4 ms·

Yeah, the timescale for the Fermi Paradox is millions of years; it'd be a hard sell that 1500 years can make a dent in it.

pmiller2 10y ago
Wikipedia claims that the entire galaxy can be traversed in ~1M years. Life on earth has been around for ~3.8G years. If life started somewhere in the galaxy a few million years earlier than that, and evolved into a spacefaring civilization, it's not too far fetched that they could either have already been here, or, if they are close enough, they could pick up our signals and come for a look-see.
- mikeash 10y ago
  Right, the Fermi Paradox isn't asking why aliens haven't come to visit us now that they've surely heard our radio signals. It's about why we're even here at all, given that it seems like aliens should have come and colonized the place ages ago, or at least why there are no signs of past exploratory visits.
- jerf 10y ago
  A while back on HN there was a discussion about whether shooting radio waves into space was a good idea, because the game theoretic solution to "why are we alone" might be that extraterrestrial civilizations pre-emptively destroy any other competition they can identify. What finally made me reject this hypothesis is that A: you shouldn't actually wait for intelligent life to develop, because even if humans are somehow progressing at the fastest possible rate and nothing could be faster, a claim I would seriously doubt, we're still developing at this rate dangerously quickly and B: Earth has been broadcasting "I very likely have life!" for not a century since the invention of radio, but approximately 2.3 billion years, since the invention of atmospheric oxygen, which is something that should be possible to determine from great distances by looking at the spectra lines when Earth occludes the Sun. We're already doing that a bit ourselves, and our telescopes are tiny compared to what a full Kardashev-1 civilization could put together, or even what we could put together if this was our top priority. Even on the cosmic scale, 2.3 billion years is a Real Amount of Time. Unless nearly every solar system has life of a similar degree of obviousness from light-years away, making Earth's signal just noise, we've been broadcasting that we're at least worth a probe for a long time. I doubt every solar system has free-oxygen-generating life or any equivalent; you don't have to believe the "Rare Earth" arguments prove that Earth is alone for it to show that even with our current understanding of physics, chemistry, etc. it is very unlikely that every, or even a majority, of systems have advanced life in them. Given that the limits of technology that we now believe in strongly suggest that an unopposed "probe" is probably on its own sufficient to colonize a planet (and thus render it no longer a threat), it remains very strange that we're here at all, not long since displaced by an aliens. In a weird way, it would almost make more sense from the Fermi paradox point of view if we obviously hadn't developed here and if humans were obviously aliens-to-Earth, but humans have an immaculate pedigree for being 100% all-natural Earth-sourced ingredients.

pmiller2 10y ago

Wikipedia claims that the entire galaxy can be traversed in ~1M years. Life on earth has been around for ~3.8G years. If life started somewhere in the galaxy a few million years earlier than that, and evolved into a spacefaring civilization, it's not too far fetched that they could either have already been here, or, if they are close enough, they could pick up our signals and come for a look-see.

mikeash 10y ago
Right, the Fermi Paradox isn't asking why aliens haven't come to visit us now that they've surely heard our radio signals. It's about why we're even here at all, given that it seems like aliens should have come and colonized the place ages ago, or at least why there are no signs of past exploratory visits.
jerf 10y ago
A while back on HN there was a discussion about whether shooting radio waves into space was a good idea, because the game theoretic solution to "why are we alone" might be that extraterrestrial civilizations pre-emptively destroy any other competition they can identify. What finally made me reject this hypothesis is that A: you shouldn't actually wait for intelligent life to develop, because even if humans are somehow progressing at the fastest possible rate and nothing could be faster, a claim I would seriously doubt, we're still developing at this rate dangerously quickly and B: Earth has been broadcasting "I very likely have life!" for not a century since the invention of radio, but approximately 2.3 billion years, since the invention of atmospheric oxygen, which is something that should be possible to determine from great distances by looking at the spectra lines when Earth occludes the Sun. We're already doing that a bit ourselves, and our telescopes are tiny compared to what a full Kardashev-1 civilization could put together, or even what we could put together if this was our top priority. Even on the cosmic scale, 2.3 billion years is a Real Amount of Time. Unless nearly every solar system has life of a similar degree of obviousness from light-years away, making Earth's signal just noise, we've been broadcasting that we're at least worth a probe for a long time. I doubt every solar system has free-oxygen-generating life or any equivalent; you don't have to believe the "Rare Earth" arguments prove that Earth is alone for it to show that even with our current understanding of physics, chemistry, etc. it is very unlikely that every, or even a majority, of systems have advanced life in them. Given that the limits of technology that we now believe in strongly suggest that an unopposed "probe" is probably on its own sufficient to colonize a planet (and thus render it no longer a threat), it remains very strange that we're here at all, not long since displaced by an aliens. In a weird way, it would almost make more sense from the Fermi paradox point of view if we obviously hadn't developed here and if humans were obviously aliens-to-Earth, but humans have an immaculate pedigree for being 100% all-natural Earth-sourced ingredients.