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Science and the Search for Other Dimensions

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Science and the Search for Other Dimensions

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Science and the Search for Other Dimensions

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IRA FLATOW, host:

You're listening to TALK OF THE NATION/SCIENCE FRIDAY. I am Ira Flatow.

Later in the hour, a look at the secret life of your garbage. Mmm.

But first, a trip to another dimension.

(Soundbite of "The Twilight Zone" theme music)

FLATOW: From Rod Serling's "Twilight Zone" to Plato's cave, the idea that other dimensions or alternate realities exist has--it's really been a constant theme. But what about science? Are there alternate universes that science has yet to decipher and describe? Realities that we don't know about, other dimensions that we have yet to explore. We'll take a look at some of those possibilities from dark energy to string theory. This program is prerecorded, so please don't try to call in.

And our guest this hour is someone who is familiar to you if you're ever a SCIENCE FRIDAY listener. Dr. Lawrence Krauss, author of the new book, "Hiding in the Mirror: The Mysterious Allure of Extra Dimensions, from Plato to String Theory and Beyond." You also may remember him as the author of "The Physics of Star Trek." Formally he is the Ambrose-Swasey professor of physics and the director of the Center for Education and Research in Cosmology and Astrophysics at Case Western Reserve University in Cleveland. He joins us now from our NPR studios in Washington.

Welcome back to the program, Lawrence.

Dr. LAWRENCE KRAUSS (Author, "Hiding in the Mirror"; Director, Center for Education and Research in Cosmology and Astrophysics, Case Western Reserve University): It's great to be back, as always.

FLATOW: Why do you go so far back in the history of science and the history of culture to explain the idea of extra dimensions?

Dr. KRAUSS: Well, because I think it's important for people to realize that not only that this idea has cropped up many times, but that in some sense, I think, we're kind of hard-wired to want there to be more out there than we can see. And it's a fascinating notion that, you know, the world is a terrifying place and I think when humans first evolved it was clearly terrifying and the hope that there was some better place where things might be fairer was certainly a part of it. And what kind of fascinated me when I started to think about writing this was this is a time when science is, again, looking at this intensively and serious people are saying there may be 10, 11, 26 dimensions. But that idea has really been around for a long time. And maybe the fact that it keeps cropping up even in science has more to do with our psyche than the universe.

FLATOW: Right.

Dr. KRAUSS: And so that's really what I wanted to explore, and that's why I looked at, you know, art and literature as well as science.

FLATOW: Well, you have a piece of Rod Serling's "Twilight Zone" opening in there. I think--you know, I think he had three different openings. You have one in the openings. There's one that starts, `You're traveling through another dimension.' But, you're right, he brings up the word `dimension' in that opening. And in the other openings, as--and you talk about in your book, you start with a physics superhero tale from "The Twilight Zone." Tell us about it and how that inspired you.

Dr. KRAUSS: Yeah. You know, it was a recovered childhood memory, if you really believe that. The--when I thought about this book, I remembered this episode that terrified me when I was a kid. It was about this little girl that disappeared, and she fell into an extra dimension. And so I...

FLATOW: In the wall or something if I remember.

Dr. KRAUSS: In the wall, exactly.

FLATOW: Right. Right.

Dr. KRAUSS: And I remember I was a kid and I was terrified and I--you know, the idea of being all alone. And so I did what I had to do, which is buy all the episodes of "Twilight Zone" 'cause I couldn't remember which was the one. And it's called `Little Lost Girl.'

FLATOW: Right.

Dr. KRAUSS: And so I remembered everything about the episode except one key fact, that the hero of the episode is a physicist and, in fact, there's a great line which I think is unique in it, in the history of television. The husband discovers the kid is missing and he runs out and he dashes out and his wife is there crying and he calls his neighbor and he returns and he comes back and he says, `Bill's coming over. He's a physicist. He ought to be able to help.'

FLATOW: There you go.

Dr. KRAUSS: And I realized, boy, that's probably--I wanted to be a physicist just like him.

FLATOW: Yeah. Those days are over about calling the next-door neighbor physicist. I think there's a series here, you know, `Desperate Physicists' or something. But actually there's something to that idea of desperate physicists because they're desperate to do lots--to explain an idea that you talk about in the book like the dark energy, things that they can't explain.

Dr. KRAUSS: Well, that's the point. I mean, I think that we are--there's--as I've tried in the book, there's a lot--we've had a long history in the 20th century of remarkable discoveries that have taken us tremendously far into the bowels of nature. And we are coming up with and asking some really fundamental questions. In fact, you know, really one of the questions that Einstein asked in a slightly different way was: `Did God have any choice in the creation of the universe?' And what he meant by that was: `Is there one consistent set of laws of physics and if you change the mass of the electron just a little bit, would everything come apart? Would it all be logically inconsistent? Or could the laws of physics be anything and we just happen to have the ones we have?'

And those are the kind of questions in some sense that we're asking, and part of the reason is because people have been driven in trying to understand the nature of gravity, which, of course, has been driving physicists for hundred of years, and the nature of quantum mechanics. And to put them together, they've been driven to this idea that perhaps there are extra dimensions in the universe...

FLATOW: Yeah.

Dr. KRAUSS: ...and most recently that suggests the question of whether, in fact, there are many, many universes and we just happen to live in one that has the laws of physics that we measure.

FLATOW: Right. And you say when it comes to the possibility of extra dimensions that you are agnostic about that. Why do you say that? What do you mean by that?

Dr. KRAUSS: Well, I'm a skeptic, which is what a scientist is, really. I think that there are fascinating mathematical reasons to be thinking about these ideas, but at the same time it's really important and I think it's--isn't stressed enough, probably, in the popular media, that there isn't a shred of evidence, not only--of empirical evidence, not only for extra dimensions but essentially also for string theory, which I think many people think is on the same level as the other sort of well-known theories...

FLATOW: Right.

Dr. KRAUSS: ...in physics. There's no--they haven't made any predictions that have been tested. And moreover, in fact, to some extent, we're still just learning what the theories are. We're just still beginning to understand them. There's certain--there's a tantalizing excitement when you look at some of the mathematics that can draw you in, and that's why I think it's certainly worth pursuing. But whether there really are extra dimensions or not I think remains to be seen, even though to me some of the recent ideas--we used to say, for instance in string theory, that--in fact, scientists throughout this century when they tried to hide the extra dimensions they were talking about, they said, `Well, maybe those extra dimensions are really, really teeny, really, really so small that we can't see them and that's why they're not there.' And that seemed to be OK. But what people have realized recently in the last decade or so is that it's actually possible to hide even infinitely large dimensions, dimensions large enough for there to be aliens and other galaxies and all the things from science fiction. And that is at least a fascinating idea. Whether it's right or not, no one knows.

FLATOW: Yeah. You don't sound very confident...

Dr. KRAUSS: Well, I think...

FLATOW: ...that there are aliens hiding in extra dimensions.

Dr. KRAUSS: Well, I don't think--they're not coming to abduct us, I know that.

FLATOW: Right.

Dr. KRAUSS: But I think that, you know, there are--some of the ideas around why there are extra-large dimensions are aimed at trying to understand yet another puzzle in physics, which is--may not sound puzzling to people, but there are these four forces in nature and they have vastly different strengths. In particular, gravity is so weak compared to electromagnetism, it's hard to...

FLATOW: Right.

Dr. KRAUSS: ...understand it. But gravity is so much weaker than electromagnetism, we don't know why that's the case. In order to explain that, people have argued for--well, an extra-dimensional explanation of that, which is plausible. The problem is if you look at the data from elementary particle physics, it sort of tends to argue that maybe that isn't quite true. We're at the cutting edge, and what I try in the book is to be honest. As I like to say, it's a fair, unbalanced treatment of string theory, in the non-FOX News sense. And I try and talk about why people are excited.

I mean, it still amazes me, when you think about it, that string theory arose in the 1970s when people were trying to understand all this host of new elementary particles that were being discovered in accelerators and they couldn't make sense of it. This theory came along that looked like it might help you make sense of it, but, by the way, it required 22 extra dimensions. And I'm amazed in some sense that physicists were willing to automatically assume that maybe all those extra dimensions exist just to solve that problem. It turned out it wasn't the solution to that problem. But then a decade later, physicists realized maybe it was the solution of another problem involving gravity. And physicists are--many of them are convinced those extra dimensions are out there.

And to the credit of the physics community, there are some people who are actually trying to think of experiments that might actually be able to test this, so it isn't just metaphysics.

FLATOW: Yeah. Do you think that string theory is going to lead to a dead end eventually?

Dr. KRAUSS: Well, if you had to bet, you'd say yes. Namely, most theories are wrong. You don't get that...

FLATOW: Right.

Dr. KRAUSS: ...sense when you read the paper, but...

FLATOW: Yeah, yeah. You've talked about that in your book that...

Dr. KRAUSS: Yeah.

FLATOW: ...most people don't know that, that most theories...

Dr. KRAUSS: Yeah, most theories are wrong. If they were all right, it'd be--anyone could do it. And so betting on a given theory, you'd most likely be wrong. Some of them every now and then work. This one has some fascinating parts to it that, as I say, people find tantalizing. But what's happened, if you think of the progression, in 1984, you probably remember everyone was talking about a theory of everything that would...

FLATOW: Yeah.

Dr. KRAUSS: ...explain everything we know about the universe and the mass of the electron and the mass of the proton. And it's really changed in the last 20 years, people who were doing string theory are now talking about, `Well, maybe it won't ever really be able to make any predictions. Or if it does, maybe it's not a theory of everything. Maybe it's a theory of nothing.'

FLATOW: Mm-hmm.

Dr. KRAUSS: You know?

FLATOW: Yeah.

Dr. KRAUSS: So it's a comedown. And--but we're also discovering that even the whole nature of the theory is changing. As one learns more about the complex mathematics, it may be that strings aren't even an important part of string theory. It's also turning out that even dimensions themselves--you know, we're kind of comfortable, you and I, sitting in three dimensions here of space and one dimension of time. But there have been suggestions we're really living in a hologram. That it's possible that a four-dimensional universe could be like a hologram of an underlying five-dimensional universe and we'd never know it. A hologram, as you know, is a--you know, if you take a picture--a regular picture, a snapshot and you look at it in, say, a classroom, if a student is sitting in front of another student, you can't see them. But if you took a holographic picture, it stores in a two-dimensional plane all of the three-dimensional information. So if you move your head around, you can actually look behind someone in the front row.

And physicists have suggested that perhaps notions of dimensions are kind of a matter of convention. We think we live in four dimensions, but maybe there's really five dimensions and it's identical to four dimensions and it's really wild and we're just--all these ideas are floating around and it's--as I say, I try to make sense of them in the book. And--but what's nice about being at the cutting edge is you don't know the answer.

FLATOW: Are you saying that it is losing favor in the physics community?

Dr. KRAUSS: It's--well, I think, certainly, the excitement has diminished from the 1980s and maybe 1990s as there hasn't been a recent string revolution. There was kind of one every 10 years that would reinvigorate the community. The most recent one is kind of amazing. It's based on this idea, it's called string landscapes, that maybe string theory can't necessarily predict anything, but maybe it doesn't have to, because it could be that string theory literally does predict that there are an infinite number of universes, and in every universe the laws of physics are different, and the only reason we measure the laws of physics to be the ones we do are because we're here to measure them, and if they were any different, we wouldn't be here. It's called the anthropic principle.

And that's, perhaps, I think, the most recent fad among some string theorists. But it's kind of a comedown in a sense. It might be true. It certainly could be true. String theory does provide the formalism to allow for an infinite number of possible universes very naturally, especially with lots of dimensions. There could be an infinite number of three-dimensional, four-dimensional, five-dimensional universes in some large space. So it allows that, but I don't think you--it's certainly not a prediction. And I think many physicists are uncomfortable with the idea that, again, as Einstein said, you know, that in some sense we--physics is an environmental science, that we're only here because, you know, we just happen to be here.

FLATOW: Right.

Dr. KRAUSS: And if it were any different, there wouldn't be astronomers to measure and there wouldn't be galaxies and we wouldn't be observing these things--like an intelligent fish asking the question, `Why is the universe made of water?' Well, if it weren't, he wouldn't be there.

FLATOW: All right. We're going to take a short break and take your questions that you've been holding very nicely on the phone lines. Talking with Lawrence Krauss, author of "Hiding in the Mirror: The Mysterious Allure of Extra Dimensions, from Plato to String Theory and Beyond." Beyond--sounds very familiar. So we'll stay with you; you say with us. We'll be right back after this short break.

I'm Ira Flatow. This is TALK OF THE NATION/SCIENCE FRIDAY from NPR News.

(Soundbite of music)

FLATOW: You're listening to TALK OF THE NATION/SCIENCE FRIDAY. I'm Ira Flatow.

We're talking this hour with Lawrence Krauss, author of the new book "Hiding in the Mirror: The Mysterious Allure of Extra Dimensions, from Plato to String Theory and Beyond."

And, Lawrence, I have to compliment you on this book. I haven't said this to you before. I've known you many years.

Dr. KRAUSS: Yeah.

FLATOW: This is the best book you've ever written, I think.

Dr. KRAUSS: Oh, well, thanks, Ira. That means a lot, coming from you.

FLATOW: This is so--I mean, this is in the spirit of George Gamow and people like that who, you know--that I read as a child, trying to explain in simple lay language some really, really heavy-duty imaginative things. And you do it very well, and it...

Dr. KRAUSS: Oh, well, you've made my day.

FLATOW: I compliment you for it, because it's hard--as a publicizer of science, I know how hard that is to do. This program is prerecorded, so please don't try to call in.

Let's go to Shanamin(ph) in Phoenix.

Hi. Welcome to SCIENCE FRIDAY.

SHANAMIN (Caller): Hi. Thanks for taking my call. What a great subject. Thank you. I'm wondering, because I've had some odd experiences in my life when I was a child: Could near-death experiences and angels be other dimensions?

Dr. KRAUSS: Well, in fact, people have argued in the past when--I mean, as people have talked about extra dimensions in--back to the 16th century, that maybe angels and the spirit world were living in extra dimensions. There's no--let me, with all respect, say that there's no documented--people have a feeling about an out-of-body experience, but there's no scientific evidence that there are actual out-of-body experiences, that it isn't just a psychological feeling that you're having. And angels--as I say, that's really not a scientific question. As far as I know, there are no documented evidence, scientific evidence, for the existence of angels, but people have...

FLATOW: How do you do an experiment, in other words, to prove angels exist?

SHANAMIN: Right. Right.

Dr. KRAUSS: Yes, to prove angels exist.

FLATOW: Yeah.

Dr. KRAUSS: But people have made that argument. You know, I spend a fair amount of time in the early part of the book talking about different notions people have had, and the notion that angels really are sort of extradimensional beings has cropped up many, many times in the spiritual literature, actually.

FLATOW: OK.

SHANAMIN: Like you said before, you know, I'm just trying to find logical explanations for things that I've experienced, so, really...

Dr. KRAUSS: No, and I understand, and...

SHANAMIN: ...I can't wait to read your book. I'm so excited. Thank you.

FLATOW: Well, you can't...

Dr. KRAUSS: Oh...

FLATOW: Think of this, Shanamin: You can't be wrong, I mean, in your own mind, right?

Dr. KRAUSS: Yeah.

SHANAMIN: Right. No, hopefully not.

FLATOW: Who--no one can prove you're wrong. I mean...

Dr. KRAUSS: No, exactly. And it's good to try and think of logical explanations. And the thing we try and do with physics is sometimes to try and find the simplest one, which may not be...

FLATOW: Yeah.

Dr. KRAUSS: ...the most exciting. But I hope you enjoy the book.

SHANAMIN: Thank you.

FLATOW: Thank you.

Dr. KRAUSS: Sure.

FLATOW: 1 (800) 989-8255. What about extra dimensions? I mean, you talked about these extra universes and the idea, I think, that goes back to John Wheeler, who thought about, you know, the original concept, as far as I remember, as coining, you know, the phrase `black hole,' but he talked about that we experience...

Dr. KRAUSS: Yeah.

FLATOW: ...what we experience; poof! Something becomes reality.

Dr. KRAUSS: Yeah.

FLATOW: Could there be other universes that we don't see around us, and other...

Dr. KRAUSS: Of course. I mean, in fact, in some sense, science has validated that notion in general, right, Ira? I mean, when--we're surrounded by an invisible universe of things: atoms we don't see. If you hold your hand out as an astrophysicist, and you just sort of curl your finger up to the sides of a dime and hold it at arm's length and hold it at a dark spot in the night sky, well, it's dark. But if you have a big enough telescope, you'll see a hundred thousand galaxies in that spot.

FLATOW: Right. Right.

Dr. KRAUSS: And so of course there are lots of things we can't see. The question is, is: Are there literally other universes out there? And, obviously, we don't know the answer, but the thing that's interesting about physics is that there are actually--other than just, you know, wanting to invent science fiction stories and hide things and--or maybe hide your ignorance, there actually are reasons to think that--and, in fact, the earliest notion of it really was after Einstein developed general relativity. When people tried to unify what were then the two forces in nature, electromagnetism and gravity, that was the first sort of modern scientific example of a reason to have an extra dimension.

FLATOW: Right.

Dr. KRAUSS: People realized that if there were a fifth dimension that we couldn't experience, and there was a kind of gravity in it, that we would experience it in our four dimensions as something that looked identical to electromagnetism. I mean, it was a really beautiful idea of two--of a mathematician...

FLATOW: Right.

Dr. KRAUSS: ...Kaluza, and a physicist, Klein. And Einstein later on picked up on it, in the 1930s. It was a fascinating idea, and really, that's been, to some extent, the basis over and over again of some of our ideas.

FLATOW: Oh, yeah.

Dr. KRAUSS: So what people should realize is that they're not being invented just, as I say, to hide our ignorance or add new things we can't see. There are real reasons to think that maybe some characteristics of the world that we live in are the way they are because there are these hidden universes.

FLATOW: Tyler in Portland, Oregon, welcome to SCIENCE FRIDAY.

TYLER (Caller): Hi. Thanks a lot. First, a comment. I'm looking forward to a book that takes a somewhat skeptical or non-judgmental view of string theory, and I'd like to comment on the idea that maybe they're chasing what author and physicist Robert Laughlin has called a `deceitful turkey,' named after the...

Dr. KRAUSS: Yeah.

TYLER: ...Mark Twain story where just--you always think you're about to solve the greatest problem in the history of mankind, and yet, no matter how close you get, you never are able to catch up. But my question relates to dark matter. I've just finished reading in your book, "Quintessence."

Dr. KRAUSS: Ah.

TYLER: I was wondering that, if string theory does have validity, would it point to any of the existing dark matter candidates as being more or less likely? And I'll take your answer off...

Dr. KRAUSS: Actually, that's a very good question, in a sense, because one of the--there's a new kind of mathematical symmetry in nature that physicists have been discussing called supersymmetry, and it says for every kind of particle we see in nature, like an electron, there's a partner that has--electrons are particles called fermions. They have--it's called half-integer spin and they behave a certain way. There are other particles like photons that have integer spin, and it turns out supersymmetry says there's--for every particle with a half-integer spin, there's another particle with an integer-type spin. And there are reasons, in fact, and I go into them in the book, to try and think that that might be true.

It turns out that that is really one of the bases of--supersymmetry is one of the bases of modern string theory, super string theory. And the interesting thing is that probably many physicists would say the most well-motivated candidate for exotic types of dark matter are these supersymmetric particles, the lightest supersymmetric particle. And the interesting thing is that there's also very, very good reason to think that it really is around the corner, that it really--that its mass scale is just on the edge of being detectable, either at the next generation of accelerators or directly here on Earth.

And so it would be a--it's going to be very important to see what happens in the next generation of accelerators, because if there's been--if there is really no evidence for supersymmetry at all, then that would really be a big blow, I think, to sort of the long set of theoretical ideas that ultimately leads to super strings and extra dimensions. But to be fair, I think most physicists would say, right now, one of the best bets for dark matter are these supersymmetric particles. And if they are there, then it's certainly one big piece of the puzzle that fits in, and string theorists are going to say that, you know, `That validates our notion.' And...

FLATOW: Well...

Dr. KRAUSS: Yeah.

FLATOW: ...are we getting any closer to simplifying things? Remember 20 years ago there was the particle zoo, and then we had...

Dr. KRAUSS: Yeah.

FLATOW: ...you know, all these particles coming out, and then we said, `Wait, maybe we can classify them into certain families and things.' And now it seems like we're going back, finding more dimensions instead of particles.

Dr. KRAUSS: Well, yeah, except the hope is that in more dimensions things will actually be simpler. I mean, everyone always says the ultimate goal of physics is to have an equation that's going to--that fits on a single T-shirt that explains everything. And the problem is, that may be true, but the T-shirt may be required to be 10-dimensional, and so...

FLATOW: 1 (800) 989-8255 is our number. Let's go to Jim in Penn Yan, New York. Hi.

JIM (Caller): Hi. Thanks for taking my call. Just going from the work of Edwin Abbott and Rucker, the notion of using the lower-dimensional models to describe the next dimension--it seems to me that as a sphere to a square appeared as a point and then grew from within, that a hypersphere to us would appear as a sphere that appeared as a point and grew from within. And, to me, that seems to align quite well with the notion of an expanding space, including space within polyparticulate material bodies. Would you comment on that?

Dr. KRAUSS: OK. Well, let's--well, OK. Let me try and deconstruct that. Let's see. The--you're absolutely right that the notion of using lower dimensions to understand higher dimensions has been around for a while. And, as I say, I talk about it--this all must begin with Edwin Abbot's wonderful story, "Flatland." Because you have to realize how hard it is to picture a higher dimension until you think of yourself as a two-dimensional being trying to think of three dimensions.

The thing is, we don't--and I talk about this--and my own area of physics is cosmology. And extra dimensions have been utilized and suggested as ways of solving big problems in cosmology. The thing that I find kind of fascinating is, ultimately, so far, they haven't really led anywhere. That--we don't need any extra dimensions to understand an expanding universe. We actually can understand it perfectly well in terms of general relativity. In fact, general relativity kind of implies it. Einstein didn't realize it, and he invented something to keep the universe static, but the theory says the universe generally has to expand or contract. And if he'd really had the courage of his convictions, he would have realized that, I think.

But--so one doesn't need to go to extra dimensions to understand our expanding universe. On the other hand, it's worth pointing out that there's a huge puzzle, and probably the biggest puzzle in physics that we've talked about before is this dark energy, the fact that the dominant energy in the universe seems to reside in empty space. And we have no understanding of why that is. Well, some people have argued that if there are extra dimensions and gravity operates on higher dimensions, that one of the remnant effects might be to cause something that looks very much like dark energy.

Hey, so that sounds interesting. And that is interesting. The problem is those same theories have a host of other problems that make them look unattractive. And so it could be that to understand our expanding universe and this weird stuff like dark energy we may need to understand extra dimensions. In fact, to put it around the other way, what could be really exciting is if dark energy was, in some sense, the first empirical evidence for something like that because then one could test these ideas. But up till now, so far, it hasn't really led anywhere, I have to say. And as far as cosmology is concerned, good, old-fashioned general relativity is doing as well as anything else.

FLATOW: Are there any experiments--you mentioned an experiment coming up--that would validate string theory and say, `Here's--this satisfies a rock-solid foundation building block of the theory'?

Dr. KRAUSS: Well, under certain conditions, there would be. I mean, and if one's hopeful about string theory, there would be. Namely, one of the suggestions that's been made is if there are large extra dimensions, the scale at which string theory gets manifested, the scale at which elementary particles reveal their higher-dimensional substructure, if you wish, isn't this microscopically small scale, 19 orders of magnitude smaller than the size of the proton, that we'll never reach with accelerators. Maybe it's at a scale that's actually much bigger, maybe only a thousand times smaller than the scale of a proton, maybe something we could probe in the next generation of accelerators. And if that's the case, you'd do experiments where you'd bang particles together, and some of the energy would disappear into an extra dimension, or you'd produce higher-dimensional black holes.

So people have made these kind of predictions for these ideas, and it's fascinating that, you know, they can make the predictions. And the problem is, of course--well, if we see it, it will be incredibly exciting.

FLATOW: Yeah. Yeah.

Dr. KRAUSS: If we don't, it won't disprove the idea.

FLATOW: Talking with...

Dr. KRAUSS: So that's the big problem.

FLATOW: Talking with Lawrence Krauss, author of "Hiding in the Mirror," on TALK OF THE NATION/SCIENCE FRIDAY from NPR News.

See if I can get one more question in from Leslie in Anchorage. Hi, Leslie.

LESLIE (Caller): Hey, Ira. Thanks for taking my call. I love your show.

FLATOW: Thank you.

LESLIE: Dr. Krauss, one of the things that I find really fascinating about this discussion--I'm a professor of biology, and one of the problems that I've had--I loved your talk about the intelligent design issue, relative to the lack of evidence for string theory...

Dr. KRAUSS: Yeah. Sure.

LESLIE: ...because one of the biggest issues I have with this whole intelligent design discussion is calling the theory of evolution a theory as opposed to a paradigm. And I'm just curious about your thoughts on sort of how we use and how we convey to the public the differences sort of between hypothesis and theories and paradigms and how that relates to sort of this idea that there's no evidence for string theory, and yet it's a theory and not a hypothesis. And I'll take my answer off the air. Thank you.

FLATOW: Thank you.

Dr. KRAUSS: Sure. That's a very good question, and a subtle one, too. You're right that one of the big problems here is semantics, that scientists have a very different definition of the term `theory.' A theory--to rise to the level of a theory, generally, in science--the kind of theory we normally talk about in public, not the kind of theories we might write down and that are disproved the next day--you have to have a well-defined, logical, consistent set of ideas that are then subject to tests and have been satisfied by many, many experiments being compared with predictions. And then something rises to the level of Newton's theory of gravity or Einstein's general theory of relativity.

And I think you're right; in some sense, it would be much more sensible to say `the string hypothesis.' And I also agree with you; I wouldn't call evolution a paradigm so much as a--I think you could almost say the law of evolution, because if you think of a law, it's usually something that's so generally--fits such a large body of evidence and involves a mechanism--in this case, natural selection, which is a theoretical construct that can be compared to experiment. So if I wanted to do my--the best terminology, I might say `the law of evolution' and `the string hypothesis.'

And I think it's important--it is incredibly important for scientists to explain what science is, and also what it isn't. And I think that's something we scientists are probably not--have been negligent in, that science can't necessarily explain everything. If it's not falsifiable, it's not science. And that doesn't mean it doesn't exist. It just means that scientists--those aren't the kind of questions that scientists discuss and test. And there are many interesting questions about the universe that aren't falsifiable, and I think responsible scientists don't want to argue that people shouldn't discuss those ideas, but they will argue that it's just not science and it's not the type of thing we should teach in science classes.

FLATOW: Mm-hmm. Well--in about a minute we have, are you watching--I know you're very vocal about this whole controversy about intelligent design. Do you think this is a real case that's going to go on to the Supreme Court in--that's going on in the Dover case?

Dr. KRAUSS: Well, in fact, I just came over here from a meeting in Washington on that very subject where I was speaking. And I think--my expectation is that it probably will go to the Supreme Court. I think it will--I'm actually convinced that, in fact, it will be decided in favor of people who don't think this lie that the teachers are being forced to read to the students in Dover will happen. But I also think, unfortunately, that that's not going to end the controversy.

FLATOW: Where do you think it will end?

Dr. KRAUSS: Well, I think it'll be...

FLATOW: Just--I mean, going to reverberate for another hundred years.

Dr. KRAUSS: Well, it may. There are a lot of people who have a lot of mo--I think based on fear, a fear of science. Really, if you come down to this, it's really nothing to do with evolution. It's a fear that somehow science makes it impossible to believe in God. And what I think we have to do is a better job of educating people, that you don't have to be an atheist to be a scientist and that science is independent of your belief in God or whether you're an atheist. And so I think education's the only way out, and I think maybe--I was just answering a question to someone today at this meeting that maybe, ultimately, the thing that will get us out of it is, as we realize that we, as a society here in the United States, are falling behind in the teaching of science. And in the 21st-century competitive world, if we want to maintain our standard of living, we've got to forget about these attacks on science. We've just got to do a better job of explaining the science so that our children can compete in the world.

FLATOW: Lawrence, thank you very much for taking the time to talk with us today, as always.

Dr. KRAUSS: It's always a great pleasure, Ira. Thanks.

FLATOW: Lawrence Krauss is author of "Hiding in the Mirror: The Mysterious Allure of Extra Dimensions, from Plato to String Theory and Beyond." A really good book. Put it on your holiday book list. And we'll be having our holiday show coming up soon, as the season progresses. He's also a professor of physics at the Case Western Reserve University in Cleveland.

When we come back, changing gears to the secret life of your garbage. Where does it go after it leaves your curbside? The answer might surprise you. Stay with us.

I'm Ira Flatow, and this is TALK OF THE NATION/SCIENCE FRIDAY from NPR News.

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