|THE BIG BANG BOOK|
April 26, 1999
| DAVID GERGEN: Brian,
"The Elegant Universe." Why do you and other physicists call
the universe elegant?
BRIAN GREENE, Author, "The Elegant Universe:" Well, I think the best way to explain what we physicists mean when we describe the universe as elegant is to reflect back on Einstein's relentless 30-year search for the so-called unified theory. By unified theory Einstein meant a theory founded on a few principles of such breadth and depth that effectively any question about the physical universe would be within the theory's ability to answer. For instance, the unified theory would describe the frantic dance of subatomic particles and the majestic swirl of heavenly galaxies using one single master idea, a master equation so to speak, and that's where we see elegance; that the universe, although it's rich and wondrous may be founded upon a few basic principles of incredible planetary power. Now, Einstein never did find theory he was searching for but we believe that we have it today.
DAVID GERGEN: But Einstein did come up with his general theory of relativity, which dealt with the swirling galaxies. What was that all about?
BRIAN GREENE: In about 1916 Einstein completed a ten-year journey to give us a new theory of how gravity works. Now, gravity is the force that is most relevant for the big stuff in the universe, stars, galaxies and so forth, and Einstein gave us a new picture of how gravity work. And to understand his picture it is useful to have in mind an idea of a large huge rubber sheet. Now, imagine you have that rubber sheet and you put a bowling ball right in the center of the sheet, well, it's going to cause the sheet to warp. And now if you have a little pellet that rolls around the sheet, it is going to go in an interesting curved path due to the presence of the bowling ball warping the membrane, the sheath itself. Einstein says take the same idea and apply it to the fabric of space itself. So the fabric of space according to Einstein is nice and flat if there is no matter or energy present, but the presence of something like the sun causes the fabric to warp and now an object, like the earth in this case, would be rolling around the distorted spatial fabric caused by the presence of the sun and in that way according to Einstein, the sun affects the motion of the earth gravitationally. So the key idea is that the fabric of space warps in response to the presence of objects, and that warp is what Einstein said actually is gravity.
DAVID GERGEN: So, that has become what the physicists think of what's happened with large objects but along behind Einstein came people who were looking at smaller objects, microscopic and they came up the theory of quantum mechanics.
BRIAN GREENE: Right. Right. That's right. Again, that was 1930 or so that another group of physicists came up with quantum mechanics and they developed it because when they applied 19th century physics to the microscopic realm, they found all sorts of incredibly wrong predictions about how the universe works. For instance, they predicted that atoms would self-destruct in a second; it doesn't happen. They knew that they needed to develop a new theory. Quantum mechanics is that theory, and it paints a strange picture of the microscopic world that says, for instance, that there is a wild turbulent frenzy happening on microscopic scales. Particles pop in to and out of existence all the time. Energy fluctuates up and down. It's a very turbulent arena, according to quantum mechanics. And that's the conflict. Einstein said it's nice and gently; curving quantum mechanics says it's not.
DAVID GERGEN: In the search to resolve that conflict, physicists began investigating the notion of super string theory. What is that?
BRIAN GREENE: That's right. So the string theory is our first hope to resolve the central conflict of 20th century physics. And let me just give the basic idea of string theory first; it answers an age-old question, a question that goes back 2,000 years to the ancient Greeks. If you take anything and you cut it in half and you cut it in half again, and you keep on cutting it in half, what ultimately do you find? Now, we've known for a while that you find atoms sooner or later but atoms are not the end of the line. You can cut them into smaller pieces because they, in turn, are made of little electrons that swarm around a central nucleus. The central nucleus itself is made up of smaller particles, protons and neutrons, and if you look deeply inside one of those particles, a proton, for instance, you find yet smaller particles. It's like a sequence of Russian dolls. You find three quarks. String theory said those basic particles - electrons, quarks, and some other particles that we don't need to go into -- are not actually indivisible. They are made of something smaller, they're made of little loops of string that vibrate to and fro inside those particles. So an electron, for instance, is a string vibrating one way, a quark is a string vibrating another way. So, in a sense, string theory takes the old idea of the music of the spheres and injects it into science, but in a microscopic setting, a very different setting than it was initially proposed.
DAVID GERGEN: You and other physicists say if super string theory holds, if it is proven over time, that it will resolve this basic conflict in Physics between quantum mechanics and the general Theory of Relativity.
BRIAN GREENE: That's right. And the way it does that is pretty interesting to describe. String theory takes the old idea of point particles, those little dots of which there is no way to cut them further, and stretches them out, it spreads them out into these little loops of string that we were discussing. Now, when you stretch anything out, when you spread anything out, for instance, you take mustard and you spread it on bread, you dilute it by spreading it out. Now, when you dilute point particles into loops of string by spreading them out, you also dilute those violent jitters of the spatial fabric on tiny microscopic scales and, in fact, you dilute the jitters just enough that quantum mechanics and general relativity can finally fit together perfectly.
DAVID GERGEN: In achieving this union between the general relativity and quantum mechanics, string theory says that there must be more than three dimensions to space. Can you tell us about that?
BRIAN GREENE: Yes, it's a very strange idea, but the only way spring theory works if there are more be the three spatial dimensions of common experience - and first what does that mean and how do we make sense of it? Well, the three dimensions of common experience are left/right, back/forth and up/down. Those are the three dimensions that we all move through freely all the time. String theory says there are at least six and actually probably seven more spatial dimensions that of yet we've never even directly seen. Now how is it possible to make seasons of a bizarre prediction? Well, think of an analogy for a moment. Imagine a piece of paper, it's nice and flat, so it has left right dimension and say the back/forth dimension. But if you roll up that piece of paper into a tube, now it has the left/right dimension but the back/forth dimension has now turned into a smaller, circular dimension and in fact if you curl up the paper really tightly, it's going to become increasingly difficult to see that there even is a second curled up dimension to your piece of rolled up paper. So that means that dimensions actually come in two varieties. They can be big and obvious, or they can be tiny and curled up, and therefore harder to see. String theory says take that idea and apply it to the entire universe, the spatial fabric of the universe. There are the three obvious dimensions of common experiences; those are the ones that we move through all the time. But if you examine the fabric of space on very tiny distances, string theory says you'll actually find new dimensions, new, curled up dimensions. So, for instance, if you had a little microscopic ant walking around down the microscopic depths, it could move in the familiar extended dimensions, but it could also walk in these hitherto unknown, curled-up dimensions, curled-up directions that you have to have incredible magnifying equipment to see directly. And that's the way in which this theory copes with the strange prediction. IT says deeply within the spatial fabric are these new curled-up spatial dimensions.
DAVID GERGEN: Brian, final question. I can understand why physicists are so excited by these theories and trying to put everything together. Why should others, the laymen, if you will, what should we conclude in thinking about this?
BRIAN GREENE: Well, I think that the essential lesson of string theory and actually 20th century physics more generally is that there is much more to the universe than we would expect by casually observing it; that is, there is a level of reality, a deeper level of how the universe works that's just below the surface of things as we experience them in day-to-day life. This theory -- it turns out -- requires that the universe have more dimensions, that the fabric of space can tear -- things we haven't had time to describe but wild ideas. And I think that the realization that there is much more to the universe than we are directly aware of is going to, in time, really help us understand and appreciate our own place in the cosmos.
DAVID GERGEN: Brian Greene, fascinating. Thank you very much.
BRIAN GREENE: Thank you.