If we live in a multiverse, it's reasonable to ask how many other distinguishable universes we may share it with. Now physicists have an answer.
One of the curious developments in cosmology in recent years has been the emergence of the multiverse as a mainstream idea. Instead of the Big Bang producing a single uniform universe, the latest thinking is that it produced many different universes that appear locally uniform.
One question that then arises is how many universes are there. That may sound like the sort of quantity that is inherently unknowable but Andrei Linde and Vitaly Vanchurin at Stanford University in California have worked out an answer, of sorts.
Their answer goes like this. The Big Bang was essentially a quantum process which generated quantum fluctuations in the state of the early universe. The universe then underwent a period of rapid growth called inflation during which these perturbations were "frozen", creating different initial classical conditions in different parts of the cosmos. Since each of these regions would have a different set of laws of low energy physics, they can be thought of as different universes.
What Linde and Vanchurin have done is estimate how many different universes could have appeared as a result of this effect. Their answer is that this number must be proportional to the effect that caused the perturbations in the first place, a process called slow roll inflation, and in particular to the number "e-foldings" of slow roll inflation.
Of course, the actual number depends critically on how you define the difference between universes.
Linde and Vanchurin have applied some reasonable rules to calculate that the number of universes in the multiverse and have totted it up to at least 10^10^10^7. A "humungous" number is how they describe it, with no little understatement.
Linde and Vanchurin say that total amount of information that can be absorbed by one individual during a lifetime is about 10^16 bits. So a typical human brain can have 10^10^16 configurations and so could never disintguish more than that number of different universes.10^10^16 is a big number but it is dwarfed by the "humungous" 10^10^10^7.
How profound is that!
Pretty profound, I'd say.
J. B. Phillips, in his classic, Your God is Too Small, suggested that we need to broaden and deepen how we imagine God. That was true when we thought there was "just" the universe with its billions of galaxies and billions and billions of stars, with its vast distances and immense age. How much more so, if we live in a multiverse? Somewhere in the Confessions, Augustine suggests the world is like a sponge floating in the middle of the Sea that is God. As I recall, he dismisses this as idle speculation.
Still, I wonder. Presumably, God is bigger and older than all universes in the multiverse. And while 10^10^16 configurations literally boggles the human mind, God knows the intimate details of each and delights in each even as we believe he delights in our world. Perhaps one way to try to understand this is to imagine God as something like an eternal effervescent Sea of Champagne in which bubbles of universes are constantly being created and eventually bursting or coming to whatever end universes come to.
It might be too clever by half and even border on being cute, but an "effervescent" God captures something of the celebration and delight we believe to be at the heart of it all while allowing for the possiblity of a multiverse.
But, that might be just as idle, and idolatrous even, as imagining the world as a sponge in the middle of the sea. Maybe it's better to just be boggled, praise the Lord God of the multiverse, and leave it at that, and avoid being one who "darkens counsel by words without knowledge".