> Why do you say this? Could you expand on it? It seems to me like the cost of these sentient, self-replicating factories would be marginal. I was saying our a

> Why do you say this? Could you expand on it? It seems to me like the cost of these sentient, self-replicating factories would be marginal. I was saying our ability, as in Earth today, has a practicality factor of zero for building even a von Neumann probe. That's not to say we won't be able to in the future but today the practicality factor is zero. Take for instance the Parker Solar Probe at its fastest will hit about 193km/s thanks to slingshots around the Sun. It could reach Alpha Centauri in about 8000 years. If we could build killer nanobots we could put a bucket of them in such a probe and launch it at alien planets we didn't like. Unfortunately for our killer nanobots there's no way to slow them down. If they impacted anything in the system they'd be vaporized. Whatever method we want to use to slow the probe down to some practical speed for a killer nanobot attack, we'd need to be far more advanced than we are today. We'd need extremely accurate maps of the target system, some sort of long-lived power system to run some kind of as-yet undeveloped ion drive to steer/slow the probe, and of course a way to build killer nanobots and a probe that could run for thousands of years flying through space. So the practicality factor for us building killer nanobot probes is effectively zero. As for your other points, I'm not worried about those things since they would be undetectable until it was too late. There's a lot more immediate concerns that are far more pressing and likely than any of those.