By “von Neumann machines”, I usually understand stored program computers. You are apparently talking about some kind of self-reproducing (nanotech?) robots. Assuming that such things exist doesn’t change the rocket fuel requirements for building an elevator, but they might help to build the rocket-fuel refineries. So, I don’t see how this assumption weakens the argument.
Oh, I assumed your last comment meant that the material would be coming from the moon and/or asteroid belt, and usually people aren’t proposing sending humans out there to mine them but von Neumann machines.
Ok, so we send a pair of robots to an asteroid and let nature take its course …
And then a few generations later we have thousands of robots heading back to earth to build an elevator for us. Yeah, that might work. And it might be cheap. But it probably won’t be particularly quick. Maybe 40 − 100 years from first arrival of robots at asteroid, I’d guess. I still don’t see how the argument is weakened by the existence of robots, but I agree it is left pretty weak.
I still don’t see how the argument is weakened by the existence of robots, but I agree it is left pretty weak.
No, it’s weakened by a variant of the conjunction fallacy, as it were. If you previously argued ‘A ~> C’ but have now changed your argument to ‘A & B ~> C’, then probablistically C has gotten less likely.
So one originally starts off arguing ‘we may have elevators soon, since when we can create miles of nanotubes, then we can create space elevators quickly’, and changes it to ‘we may have elevators soon, since when we can create miles of nanotubes and we have also finally developed space robots to go synthesize it in orbit for us, then we can can create space elevators quickly’.
You have narrowed the possible routes to creating a space elevator by ruling out routes that don’t involve von Neumann machines; that ought to reduce our probability.
Ah! I’ve got it now. The assumption that bots are available doesn’t weaken the case for an early elevator. The assumption that bots are necessary does weaken the case.
I don’t know why it took me so long to pick up on that. Sorry.
No problem. I wasn’t sure I was being fair in inferring that the bots were necessary. If they aren’t necessary, then by the same exact logic, our probability ought to go up - ‘A v B ~> C’ is stronger than ‘A ~> C’. (The more independent pathways to a result, the more likely one will work within a certain time span.)
By “von Neumann machines”, I usually understand stored program computers. You are apparently talking about some kind of self-reproducing (nanotech?) robots. Assuming that such things exist doesn’t change the rocket fuel requirements for building an elevator, but they might help to build the rocket-fuel refineries. So, I don’t see how this assumption weakens the argument.
FYI.
Oh, I assumed your last comment meant that the material would be coming from the moon and/or asteroid belt, and usually people aren’t proposing sending humans out there to mine them but von Neumann machines.
Ok, so we send a pair of robots to an asteroid and let nature take its course …
And then a few generations later we have thousands of robots heading back to earth to build an elevator for us. Yeah, that might work. And it might be cheap. But it probably won’t be particularly quick. Maybe 40 − 100 years from first arrival of robots at asteroid, I’d guess. I still don’t see how the argument is weakened by the existence of robots, but I agree it is left pretty weak.
No, it’s weakened by a variant of the conjunction fallacy, as it were. If you previously argued ‘A ~> C’ but have now changed your argument to ‘A & B ~> C’, then probablistically C has gotten less likely.
So one originally starts off arguing ‘we may have elevators soon, since when we can create miles of nanotubes, then we can create space elevators quickly’, and changes it to ‘we may have elevators soon, since when we can create miles of nanotubes and we have also finally developed space robots to go synthesize it in orbit for us, then we can can create space elevators quickly’.
You have narrowed the possible routes to creating a space elevator by ruling out routes that don’t involve von Neumann machines; that ought to reduce our probability.
Ah! I’ve got it now. The assumption that bots are available doesn’t weaken the case for an early elevator. The assumption that bots are necessary does weaken the case.
I don’t know why it took me so long to pick up on that. Sorry.
No problem. I wasn’t sure I was being fair in inferring that the bots were necessary. If they aren’t necessary, then by the same exact logic, our probability ought to go up - ‘A v B ~> C’ is stronger than ‘A ~> C’. (The more independent pathways to a result, the more likely one will work within a certain time span.)