density only about twenty times water.The universe was practically a vacuum, they complained, and its best days were already behind it.
     The universe was three minutes old.

---

• 

     The impoverished universe expanded relentlessly.
     Space was filled with a bath of radiation, reddening as the expansion stretched it, and by a thin fog of matter. Most of this was dark matter, engaged in its own slow chemistry. The baryonic matter—“light” matter—was a trace that consisted mostly of simple nuclei and electrons. Any atoms that formed, as electrons hopefully gathered around nuclei, were immediately broken up by the still-energetic radiation. Without stable atoms, no interesting chemistry could occur. And meanwhile the ionic mist scattered the radiation, so that the universe was filled with a pale, featureless glow. The cosmos was a bland, uninteresting place, endured with resentment by the survivors of gaudier eras.
     Nearly four hundred thousand years wore away, and the universe inflated to a monstrous size, big enough to have enclosed the Galaxy of Pirius’s time.
     Then the epochal cooling reached a point where the photons of the radiation soup were no longer powerful enough to knock electrons away from their nuclear orbits. Suddenly atoms, mostly hydrogen and helium, coalesced furiously from the mush of nuclei and electrons. Conversely, the radiation was no longer scattered: the new atomic matter was transparent.
     The universe went dark in an instant. It was perhaps the most dramatic moment since the birth of light itself, many eras past.
     To the survivors of earlier times, this new winter was still more dismaying than what had gone before. But every age had unique properties. Even in this desolate chill, interesting processes could occur.

     The new baryonic atoms were a mere froth on the surface of the deeper sea of dark matter. The dark stuff, cold and gravitating, gathered into immense wispy structures, filaments and bubbles and voids that spanned the universe. And baryonic matter fell into the dark matter’s deepening gravitational wells. There it split into whirling knots that split further into pinpoints, that collapsed until their interiors became so compressed that their temperatures matched that of the moment of nucleosynthesis.
     In the hearts of the young stars, nuclear fusion began. Soon a new light spread through the universe. The stars gathered into wispy hierarchies of galaxies and clusters and superclusters, all of it matching the underlying dark matter distribution.
     Stars were stable and long-lasting fusion machines, and in their hearts light elements were baked gradually into heavier ones: carbon, oxygen, nitrogen. When the first stars died, they scattered their heavy nuclei through space. These in turn were gathered into a second generation of stars, and a third—and from this new, dense material still more interesting objects formed, planets with rocky hearts, that swooped on unsteady orbits around the still-young stars.
     In these crucibles life evolved.
     Here, for instance, was the young Earth. It was a busy place. Its cooling surface was dotted with warm ponds in which a few hundred species of carbon-compound chemicals reacted furiously with each other, producing new compounds which in turn interacted in new ways. The networks of interactions quickly complexified to the point where autocatalytic cycles became possible, closed loops which promoted their own growth; and some of these autocatalytic cycles chanced upon feedback processes to make themselves stable; and, and . . .
     Autocatalysis, homeostasis, life.
     Shocked into awareness, humans mastered their environment, sailed beyond the planet of their birth, and wondered where they had come from.

     It seemed to the humans that the ages that had preceded their own had been impossibly brief, a mere flash in the afterglow of the singularity, and they saw nothing but a cold dark tunnel ahead. They thought that it was only now that a life as rich as theirs was possible. It was a common mistake. Most humans never grasped that their existence was a routine miracle.
     But they did learn that this age of stars was already declining. The peak of star formation had come, in fact, a billion years before the birth of Earth itself. By now more stars were dying than were being born, and the universe would never again be as bright as it had in those vanished times before.
     Not only that, humans started to see, but other forces were at work to accelerate that darkening.
     For humans, the universe suddenly seemed a dangerous place.

---

     In this age of matter the proto-Xeelee found new ways to survive. Indeed, they prospered. They formed new levels of symbiosis with baryonic-matter forms. The new form—a composite of three ages of the universe—was the kind eventually encountered by humans, who would come to call them by a distorted anthropomorphic version of a name in an alien tongue: they were, at last, Xeelee.
     But soon the new Xeelee faced an epochal catastrophe of their own.
     They still relied on the primordial black holes, formed in the earliest ages after the singularity; they used the holes’ twisted knots of spacetime to peel off their spacetime-defect “wings,” for instance. But now the primordial holes were becoming rare: leaking mass-energy through Hawking radiation, they were evaporating. By the time humanity arose, the smallest remaining holes were the mass of the Moon.
     It was devastating for the Xeelee, as if for humans the planet Earth had evaporated from under their feet.
     But a new possibility offered itself. New black holes were formed from the collapse of giant stars, and at the hearts of galaxies, mergers were spawning monsters with the mass of a million Sols. Here the Xeelee migrated. The transition wasn’t easy; a wave of extinction followed among their diverse kind. But they survived, and their story continued.
     And it was the succor of the galaxy-center black holes that first drew the Xeelee into contact with dark matter.

---

     There was life in dark matter, as well as light (baryonic matter).
     Across the universe, dark matter outweighed the baryonic, the “light,” by a factor of six. It gathered in immense reefs hundreds of thousands of light-years across. Unable to shed heat through quirks of its physics, the dark material was resistant to collapse into smaller structures, the scale of stars or planets, as baryonic stuff could.
     Dark and light matter passed like ghosts, touching each other only with gravity. But the pinprick gravity wells of the new baryonic stars were useful. Drawn into these wells, subject to greater concentrations and densities than before, new kinds of interactions between components of dark matter became possible.
     In this universe, the emergence of life in dark matter was inevitable. In their earliest stages, these “photino birds” swooped happily through the hearts of the stars, immune to such irrelevances as the fusion fire of a sun’s core.
     What did disturb them was the first stellar explosions—and with them the dissipation of the stars’ precious gravity wells, without which there would be no more photino birds.
     Almost as soon as the first stars began to shine, therefore, the photino birds began to alter stellar structures and evolution. If they clustered in the heart of a star they could damp the fusion processes there. By this means the birds hoped to hurry a majority of stars through the inconvenience of explosions and other instabilities and on to a dwarf stage, when an aging star would burn quietly and coldly for aeons, providing a perfect arena for the obscure dramas of photino life. A little later the photino birds tinkered with the structures of galaxies themselves, to produce more dwarfs in the first place. Thus it was that humans found themselves in a Galaxy in which red dwarf stars, stable, long-lived and unspectacular, outnumbered stars like their own sun by around ten to one. This was hard to fit into any naturalistic story of the universe, though generations of astrophysicists labored to do so: like so many features of the universe, the stellar distribution had been polluted by the activities of life and mind. It would not be long, though, before the presence of the photino birds in Earth’s own sun was observed.
     The Xeelee had been troubled by all this much earlier.
     The Xeelee cared nothing for the destiny of pond life like humanity. But by suppressing the formation of the largest stars, the birds were reducing the chances of more black holes forming. What made the universe more hospitable for the photino birds made it less so for the Xeelee. The conflict was inimical.
     The Xeelee began a grim war to push the birds out of the galaxies, and so stop their tinkering with the stars. The Xeelee had already survived several universal epochs; they were formidable and determined. Humans would glimpse silent detonations in the centers of galaxies, and they would observe that there was virtually no dark matter to be observed in galaxy centers. Few guessed that this was evidence of a war in heaven.
     But the photino birds turned out to be dogged foes. They were like an intelligent enemy, they were like a plague, and they were everywhere; and for some among the austere councils of the Xeelee there was a chill despair that they could never be beaten.
     And so, even as the war in the galaxies continued, the Xeelee began a new program, much more ambitious, of still greater scale.
     Their immense efforts caused a concentration of mass and energy some hundred and fifty million light-years from Earth’s Galaxy. It was a tremendous knot that drew in galaxies like moths across three hundred million light-years, a respectable fraction of the visible universe. Humans, observing these effects, called the structure the Great Attractor—or, when one of them journeyed to it, Bolder’s Ring.
     This artifact ripped open a hole in the universe itself. And through this doorway, if all was lost, the Xeelee planned to flee. They would win their war—or they would abandon the universe that had borne them, in search of a safer cosmos.
     Humans, consumed by their own rivalry with the Xeelee, perceived none of this. To the Xeelee—as they fought a war across hundreds of millions of light-years, as they labored to build a tunnel out of the universe, as stars flared and died billions of years ahead of their time—humans, squabbling their way across their one Galaxy, were an irritant.
     A persistent irritant, though.

---

     The monads cared nothing for humans, of course, or for quagmites, or Xeelee, or photino birds, or any of the rest of the universe’s menagerie at this or any other age. But they liked their universes to have story; and it was living things that generated the most interesting sagas.
     And so in the time before time, when they picked out their seedling universes from the reef of possibilities, the monads, midwives of reality, exerted a subtle selection pressure. They chose for enrichment only the brightest bubbles in the cosmic spindrift: bubbles with a special, precious quality. A tendency to complexify.

     Thoughtful beings, human and otherwise, would wonder at the endless fecundity of their universe, a universe that spawned life at every stage of its existence—and wonder why it had to be so.
     Some of them came to understand that it was the universe’s own innate tendency to complexify that had created the richness of structure within it.
     Simple laws of molecular combination governed the growth of such intricate, inanimate forms as snowflakes and DNA molecules. But autocatalysis and homeostasis enabled simple structures to interact and spin off more complex structures still, until living things emerged, which combined into ever more complicated entities.
     The same pattern showed in other aspects of reality. The hive structures of ant colonies and Coalescent communities emerged without conscious design from the small decisions of their drones. Even in the world of human ideas, the structures of religions, economies, and empires fed back on themselves and became ever richer. Even mathematical toys, like games of artificial life run in computer memories, seemed to demonstrate an unwavering tendency to grow more complicated. But then, human mathematics was a mirror of the universe humans found themselves in; that was why mathematics worked.
     Complexifying seemed inevitable. But it was not. A universe could be imagined without this tendency.
     If the ability to complexify had suddenly been turned off, the universe would have seemed very different. Snowflakes would not form, birds would not flock, ants and Coalescents would have tumbled out of their disintegrating hives, baffled. On larger scales, economic and historical cycles would break up. Ecosystems would fail; there would be no coral reefs, no forests. The great cycles of matter and energy, mediated by life, on a living world like Earth would collapse.
     But of course there would be no observers of such catastrophes, for without complexity’s search for feedback loops and stable processes, hearts could not beat, and embryos could not form.
     Humans had the good fortune to exist in a universe in which there was no law of conservation of complexity, no limit to its supply.
     But it didn’t have to be that way. That the universe could complexify, that richness of existence was possible at all, was thanks to the monads, and their subtle pan-cosmic selection. The monads had selected, designed, nurtured a universe that would be fruitful forever, in which there was no limit to the possibilities for life and energy, for life and mind, as far ahead as it was possible to look. While empires rose and fell, while the universe continued its endless unraveling of possibility after possibility, the monads slumbered. They had done their work, made their contribution. Now they waited for the precious moments of the furthest future when this universe, in turn grown old, spawned new fragments of chaos, and they could wake again.
     But in their epochal sleep, even the monads could be drawn into history. And even they could be harmed.

...The thing's bodily structure was RTSL, to four places. No gross digestive tract - atmosphere-nourished or an energy-converter, perhaps. Beyond four places was pretty dim, but Q P arms and legs - Dhilian, eh? - would fit, and so would an R-type hide.

...As she was wafted gently across the intervening space upon a pencil of force, Kathryn took her first good look at the precisionist himself-or herself. She - it - looked something like a Dhilian, she thought at first. There was a squat, powerful, elephantine body with its four stocky legs; the tremendous double shoulders and enormous arms; the domed, almost immobile head. But there the resemblance ended. There was only one head-the thinking head, and that one had no eyes and was not covered with bone. There was no feeding head-the thing could neither eat nor breathe. There was no trunk. And what a skin!

It was worse than a hide, really-worse even than a Martian's. The girl had never seen anything like it. It was incredibly thick, dry, pliable; filled minutely with cells of a liquid-gaseous something which she knew to be a more perfect insulator even than the fibres of the tegument itself.

"R-T-S-L-Q-P." She classified the creature readily enough to six places, then stopped and wrinkled her forehead. "Seventh place-that incredible skin-what? S? R? T? It would have to be R . . .

..."VWZY, to four places." Con concentrated. "Multi-legged. Not exactly carapaceous, but pretty nearly. Spiny, too, I believe. The world was cold, dismal, barren; but not frigid, but he-it-didn't seem exactly like an oxygen-breather - more like what a warm-blooded Palainian would perhaps look like, if you can imagine such a thing. VWZYTXSYZY to ten places.

...Classification, straight Z's to ten or twelve places, she - or it - seemed to be trying to specify. A frigid race of extreme type, adapted to an environment having a temperature of approximately one degree absolute.

...physically, his classification to four places is TUUV; quite a bit like the Nevians, you notice.To ten places it was TUUVWYXXWT.

Conway muted the speaker which carried the conversation between ship and receptionist into the gallery and said, "This is as good a time as any to explain our physiological classification system to you. Briefly, that is, because later there will be special lectures on this subject."

Clearing his throat, he began, "In the four-letter classification system the first letter indicates the level of physical evolution, the second denotes the type and distribution of limbs and sense organs and the other two the combination metabolism and pressure and gravity requirements, which in turn give an indication of the physical mass and form of protective tegument possessed by the being. I must mention here, in case any of you might feel inferior regarding your classification, that the level of physical evolution has no relation to the level of intelligence...

Species with the prefix A, B and C, he went onto explain, were water breathers. On most worlds life had originated in the sea and these beings had developed high intelligence without having to leave it. D through F were warm-blooded oxygen-breathers, into which group fell most of the intelligence races in the galaxy, and the G and K types were also oxygen breathing but insectile. The Ls and Ms were light-gravity, winged beings.

Chlorine-breathing life-forms were contained in the 0 and P groups, and after that came the more exotic, the more highly-evolved physically and the downright weird types. Radiation-eaters, frigid-blooded or crystalline beings, and entities capable of modifying their physical structure at will. Those possessing extra-sensory powers sufficiently well-developed to make walking or manipulatory appendages unnecessary were given the prefix V, regardless of size or shape.

Conway admitted to anomalies in the system, but these could be blamed on the lack of imagination by its originators. One of the species present in the observation gallery was a case in point - the AACP type with its vegetable metabolism. Normally the A prefix denoted a water breather, there being nothing lower in the system than the piscatorial life forms. But the AACPs were vegetables and plants had come before fish.