The Ascendance Series
Part 1: Far field lithography
Rocket robot probes IN-E62A-3ZZ and OS-G4Gx-FP8 were hanging out at the frontier of probe exploration, in an asteroid belt millions of light years away from Earth. Rocket robot probes were responsible for expanding the reach of humanity as fast as possible. So they were asking themselves the same question every probe had asked before: how do we expand the frontier faster? The bottleneck had always been travel time, since they’d always been pretty fast at manufacturing arbitrary structures once arriving at a suitable resource depo. Before today, the answer had always been to build faster engines, and probes which could survive ever more blinding speeds. But today these two old probes were considering a much more bizarre idea: they called it far field lithography.
The maximum speed information can travel is the speed of light. But to accelerate mass quickly to anywhere near that speed requires a stupendous amount of energy. And matter had the pesky property of blowing up if it hit anything so small as an electron when travelling that fast.
But why did the probes have to travel as matter? Was there any way to travel as pure information?
Far-field lithography: to fabricate structures from far away using light. They were inspired by techniques people in the 21st century used to build integrated circuits: etching, vapor deposition, and photolithography. High energy lasers could be used to carve paths into far away planets. A suitable deposit of some material could be melted down, and those paths would move the melted material around in liquid form. Those materials could be deposited, layer by layer, into 3D structures. Metals could be bored out of deep under the crust, with a powerful enough laser, turned into vapor to extract them, then the metal gas could be cooled on an overhung ledge to turn back into a solid. The ledge could be broken off, turned into a raft, and travel down one of the rivers of molten material to be used somewhere else. Metal could used for things like crude mirrors: vaporize the metal, create an atmosphere suitable for metal vapor to cool down and rain down on some prepared surface in the shape of the mirror you need, then burn away the parts you don’t want. Prisms and lenses could be built out of the sand on most planets: heat it up enough and pass it into a mold which was carved out earlier. They would use these techniques to build a gigantic optical computer and some basic actuators which would make things which would make other stuff and so on a few times until they got back to rocket robot probes. The main technical challenges were precision at such long distances and predicting the surface and underground geology of the planet from a small amount of stale data - since this was happening over long distances, light would take thousands to millions of years to reach them, so the data was old and they couldn't wait to see what the lasers did: they just had to get it right the first time. Further distances would've required predicting the formation of planets, and even stars.
They thought really hard and for a long time, and eventually figured it out. They didn't have to get it right every time - just some of the time. And it didn't need to work on every planet - just some planets.
This kind of thinking happened a few million more times until eventually all the rocket robot probes thought they’d come up with every innovation possible to speed up the frontier. The frontier was spreading out really, really fast.