SCIENCE
10/25/2012 07:55 am ET Updated Oct 25, 2012

Multiverse: Could Parallel Universes Be Real? Brian Greene Explains (VIDEO)

The size of our universe is nearly incomprehensible. It's so vast, the thought of anything greater is a little hard to swallow. But could there be a parallel universe out there? Could our universe be part of a grander whole, a multiverse?

Earlier this year, I had the opportunity to sit down with theoretical physicist Brian Greene, author of "The Hidden Reality" and "The Elegant Universe," in a previous episode of Talk Nerdy To Me. We talked nerdy about black holes and how the universe may be nothing more than a giant hologram. Now, we delve into the bizarre physics of the multiverse theory.

CARA SANTA MARIA: Hi everyone. Cara Santa Maria here. Is our universe the only one out there? Or is there something even more vast, even more difficult to comprehend? What if there were a parallel universe, much like our own, with copies, even infinite copies of the sun, the Earth, ourselves? I spoke with theoretical physicist Brian Greene, author of "The Hidden Reality" and "The Elegant Universe," about the bizarre physics of the multiverse theory.

BRIAN GREENE: It’s a weird idea at first. I mean, most of us imagine that the word universe by definition means everything. But what we have found from a variety of perspectives, from black hole physics, from quantum physics, from string theory, even from classical physics, that there are reasons to at least take seriously the possibility that what we have thought to be everything may actually be a tiny little part of a much grander whole. And that grander whole might contain other realms that would rightly be called universes of their own. And the grander realm we would refer to then as the multiverse.

CSM: You may have heard about other universes, or other dimensions, before. But can you picture what they'd look like? I often wonder if theoretical physicists have visualization skills that I simply do not possess.

BG: I’ve worked on the idea of extra dimensions of space since I was a graduate, more years ago than I care to recount, something like 30 years ago, and I can’t picture these other dimensions at all. What I have trained myself to do is get good at developing analogies, visualization analogies, that can capture the heart hopefully of the particular idea that I’m studying at one point or another. But ultimately, I rely upon the mathematical equations to try to give insight into what it would be like to experience more than left, right, back, forth, up, down--the three dimensions that we all know and love and move through freely in day-to-day life. What would it be like for there to be a fourth or a fifth or a sixth dimension of space?

CSM: Honestly, I have no idea. But, I'm glad I'm not the only one who can't see in multiple dimensions. I mean, we're not talking about some parallel bizarro universe where my evil doppelganger has a goatee, are we?

BG: One of the things that makes the whole multiverse concept seem like science fiction, perhaps just seem like utter nonsense, is that there are some strange conclusions that you are led to if you take the idea seriously. And one of those conclusions is that there could be copies of us. There could be copies of the earth and the solar system and even individuals, you and I, having conversations in distant realms. There might even be infinite copies of us. And this is a fairly straightforward consequence of certain proposals for how there could be other universes. But when you hear it, it sounds utterly nutty. Now, do I believe there are these other universes with copies of us? Let me say straight out, I don’t believe a darn thing until it has observational or experimental support, proof of that sort. So no I don’t believe any of these ideas, but I do think that they’re sufficiently compelling and built upon sufficintly well-established mathematical ideas that they deserve our attention.

CSM: But how could we ever really know if the multiverse is real? I mean, scientists thrive on empirical evidence. Could we ever see another universe?

BG: We have to find a way to have some kind of interaction or some kind of way of even through the mathematics of really accessing what’s happening in other realms. Now could we travel to one of those other universes? The most concrete way of establishing that they’re there? No, in most of these approaches, absolutely not. But there is one version of the multiverse, it’s called the inflationary multiverse, although the name doesn’t matter much. But it envisions that our universe is one expanding bubble in what might be called a grand cosmic bubble bath, where the other bubbles are other universes. And as in any bubble bath, bubbles can sometimes collide, and the math says that sometimes these universes in this multiverse might collide too. And if that happened, again mathematical analysis suggests, that we might see an imprint of that kind of cosmic fender-bender if you want to call it that. The imprint would be temperature variations of a particular sort in something known as a cosmic microwave background radiation, which is something that astronomers study with diligence all the time. So people are looking for these signatures and who knows maybe one day there’ll be some kind of indirect evidence of that sort that the other universes are really there.

CSM: And if that day comes, it'll open our eyes to the possibility of so much more. Tell me your thoughts on the multiverse. Reach out on Twitter, Facebook, or leave a comment right here on The Huffington Post. Come on, talk nerdy to me!

See all Talk Nerdy to Me posts.
Like Cara Santa Maria on Facebook.
Follow Cara Santa Maria on Twitter.

HuffPost

BEFORE YOU GO

PHOTO GALLERY
59 Incredible Space Photos
CONVERSATIONS