That doesn’t work. If a civilization reached slightly beyond our tech level around twenty million years ago (a blink in the eye as far as the universe is concerned) anywhere in our galaxy then we should expect to have seen some sign of them. Radio and visitation aren’t the only issues. We don’t see any evidence of Dyson spheres or ringworlds (although the second is something we’ve only recently been able to detect- Kepler should be able to detect ringworlds albeit I don’t know if anyone is looking for them.) We see no evidence of any form of stellar engineering or large scale structures at all. And distance only matters when you look into the near past. Civilizations that have had millions of years to prosper should have spread much farther. Note that our galaxy is only about 10,000 light years across. (ETA: 100,000 not 10,000 see roystgnr remark below.)
100,000 light years across; you may be thinking of 10,000 light years thick.
But in any case, small enough for an expansive civilization to colonize, slower than light using nothing more “speculative” than fission-based rockets, in a fraction of a percent of the age of the galaxy.
Why would we expect such things to begin with? That we don’t detect the elements of Anglophone science fiction doesn’t seem particularly worrying. Should we be updating our belief in extraterrestial civilizations based on their absence or should we be updating the credence lent to these speculated technologies?
That we don’t detect the elements of Anglophone science fiction doesn’t seem particularly worrying. Should we be updating our belief in extraterrestial civilizations based on their absence or should we be updating the credence lent to these speculated technologies?
Presumably this should be an update in both directions, but the update should be much more towards an absence of civilizations since these are all technologies which seem to be both doable and desirable for a civilization. Moreover, it isn’t just an absence of these technologies. We don’t see anything that looks like a sign of stellar engineering. That isn’t just the “Anglophone science fiction” but the fact that the universe looks essentially natural. It is possible (indeed likely) that there would be other technologies out there that we haven’t thought about yet that would also involve large scale harnessing of energy and other resources. But we don’t see anything anomalous.
The universe looks natural; it also looks homogeneous. This militates in favor of alien civilization and is settled. You’re proposing that I should doubt either naturalness or homogeneity because a purely speculative technology is not observed.
You’re proposing that I should doubt either naturalness or homogeneity because a purely speculative technology is not observed.
Not just a speculative technology. Those technologies are just some examples. As noted, there’s also a complete lack of radio sources. There’s no sign of any sort of alien life at all. If an alien civilization arose and prospered a billion years ago in our galaxy, we’d expect to see some sign of it, such as colonizing planets. And the lack of specific speculative technologies isn’t the problem, it is the lack of any sign of any sort of larescale use of the massive quantities of energy available to stars. It is all getting wasted. And that’s not just true for our galaxy, every galaxy we look at looks completely natural as far as we can tell.
Of course if you are absolutely set on preserving a strong form of homogenity and the naturalness of the universe there’s one obvious solution: There’s a Great Filter in front of us. Things are homogenous, and species get wiped out by something, probably a technology they decide to play with. If you are convinced of homogenity and naturalness then the Great Filter should frighten you.
That doesn’t work. If a civilization reached slightly beyond our tech level around twenty million years ago (a blink in the eye as far as the universe is concerned) anywhere in our galaxy then we should expect to have seen some sign of them. Radio and visitation aren’t the only issues. We don’t see any evidence of Dyson spheres or ringworlds (although the second is something we’ve only recently been able to detect- Kepler should be able to detect ringworlds albeit I don’t know if anyone is looking for them.) We see no evidence of any form of stellar engineering or large scale structures at all. And distance only matters when you look into the near past. Civilizations that have had millions of years to prosper should have spread much farther. Note that our galaxy is only about 10,000 light years across. (ETA: 100,000 not 10,000 see roystgnr remark below.)
100,000 light years across; you may be thinking of 10,000 light years thick.
But in any case, small enough for an expansive civilization to colonize, slower than light using nothing more “speculative” than fission-based rockets, in a fraction of a percent of the age of the galaxy.
Yes, thanks. That’s what I was thinking of.
Why would we expect such things to begin with? That we don’t detect the elements of Anglophone science fiction doesn’t seem particularly worrying. Should we be updating our belief in extraterrestial civilizations based on their absence or should we be updating the credence lent to these speculated technologies?
Presumably this should be an update in both directions, but the update should be much more towards an absence of civilizations since these are all technologies which seem to be both doable and desirable for a civilization. Moreover, it isn’t just an absence of these technologies. We don’t see anything that looks like a sign of stellar engineering. That isn’t just the “Anglophone science fiction” but the fact that the universe looks essentially natural. It is possible (indeed likely) that there would be other technologies out there that we haven’t thought about yet that would also involve large scale harnessing of energy and other resources. But we don’t see anything anomalous.
The universe looks natural; it also looks homogeneous. This militates in favor of alien civilization and is settled. You’re proposing that I should doubt either naturalness or homogeneity because a purely speculative technology is not observed.
Not just a speculative technology. Those technologies are just some examples. As noted, there’s also a complete lack of radio sources. There’s no sign of any sort of alien life at all. If an alien civilization arose and prospered a billion years ago in our galaxy, we’d expect to see some sign of it, such as colonizing planets. And the lack of specific speculative technologies isn’t the problem, it is the lack of any sign of any sort of larescale use of the massive quantities of energy available to stars. It is all getting wasted. And that’s not just true for our galaxy, every galaxy we look at looks completely natural as far as we can tell.
Of course if you are absolutely set on preserving a strong form of homogenity and the naturalness of the universe there’s one obvious solution: There’s a Great Filter in front of us. Things are homogenous, and species get wiped out by something, probably a technology they decide to play with. If you are convinced of homogenity and naturalness then the Great Filter should frighten you.