Panspermia makes the Bayesian prior of aliens visiting us, even given that the universe can’t have too much advanced life or we would see evidence of it, not all that low, perhaps 1⁄1,000.
Is this estimate written down in more detail anywhere, do you know? Accidental panspermia always seemed really unlikely to me: if you figure the frequency of rock transfer between two bodies goes with the inverse square of the distance between them, then given what we know of rock transfer between Earth and Mars you shouldn’t expect much interstellar transfer at all, even a billion years ago when everything was closer together. But I have not thought about it in depth.
I am unaware if Hanson has written about this. Panspermia could happen by the first replicators happening in space perhaps on comets and then spreading to planets. As Hanson has pointed out, if life is extremely rare it is strange that life would originate on earth when there are almost certainly super-earths on which you would think life would be much more likely to develop. A solution to this paradox is that life did develop on such an Eden and then spread to earth billions of years ago from a star system that is now far away. Our sun might have been very close to the other star system when life spread, or indeed in the same system at the time.
Is this estimate written down in more detail anywhere, do you know? Accidental panspermia always seemed really unlikely to me: if you figure the frequency of rock transfer between two bodies goes with the inverse square of the distance between them, then given what we know of rock transfer between Earth and Mars you shouldn’t expect much interstellar transfer at all, even a billion years ago when everything was closer together. But I have not thought about it in depth.
I am unaware if Hanson has written about this. Panspermia could happen by the first replicators happening in space perhaps on comets and then spreading to planets. As Hanson has pointed out, if life is extremely rare it is strange that life would originate on earth when there are almost certainly super-earths on which you would think life would be much more likely to develop. A solution to this paradox is that life did develop on such an Eden and then spread to earth billions of years ago from a star system that is now far away. Our sun might have been very close to the other star system when life spread, or indeed in the same system at the time.