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The Fermi paradox may not be a paradox, depending on the values you assign to various probabilities. It's more of a observational heuristic for guessing the pro

The Fermi paradox may not be a paradox, depending on the values you assign to various probabilities. It's more of a observational heuristic for guessing the probabilities... if intelligent life was common, we should see some signs of it.

jerf 9y ago
To elaborate, independent probabilities multiply, resulting in exponentially smaller probabilities, whereas as you look out into space, the number of possible places for life increases only at somewhere around O(n^2)ish as distance increases. (It is not O(n^3) as you might naively think as matter is far from uniformly distributed. I don't recall what it is exactly, it's not O(n^2.000), but it's somewhere in there.) It doesn't take hypothesizing all that many low probability events for the creation of life, or intelligent life, before you get to numbers like "less than one per galaxy", and it isn't all that far from a logarithmic perspective to get to "less than one per universe". So it is indeed the case that our ignorance is such that we can't simply look up at the universe and go "it has to be teeming with life!", because we do not yet know that the probability of life is not in fact orders of magnitude smaller than the observable universe. We don't know that it isn't teeming with life either, but that's where you get into the Fermi paradox and the Great Filter arguments.
TheOtherHobbes 9y ago
Assuming we'd recognise it. Bacteria, plants, insects, and even some animals can all live in a human city and not realise their environment is artificial. The city is conceptually invisible to them, and interactions with it will appear random, or at least extremely unpredictable. Recognisable interspecies intelligence may be a question of relative cognitive ability, not of physical presence.
- civilian 9y ago
  I don't think that's a fair comparison. Even though humans are limited in our senses, we've built machines to see and monitor every frequency of light. And we're also really good at finding patterns. If there was an active intelligence that had colonized most of the galaxy, we'd know it. (Unless the intelligence was actively trying to hide from us?)
  - monocasa 9y ago
    Why would we? Our own EM emissions drop below the noise floor at only a few light years out, and AFAIK our total emissions have been going down as we transition away from pure broadcast to cell and wifi. Even assuming that there was a large civilization out there that communicated via EM across interstellar distances, they'd almost certainly use point to point lasers to keep the SNR usable.

jerf 9y ago

To elaborate, independent probabilities multiply, resulting in exponentially smaller probabilities, whereas as you look out into space, the number of possible places for life increases only at somewhere around O(n^2)ish as distance increases. (It is not O(n^3) as you might naively think as matter is far from uniformly distributed. I don't recall what it is exactly, it's not O(n^2.000), but it's somewhere in there.) It doesn't take hypothesizing all that many low probability events for the creation of life, or intelligent life, before you get to numbers like "less than one per galaxy", and it isn't all that far from a logarithmic perspective to get to "less than one per universe". So it is indeed the case that our ignorance is such that we can't simply look up at the universe and go "it has to be teeming with life!", because we do not yet know that the probability of life is not in fact orders of magnitude smaller than the observable universe. We don't know that it isn't teeming with life either, but that's where you get into the Fermi paradox and the Great Filter arguments.

TheOtherHobbes 9y ago

Assuming we'd recognise it. Bacteria, plants, insects, and even some animals can all live in a human city and not realise their environment is artificial. The city is conceptually invisible to them, and interactions with it will appear random, or at least extremely unpredictable. Recognisable interspecies intelligence may be a question of relative cognitive ability, not of physical presence.

civilian 9y ago
I don't think that's a fair comparison. Even though humans are limited in our senses, we've built machines to see and monitor every frequency of light. And we're also really good at finding patterns. If there was an active intelligence that had colonized most of the galaxy, we'd know it. (Unless the intelligence was actively trying to hide from us?)
- monocasa 9y ago
  Why would we? Our own EM emissions drop below the noise floor at only a few light years out, and AFAIK our total emissions have been going down as we transition away from pure broadcast to cell and wifi. Even assuming that there was a large civilization out there that communicated via EM across interstellar distances, they'd almost certainly use point to point lasers to keep the SNR usable.