From whatever pre-existing state started it, inflation predicts that a series of independent universes will be spawned as inflation continues, with each one being completely disconnected from every other one, separated by more inflating space. One of these “bubbles,” where inflation ended, gave birth to our Universe some 13.8 billion years ago, with a very low entropy density, but without ever violating the 2nd law of thermodynamics. Are any of the other universes that spawned during this phase identical to our own? (Credit: Nicolle Rager Fuller)

Ask Ethan: Do infinite copies of me exist in the Multiverse?

Our huge, expanding Universe may truly be infinite. But if the set of possible quantum outcomes is also infinite, which “infinity” wins?

When we look out into the Universe, we find that even if we restrict ourselves to what we can observe, the Universe itself is absolutely tremendous. There are trillions upon trillions of galaxies present within it, strewn across several tens of billions of light-years in space. Further out there, beyond the observable limits of our cosmic horizon, is certainly more Universe: with more galaxies, more stars, and more planets, perhaps even an infinite number of them all told. But there are also a very large, perhaps even infinite, number of possible quantum outcomes that can occur within the Universe. Could there be enough galaxies, stars, and “copies” of what we know of to contain all of these quantum possibilities?

One of the most surprising mathematical facts that people learn is that the concept of infinity — that no matter how high you count, or how large you imagine a number to be, it’s always infinitely far away from “infinity” — is that not all infinities are the same. Some types of infinity truly are larger than others: like they’re somehow a greater degree of “infinite” than other…