Tristan Cook has posted an impressive analysis, “Replicating and extending the grabby aliens model.” We are grateful for his detailed and careful work.
I don't know that hard steps n has been very well defined. Preconditions like the oxygen absorbing into free elements, and allowing oxygen levels to rise, or the crust not being molten seem to constrain various hard step intervals. Admittedly our uncertainty is large enough that you could argue for dozens of hard steps, but the other end of estimates also seem to put it at 1 or none.
"Sun-like" - in what respect(s)? AFAIK, "sun-like" is a vague term which does not specify how the other star is like our sun. A claim like "sun-like stars are early stars" thus seems pretty vacuous.
The Sun isn't early compared to Sun-like stars. And Sun-like stars are early stars. So the only thing our earliness is telling us is that Sun-like stars are necessary for any civ.
I don't know that hard steps n has been very well defined. Preconditions like the oxygen absorbing into free elements, and allowing oxygen levels to rise, or the crust not being molten seem to constrain various hard step intervals. Admittedly our uncertainty is large enough that you could argue for dozens of hard steps, but the other end of estimates also seem to put it at 1 or none.
Thanks for your response Robin! I have written a reply here
"Sun-like" - in what respect(s)? AFAIK, "sun-like" is a vague term which does not specify how the other star is like our sun. A claim like "sun-like stars are early stars" thus seems pretty vacuous.
That's only a weak inference. It is still quite believable that other stars could also birth civs.
The Sun isn't early compared to Sun-like stars. And Sun-like stars are early stars. So the only thing our earliness is telling us is that Sun-like stars are necessary for any civ.