A parallel universe is a fun topic in physics, but it’s difficult to understand the concept. That’s why Paul Sutter, a theoretical cosmologist, award-winning science communicator, NASA advisor, U.S. Cultural Ambassador, and a globally recognized leader in the intersection of art and science, dives into this topic and helps us understand if parallel universes could help us search for extraterrestrial life.

Hear from Sutter himself as we ask him this question: Are parallel universes possible and can they help us search for extraterrestrial life?

Do Parallel Universes Exist?

Parallel universes are such a tricky topic for me to explore. On the one hand, they are beyond interesting – the possibility of an alternate cosmos right over there is such a mind-meltingly fun idea. But on the other hand, at present we have no way of testing if the multiverse hypothesis is correct, and we’re not even sure we can test it, which is a bit difficult to confront.

Read More: Are Strange Space Signals in Antarctica Evidence of a Parallel Universe?

How Does Quantum Physics Relate to the Multiverse Theory?

Let me take a few steps back. The “multiverse” is the very old and generic idea, stretching all the way back to at least antiquity, that our universe is not alone. That there are other worlds/dimensions/realities alongside our own. In modern times, the multiverse appears in two completely separate areas of physics.

One of the places is in quantum mechanics. It turns out that the physics of the really small is dominated by randomness. We can never exactly predict what subatomic particles are going to do at any moment. We can only make guesses about what they might do. We have no idea how this all works. By which I mean that while we have a very sophisticated set of tools for making probability-based predictions, we don’t have a picture of what’s really going on down there.

Read More: Is the Multiverse Theory Science Fiction or Science Fact?

What Is the Many-Worlds Interpretation of Quantum Mechanics?

There are many “interpretations” of quantum mechanics that offer such pictures, and one of them is known as the Many-Worlds Interpretation. In that interpretation, every time a random quantum event happens (which is…a lot), the universe “splits” into multiple branches, with each branch carrying one of the outcomes of the event.

The other place that the multiverse appears in physics is through our theories of the extremely early universe. For a variety of reasons, cosmologists believe that in the first second after the big bang, the cosmos underwent a period of extremely fast inflation. Some theories of inflation suggest that it never ended. What we call the universe is just a small piece of a much larger cosmos that has been rapidly expanding since well before we came on the scene. Other individual universes can appear in this multiverse, like bubbles of soap in an expanding foam

Read More: How Does Multiverse Theory Relate to Time Travel?

Can we Prove the Existence of a Parallel Universe?

One issue is that we have no idea how to test if these theories of the multiverse are correct or not. The Many-Worlds Interpretation is just that: an interpretation. It’s not a theory of physics.

As for the multiverse from inflation, we are working towards finding ways to test inflation itself, but we’ll never be able to know if other universes exist outside our own cosmos, because by definition our cosmos is the limit of what we can observe.

Read More: Are We Alone In The Multiverse?

Could Alien Life Exist in Parallel Universes?

What does all of this have to do with alien life? We have no idea if we are alone in the universe or not. In fact, all the evidence we have collected so far indicates that there’s nobody else out there, but we haven’t exactly been searching for very long.

It’s a big universe: our Milky Way is home to around 300 billion stars, and there are about 2 trillion galaxies in the observable universe. The multiverse opens up the possibilities of where life could also exist. Even if the entirety of our cosmos is absolutely devoid of life, and we are the only living creatures in the whole shebang, then the multiverse allows for more room.

For example, there could be another “branch” of quantum possibilities that leads to a universe filled with strange alien lifeforms. Or somewhere out there in the inflation-powered multiverse is a bubble containing life of its own.

Both versions of the multiverse increase the probability of alien life existing somewhere. But I personally can’t use this to make a definite statement that life is out there. We can’t access the multiverse; we can’t go to any other universe or branch and look around. We can guess, which is fun, but it’s not scientific.

If we want to know for sure if we are alone or not, then we have to limit ourselves to this universe and this universe alone. But don’t worry, with a diameter of over 90 billion light-years, we’ve got plenty of places to look.

Read More: Fact or Fiction: What Is The Truth Behind Alien Conspiracy Theories?

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