Steven0461 points out that particle accelerator disasters are ruled out, as we could in principle colonize the universe using Project Orion spaceships right now, without doing any more particle physics experiments.
If we’re talking about supercollider-induced vacuum decay (where the disaster actually renders the whole future light-cone uninhabitable), then every part of your Orion-type civilization must avoid conducting the dangerous experiment, forever, or at least for long enough to matter, astro-demographically. It might be argued that this is improbable enough to offset the existence of the rare civilization which does have such discipline.
What if the first civilization in any given universe carries out some universe-sterilizing experiment, which effectively results in an entirely new universe, whose first civilization then carries out an equally universe-sterilizing experiment?
Good point, of course, but since life like us could (it seems) have arisen billions of years ago, if intelligent life were common and mostly destroyed universes we would expect to see a younger universe. (I remember seeing a paper (by Milan Cirkovic, maybe?) about this, but am too tired to find it right now.)
This also applies to DanielVarga’s suggestion of relativistically expanding civilizations, if they don’t contain observers in our reference class (if they did, obviously we’d expect to be there).
Let me promote my idea that other civilizations are unobservable to us because they are expanding with the speed of light. See a bit more detail here and the small thread below it.
If we’re talking about supercollider-induced vacuum decay (where the disaster actually renders the whole future light-cone uninhabitable), then every part of your Orion-type civilization must avoid conducting the dangerous experiment, forever, or at least for long enough to matter, astro-demographically. It might be argued that this is improbable enough to offset the existence of the rare civilization which does have such discipline.
Disasters that sterilize the whole universe don’t solve the Fermi problem, they exacerbate it.
It has to be a disaster that kills of each civ just at the point that we’re at, or a little after, without preventing our existence.
What if the first civilization in any given universe carries out some universe-sterilizing experiment, which effectively results in an entirely new universe, whose first civilization then carries out an equally universe-sterilizing experiment?
Elementary anthropic logic tells us that we cannot find ourselves in a universe where we never got to exist!
Good point, of course, but since life like us could (it seems) have arisen billions of years ago, if intelligent life were common and mostly destroyed universes we would expect to see a younger universe. (I remember seeing a paper (by Milan Cirkovic, maybe?) about this, but am too tired to find it right now.)
This also applies to DanielVarga’s suggestion of relativistically expanding civilizations, if they don’t contain observers in our reference class (if they did, obviously we’d expect to be there).
Let me promote my idea that other civilizations are unobservable to us because they are expanding with the speed of light. See a bit more detail here and the small thread below it.