The earliest fossils we have of primordial life forms on Earth date back nearly 4.3 billion years, almost immediately after the Earth formed.
That's the optimistic analysis. It's more likely a billion years after Earth formed.
If there was ever life on Mars or Venus, it's not there now.
It's better than that. It's almost certain that there was life on Mars, and there may yet be life on Mars right now. ... may...
Of course it's possible for it to have happened somewhere else, but if it has then it's almost certainly so rare, and so distant that we will never meet them. For all practical purposes of the word, we are alone, and we almost certainly always will be.
That still remains to be seen. I don't expect there to be even 1 alien encounter per civilization; but just under 1 per species? Hmmm. Maybe. Yes, sure we have our specific issues. But there may still be life on Mars, and there may still be life on Io, and there may have been life on other moons and planets in our system. Life surviving is pretty tough, but clearly, life is an aggressive sumbitch that exploits any and all available opportunities it encounters. I never thought any human in my lifetime would see an interstellar object enter our solar system, but that's already happened. The coincidence is like building two gravitational space telescopes and discovering the "blip" of two black holes colliding over 2 billion years ago, 2 weeks after you finish building them.
Space has a nasty habit of making the obviously, totally, impossible seem utterly mundane.
The Cambrian explosion the led to the development of multicellular life on Earth only happened less than 600 million years ago. Regardless of how early we carbon date stromatolite fossils, that still tells us that life on Earth was constrained to single-celled organisms for billions of years. Just as it would be in the extremely unlikely event that it does still exist anywhere else in the solar system.
Again, I would argue that this counts significantly against the possibility of multi-celled organisms eventually evolving into civilizations with any kind of regularity.
It's only a paradox because Fermi, like a lot of intellectuals, doesn't think about the law of diminishing returns. It's not just life that hits barriers, it's literally everything.
That's the optimistic analysis. It's more likely a billion years after Earth formed.
It's better than that. It's almost certain that there was life on Mars, and there may yet be life on Mars right now. ... may...
That still remains to be seen. I don't expect there to be even 1 alien encounter per civilization; but just under 1 per species? Hmmm. Maybe. Yes, sure we have our specific issues. But there may still be life on Mars, and there may still be life on Io, and there may have been life on other moons and planets in our system. Life surviving is pretty tough, but clearly, life is an aggressive sumbitch that exploits any and all available opportunities it encounters. I never thought any human in my lifetime would see an interstellar object enter our solar system, but that's already happened. The coincidence is like building two gravitational space telescopes and discovering the "blip" of two black holes colliding over 2 billion years ago, 2 weeks after you finish building them.
Space has a nasty habit of making the obviously, totally, impossible seem utterly mundane.
The Cambrian explosion the led to the development of multicellular life on Earth only happened less than 600 million years ago. Regardless of how early we carbon date stromatolite fossils, that still tells us that life on Earth was constrained to single-celled organisms for billions of years. Just as it would be in the extremely unlikely event that it does still exist anywhere else in the solar system.
Again, I would argue that this counts significantly against the possibility of multi-celled organisms eventually evolving into civilizations with any kind of regularity.
The point is "regularity".
We're so far outside the bounds of that word already that it's use doesn't make sense here.
I disagree. I think the only reasonable answer to the so-called Fermi paradox is that we haven't seen any sign of them because they're not there.
It's more of a logic issue.
It's only a paradox because Fermi, like a lot of intellectuals, doesn't think about the law of diminishing returns. It's not just life that hits barriers, it's literally everything.