This analysis remains predicated on the assumption that a long-lasting intelligent system is easily visible over cosmological or galactic distances with the sorts of investigations that have already been performed by us.
No it’s the opposite. If (as they argue) we don’t expect many nearby aliens then it’s irrelevant whether or not we would be able to see them.
The perils of posting quickly in the middle of rapid apartment hunting (for a new postdoc position at a university with a bunch of yeast cell biologists AND astrobiologists! YES!).
I was referring to slide 27, with the various probability distribution graphs conditioned on various observations. The ‘no colonization’ conditional graphs all leave the left low-number tail intact while chopping off the probability bulge to the right of ‘one in our galaxy’ in various different ways. But this is only valid under the assumption that exponential colonization/galactic scale visibility with a few decades of rather poor observations against the screaming burning backdrop of the astrophysical universe is POSSIBLE. (Allow me to preemptively counter the ‘but only one has to be able to’ argument, this is an event that would be extraordinarily correlated across everybody). There are vast numbers of possibilities for the fate of intelligent systems that are not rapid extinction or consuming the universe that are insufficiently explored by so many people.
Without these conditional probability bounds, the given probability distribution is distinctly uninformative. It basically says ‘with the distribution of probabilities that can be extracted from literature on the subject, no intelligent systems in the visible universe is as likely as thousands to a billion in our galaxy’, that little bump on the right side of the distribution is pretty intense). I also happen to think that the given abiogenesis probability distributions are far too wide to the low side, that we have not excluded the possibility of multiple completely independent biospheres in our own solar system at all, and that complex life has some possibility of being limited more by geological/orbital/energetic issues than evolution which introduces interesting bimodality to that probability distribution, but that’s just me (and the people whose work I follow).
No it’s the opposite. If (as they argue) we don’t expect many nearby aliens then it’s irrelevant whether or not we would be able to see them.
The perils of posting quickly in the middle of rapid apartment hunting (for a new postdoc position at a university with a bunch of yeast cell biologists AND astrobiologists! YES!).
I was referring to slide 27, with the various probability distribution graphs conditioned on various observations. The ‘no colonization’ conditional graphs all leave the left low-number tail intact while chopping off the probability bulge to the right of ‘one in our galaxy’ in various different ways. But this is only valid under the assumption that exponential colonization/galactic scale visibility with a few decades of rather poor observations against the screaming burning backdrop of the astrophysical universe is POSSIBLE. (Allow me to preemptively counter the ‘but only one has to be able to’ argument, this is an event that would be extraordinarily correlated across everybody). There are vast numbers of possibilities for the fate of intelligent systems that are not rapid extinction or consuming the universe that are insufficiently explored by so many people.
Without these conditional probability bounds, the given probability distribution is distinctly uninformative. It basically says ‘with the distribution of probabilities that can be extracted from literature on the subject, no intelligent systems in the visible universe is as likely as thousands to a billion in our galaxy’, that little bump on the right side of the distribution is pretty intense). I also happen to think that the given abiogenesis probability distributions are far too wide to the low side, that we have not excluded the possibility of multiple completely independent biospheres in our own solar system at all, and that complex life has some possibility of being limited more by geological/orbital/energetic issues than evolution which introduces interesting bimodality to that probability distribution, but that’s just me (and the people whose work I follow).