> This poses a challenge for anthropic reasoning as a viable explanation for cosmic coincidences and the apparent fine-tuning of the Universe
It's a philosophical matter and it's been debated uncountable times but isn't that line of reasoning moot? Pick a value out of a probability distribution, if it's not incompatible with life here we are no matter how extreme that value is. If it is incompatible we are not here to reason about it.
You're not getting the point. The issue is this severely limits the proposition that a multiverse explains the finetuning. There is no evidence for a multiverse, the only real arugment that can be made for it is that such a fine tuned universe as ours should be likely. If it isn't likely, then there goes your main argument for a multiverse as a scientific hypothesis.
I mean, the fact there is no observational/experimental evidence of a multiverse already should give anyone pause, but even shrinking from that, one of the better arguments that proponents use for this is now shaky.
The multiverse is a scientific hypothesis only if we can devise experiments to verify it. If not, it's an matter of conversation. Anyway, any single universe in a multiverse is unlikely, just like the result of any roll of a 100 sided die is unlikely. Our universe might be more unlikely than other ones but we got one roll of the cosmological die and we have to do our best with it. I don't see any difference if this universe is part of a multiverse or is alone, unless we find a way to move to other universes with different values of the cosmological constant inside the multiverse (I'm assuming it's really constant during all the lifetime of a give universe.) That would be a great proof by the way.
I would think the most difficult part is figuring out if it's even possible to tweak the universe to be more favorable to life than it already is. Maybe it is possible to form more stars, but the same tweak would also form too many sterilizing supernovae?
In any case, I'm inclined to believe that other universes exist simply due to how easy they are to find by extending a penrose diagram [1], and that the "natural selection" of "universe reproduction" eventually leads to a universe with parameters that enable life and consciousness. [2] Unfortunately, this method still can't tell us how often alternate universes are capable of life or how much the parameters can vary.
no, a lot of things aren't likely, and yet they just need to happen once for a lot of the ensuing process to be very different.