We took up the appearance of fine-tuning of the universe, in Gravity. Now we proceed to the multiverse, and, if it exists, how it affects the apparent fine-tuning.
What if there are multiple universes? Why couldn’t there be other universes that not only might have existed under different conditions, but actually do, presently, co-exist? In speculative cosmology there are many instances of exploring exactly this intriguing idea. The idea is that in one of the alternate universes, the mathematical constants that make the universe appear to be finely-tuned can in fact be different. What that does for the atheist point of view is take away the uniqueness of the universe in which we live. Perhaps the gravitational force doesn’t have to be just so in one or more of the alternative universes.
The problem with this is that atheist orthodoxy also holds that the physical reality of space-time is all there is of reality. That means that everything that exists, exists in a material form within space-time. If there are other universes, where are they? In what space-time do they exist? It would seem that a multiverse requires multiple dimensions, not just the three dimensions of space and one of time, with which we are familiar.
An entirely new dimension opens up a lot of possibilities, to be sure, but what then would we say are the cosmological constants that apply there? If gravity is different in another universe, for example, it could not exist, so for that other universe to exist with a different constant for gravity, we have to also conceive of such a universe with additional dimension(s) having entirely distinct sets of physical laws.
The obvious problem with that is that the alternative to our universe is nothing, not merely a different sort of universe. Nothing is not merely empty space in which physical laws would apply if there were anything physical to act upon. Instead: Nothing. No thing, and no physical laws to act upon things. So it makes no sense to say that perhaps with more dimensions there could be different physical laws in play. There could not be different physical laws because there would be nothing, and that includes physical laws. No physical laws at all, not just “different” physical laws.
Now with alternative universes there would not be just the space-time we know of as comprising all of physical reality. There would be something else. It could be a kind of expanded space; perhaps a parallel time. But the problem with it is that our conception of material things comprising all of reality begins to slip away. At what point do we re-define nature so much that we’ve essentially made it include super-nature? At what point does the very concept of material reality no longer make sense, especially when we include in it the laws of physics which underlie it all, and our conscious ability to have this conversation, and the obviously non-physical ideals associated with the good, the true, and the beautiful?
In any event, the thing to be on the look-out for with multiverse theory is that it is entirely speculative on the part of cosmologists, and if true, would not rule out a God who is that much greater in creative capacity than we dreamed.
It’s also questionable whether the theory really does what atheists propose it to accomplish: provide a way out of the “fine-tuning” conundrum. If there are parallel universes, they would have to be bound by the same laws of physics, or else we have to imagine an entirely new set which would nonetheless sustain a universe, and that’s speculation layered upon speculation.