The point being that if there is intelligent life elsewhere in the universe and it hasn’t spread (in order to maintain the Great Silence), then the odds of our 1 galaxy, out of the millions or billions known, being the host ought to be drastically smaller even if we try to appeal to reasons to think our galaxy special because of ourselves (eg. panspermia).
Such a set of probabilities may be justified if you’re very uncertain (as seems superficially reasonable) about the baseline probability of life arising in any given galaxy. So perhaps one might assign a ~40% chance that life is just incredibly likely, and most every galaxy has multiple instances of biogenesis, and a ~40% chance that life is just so astronomically (har har har) improbable that the Earth houses the only example in the universe,
This is almost certainly much less reasonable once you start thinking about the Great Filter, unless you think the Filter is civilizations just happily chilling on their home planet or thereabouts for eons, but then not everybody’s read or thought about the Filter.
The bigger problem to me seems that both the numbers (galaxy and universe) are way too high. It seems like it should be more in the range of “meta-uncertainty + epsilon” for both answers. Maybe “epsilon * lots” for the universe one but even that should be lower than the uncertainty component.
If the strong filter is propagation through space, then for rates which people could plausibly assign to the rate of occurrence of intelligent life, the probabilities could be near identical.
What are the odds that a randomly selected population of 10000 has any left handed people? What are the odds that an entire country does?
Ditto if the strong filter is technological civilization (which strikes me as unlikely, given the anthropological record, but it is one of the Drake terms). If there are ten thousand intelligent species in the galaxy but we’re the only one advanced enough to be emitting on radio wavelengths, we’d never hear about any of the others.
“20% difference” between what and what?
The point being that if there is intelligent life elsewhere in the universe and it hasn’t spread (in order to maintain the Great Silence), then the odds of our 1 galaxy, out of the millions or billions known, being the host ought to be drastically smaller even if we try to appeal to reasons to think our galaxy special because of ourselves (eg. panspermia).
Such a set of probabilities may be justified if you’re very uncertain (as seems superficially reasonable) about the baseline probability of life arising in any given galaxy. So perhaps one might assign a ~40% chance that life is just incredibly likely, and most every galaxy has multiple instances of biogenesis, and a ~40% chance that life is just so astronomically (har har har) improbable that the Earth houses the only example in the universe,
This is almost certainly much less reasonable once you start thinking about the Great Filter, unless you think the Filter is civilizations just happily chilling on their home planet or thereabouts for eons, but then not everybody’s read or thought about the Filter.
I was kind of hoping most LWers at least had heard of the Great Silence/Fermi controversy, though.
Maybe there should be a question or two about the Fermi paradox.
The bigger problem to me seems that both the numbers (galaxy and universe) are way too high. It seems like it should be more in the range of “meta-uncertainty + epsilon” for both answers. Maybe “epsilon * lots” for the universe one but even that should be lower than the uncertainty component.
If the strong filter is propagation through space, then for rates which people could plausibly assign to the rate of occurrence of intelligent life, the probabilities could be near identical.
What are the odds that a randomly selected population of 10000 has any left handed people? What are the odds that an entire country does?
Ditto if the strong filter is technological civilization (which strikes me as unlikely, given the anthropological record, but it is one of the Drake terms). If there are ten thousand intelligent species in the galaxy but we’re the only one advanced enough to be emitting on radio wavelengths, we’d never hear about any of the others.