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It always struck me as weird that proponents of the Fermi paradox use lack of radio signals as indication we're alone. Ignoring that radio signals were audible

It always struck me as weird that proponents of the Fermi paradox use lack of radio signals as indication we're alone. Ignoring that radio signals were audible from Earth for maybe 100 years before we significantly reduced the power associated (& switched to digital) and started encrypting everything (makes everything look like noise). Once you start to consider neutrinos as a communication medium which we're just barely scratching the surface of, or whatever future technology might be possible with advances in science and engineering, then it becomes clear we don't know what to look for on the technological front for an advanced civilization (other than knowing it's unlikely to be 1950s analog radio waves).

cthalupa 2y ago
Lack of radio signals is a pretty tiny portion of the Fermi paradox. Fermi himself wasn't even thinking of them at the time according to the other Los Alamos scientists that were part of the conversation, but instead about having evidence of actual visitation. While the galaxy is mindbogglingly vast, even with the slower methods of interstellar travel that we could feasible achieve based on our current knowledge, we're talking about timeframes to traverse it that are not large on geological timescales, much less cosmological ones. There's lots of interesting reasons to pay attention to radio signals beyond 'Aliens broadcasting TV, music, and talk radio' - lots of neat stuff has radio waves as a consequence - and since we're already listening in and interpreting that data, it's pretty cost effective for us to also look for it in a technosignature context. But there's a reasonably wide variety of other technosignatures we actively look for today, and others that scientists attempt to infer out of data gathered for other reasons. Also, the whole way you've phrased your comment is kind of strange. The Fermi paradox doesn't advocate the idea that we're alone - it's about the discrepancy between how ubiquitous intelligence life should be in the universe at large based on our understandings of how life came into existence and how little evidence we have that that is the case. "We weren't looking at/for the right things" would 100% be a reasonable answer to the paradox that the overwhelming majority of scientists in the related fields would take no issue with if we suddenly discovered alien life through some different technosignature than we currently look for. Something like a dyson sphere or swarm would never have come into the conversation when Fermi first proposed the question (and he wasn't the first person to ask where everybody was, either) but are now seen as plausible enough that respected scientists in the field pour over things like the Kepler data looking for evidence of them. The Fermi paradox doesn't really need "proponents" - as long as we have no evidence of intelligent life or our understandings of how common intelligent life should be in the universe change, the paradox will stand. But I don't think there's any real faction of people that want it to stand, though. Every scientist or enthusiast on the subject I've ever spoken to or read thoughts on the subject would love to have an answer to the paradox.
- vlovich123 2y ago
  If the probability works out to 1 intelligent civilization per galaxy on average, then we wouldn't expect any other civilizations in our neck of the woods to discover (i.e. we could be the first or at least the only currently active one in our galaxy). If the probability works out to a few per galaxy, we don't actually know that it's possible for a civilization to practically leave their own solar system. Or it could be that in the amount of time since the Big Bang, we'd be the only ones that have had time to develop in our galaxy since the Big Bang. Or we could be the only ones to have developed in our neck of the woods for distances that aren't horribly relativistic (e.g. our furthest telescopes are looking back billions of years so who knows the current state of those places). As for the assumption that the galaxy would be teeming with life, it's not even clear that we can ever get to Alpha Centauri in a reasonable time frame. 80 years would require an average 5% the speed of light to get there (meaning much faster peak to do accelerate halfway / decelerate halfway). That's a lot of fuel so it's a huge stretch to claim we have that technology today. A 1% speed of life average speed would be a 400 year one-way trip. And even if we do build technology capable of this and go there, does that mean that Alpha Centauri then has the resources needed to bootstrap & proceed to the next star system or does it take a long time to build up a manufacturing base in the local star system to continue on the journey (i.e. you may be able to get to 1% the speed of light to travel between systems but traveling between planets within a system might still take a long time to collect resources & build out another space port)? In other words, how quickly do we go from star system to star system colonizing? There's no reason to believe that any intelligent civilization would be immune from economic pressures similar to humanity in terms of not taking on centennial or millennial interstellar projects. And as we can tell from humans on earth, there are economic, resource, technological, & timing reasons why we don't just start firing probes out into other star systems to try to do exploration. We also don't know how long the universe needed to cool & coalesce for before life had the appropriate conditions to evolve; it's not like life existed from the first moment Earth formed. It likely needed to exist for billions of years after the solar system coalesced & then for billions of years it was still getting pummeled by asteroids & comets within the orbital plane until it got cleared out. After all, Mars seems to have been similar in many ways but ended up dead so it's clearly a knife's edge (e.g. Jupiter protecting us from a bunch of incoming asteroids and comets). Finally, we have no idea whether intelligent civilizations have enough resources and survive long enough to leave their star system & to remain stable continuing to explore well beyond or collapse. And all of that isn't even touching that our ability to look for these technosignatures is extremely limited because we don't know what we're looking for, we don't know where to look for it, & we are blindly guessing at the signatures we might find. My point is - it's not a paradox unless you make some pretty wild assumptions that have no basis for them in the first place - we have no priors to inform probabilities to determine how many civilizations to look for. Nor do we even have search criteria for where to look. And we know that some pretty crazy technology that we have no way to detect is possible. As for visitation, I think people are way too optimistic about the ease with which such problems could be solved. & even if it does, we're at the outermost arm of the galaxy. Why would we be particularly interesting for aliens to visit? e.g. what star system would we pick to visit? Probably one with more resources that we've run out of rather than one with life if we've already convinced ourselves life is abundant in the universe & uninteresting to find.

cthalupa 2y ago

Lack of radio signals is a pretty tiny portion of the Fermi paradox. Fermi himself wasn't even thinking of them at the time according to the other Los Alamos scientists that were part of the conversation, but instead about having evidence of actual visitation. While the galaxy is mindbogglingly vast, even with the slower methods of interstellar travel that we could feasible achieve based on our current knowledge, we're talking about timeframes to traverse it that are not large on geological timescales, much less cosmological ones. There's lots of interesting reasons to pay attention to radio signals beyond 'Aliens broadcasting TV, music, and talk radio' - lots of neat stuff has radio waves as a consequence - and since we're already listening in and interpreting that data, it's pretty cost effective for us to also look for it in a technosignature context. But there's a reasonably wide variety of other technosignatures we actively look for today, and others that scientists attempt to infer out of data gathered for other reasons. Also, the whole way you've phrased your comment is kind of strange. The Fermi paradox doesn't advocate the idea that we're alone - it's about the discrepancy between how ubiquitous intelligence life should be in the universe at large based on our understandings of how life came into existence and how little evidence we have that that is the case. "We weren't looking at/for the right things" would 100% be a reasonable answer to the paradox that the overwhelming majority of scientists in the related fields would take no issue with if we suddenly discovered alien life through some different technosignature than we currently look for. Something like a dyson sphere or swarm would never have come into the conversation when Fermi first proposed the question (and he wasn't the first person to ask where everybody was, either) but are now seen as plausible enough that respected scientists in the field pour over things like the Kepler data looking for evidence of them. The Fermi paradox doesn't really need "proponents" - as long as we have no evidence of intelligent life or our understandings of how common intelligent life should be in the universe change, the paradox will stand. But I don't think there's any real faction of people that want it to stand, though. Every scientist or enthusiast on the subject I've ever spoken to or read thoughts on the subject would love to have an answer to the paradox.

vlovich123 2y ago
If the probability works out to 1 intelligent civilization per galaxy on average, then we wouldn't expect any other civilizations in our neck of the woods to discover (i.e. we could be the first or at least the only currently active one in our galaxy). If the probability works out to a few per galaxy, we don't actually know that it's possible for a civilization to practically leave their own solar system. Or it could be that in the amount of time since the Big Bang, we'd be the only ones that have had time to develop in our galaxy since the Big Bang. Or we could be the only ones to have developed in our neck of the woods for distances that aren't horribly relativistic (e.g. our furthest telescopes are looking back billions of years so who knows the current state of those places). As for the assumption that the galaxy would be teeming with life, it's not even clear that we can ever get to Alpha Centauri in a reasonable time frame. 80 years would require an average 5% the speed of light to get there (meaning much faster peak to do accelerate halfway / decelerate halfway). That's a lot of fuel so it's a huge stretch to claim we have that technology today. A 1% speed of life average speed would be a 400 year one-way trip. And even if we do build technology capable of this and go there, does that mean that Alpha Centauri then has the resources needed to bootstrap & proceed to the next star system or does it take a long time to build up a manufacturing base in the local star system to continue on the journey (i.e. you may be able to get to 1% the speed of light to travel between systems but traveling between planets within a system might still take a long time to collect resources & build out another space port)? In other words, how quickly do we go from star system to star system colonizing? There's no reason to believe that any intelligent civilization would be immune from economic pressures similar to humanity in terms of not taking on centennial or millennial interstellar projects. And as we can tell from humans on earth, there are economic, resource, technological, & timing reasons why we don't just start firing probes out into other star systems to try to do exploration. We also don't know how long the universe needed to cool & coalesce for before life had the appropriate conditions to evolve; it's not like life existed from the first moment Earth formed. It likely needed to exist for billions of years after the solar system coalesced & then for billions of years it was still getting pummeled by asteroids & comets within the orbital plane until it got cleared out. After all, Mars seems to have been similar in many ways but ended up dead so it's clearly a knife's edge (e.g. Jupiter protecting us from a bunch of incoming asteroids and comets). Finally, we have no idea whether intelligent civilizations have enough resources and survive long enough to leave their star system & to remain stable continuing to explore well beyond or collapse. And all of that isn't even touching that our ability to look for these technosignatures is extremely limited because we don't know what we're looking for, we don't know where to look for it, & we are blindly guessing at the signatures we might find. My point is - it's not a paradox unless you make some pretty wild assumptions that have no basis for them in the first place - we have no priors to inform probabilities to determine how many civilizations to look for. Nor do we even have search criteria for where to look. And we know that some pretty crazy technology that we have no way to detect is possible. As for visitation, I think people are way too optimistic about the ease with which such problems could be solved. & even if it does, we're at the outermost arm of the galaxy. Why would we be particularly interesting for aliens to visit? e.g. what star system would we pick to visit? Probably one with more resources that we've run out of rather than one with life if we've already convinced ourselves life is abundant in the universe & uninteresting to find.