Today I'm talking about the Fermi Paradox in my astro-for-physics-majors class (and I'll talk about it again on Friday in my astro 101 class).
It's a really simple question with completely terrifying/mind-blowing implications, first asked by Enrico Fermi (who, ironically, was one of the Manhattan project scientists...)
Our universe is 13.8 billion years old, our Galaxy is at least 10 billion years old, other planets are surely much older than Earth, with more time to involve intelligent life.
"So where is everybody?"
A few possibilities for how to resolve the paradox. I'm going to list them all and put a poll at the end of this thread so you can vote for your favourite!
1. We are alone. We are the first intelligent life that has ever evolved in the Universe.
(Generally in astronomy any explanation that requires us to be special is a bad one. Then again, we are here asking this question, which is kind of the mother of all observation biases)
2. There are other civilizations out there, but they don't travel. This could be because it's just too hard (our furthest probe has traveled something like 0.004% of the distance to the closest star). Or maybe the drive to explore/colonize is a human trait and other intelligent life wouldn't have that drive.
3. The absolutely most depressing option: there are other civilizations, but technologically advanced civilizations just don't last very long, so the chances that we'd overlap with another civilization nearby and notice their presence is super unlikely.
4. A galactic civilization exists! But they are avoiding us, either because we're morally reprehensible, or because we're in a kind of "wildlife preserve" (though I find these ideas pretty weirdly human-centric...)
@sundogplanets I thought Neil DeGrasse Tyson had an interesting point when he suggested that an extraterrestrial race appreciably smarter than we are might simply not be very interested in talking to us. Sort of in the way that very few humans are really interested in talking to chimpanzees, or would go out of their way to try.
@sundogplanets
(I do see a defect in this angle however, inasmuch as if chimpanzees (or orcas or parrots or octopuses or whatever) showed a marked curiosity about the universe, to the point of making tools and developing systems to understand it further, I rather think a lot of us would be very interested in trying to talk to them.)