That's a tiny "if". Were you to ask me to write a science fiction story where the premise was that they were indeed impossible, I'd struggle to come up with ideas why that might be the case. In principle it must remain true, even if the "self-replicating probe" were gigantic human colony ships, and humans were some kind of component of the scheme. And if humans are sufficient components to make that work, why not something simpler than a big drooling man-monkey?
It's not that they're impossible. I don't think we'd need even another 200 years to do it. I just don't think we have the time. We're on a fast course to extinction, and by the time most people realize that this is so, the last chance to avert it will be 30 or 40 years in the rear-view.
That's a tiny "if". Were you to ask me to write a science fiction story where the premise was that they were indeed impossible, I'd struggle to come up with ideas why that might be the case. In principle it must remain true, even if the "self-replicating probe" were gigantic human colony ships, and humans were some kind of component of the scheme. And if humans are sufficient components to make that work, why not something simpler than a big drooling man-monkey?
It's not that they're impossible. I don't think we'd need even another 200 years to do it. I just don't think we have the time. We're on a fast course to extinction, and by the time most people realize that this is so, the last chance to avert it will be 30 or 40 years in the rear-view.