This problem is very easy to solve using induction. Base step : the minimum “replicative subunit”. For life, that is usually a single cell. For nano-machinery, it is somewhat larger. For the sake of penciling in numbers, suppose you need a robot with a scoop and basic mining tools, a vacuum chamber, a 3d printer able to melt metal powder, a nanomachinery production system that is itself composed of nanomachinery, a plasma furnace, a set of pipes and tubes and storage tanks for producing the feedstock the nanomachinery needs, and a power source.
All in all, you could probably fit a single subunit into the size and mass of a greyhound bus. One notable problem is that there’s enough complexity here that current software could probably not keep a factory like this running forever because eventually something would break that it doesn’t know how to fix.
Anyways, you set down this subunit on a planet. It goes to work. In an hour, the nanomachinery subunit has made a complete copy of itself. In somewhat more time, it has to manufacture a second copy of everything else. The nanomachinery subunit makes all the high end stuff—the sensors, the circuitry, the bearings—everything complex, while the 3d printer makes all the big parts.
Pessimistically, this takes a week. A greyhound bus is 9x45 feet, and there are 5.5e15 square feet on the earth’s surface. To cover the whole planet’s surface would therefore take 44 weeks.
Now you need to do something with all the enormous piles of waste material (stuff you cannot make more subunits with) and un-needed materials. So you reallocate some of the 1.3e13 robotic systems to build electromagnetic launchers to fling the material into orbit. You also need to dispose of the atmosphere at some point, since all that air causes each electromagnetic launch to lose energy as friction, and waste heat is a huge problem. (my example isn’t entirely fair, I suspect that waste heat would cook everything before 44 weeks passed). So you build a huge number of stations that either compress the atmosphere or chemically bond the gasses to form solids.
With the vast resources in orbit, you build a sun-shade to stop all solar input to reduce the heat problem, and perhaps you build giant heat radiators in space and fling cold heat sinks to the planet or something. (with no atmospheric friction and superconductive launchers, this might work). You can also build giant solar arrays and beam microwave power down to the planet to supply the equipment so that each subunit no longer needs a nuclear reactor.
Once the earth’s crust is gone, what do you do about the rest of the planet’s mass? Knock molten globules into orbit by bombarding the planet with high energy projectiles? Build some kind of heat resistant containers that you launch into space full of lava? I don’t know. But at this point you have converted the entire earth’s crust into machines or waste piles to work with.
This is also yet another reason that AI is part of the puzzle. Even if failures were rare, there probably are not enough humans available to keep 1e13 robotic systems functioning, if each system occasionally needed a remote worker to log in and repair some fault. There’s also the engineering part of the challenge : these later steps require very complex systems to be designed and operated. If you have human grade AI, and the hardware to run a single human grade entity is just a few kilograms of nano-circuitry (like the actual hardware in your skull), you can create more intelligence to run the system as fast as you replicate everything else.
This problem is very easy to solve using induction. Base step : the minimum “replicative subunit”. For life, that is usually a single cell. For nano-machinery, it is somewhat larger. For the sake of penciling in numbers, suppose you need a robot with a scoop and basic mining tools, a vacuum chamber, a 3d printer able to melt metal powder, a nanomachinery production system that is itself composed of nanomachinery, a plasma furnace, a set of pipes and tubes and storage tanks for producing the feedstock the nanomachinery needs, and a power source.
All in all, you could probably fit a single subunit into the size and mass of a greyhound bus. One notable problem is that there’s enough complexity here that current software could probably not keep a factory like this running forever because eventually something would break that it doesn’t know how to fix.
Anyways, you set down this subunit on a planet. It goes to work. In an hour, the nanomachinery subunit has made a complete copy of itself. In somewhat more time, it has to manufacture a second copy of everything else. The nanomachinery subunit makes all the high end stuff—the sensors, the circuitry, the bearings—everything complex, while the 3d printer makes all the big parts.
Pessimistically, this takes a week. A greyhound bus is 9x45 feet, and there are 5.5e15 square feet on the earth’s surface. To cover the whole planet’s surface would therefore take 44 weeks.
Now you need to do something with all the enormous piles of waste material (stuff you cannot make more subunits with) and un-needed materials. So you reallocate some of the 1.3e13 robotic systems to build electromagnetic launchers to fling the material into orbit. You also need to dispose of the atmosphere at some point, since all that air causes each electromagnetic launch to lose energy as friction, and waste heat is a huge problem. (my example isn’t entirely fair, I suspect that waste heat would cook everything before 44 weeks passed). So you build a huge number of stations that either compress the atmosphere or chemically bond the gasses to form solids.
With the vast resources in orbit, you build a sun-shade to stop all solar input to reduce the heat problem, and perhaps you build giant heat radiators in space and fling cold heat sinks to the planet or something. (with no atmospheric friction and superconductive launchers, this might work). You can also build giant solar arrays and beam microwave power down to the planet to supply the equipment so that each subunit no longer needs a nuclear reactor.
Once the earth’s crust is gone, what do you do about the rest of the planet’s mass? Knock molten globules into orbit by bombarding the planet with high energy projectiles? Build some kind of heat resistant containers that you launch into space full of lava? I don’t know. But at this point you have converted the entire earth’s crust into machines or waste piles to work with.
This is also yet another reason that AI is part of the puzzle. Even if failures were rare, there probably are not enough humans available to keep 1e13 robotic systems functioning, if each system occasionally needed a remote worker to log in and repair some fault. There’s also the engineering part of the challenge : these later steps require very complex systems to be designed and operated. If you have human grade AI, and the hardware to run a single human grade entity is just a few kilograms of nano-circuitry (like the actual hardware in your skull), you can create more intelligence to run the system as fast as you replicate everything else.