N-Space

by Larry Niven

  “Guardian, that’s classified.”

  The man was within his rights. Maxell changed the subject. “Captain Ling, we are gathering civilization. Why is it that any tree doesn’t come to us right away?”

  Harp’s music had faded: she was listening.

  “Our ships go out through the Smoke Ring to find the places of Man. We talk. We leave word how to find the Admiralty. We leave plans for steam rockets. You need a way to move your tree anyway, because any passage past Gold can hurl you out into the gas torus where you’ll suffocate.”

  “We built our rocket without help,” Ling said. Alin Newbry said nothing.

  A tree couldn’t just drift into the Grove, could it? Sure it could. It wasn’t likely, but it could happen…and a treeful of climbers might well enjoy bewildering the all-powerful Admiralty.

  “The Admiralty is the center of knowledge throughout the Smoke Ring. Why would any tribe hesitate?”

  Harp was quietly settling between Curtz and Stevn.

  Ling said, “I wouldn’t want to offend our rescuers.”

  “I seriously want to know, Captain.”

  Captain Ling said, “Well, your Admiralty isn’t all good.”

  “How so?”

  “The air’s thick with garbage.”

  “There are garbage collectors.”

  “They don’t collect it all.”

  Ling had hit a nerve. The garbage problem had increased with the population, even in Maxell’s brief lifespan.

  Ling said, “We don’t visit the Clump that often, but word does pass among the trees, Guardian. We’re told about the garbage, the crime rate…theft…violence…fringe addiction.”

  “Don’t you have these things in a tree?”

  “Not really. We know each other, don’t you see? You can’t use what you steal. It’ll be recognized. If you’re a bully, six of us other bullies will give you flying lessons, and if it keeps up, you’ll do it without wings. Fringe…well, fringe is fun, but it messes up your head. But nobody robs somebody for fringe. He finds it on the trunk. If he gets too fond of the stuff, we’ll still take care of him. He’ll be keeping the cookpot clean instead of hunting.”

  He was getting reasonable answers. Joy! Maxell asked, “Couldn’t you be robbed by another tree?”

  “They’d face hunting tools. Knives, harpoons, bows. But your Navy doesn’t like it when climbers carry those things in the Clump, so we can be robbed there.”

  “Rescue?”

  Harp spoke just beside him. “We hear stories about that too. We’re in debt now, aren’t we?”

  Again? “Well, yes and no, Harp. The Admiralty thinks that charity works best if it pays for itself.”

  “If I don’t understand that right away, it’s because Capability Tree never heard about money until we reached the Grove. So how are we expected to pay?”

  “Labor, and there’s no hurry. You’ll pay some of the debt in mud.”

  “Mud?”

  “You have property rights in the mud that was the core of your tree. That stuff makes fine fertilizer.”

  Harp laughed.

  Dunninger said, “I hauled mud myself before I joined the Navy.”

  Alin Newbry asked, “Can that be done with kites?”

  “That’s how we did it.” Dunninger lifted his arms. “See?”

  “Kiteman?”

  “Right.”

  “If Brighton had had money, we could have just bought kites from a passing citizen. And kite-making instructions. And flying lessons. I don’t mind how hard I had to work for my kites,” Newbry said, “but what are we missing that we never thought of? We should have gone to the Clump long before. Then again…mud. We’d be competing with Admiralty kitemen. And you’ve been at it a lot longer than we have.”

  “Yup. And we’ve got ships to haul the bigger blocks. Too bad,” said Dunninger.

  Renho said, “You’re closer, though.”

  “About ten times closer.” Newbry was suffering badly from indecision.

  “You could be in there now,” Dunninger said. “Can’t deal with the Admiralty unless you tree has money. The Vivarium pays money for mud. Half goes to the hauler. And if you’re in there pulling mud around, you might run across a last refugee, the one who’s injured and can’t yell for help.”

  Curtz was wishing he’d planned this. He thought he knew what would end Newbry’s hesitation. “The Admiralty merchants won’t even be in the easterly fringes for twenty or thirty days. Take some time to rest, you’d still make it.”

  “Maybe.” Newbry pulled himself out of the water. “Time we were going. Come on, Stevn.”

  YEAR 419 DAY 121

  Where the lift lines turned at the midpoint, Alin and Stevn let go and kept coasting along the bark. Their kites were furled in their hands.

  “You’re going,” Stevn said.

  “I think so. Tow some of the mud from Capability Tree to the Vivarium. You want to come along?”

  “Do I have a choice?”

  Alin heard bitterness and didn’t like it. “This isn’t lives at stake, and the other boys have had time to rest. So?”

  No answer.

  “Bertam and Gilly and Marlow must have had five days’ sleep already. I’m dead tired, but I’m the Kitemaster, and Hell can freeze over before I let the Admiralty take all our mud. You’re dead tired too. So stay in the tuft.”

  Stevn said, “I was scared all the time.”

  “Ah.”

  “I got the sails set, and I was never sure they were right. At first I was going way wide of the Navy ship, but I got myself turned, and then I still wasn’t sure. How far in can I go before the tree’s too far behind me to ever get back? What if the fog thickens up and I get lost? The sky goes on forever. What if the navvies never see me? The Scientist says if I get too far from the air I’ll pass out. Then what?”

  “Yeah.”

  “I didn’t want to say so.”

  The other pulley was near. Alin snatched at an edge of bark sheet with one hand, got Stevn’s ankle with the other, and stopped their flight. “Here’s your ride down.”

  Stevn didn’t move.

  “I thought I was going to die, my first solo flight,” Alin said. “Everything I did took me farther from the tree. A triune family looked me over and never even bothered to separate.”

  Stevn laughed.

  “The only reason I was out there was, I didn’t want to be Liftmaster’s Apprentice the rest of my life. It looked like Liftmaster Kent was going to live forever. Still does.

  “So you go on. Tell the Captain what’s going on, and ask him to send the other boys up. Tell your mother I’m going to make Brighton rich—”

  “Dad, why don’t you tell them yourself?”

  “No, I’ll stay on the trunk. I need the rest.”

  “The Silver Man says you’ve got twenty or thirty days to rest! Talk things over with the Captain. See what we want from the Clump. You might even talk Mom into something.”

  “Hah.”

  Stevn’s face closed down. He reached for the lift line.

  Alin said, “Hold it. I see a lob. Let’s get a meal before we go down.”

  “Where?”

  “He’s poking an eye over the bark, just there. That must be where his burrow is. Got your harpoon?”

  “Yeah.”

  “I just don’t like arguing,” Alin said. “I’d rather fly away, and I damn sure know some places nobody can follow me. I know I have to talk sometime, but it’s…it’s just…But if I can’t talk to your mother, my children’s mother, then I can’t talk to anyone, can I? Even you.”

  “You’re coming down?”

  “Yeah. But first I’ll show you how to boil a lob in zero tide.”

  • • •

  • • •

  In the aft and side views, all detail had become tiny: integral trees were toothpicks, ponds were drops of glitter, everything seemed embedded in fog. Gold had become a bulge within a larger lens of cloud patterns that trailed off to east a
nd west: a storm pattern that spread across the Smoke Ring. The hidden planet seemed indecently close.

  THE INTEGRAL TREES, 1983

  THE ALIEN IN OUR MINDS

  I

  The only universal message in science fiction reads as follows: There are minds that think as well as we do, or better, but differently.

  The appropriate questions are, why do you care? Why should they care? And, where are they?

  I want to call your attention to humankind’s ancient fascination with aliens. There’s evolution at work here.

  1)

  Meeting aliens has been a normal thing for humankind. For most of human history, successful tribes have numbered about a hundred. Hunter-gatherer economies need lots of territory, and they have to move frequently.

  A hundred thousand years ago, or a million, all humankind was hunter-gatherers. There were strangers around. A wandering tribe might stumble across something different, with odd, ugly faces, bizarre customs, strangely colored skin—and new and useful tools, or new and fearsome weapons.

  People who couldn’t deal with aliens had to fight when they met. People who could, had their choices. They could trade, they could make agreements including treaties, they could postpone a fight until they had the advantage, they could set rules for war that would allow more survivors. And…a man who can talk persuasively to aliens, can also talk persuasively to his own tribe. A persuasive speaker was likely to become the chief.

  But even without the external aliens, there were aliens enough.

  2)

  There were wolves. There were horses. There were saber-toothed cats. There were caribou and pigs and rabbits and woolly mammoths.

  A recent article in Analog pointed out that men are cursorial hunters. Most predators sprint after their prey. Our ancestors didn’t. They picked their target and chased it down over hours or days. A hunter had a better chance of feeding his tribe if he could learn to think like a deer.

  So. Somewhere there was a man who found and kept a litter of wolf pups and raised them to know obedience. The tame wolves that didn’t learn to think like men didn’t live to breed. And somewhere there was a man who leapt on a horse’s back and rode it to exhaustion. That tribe had enough to eat, so they didn’t eat the horse. Presently they were riding horses.

  So there were horses and dogs within certain tribes of men; but there were aliens closer yet.

  3)

  We are a species of two intelligent genders. Men and women don’t think alike, but we can learn to talk to each other. Some of us. When we choose our mates, we breed for certain traits.

  Adults and children don’t think alike. Successful human beings talk to their children. They teach their children to become successful adults. Successful children learn new means of hunting or farming and teach them to their elders. Where the generation gap is too great, that tribe or that family doesn’t survive.

  We have dealt with alien intelligences for all of history and prehistory. Wouldn’t that hold for any extraterrestrial intelligence? Maybe not. Aliens may have taken other paths, paths that don’t force negotiation upon them.

  Parthenogenesis. Budding instead of sex: no opposite gender.

  Children might have no intelligence. A human child’s brain is big; it doesn’t grow much while he’s becoming an adult. An alien child’s brain might be the last thing to develop. Or children might hatch from eggs and have to fend for themselves. An adult may never see a child until a young adult comes wandering back out of the breeding grounds. There would then be no intellectual contact with children.

  An alien species may have radically divergent genders (as with most insects). If one sex is nonsapient, there is no negotiation. It doesn’t take brains to mate!

  Mating seasons are common enough in Earthly life, but look at the result. In mating season both genders might lose all intelligence. Intelligence might be a handicap as regards breeding, even for us, from the evolutionary viewpoint. An intelligent being is likely to think of reasons for not mating with an available partner, or for not having children just now, or at all.

  But in mating season male and female do not negotiate before they mate. Males may negotiate with each other, but two males butting heads are very much alike. You might picture the elders of one gender arranging a mating before the season comes on. This could be done using cages. Lock ’em up together.

  Humankind has been fiddling with reproduction for a long time. Before the Pill there were abortifacients and French letters. Technology may supplant our present modes of reproduction. War between sexes finally becomes a real possibility. One gender exterminated. Technology for reproduction from then on.

  What I’m getting at is this. We assume that an alien intelligence will want to talk to us. Or to someone! But it ain’t necessarily so. The evolutionary pressure may not be there.

  II

  Where are they?

  The universe is far older than the oldest known intelligent species. Why haven’t they come visiting? It’s the most interesting question now being asked.

  You’ve read tales of the interstellar commonwealth that has been ignoring Earth, or has made Sol system into a zoo or national park; but that won’t wash. The kind of power it takes to cross interstellar space is difficult to ignore. Any decent interstellar reaction drive must convert more mass to energy than the mass of the payload; you have to get up to at least a tenth of lightspeed and back down! To take advantage of relativity you would need .9 lights or greater. There would be side effects on a cosmic scale. For laser-augmented light-sails, same remark. We would have seen something—something as powerful as the pulsars, which were assumed to be interstellar beacons until we learned better.

  How long does it take to make an intelligent spacegoing species?

  Our sample case is the solar system, Earth, and the human species. We’ll stick with our only sample and generalize from there.

  The human species seems to be within a thousand years of reaching across to the nearest stars. Our sample is a world big enough to hold a thin atmosphere, orbiting within the liquid water domain of a yellow dwarf star. If we want an oxygen atmosphere we must wait for the life-forms to develop photosynthesis. Our first guess is that it takes four and a half billion years for a planet of this specific type to produce thinking beings.

  Keep in mind that other chemistries may form other kinds of life. Even so—

  Nothing in our temperature domain works as well as water and oxygen and carbon. In hot environments, chemistries are probably too unstable. Within the atmospheres of gas giant planets there are conditions that might give rise to organic life: you find a layer of Earthlike environment. But escape velocity is very high, and what would they have for tools? In very cold conditions, on Pluto or Titan, or in the black oceans beneath the ice crusts of some of the moons of Jupiter and Saturn, there may be exotic chemistries that can support life. Then again, chemical reactions happen slowly at such temperatures. We might have to wait longer than the present age of the universe before anything interesting happens.

  If we’re looking for something that can build spacecraft, we can stick with our sample and not be too far off.

  Four and a half billion years. Look again and the number goes up. To build a solar system we need gas clouds, galaxies, gravity, heavy elements, and stellar explosions.

  The solar system condensed from a relatively dense interstellar cloud. Those aren’t rare, they’re all over the place. The cloud included supernova remnants, the materials that became the cores of planets and the elements of our bodies. The event that caused the condensation may have been a shock wave from a more recent supernova explosion. We need to allow time for previous supernovas, and time to make a triggering supernova.

  The galaxies formed near the beginning of the universe. Supernovas have been occurring since a billion years afterward. It’s fair to assume that it takes seven billion years to make an intelligent species.

  The universe is generally given as fifteen to eighteen billion years
old. Atoms didn’t form for the first half-million years. Call it two billion years to spread supernova remnants throughout the galaxies. The first intelligent species should have evolved seven to ten billion years ago. Based on our own sample, they began exploring space almost at once: say, two or three million years after the taming of fire.

  Large numbers of stargoing species should have been expanding though the universe for up to eight billion years. Somewhere a successful industrial species should have gone past the Dyson shell stage into really ambitious engineering projects.

  We’re alert enough to recognize Dyson shells now!

  Where are they?

  Something’s wrong with our assumptions.

  III

  Maybe they’re all dead.

  We can postulate events that regularly destroy an intelligent species before it can reach out to Earth. What follows is likely to be depressing. Hang on. There are answers you’ll like better.

  Intelligences may tend to destroy the ecological niche that produced them. We do tend to fiddle. The Zuider Zee is still the world’s biggest successful planetary engineering project, but the Sahara Desert seems to have been caused by goat herding. Rabbits in Australia, garden snails in Tarzana, mongooses in Maui.

  We fiddle with life-forms too. Broccoli and pink grapefruit are recent inventions. There are hundreds of breeds of dogs shaped over tens of thousands of years of fooling around. It’s a simple technique: what you don’t like doesn’t breed. But now we know how to fiddle with genetic coding. What are the odds of our making one irrecoverable mistake in the next thousand years?

  Destroying one environment in this fashion wouldn’t bother us much if enough of us have left the planet. But let’s look at the energy considerations. Dogs were shaped by primitives who used the wheel if they were wealthy enough. Modern biological experiments can be run for millions of dollars, or less. A decent space station might be built for tens of billions. The odds are that your random ETI developed genetic engineering long before he thought of leaving his planet, because it’s so much cheaper. Where are they? They made one mistake.