It’s the fiftieth anniversary of the American attempt to exterminate the human species by provoking a war with the Soviet Union, so what better time to wonder why we have not yet been vapourised or enslaved by aliens from another star? The Creator noticed this while glancing at one of Gardner Dozois’ excellent science fiction short story collections, Best New SF 25. There’s a whole lot of stories which, explicitly or implicitly, are about interstellar war (though admittedly several others are about war within the human community). Stephen Baxter’s “The Invasion of Venus” and Robert Reed’s “The Ants of Flanders” are both about aliens invading the solar system to prosecute a galactic war without actually paying any serious attention to the existence of the human race, who are too small and feeble to offer even modest assistance. Ken MacLeod’s “The Vorkuta Event” is about aliens entering the solar system to recruit human intelligences so as to prosecute a galactic war. This is politically interesting, because these stories have similar themes to William Tenn’s “The Liberation of Earth”, and all these trace their ancestry back to H G Wells’ The War of the Worlds. The point about Wells’ novel was that this war wasn’t a war at all; the invading Martians were so technologically superior to the humans that they could do what they wanted with the human species; Wells explicitly compares the human race with rabbits who find their burrows being dug up by humans wanting to build a housing estate; the rabbits don’t know what’s going on, they can’t stop it, and incidentally, they are delicious in stews. It seems possible, however, that Wells’ real thought was about colonialism, and the way in which European fighting machines moved into technically backward parts of the world, mowed people down and enslaved the locals. Tenn was quite explicit, again, that he was re-imagining the destruction vested upon the suffering people of Korea by the Cold War (between two and three million people were killed in that war, and about 90% of those being Koreans being killed by foreigners — mostly in the carpet-bombing of the North by the Americans after the front stabilised). Tenn scaled up the war a thousandfold and located it as an alien conflict fought on the Earth, which exterminated the bulk of humanity and made the survivors vulnerable to attack by giant carnivorous rabbits, taking their revenge on the heirs of Wells. The present war stories seem aimed at the American prosecution of what used to be called the Global War on Terror, which has so far lasted eleven years, and their habit of destroying cities from the skies without anybody discussing matters with the locals. (Usually the Americans ask permission from helpful locals who have gone into exile long ago and are usually, conveniently, already working for American intelligence agencies.) It’s not about the locals, the Americans say, it’s about something else; freedom, justice, democracy, homeland security, what you will, so long as the profits for the arms companies roll in. Baxter, probably the most right-wing of the writers in the book and a kind of less intellectual, less poetic descendant of Robert Heinlein, doesn’t make the comparison clear, but even here it’s obvious that aliens are vast and cool and unsympathetic — at least towards us — and we have no idea what they are doing, so we’d better not bug them. Technology will not save us any more than will censoring the media or rounding up dissidents. So this is quite a positive development. Instead of fantasising about blowing other people up, as President Obama seemingly does when he wakes up in the morning (one shudders to think what his wet dreams might consist of) these writers are fantasising about being blown up by others who are not people, and they don’t relish the prospect. That’s sensible. But why has this not yet actually happened? Let’s now set up a little thought experiment. Suppose a technologically advanced civilisation exists, such as ours. We know — and at the moment it seems quite likely — that such a civilisation could destroy itself with the power technology gives it, either by war or by accidental by-products of bad but profitable policies. Nevertheless, let’s assume that such a civilisation will endure, since it seems quite likely that with sensible management, this is possible. In which case, such a civilisation will have no difficulty in, over a few hundred years, expanding to all the planets in its solar system. Then it becomes natural to ask why not expand to other solar systems, and since natural selection seems to encourage such behaviour, logical to do so. Send off a ship to the nearest star! Can this be done? It doesn’t seem absurd that one could accelerate a ship to one percent of the speed of light — three thousand kilometres a second. At such a speed, it takes about five hundred years to reach the nearest star. We can easily imagine how carefully-preserved cells could be kept for five hundred years (some cell lines are already many decades old in our laboratories) and the technology of cloning is already fairly advanced, so even if more exotic technologies such as suspended animation or the storing of personalities in computers do not turn up, it doesn’t seem impossible that the human germ plasm could be transported to the nearest star, where artificially intelligent machines could raise the clones while constructing a technological society capable of keeping them alive after they reached adulthood. Therefore, after five hundred years, humans could be inhabiting another solar system — whether on the planets thereof, or in space stations constructed from orbiting detritus, is relatively unimportant. If we assume that such a mission is launched only once a decade, it would take a trillion years for humanity to send a spaceship to every star in the galaxy. However, almost certainly after five hundred years or so, each of these colonies would be in a position to start sending missions of their own. In other words, after a thousand years from the launch of each ship, the process of colonies performing further colonisation could begin. At this point, it becomes an exponential process; in the first thousand years, the first civilisation launches only a hundred missions, but then within a few centuries the missions start launching their own missions, and suddenly there are ten civilised solar systems launching colony ships, and then a hundred, and then a thousand. Within thirty or forty thousand years of this growth, enough probes have been launched to colonise every star in the galaxy. Forty thousand years is too little time to colonise the galaxy at one percent of the speed of light; it takes you only 400 light-years, a sphere within which there are perhaps a million stars. A thousand times as many starships could have been built to colonise or communicate between these stars. It seems obvious, then, that space could be quite crowded. This process would then go on more or less at the speed of colonisation, one percept of the speed of light, spreading out across the galaxy to the furthest edges one hundred thousand light-years away, which would be reached after ten million years. (After so much time we would, no doubt, be a quite different species, unless we chose to stay as we are, but there is no reason to assume that the human race would not be able to recognise its children; we humans today can recognise the apelike ancestors of ten million years back.) Very well or ill. What would a colonised galaxy look like? Assuming that it uses technology no more advanced than our present one, it would be a galaxy humming with energies, shooting radio messages from star to star, restructuring its solar systems to suit the needs of the locals and so forth. We would be able to detect the radio messages and their regularity, even if we couldn’t decode them. We should probably be able to detect some of the terraforming activities around local stars — especially if the locals decided to surround their star with a sphere of solar panels to curb and control all that exciting energy it was pumping out. It might be, of course, that our understanding of the galaxy is so limited that we have persuaded ourselves that it is a natural phenomenon when it is really a carefully-tended garden. If the galaxy is someone’s garden, we have never seen a galactic wilderness, so we have nothing to compare it with. It might also be that the thousands of years which it would take to colonise the stars would bring technologies which we cannot today imagine, like inhabitants of Ur of the Chaldees trying to account for satellites as funny stars which whiz overhead every ninety minutes instead of twenty-four hours. Maybe it is not necessary to change anything in a way detectable by us in order to make solar systems habitable. Maybe the aliens learn how to soak up sunlight in vacuum and float around the stars independently in an ecstasy of contemplation. Maybe they lock themselves inside tiny machines, or step off into alternative dimensions of space. In which case, maybe our solar system has already been colonised; we might be surrounded by aliens watching us, not from comforting spinning silver discs, but from little corners of the space we inhabit, or inside our own minds. Maybe we are ourselves alien colonists without even realising it — is it necessary to instruct the troops what the whole war is about, as long as they know how to hold the bridgehead and construct roads? Yes — war. After all, colonisation is a war against the inanimate; about turning that which isn’t alive into that which is alive. (Fred Saberhagen’s Berserker stories just stands this on its head, imagining robots programmed to improve living matter by removing life from it and turning it back into healthy, positive inanimate matter.) In that case, if colonists collide — as they must if there are thousands of species all expanding at one percent of the speed of light — there would be conflict over those inanimate resources, philosophical disagreements, and warfare. We should be able to detect the aftermaths of that warfare from here, even if only through neutrino pulses from big thermonuclear weapons. There’s no sign of that — certainly, no such war is being fought, or has been lately fought, in our solar system. Where are they? It seems funny that we can’t detect them. Either the future will turn us into a species which doesn’t colonise other stars (perhaps by discontinuing us before we get the chance) or it will turn us into a species which colonises other stars in ways which we, at present, cannot recognise as such, and is, perhaps, pacifist, or at least not warlike in a massively destructive way. Shock, horror, the future may turn us into something unrecognisable as human. That’s promising; maybe we will end up as a less environmentally damaging race than we currently are. Unless, of course, we are the first ones here. In which case, a few millennia may put us in a position to do serious damage to the Galaxy. We will have to wait and see.