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> Within two decades, SETI experiments will be able to complete a reconnaissance of 1 million star systems, which is hundreds of times more than have been caref

> Within two decades, SETI experiments will be able to complete a reconnaissance of 1 million star systems, which is hundreds of times more than have been carefully examined so far. SETI practitioners from Frank Drake to Carl Sagan have estimated that the galaxy currently houses somewhere between 10,000 and a few million broadcasting societies. If these estimates are right, then examining 1 million star systems could well lead to a discovery. I think he's basing the date on the assumption that we'll have searched 1 million star systems by 2037 and there are a few million broadcasting societies. Personally I think the odds are pretty damn long, even on the optimistic end of Sagan's and Drake's assumptions. Assuming there are 200-400 billion star systems in our galaxy, that gives us a 1 in 200-400k odds of finding one by 2037? I'll take the bet. Still a great read, I'm much more fascinated by the idea of artifacts. I believe that the longer we go without finding things, the more seriously we should be thinking about leaving things.

jackmott 9y ago
would need to be a few million broadcasting societies, broadcasting in a way we can detect. and there could be aliens in other galaxies! we wouldn't detect them by 2035 article was pretty nonsense imho
aetherson 9y ago
On the optimistic end of Sagan's range, there are "a few million" broadcasting societies, call it 2 million. If there are 400 billion stars, that means that there's one broadcasting society per 20,000 stars. If they're evenly distributed, and we sample 1M stars, then our odds of missing with all 1M samples are negligible (about 1/10^22). (I don't think that there are a few million broadcasting societies in our galaxy. But if there are, we'd expect to find them soon.)
- cgore 9y ago
  I have trouble believing there's more than a handful of spacefaring species per galaxy. Even without FTL travel, one species could fill up all of the habitable planets in a galaxy the size of ours in a few million years or less, thanks to the fact that we breed exponentially. And there's been Sun-like stars for a while now in our galaxy, presumably with Earth-like planets orbiting them. So it's a matter of getting there first.
  - aetherson 9y ago
    If there are a "handful," then there are probably 0 (besides us). You have to believe that there's a very narrow range of values to get precisely to a handful. Like, the range quoted above is from "10,000 to a few million," so a factor of 200ish from high to low range. If you think that there are 10, per galaxy, why don't you believe instead that there are 0.3 per galaxy (only off by a factor of 30?)? How much confidence can you have in your highly speculative variables that your output can be constrained down to just a single order of magnitude or so?
    - cgore 9y ago
      By handful I mean < 5. Probably usually just one. Because no others would get a chance to evolve, with all the habitable planets quickly being occupied by whichever species figures out interstellar travel first.
      - civilian 9y ago
        I think you have a very Golden-Era-of-Sci-Fi space-opera conquering view of spacefaring. Why do we need to expand? Our population growth is already levelling off. Why do we need to send _our bodies_ rather than with AI, or with our consciouses uploaded into computers? (a la Charles Stross' Accelerando or Greg Egan's Diaspora) If we're sending AI probes around, why do we need to take all resources to the extent that we prevent other species from developing? Most of the fundamental science that we want to do can be done right here in our own solar system. There's just not a need to expand.
        voidmain 9y ago
        Once you have sufficiently advanced technology, unless you also have some kind of totalitarianism, it only takes a few groups of people who disagree about the allocation of resources (or, really, anything else) in this star system and want to leave. And then the same thing happens recursively in whatever star systems they go to, and you have exponential growth until it saturates to cubic or whatever. Yes, of course, they will be AIs or uploads or body printers. Even for an advanced civilization, shipping bags of meat to other star systems would be wasteful. That doesn't mean they won't want to use resources, or that there would be no evidence of them if they were already here. edit: There's certainly scenarios in which the first species to explore a galaxy doesn't literally prevent other species from evolving. But that doesn't mean they wouldn't be obviously detectable. The likely number of starfaring species in the galaxy given our observations is zero.
- deleted 9y ago
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platz 9y ago
discounts great filters

jackmott 9y ago

would need to be a few million broadcasting societies, broadcasting in a way we can detect. and there could be aliens in other galaxies! we wouldn't detect them by 2035 article was pretty nonsense imho

aetherson 9y ago

On the optimistic end of Sagan's range, there are "a few million" broadcasting societies, call it 2 million. If there are 400 billion stars, that means that there's one broadcasting society per 20,000 stars. If they're evenly distributed, and we sample 1M stars, then our odds of missing with all 1M samples are negligible (about 1/10^22). (I don't think that there are a few million broadcasting societies in our galaxy. But if there are, we'd expect to find them soon.)

cgore 9y ago
I have trouble believing there's more than a handful of spacefaring species per galaxy. Even without FTL travel, one species could fill up all of the habitable planets in a galaxy the size of ours in a few million years or less, thanks to the fact that we breed exponentially. And there's been Sun-like stars for a while now in our galaxy, presumably with Earth-like planets orbiting them. So it's a matter of getting there first.
- aetherson 9y ago
  If there are a "handful," then there are probably 0 (besides us). You have to believe that there's a very narrow range of values to get precisely to a handful. Like, the range quoted above is from "10,000 to a few million," so a factor of 200ish from high to low range. If you think that there are 10, per galaxy, why don't you believe instead that there are 0.3 per galaxy (only off by a factor of 30?)? How much confidence can you have in your highly speculative variables that your output can be constrained down to just a single order of magnitude or so?
  - cgore 9y ago
    By handful I mean < 5. Probably usually just one. Because no others would get a chance to evolve, with all the habitable planets quickly being occupied by whichever species figures out interstellar travel first.
    - civilian 9y ago
      I think you have a very Golden-Era-of-Sci-Fi space-opera conquering view of spacefaring. Why do we need to expand? Our population growth is already levelling off. Why do we need to send _our bodies_ rather than with AI, or with our consciouses uploaded into computers? (a la Charles Stross' Accelerando or Greg Egan's Diaspora) If we're sending AI probes around, why do we need to take all resources to the extent that we prevent other species from developing? Most of the fundamental science that we want to do can be done right here in our own solar system. There's just not a need to expand.
      - voidmain 9y ago
        Once you have sufficiently advanced technology, unless you also have some kind of totalitarianism, it only takes a few groups of people who disagree about the allocation of resources (or, really, anything else) in this star system and want to leave. And then the same thing happens recursively in whatever star systems they go to, and you have exponential growth until it saturates to cubic or whatever. Yes, of course, they will be AIs or uploads or body printers. Even for an advanced civilization, shipping bags of meat to other star systems would be wasteful. That doesn't mean they won't want to use resources, or that there would be no evidence of them if they were already here. edit: There's certainly scenarios in which the first species to explore a galaxy doesn't literally prevent other species from evolving. But that doesn't mean they wouldn't be obviously detectable. The likely number of starfaring species in the galaxy given our observations is zero.
deleted 9y ago
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platz 9y ago

discounts great filters