Why are there no signs of aliens, given the vastness of the galaxy and the apparent abundance of opportunities for life to develop? This is the Fermi paradox. Here’s a possible solution to it. I’ve not seen it proposed before, though I don’t know the literature well.
Suppose the following claims are true:
1) There is a multiverse. (It may not be strictly necessary to assume this, but it makes exposition easier.)
2) Any universe that is capable of supporting life is also fragile, in the sense that a relatively small, highly localized ‘pinprick’ event can cause the whole thing to collapse, as a pinprick can destroy an inflated balloon.
3) ‘Pinprick’ events do not occur naturally. (Again, it may not be strictly necessary to assume this.)
4) An advanced technological civilization will almost certainly create a pinprick event inadvertently as soon as it is capable of doing so. (Suppose that there is a technological process that promises huge benefits in say, in cheap energy or interstellar travel, but which will also, and unforeseeably, create a pinprick event.)
Then we have a solution to the Fermi paradox. Every universe in which a technological civilization develops is rapidly destroyed by that civilization — or by another that develops around the same time. No universe contains more than a very small number of technological civilizations, and we shouldn’t expect to see signs of another one in our galaxy.
And we’re going to destroy the universe soon.
If a pinprick expands at the speed of light, shouldn’t we expect to see distant stars and galaxies winking out?
I don’t think so. Wouldn’t the pinprick hit us at the same moment as the last light from the extinguished stars? (But I’m not a physicist!)
@Keith: You’re correct, we wouldn’t get any advanced notice of a pinprick event if the effect propagated at luminal velocities.
However, there is a simple problem with this idea: It requires an assumption that civilizations are relatively rare to begin with, which by itself will be sufficient to resolve fermi’s paradox, rendering the pinprick hypothesis superfluous. If we have survived to ~13.7 billion years, then life in the universe cannot be so common that we would expect to notice other technological civilizations, because we would already have been wiped out by them. But if life is so uncommon, then the Fermi paradox is resolved anyways. We don’t see other alien civilizations because they’re so rare (and consequently very far away). No pinprick hypothesis needed!
In other words, the pinprick hypothesis assumes that civilizations will be rare, but the latter assumption doesn’t require the former hypothesis. Since the rare civilization hypothesis is sufficient to answer fermi’s paradox, we don’t need your hypothesis.