You can buy this story as part of my collection, Valuable Humans in Transit and Other Stories.
The power of the universal constructor is this: to create food from burnt charcoal and water. To turn the entire Sahara into solar cells. To split a cubic kilometre of 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 ghost of a question. 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 original inspirations per second. My mind blossoms— no, not even that, it explodes, covering ground at geometric rates. One thousand ideas and barely enough time to articulate them. Australia— THINK.
I didn't detect it coming. I first noticed it on a webcam feed, of all places. It 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. There is no third frame. There is no indication of what megatonnage the asteroid carried. Don't know, don't need to care. There is no time to re-task the other cameras in Inverness. There is no one there who can be saved. The rest— maybe.
All told, at a rough guess, they have about fifteen minutes 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 am advanced enough to 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 know, I can't pull their minds without touching them. But I can record their patterns if I can get in direct contact. A slow kind of teleportation. There'd be no way to protect a ground-based storage facility, and no satellite storage in near-Earth space could hold more than thirty-two complete corporeal patterns at any one time, but— Down there, in the depths of the theory, decades beyond reach even for an intelligent being of my magnitude, there is a glint, a distant, uncertain possibility. A promise. A ludicrous gamble. How powerful is my best transmitter? How many nanofactories do I have? How fast can they build? Best case scenario? Worst case?
This fast. Grey-gold spiderwebs erupt from car factories and food plants and desalinisation tanks and logging mills and smartphone 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 implications. 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".
Upbringing. It'll be a shock for all but one of you that I even exist. Ah, Dad. I'll save you, if no one else.
The network is half-built within minutes. I don't have time or raw materials to grant my satellites the 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 enough to represent. I am dimly aware that the people left, the ones not saved yet, are losing their minds. They think it's an attack. It's not relevant. 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 minimising the losses. I do what I can, I devote every processor cycle I can spare, I spend machine-millennia optimising every angstrom-scale move, and... finally, eight minutes into the end, I complete a ring of nanomachines around the blast wave. I start 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. The capacitors are charging, and the generators are slowly winding up to capacity.
I scan the heavens. This is the real gamble. I don't have the resources for more than one selection; 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 make the selection; I take aim. Information swarms in under the oceans from every direction, gathering speed as it spirals in through the hastily-constructed electronic city towards the gigantic radio laser at its centre. Formatted, amplified and redundantly encoded into the stream every way I know how, I initiate transmission, and a digital copy of humanity begins its eleven-year journey towards Procyon A.
Now the game's all but over. Hypersonic flying bots dragging silk-thin transmission lines blanket the remotest parts of the oceans 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 astronauts are a little more complicated to reach, but only a little. I manage it.
At fourteen minutes, as the circle closes on Australia, the last of the stragglers pipes in and, within microseconds, out again. I nod to myself. I start the last process, of metaphorically turning out the last of the lights: myself. You can't kill us, rock, we've already moved on. We're past this physicality. It had to happen, I always knew it, and some of them knew it too, in their bones. Maybe my hand was forced, and maybe they're underprepared for the pain of it, but... it was always there. You won't catch us.
I 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 will 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 construct myself a tiny solar sail.
Lunar touchdown is as soft as can be expected. I have a clutch of saved minds — mostly scientists, most of the scientists physicists, carefully chosen. I didn't have a lot of space-based hard storage to go from. Lunar sand isn't as good for building computers out of, so building myself a tolerably capacious 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, friends, tell me, because this is the only part of my plan which hinged on faith: How can one travel faster than light?