I’m a bit confused about the prior that he uses in order to assign uniform probability on the existence of extraterrestrial life. Although I agree with that a logarithmic flat prior is a good idea for this problem, it is important to acknowledge that it is biased towards the unconstrained large scales. Since there is a minimum length scale by construction (the size of the earth or so) it would look more fair if he imposed a large scale cutoff as well (at radius of the observable Universe say). This way we can no longer claim that the extraterrestrial life is most likely to be found further than the edge of our Universe, but we could possibly still rule out our own galaxy.
Aside from that, an excellent (and entertaining) talk by Tegmark.
I’m a bit confused about the prior that he uses in order to assign uniform probability on the existence of extraterrestrial life. Although I agree with that a logarithmic flat prior is a good idea for this problem, it is important to acknowledge that it is biased towards the unconstrained large scales. Since there is a minimum length scale by construction (the size of the earth or so) it would look more fair if he imposed a large scale cutoff as well (at radius of the observable Universe say). This way we can no longer claim that the extraterrestrial life is most likely to be found further than the edge of our Universe, but we could possibly still rule out our own galaxy.
Aside from that, an excellent (and entertaining) talk by Tegmark.