Astrophysicist Ethan Siegel has written an article explaining how the infinite number of parallel universes, as hypothesized by quantum theorists, could actually be real.
After explaining the quantum theory behind the idea, Siegel gives three possibilities of how infinite universes could be a reality. If it is, he says, “everything that was ever possible happened somewhere.”
“Somewhere, the Nazis won World War II; somewhere, Hillary Clinton is president; somewhere, humans have driven themselves to extinction; somewhere, we’ve achieved world peace.”
I am astonished at how these scientists can bandy about “infinity” as they do, positing an infinite number of infinities, since each quantum reaction–and how many of those are there?–creates a new universe. And yet I’m sure that they would not allow for a single infinite God who holds together all contingent events.
“But there is no evidence for a God!” they will say. But there is certainly no evidence for infinite universes, nor is such evidence even theoretically possible, since we can only observe our own universe. This theory is a deductive philosophical construction based on mathematical projections. But it’s hard to see how it is qualitatively superior than philosophical metaphysics or theological speculation.
From Ethan Siegel, The 3 Ways That Parallel Universes Could Be Real:
1.) The Universe, of which our observable Universe is a small part, was born infinite. No matter how many particles we have in our Universe, no matter how arbitrary their initial configurations and no matter how many possible outcomes their interactions could have given rise to, that number will still be finite. But the Universe could have been born infinite! Beyond the stars, galaxies, matter and energy that we can see, we have every reason to believe that there is more “Universe” just like our own, and that it’s simply not observable to us due to the fact that the speed of light and the age of the Universe (since the Big Bang) are both finite. If there’s an infinite amount of Universe like this, then the exact configuration starting off our Universe occurred an infinite amount of times, and everything that was ever possible happened somewhere.
2.) Our Universe was born finite, but there were an infinite number of them born. The Big Bang was not the very beginning of everything, as we once thought, but was merely the birth of our observable Universe. It was the first moment that our Universe could be described as hot, dense, full of matter/antimatter/radiation, and simultaneously expanding and cooling. This happened a finite amount of time ago — 13.8 billion years — and was preceded by a period of cosmic inflation. Inflation creates an exponentially growing spacetime, which means, if it occurred for an infinite amount of time to the past, could have created an infinite number of finite Universes, one of which contains ours.
3.) Our Universe was born finite, there are a finite number of Universes, but there are enough of them around that all possible outcomes still occur. This is the trickiest case of all, because nothing — not even exponentially-growing, inflating spacetime — grows as fast as the number of possible quantum outcomes for the Universe. But a big enough, possibility-rich enough multiverse will have created a Universe with identical initial conditions to our enough times that all the possible outcomes to date have been realized somewhere. This will change, given enough time; as interactions continue and quantum systems evolve, we will eventually see the number of possibilities surpass the number of Universes available to realize all of them.
Somewhere, the Nazis won World War II; somewhere, Hillary Clinton is president; somewhere, humans have driven themselves to extinction; somewhere, we’ve achieved world peace. We still have just the one Universe, though, and still have no prospects for gathering information outside of what’s observable to us. But if the Universe was born infinite, if the state that gave rise to it existed for an infinite amount of time, or we simply created enough pocket Universes for these parallel Universes to exist today, then they’re real. And they could be real if any of these three possibilities are true; there are three different paths to success. But until we have some way of testing it, we have no way of knowing what the ultimate truth of the matter is, and whether parallel Universes truly are real.
Illustration by User:K1234567890y (Own work) [Public domain or Public domain], via Wikimedia Commons
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