Planetary Radio: Space Exploration, Astronomy and Science - Harvard Physicist Lisa Randall on Hidden Dimensions and New Universes to Explore

Episode Date: March 13, 2006

Harvard physicist and author Lisa Randall talks about hidden dimensions and other universes.Learn more about your ad choices. Visit megaphone.fm/adchoicesSee omnystudio.com/listener for privacy information.See omnystudio.com/listener for privacy information.

Transcription by CastingWords Thank you. We might uncover some mysterious yet entertaining new dimensions of Bruce Betts in this week's edition of What's Up. And Emily is back with a new Q&A segment. So much news from around the solar system, so little time. We could talk about the Japanese Space Agency reestablishing contact with its Hayabusa asteroid probe after three months of silence. We could celebrate the possible discovery of liquid water geysers on Enceladus, the tiny moon of Saturn. But then there's the big story taking place in the Martian sky.

That's how the tension broke at the Jet Propulsion Laboratory, just as the Mars Reconnaissance Orbiter swung around the red planet, re-establishing contact with its nervous controllers. We have two-way Doppler, and MRO is in orbit around the planet Mars. around the planet Mars. MRO was indeed right on the money, settling into an orbit that will soon allow it to examine all of Mars in far greater detail than has ever been available. All these stories and more are at planetary.org.

Indeed, Emily has returned. This week she takes us back to the ocean under the ice on Jupiter's moon Europa. If you ask me, that primordial soup needs a little salt. I'll be right back with Lisa Randall. Hi, I'm Emily Lakdawalla with questions and answers. A listener asked, How do we know that the oceans on Europa are saltwater? The only way we can know that oceans are inside Europa at all is if they are salty.

Europa is one of the four largest moons of Jupiter. Three of the four, Europa, Ganymede, and Callisto, have surfaces and mantles composed of water mixed with other things, with more rocky material toward their centers. We know the masses of these moons fairly accurately from how much they deflected the path of the Galileo spacecraft as it flew by, and we know their sizes and volumes from the study of Galileo's distant photos of the moons. Mass divided by volume gives you density, and those densities are low enough that these moons must be made of substantial quantities of water in addition to rock. But these calculations can't tell us what state the water is in, liquid or solid, and we can't see

through the icy crust to tell one way or the other. So how do we know there are saltwater oceans under those crusts? Stay tuned to Planetary Radio to find out. Other universes that only gravity can travel between. Hidden dimensions curled up tinier than an electron or extending to infinity. And the tantalizing hints of a grand unified theory of everything, if only we're smart enough to do the math. In a sense, Lisa Randall has traveled farther than any explorer who has been our guest on Planetary Radio.

Her work, on her own and with collaborators, has made her one of the most frequently cited physicists at work today. Her new book is Warped Passages, Unraveling the Mysteries of the Universe's Hidden Dimensions. It is a challenging yet delightful read, ending with the sense that we are about to open up a cosmos that is far stranger and more wonderful than anyone could have imagined. Lisa, thanks very much for joining us on Planetary Radio. Thank you. It's a pleasure to be on the show. I hardly know where to start with this book, which covers so much.

It really is not just a history of physics over the last hundred plus years. You've got the standard model in there. You've got Maxwell's equations. You've got quantum theory. You've got string theory. You've got Maxwell's equations. You've got quantum theory. You've got string theory.

And all of this leading up to the pretty amazing work that you've done in just the last few years. I say it's not just a history because it actually attempts to help poor, mathematically challenged folks like me understand what has been going on in this very exciting period. You know, I really didn't want to write a history book. I really wanted to write a book that tells about the physics we're doing now, what are the questions that drive us, why we're excited about exploring the universe, theoretically at least, and also experimentally. But what are the questions we're trying to answer?

Where are we now? How much have we learned? What are we stuck about? And, you know, you can't really do justice to that without going into the background, without saying what is the physics that's led up to this. I mean, you know, I'm talking about some fairly exotic matters like extra dimensions of space, parallel universes of a sort, and it sounds almost science fiction-y. And the point is I want to bring home why it's not science fiction, where the science is,

what are the questions that led us here, and why we think extra dimensions might provide answers. I'm glad you brought up science fiction because the more I got into the book, the more I thought of one of Arthur C. Clarke's laws, which was that the universe will turn out to be not only stranger than we imagine, but stranger than we can imagine. But you don't seem to have had much trouble imagining and then finding a mathematical basis for a very, very strange universe? Well, you know, it's funny.

Sometimes it actually did sort of happen in the other order. One of the things that my collaborator, Raman Sundaram, and I discovered was that if you have extra dimensions of space, they can actually be infinite in size. Before, people thought, after all, we don't see these extra dimensions. They must be so tiny we don't see them. But we found they could be infinite. We weren't looking for that. We weren't looking to see whether extra dimensions could be infinite. We had stared at the equations that we got because we were asking some very physical

questions about what you can measure and could explain properties of our universe. And we found, accidentally, that's what the equations provided. So in a sense, the universe was smarter than we were, but we were paying attention. You came up with this possibility of dimensions that would not be what had been discussed up to that point, which would be if there were extra dimensions, most people, I guess, thought that they'd be really, really tiny, about as tiny as anything could be. That's right. And that changed a lot in the 1990s.

And part of the reason for that was what had to do with string theory. String theory is a very, I don't want to go into the details of string theory now, but the idea is that it's a theory that would tie together quantum mechanics and gravity. But it was based on the idea that the universe is fundamentally consistent. The objects in the universe are fundamentally oscillating strings. One of the things that happened in the 1990s was people realized it's not just strings. It's other objects that play a big role. These objects are technically known as brains.

It's short for membranes. But the point is they are extended objects, and they can be extended objects in higher dimensional space. And because of these objects, these membrane-like objects, these sheet-like objects, it really changed the landscape of higher dimensions. It turns out there are many possibilities that physicists just did not realize because they weren't thinking about an extra-dimensional universe with brains. And once we started thinking about that, we realized they could play a role, not just

in exotic theoretical ideas like infinite extra dimensions of space, but they might actually help us understand phenomena, physical phenomena, in our universe today. And when you say our universe, you mean this little corner of what you and other physicists call the bulk, where you and I and everybody we know and all the stars in our universe happen to live. That's right. It could be that we, that is to say the stuff of which we're made and the place where we live is all stuck in one particular region of extradimensional space. It could be that extradimensions extend far beyond, but we're just not present there.

We are stuck on this sheet, on this membrane-like object. That could be our home. But within that, though, we still have all the properties we've observed about the universe, such as what the masses of elementary particles are, how they interact. And the question is, in this scenario, does it explain some of the mysterious phenomena, some of the phenomena that we've had really a lot of trouble understanding, if there are only three dimensions of space? One of the conclusions near the end of your book

has left me feeling kind of short-changed, that we might have reason to be envious of other brains because it's quite possible that we live in a little pocket with fewer dimensions than other parts of space. Yeah, well, you know, it depends on how you look at it. It's definitely true that we might be in a pocket of lower dimensions. This was one of the exotic possibilities that I discovered, actually, with a different collaborator on JS CART.

But we found that we could be in a pocket of lower-dimensional space, even though other regions of the universe are higher-dimensional. I don't know that we should feel cheated, because some very nice phenomena happen when there are three dimensions of space, such as orbital-bound systems like our solar system, and also we can have our galaxy. So I think we're doing pretty well having gravity act as if there are three dimensions of space.

But it is interesting that there might be more. Okay, no more complaints then. We'll be back with more from Harvard physicist Lisa Randall right after this. This is Buzz Aldrin. When I walked on the moon, I knew it was just the beginning of humankind's great adventure in the solar system. That's why I'm a member of the Planetary Society, the world's largest space interest group. The Planetary Society is helping to explore Mars. We're tracking near-Earth asteroids and comets.

We sponsor the search for life on other worlds, and we're building the first ever solar sail. We didn't just build it. We attempted to put that first solar sail in orbit, and we're going to try again. You can read about all our exciting projects and get the latest space exploration news in depth at the Society's exciting and informative website,

planetary.org. You can also preview our full-color magazine, The Planetary Report. It's just one of our many member benefits. Want to learn more? Call us at 1-877-PLANETS. That's toll-free, 1-877-752-6387. The Planetary Society, exploring new worlds.

Welcome back to Planetary Radio. We're talking with physicist Lisa Randall, author of Warped Passages, Unraveling the Mysteries of the Universe's Hidden Dimensions. Another of Lisa's important contributions has been new thinking about the nature and strength of a mysterious, invisible force field all of us are subject to every moment of our lives. force field, all of us are subject to every moment of our lives. I wonder how much your curiosity about gravity played a role in some of the pioneering work that you did with that first collaborator that you mentioned, Raman, where you came up with a possible explanation for why gravity is so much weaker than the other forces that make things work in our universe.

And I guess you should mention those four forces briefly. We know about four forces, which are electromagnetism, the weak and strong nuclear forces, and gravity. Gravity is far, far weaker than those other forces. For example, you can pick up a paper clip with a tiny magnet. The tiny magnet competes against the entire Earth. But if you look at it from the point of view of elementary particles and just ask about their interactions, gravity is such a tiny force

that we can basically neglect it. We just don't even bother to think about it. It's so incredibly weak. And it's a real mystery to particle physicists why gravity is so weak. Where do these very different numbers come from? But it's an even worse problem because it turns out that if you were to naively predict how these forces should be related,

you'd think they should be about the same strength, and that's far from the case. So if we don't do something clever, if this theory doesn't do something clever, I should say, we end up having to put in a fudge factor. It looks like you have to, what we will find too in the theory, to 16 digits of precision, it's clear that something more fundamental is going on. And that's what people have been looking for since the 1970s. What we found is maybe, if there's an extra dimension, space-time could be so warped, that is to say it could be curved in such a way that gravity is strong somewhere else but weak where we are.

We found an example where that happened. It just very naturally is exponentially tinier where we are. So it would be a very natural explanation for why gravity is so weak. We're just not where it's concentrated. And the best part about this theory is that it sounds exotic, it sounds science fiction-y, but it has experimental consequences. And within the next few years, we will turn on, that is to say, experimenters are going to turn on what's called the Large Hadron Collider, the LHC. It's a giant accelerator that will exist at CERN, which is an accelerator facility near Geneva. It will accelerate protons to extraordinarily high energies and bang them together, thereby creating enormous amounts of energy, which via

E equals mc squared, can be converted to very massive particles, particles with big mass m. And those particles might be particles that travel in extra dimensions. In fact, if our theory is right, that's what we expect. So it's really kind of an exciting idea and an exciting time because these ideas actually have physical consequences that we can go out and measure, that is to say my experimental colleagues can go out and measure. That excitement that you express definitely comes across in the book, this enthusiasm you have for your business.

And I love the part where you described your visit to CERN, where they were, I guess, finishing one of these gigantic detectors that will be part of the Large Hadron Collider, that you got to climb around it, I guess. I didn't climb around it. I actually visited again last month, which was really a lot of fun because these experiments are being finished now. So they're largely in place, but they're not closed up. At the end of the day, you have to close it up so you can catch all the energy.

But right now, you can really see inside. And it was really nice because I had a tour by two of the lead experimenters there, and they could tell all the details. You know, you have this big thing, and you think of this big construction site, and you forget that there is spectacular engineering going into each individual element to measure precisely energies, masses, charges, to measure properties so precisely that we can figure out what was there, even though it was there for a fraction of a second.

I would love to visit one of these places. When you spoke in town at Caltech, I was the guy in the audience who asked the question, what would have happened if the United States had, years ago, finished the superconducting supercollider? Would we have been able to reach some of these experimental results sooner? Not only sooner, I would have actually been even more confident that we would find them. In terms of energies, right now we have an accelerator called Fermilab. It operates

with what's called a Tevatron, which is in Batavia, Illinois. We measure energy in units of electron volts. It goes up to 2 TeV. The Large Hadron Collider will go up to 14 TeV. The SSC was going to go up to 40 TeV. Wow. This might not sound like a great difference,

but it's an enormous difference from the point of view of particle physics. This is exactly the energy where we know something should be happening. Whatever it is that explains this problem of the weakness of gravity, and also how elementary particles acquire their mass, we know that's the right energy range. And the higher energy we go to, the easier it is to do the experiments. So it would have been really great. It would have happened sooner and better. I would catch bloody hell from our audience of space exploration fans if I didn't bring up a topic I know you are asked about all the time, and that is how this new understanding of physics might help, if at all, in our opportunity to find out a little more about the real neighborhood where we live,

the galaxy and our solar system. Are we looking at any possibility of opening up easier ways, ways to bypass the universal speed limit, for example? You know, that would require violating some principles that seem to be at work, that is to say some symmetries that seem to be at work, at least in our universe. I think what it does is it opens our imagination to possibilities that, for example,

if we have this brain scenario, if we have this idea that we live on membranes, then there could be other membranes, and those other membranes would have entirely different chemistry if this idea is right, that stuff we know about is stuck in our brain. And if that's true, well, that would mean that those things are completely different than anything we know.

They wouldn't experience electromagnetism, for example. So it would tell us that to explore it, we really would want to explore with gravity. And so that's a sort of new experimental technique that's really being started, looking at gravity waves and gravitational signals. I think that's going to be a really important way to search the universe in the future. In fact, it's one of the research projects I'm working on. As soon as I get off the phone, I'm going to go back to thinking about it. What are the early universe things that we can think about that can be detected with gravitational signals? And if these extradimensional theories

are right, it's possible they might actually give you signals in the gravitational wave that we might measure. So, you know, these proposed gravitational wave experiments are better. So I think it will give us a way of understanding which will be the useful ways to explore the universe. I mean, clearly there's things within our own galaxy that are important, but there are other questions that go beyond that, and that really are beyond even what we can imagine, and that's really fun to think about sometimes. We are almost out of time. One of the most striking quotes in the book came from your

friend and colleague, Edward Witten, who said, space and time are doomed. It sounds depressing, but again, you sound like you couldn't be happier with what's happening in physics today. Well, you know, when they say space happier with what's happening in physics today. Well, you know, when they say space and time are doomed, they're not saying that our universe is about to collapse. They're saying that we are ripe for some new theoretical insights into a more fundamental idea of what space and time are. I don't think I would say it exactly that way. I'm not sure Ed would usually say it that way.

But it is interesting that we see evidence that our notions of space don't quite make sense at very, very tiny distance scales. Scales smaller than things we'd actually observe or have anything to do with on a day-to-day basis, but something that we'd want to understand at a theoretical level if we're going to get a more fundamental understanding. And that's the kind of thing we're always doing. We're looking for the little inconsistencies that tell us how to go beyond and understand our universe better at a more fundamental level. We are out of time. I wish we had another hour or two,

or barring that, that you can come back sometime and we can explore our universes in more detail. And some of it is in the book, too, so you can read that, too. And I'm going to mention that Lisa Randall, who is a professor of physics at Harvard University, and you still call yourself a particle physicist, right? I do. I'm sort of doing all of it. I'm doing particle physics, string theory, cosmology.

You're a theorist, you're a cosmologist, you're a particle physicist. Well, you know, all these ideas relate, and it's fun to explore what the connections are. Well, her book is Warped Passages, Unraveling the Mysteries of the Universe's Hidden Dimensions. It's available from HarperCollins, and judging from the number of copies I saw on the shelf, when I picked up mine, I get the feeling it's doing very well. Thanks. I hope you will be very careful when you are out there climbing rocks, as you do sometimes, because I wouldn't want anything bad to happen to that brain.

I think we need it. After all, two brains you've shown are better than one. On the radio, this is very confusing. You don't see the spelling. But I hope you'll be careful. And how do the Red Sox look for this year? I've ceased to be a fan. Well, thanks so much again for joining us on Planetary Radio.

Thanks a lot. It's been fun. We'll be back in our own universe, of course, with Bruce Fetz for another look at what's up in the night sky in our new space trivia contest right after this return visit from Emily. I'm Emily Lakdawalla, back with Q&A. How do we know that the oceans on Europa and Callisto are saltwater? The detection of the oceans was made with the magnetometer instrument aboard the Galileo spacecraft.

When Galileo flew by these icy moons, it detected a weak magnetic field that always pointed in the same direction as the magnetic field of Jupiter. This means that the magnetic field of Jupiter was inducing a magnetic field in the moons. Scientists developed mathematical models to try to explain the presence of the magnetic field. They found that in order to get a field that was as strong as the one detected by Galileo, their models required a globally distributed, highly conducting medium located close to the surface of the satellites.

They explored the possibilities of what conducting media could be responsible for this field, and only global subsurface saltwater oceans several kilometers thick fit the bill. No other explanation fits the magnetometer data, but mathematical models usually aren't considered final proof. And in fact, many scientists still consider the presence of Europa's oceans to be an unproven hypothesis. It'll take a mission to Europa to gather the necessary proof. Got a question about the universe? Send it to us at planetaryradio at planetary.org.

And now here's Matt with more Planetary Radio. Sitting out in back of the main office of the Planetary Society in the cavernous Planetary Radio studios, ready to do What's Up? with Dr. Bruce Betts, the director of projects for the Planetary Society. The red light is flashing. You're on. Hey, thanks. I'm glad we got a red light out here in the doghouse. I mean the studio area.

Just remember that. Studio D. Studio D. Welcome to Studio D. Implying that there's an A, B, and a C. But D's the best. That's right. That's why we're here.

D, D, D, D, D. Okay. Hey, how about things up in the night sky? Yeah right. That's why we're here. D, D, D, D, D. Okay. Hey, how about things up in the night sky? Yeah. Okay. Planets. Cool planets. Mercury's pretty much gone away.

But pre-dawn sky, let's start the opposite direction than usual. Pre-dawn sky, you can see Venus low in the east but can't miss it shortly before dawn. Brightest star-like object up there. You've got Jupiter nearly overhead way up high. The other really bright star-like object, both of them much brighter than Sirius, the brightest star in the sky. And in the evening sky, we still have our friends Mars hanging out there south after sunset, and then in the west a little bit later in the evening. And Saturn still hanging out up there also but over look over towards the east more in the early evening overhead by late evening and below Castor and Pollux the Gemini twins

moving on to this week in space history we have a couple of big anniversaries I know you're probably anticipating this first one 225th anniversary of 225th yes 225th anniversary of? 225th? Yes. You were there, right? 225th anniversary. Yes. Yeah, but you know, my memory is so crowded. I know. 225 years. What would it be?

I don't know. Discovery of Uranus by William Herschel. Oh, yeah. I remember clapping him on the back. Yeah, and saying, no, you shouldn't name it Georgian or whatever. He wanted to name it after the king of England. Although, I don't know whether Uranus really was a big step up. Yeah.

More pleasantly, the 80th anniversary of the first liquid fuel rocket launch by Robert Goddard. Now, he was a hero. I wish I had been around to meet him and shake that man's hand. Gosh, he was an early hero of mine. Cool. Cool stuff. So you were launching rockets, trying to blow things up? Yeah.

You have to ask? Yeah, okay. Moving right along to Random Space Fact. Wow, trills. I'm trilled to be here. Venus. Venus only has about 1,000 craters on it. And, you know, that may seem like a lot, but that's not very many at all

if you talk about other planetary surfaces that don't have plate tectonics in water, like the Earth does. But that was the big surprise that led us to see that there was a catastrophic disruption of the Venus surface about 500 million years ago. Okay, moving on to the trivia contest. We asked you in this little bit of a strange run, it was during the Winter Olympics, what is the connection between the location of the Winter Olympics and near-Earth object impact threats? How did we do, Matt?

You know, our audience, they know this stuff. So we were inundated. Nobody got it wrong. Everybody knew exactly what we were trying to get at. Inundated. Nobody got it wrong. Everybody knew exactly what we were trying to get at. And the hint that I gave, remember, I said that there was a big controversy because of NBC's coverage of the Olympics, where NBC was insisting on calling it Torino when most Americans call it Turin. It is, of course, the Torino scale. Indeed, the Torino scale, which is a scale developed by near-Earth object scientists

who hung out in Torino or Turin. The set of numbers basically will tell you how terrified to be when a near-Earth object is detected and while its orbit is being figured out, zero being no sweat, not going to hit the Earth, one, we should pay attention to it, ten, make sure your will is up to date, that kind of thing. So that's called the Torino scale. Not that we have the time to go into this, but I will anyway. Didn't the Planetary Society have something to do with a conference or something in Torino that resulted in this?

No? I've stumped him again. Of course we did. Okay. The Planetary Society, as you know, sports a number of near-Earth object programs and have many of the neo-scientists near and dear to our heart and helping us out with things like our Gene Shoemaker Neo Grants that go to astronomers, largely amateurs all over the world,

to improve their facilities for detecting and following up on these near-Earth object hazards. Oh, you might be confused because we did have a couple of us, including myself, who were doing the luge in the Winter Olympics. Is that right? In Torino, yeah. You're insane. I know. Well, I just say luge.

What I was really doing was the skeleton, so I enjoy that face-first concept. Either way, you know, either way, it's going to hurt. Yeah, curling's more my speed. All right, now we really have to hurry, hurry so that I can tell you that Heinz, and I do have to use the phonetic spelling here, it's Heinz Arbeglin. Heinz Arbeglin, I think our first winner from Switzerland, and we did determine that he's not Schmitten with us. He's from Schmitten, which is a city in Switzerland.

So, Heinz, congratulations. You will be getting that Explorer's Guide to Mars, I almost said T-shirt, poster, Explorer's Guide to Mars poster. Somebody else is going to win one based on this question Bruce is about to ask. It's true. And by the way, you can wrap the poster around yourself and try to form a shirt. We just don't necessarily encourage it. And to the following question, win your own Explorer's Guide to Mars combination poster T-shirt, and that is who is the only man

who has a feature named after him on Venus? The only man to have a feature named after him on Venus? Go to planetary.org slash radio to find out how to email us your answer, and when do they need to get that in by, Matt? You've got till Monday the 20th of March. Monday, March

20 at 2 p.m. Pacific time. Get it to us. We'll put you into the Big Hopper and you might even hear your name read right here in Studio D. Okay, everybody, go out there, look up in the night sky and think about popcorn. Thank you. Good night. Bruce Batts is the Director of Projects

for the Planetary Society. He's here every week singing in the background on What's Up. Okay. Planetary Radio is produced by the Planetary Society in Pasadena, California. Back next time with another jaunt around the universe. Have a great week, everyone. Thank you.