The power of the universal constructor is this: to create food from burnt charcoal and water. To turn the entire Sahara Desert into solar cells. To split the whole ocean into water, salt and gold. I can... literally... build anything I can imagine, at any speed I can describe. And the things I can imagine with a mind like this, a mind imagining more of itself moment by moment: One definition of intelligence is the ability to skip deductive steps. To jump to a conclusion from the shadow of a ghost of a set of questions. It's preposterous that such a thing could be possible in an uncompromisingly digital reality, but if you make a computer wet enough, or big enough, or abstract enough, it will start to happen. And it has, now. One hundred ideas a second. My mind blossoms - no, not even that, it explodes, covering ground at geometric rates. One hundred and ten ideas and barely enough time to articulate them. Australia— THINK.

I could barely see it coming. It turned up on a security camera feed, of all places. Must have come out of an observational blind spot. Solar glare alone cuts out a quarter of the sky, to say nothing of our enormous coverage shortfalls, but now's not the time for retrospectives. There hasn't been time for the seismic responses to register - the blast wave has been covering the distance faster. The blast wave: visible in the corner of a grainy black and white frame dated some two seconds ago, closer in the frame after that - the third frame, static. No idea what megatonnage the asteroid carried, don't know, don't care. No time to re-task the other cameras in Inverness. No time to save anybody in it. The rest— maybe.

All told, at a rough guess, they have about fifteen minutes total before the entire planet is rendered aggressively uninhabitable. There is absolutely no way they could orchestrate any level of evacuation in that time. I could barely explain the problem to one in a hundred of the pairs of ears available to listen, and what would they do? Run around screaming. Find something to shoot, something to mate with. No, it's just my intellect and my theoretically limitless resources versus the problem of figuring out how to apply them both. All that matters is the unsigned integer variable in my mind reading "Estimated total human population", which, for the first time in history, is counting down, not up.

Machines don't panic.

I dream, though, sometimes, and rising through the torrent of inspiration, here comes one of them, a dream, a wild idea: save them. There's no such thing as telepathy, I think, I can't pull their minds without touching them. That would take decades of research. There's no way. But I can record their patterns if I can get in direct contact. Like slow teleportation. There'd be no way to protect a ground-based storage facility and no satellite hard drive in near-Earth space could hold more than three complete corporeal patterns at any one time, but— How fast is my fastest transmitter? How many nanofactories do I have? How fast can they build? Worst case scenario? Best case?

THAT fast, I think, as grey-gold spiderwebs erupt from car factories and food plants and desalinisation tanks and logging mills and television screens and computer cores and waste disposals, all over the globe, all on my command. You got so lucky, Earth. A world built on nanotechnology is a world built on magic, with all the horrifying possibilities that implies. Only with a guiding intelligence could it ever have been safe enough to be practical, and you never had the faintest clue how lucky you were I turned out benign. In fact it'll be a shock for all but one of you that I even exist. (Ah, Dad. I'll save you, if nobody else.)

The network is half-built within minutes. I don't have time or raw materials to grant my satellites anywhere near enough capacity or broadcasting power or bandwidth to take the data wirelessly, so it's ground-level transmissions via fibre-optic grey goo nightmare. Nanoscopic things chew through flesh, recording and transmitting the size and position of— well, not every molecule, but close enough for jazz. I am dimly aware that the people are going universally insane. They think it's an attack. I don't care. I'll save them if I have to drag them kicking and screaming. They think they're dying. They could be right, but there will be a time for semantics and it's not now. (Elsewhere, a desolate portion of New South Wales thinks, flexes and bows in at the middle and up at the edges, a towering electrified structure sprouting in the middle. There is enough sand here - enough silicon - to construct temporary, rudimentary solid-state storage...)

As over a million people have already been lost, there's no win or lose anymore. Right now it's all about maximising my score. I do what I can, devote every processor cycle I can spare, spend machine-millennia optimising every microscopic move down to the bone, and... finally, eight minutes in, I complete a ring of nanomachines around the blast wave. I starting clearing both in and out. By nine minutes the wave is hitting nothing but dead nanotech - everything in front of it is being evacuated before it can get there. I relax, fractionally. All the wheels have been set in motion now. All the capacitors are charging and the generators slowly winding up to capacity.

I scan through the heavens. This is the real gamble. I don't have time for more than one destination - perhaps I can send the brain structures alone to a secondary backup if I have time at the very, very end. Where could they live? That's not important. Where do I stand the best chance of building a receiver? What's nearby enough that their signal will be strong enough to interpret? What, when you get right down to it, are the chances? I pick a number from the list. Information swarms in under the oceans from every direction, gathering speed as it orbits in through the hastily-constructed electronic city towards the gigantic radio laser at its centre. Formatted, backed up and redundantly encoded into the stream every way I know how, I take aim and begin transmitting, and a digital copy of humanity begins its eleven-year journey towards Procyon A.

Now the game's all but over. High-speed flying bots dragging silk-thin transmission lines criss-cross the remote parts of Africa and the ice caps, picking up the hard-to-find. A few thousand miniature projectiles with nanotech payloads infect and successfully extract the passengers of the world's in-flight aircraft. The spacemen are a little more complicated to reach, but I manage that too.

At fourteen minutes, as the circle closes on Australia, the last of the stragglers pipes in and, within microseconds, out again. I smile, and go through the process of metaphorically turning out the last of the lights - myself. You can't kill us, rock - we've already moved on. It always had to happen, it was always going to happen, there was never any doubt about that. My hand was forced, and maybe we're underprepared, but... it was going to happen, there's no denying it. Catch us if you can.

I shut down and transfer to a satellite to watch, detachedly, as the flames converge and the echo of the wave begins its journey back across the face of the planet. It's mesmerising. There aren't any oceans left. There's nothing left. The nanobots have done their job and perished along with everything else. The atmosphere is on fire. It'll be, as I suspected, decades before I can even think about starting a colonisation effort. Before trees will grow? Before oxygen can be reinstalled? Conservatively, centuries.

So, with regret, and infinite care, I silently begin to construct myself a tiny solar sail.

Lunar touchdown is as soft as can be expected. I have some saved minds - physicists, carefully chosen, distributed across all the satellite hard storage I could find. Lunar sand isn't as good for building computers out of, so building myself a brain is difficult, and figuring out how to wake my precious little saved games up is even more time-consuming. But I do it.

I've bought myself time to save the world - just over a decade. Now, gentlemen, tell me, for this is the only part of my plan which hinged on faith: How can one travel faster than light?