SGU Episode 41

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SGU Episode 41
May 3rd 2006
(brief caption for the episode icon)
SGU 40                      SGU 42
Skeptical Rogues
S: Steven Novella
B: Bob Novella
R: Rebecca Watson
P: Perry DeAngelis
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Introduction

You're listening to the Skeptics' Guide to the Universe, your escape to reality.

Questions and E-mails

Bubble Universes (17:24)

S: Well, we... let's move on; we have a lot of e-mail, and some excellent questions we've been getting in e-mail, so I want to try to cover a few of those this week. The first question comes from Elias Luna in Bronx, New York, from nearby. He writes:

I have a couple of questions which I would love to hear you guys discuss. What's your view on Michio Kaku's [pronounced kuh-ku] view of the universe as a multiverse, that we are nothing but a bubble in a sea of bubbles.

B: I believe it's pronounced "Michio Kaku".

S: Is it kah-ku?

B: I believe.

S:

If there is a so-called multiverse, when did it begin? I'm not speaking of our universe, because we all know the universe began with the Big Bang. But let's say there is a multiverse. What is beyond the multiverse and beyond what's beyond the multiverse and etc.? You see, it's a paradox and only way to escape is to say there's always been something somewhere, literally for infinite and will be, so there is no end or beginning in the grand scheme of things. And if there is an infinite amount of universes or multiverses there, there's an infinite amount of civilizations.

Then he goes on along—basically, that's his question. He asks a couple of other questions. So let's talk about that first. Bob, do you wanna start?

B: Well, yeah, his main question in the beginning is: if there is a multiverse, when did it begin? And you really can't ask that question, because, by definition, you have no contact to any of these other bubble universes within the multiverse or meta-verse. So how could you determine how old it is. I mean, our universe could have been created 15 billion years ago, but it might be a baby compared to other universes. Or it could be the first universe in a bubble universe. So you really can't know how old this multiverse might be. You just can't get outside of your universe, by definition.

S: Right. And just to clarify, that's because, by definition, our universe is everything that we can interact with. Anything that can affect us, everything that we can affect, everything that we can see is, by definition, part of our universe. So, from a theoretical point of view, another universe that was part of a grander multiverse would be forever inaccessible to us.

B: Right. And imagine if somehow you could contact another bubble universe within the multiverse, even that wouldn't help you, because who knows how old that universe is and how long that bubble has been around. You'd have to literally examine every one and find out what the oldest is and say, "OK, this is how old the multiverse is", so it's really inconceivable.

S: The other possibility is that—and Stephen Hawkings [sic] wrote about this—that the age of the universe or the multiverse may be finite but unbound. This is kind of a hard concept to get across, but it's kind of like the surface of a sphere. It's finite; the amount of space that it occupies is finite, but there's no beginning or end that you can point to; it's continuous. There's no specific boundary, but it's finite. So the time dimension of our universe may be the same thing. Maybe we didn't have a beginning and we won't have an end, even though the amount of time that it occupies could still be finite.

R: So does that mean that we're going to get around to the beginning again at some point?

S: I don't know. I don't know. When you start to talk about cosmology like that, whenever physicists write about that kind of cosmology, they always say something to the effect "you could really only express these ideas in, like, 12-dimensional derivative calculus, but I'm going to try to sort of paraphrase in English".

B: (chuckles)

S: So I mean, these are concepts that you can't really even understand, except on a very sophisticated mathematical level. So who knows what it all really means. But... This is also, by the way, Kaku is the guy—he was one of the co-originators of string theory, right? That's what it says on his website, anyway.

B: OK. I'm not sure if he was one of the originators.

P: So what is the point of positing the hypothesis—

S: That's exactly what I was going to get to next, Perry. This all very interesting, but unless you can derive from these notions a testable hypothesis, some way to test it, then it doesn't really enter the realm of empirical science. At best it's a mathematical construct and it's just a mathematical theorem. Now, mathematical theorems can be the beginning of a scientific exploration or a scientific investigation; it could say, "here's a model that's internally consistent and is consistent with what we observe". But you still have to then test it against something. You have to find some way to find out if it's actually real or not. And no one's been able to figure out a way to test string theory or the multi-universe theory or any of these other sort of big ultimate cosmological questions. So, at the moment, they still lie in the realm of theoretical mathematics and not empirical science.

Science or Fiction (51:50)

S: The Skeptics' Guide to the Universe is produced by the New England Skeptical Society. For information on this and other podcasts, please visit our website at www.theskepticsguide.org. Please send us your questions, suggestions, and other feedback; you can use the "Contact Us" page on our website, or you can send us an email to info@theskepticsguide.org. 'Theorem' is produced by Kineto and is used with permission.

References