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Elegant Universe: String Theory

The final installment of a three-part NOVA series about "String Theory," a new branch of science that seeks to explain nothing less than how the universe works, airs on PBS. Ray Suarez speaks with series host Brian Greene.

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  • NARRATOR:

    String theory says we may be living in a universe where reality meets science fiction: A universe of 11 dimensions, with parallel universes right next-door. An elegant universe composed entirely of the music of strings. But for all its ambition, the basic idea of string theory is surprisingly simple. It says that everything in the universe, from the tiniest particle to the most distant star, is made from one kind of ingredient: Unimaginably small vibrating strands of energy called strings. Just as the strings of a cello can give rise to a rich variety of musical notes, the tiny strings in string theory vibrate in a multitude of different ways, making up all the constituents of nature — in other words, the universe is like a grand cosmic symphony, resonating with all the various notes these tiny vibrating strands of energy can play. String theory is still in its infancy, but it's already revealing a radically new picture of the universe, one that is both strange and beautiful.

  • JIM LEHRER:

    Earlier, Ray Suarez spoke with the program's host.

  • RAY SUAREZ:

    Several years ago Brian Greene's book about string theory, called "The Elegant Universe," became a surprise best-seller. Now the Columbia University professor of physics and mathematics is bringing string theory to television.

    Professor Greene, welcome.

  • BRIAN GREENE:

    Thank you.

  • RAY SUAREZ:

    If at the upper reaches of theoretical physics, at the blackboard and in the lab, string theory finally gets worked out and agreed upon, how will it change rank and file citizens of planet Earth's ideas about how the world works?

  • BRIAN GREENE:

    Well, it's won't change things in any real dramatic way immediately. I think that it will really put life as we know it in a larger context if we truly understood the basic laws that govern everything in the world– the small, the big and everything in between– and that's what string theory promises. But it's probably also worth pointing out that were you to have asked in the 1920s how the work on quantum mechanics would affect the world, I don't think people would have had much to say. But today we have cell phones, lasers, medical equipment, CD's, personal computers, all of which rely on the physics of quantum mechanics. So that's the wonder of it all. We don't know where it will lead, but it could lead to spectacular new places.

  • RAY SUAREZ:

    Well, did atoms and then did figuring out that atoms were made of even smaller things and now quantum mechanics and string theory, are they all following the same path– an idea that eventually gets proven and worked out, and then the changes starts from there?

  • BRIAN GREENE:

    Yeah, sometimes there's a sense that developments in science overthrow previous ideas in thinking about the world, but that's usually not what really happens. More often than not, a development in science builds on what went before. So we are in fact following the same path, a path, if you, will that was laid down by the Greeks 2,500 years ago of trying to find the fundamental indivisible elements that make up the world. And our mathematical studies have taken us beyond atoms, beyond electrons, beyond neutrons and protons and quarks. They've taken us to this idea of little vibrating filaments of string. That is where the mathematics have so far taken us.

  • RAY SUAREZ:

    Is there a place though where our human limitations bump up against what can be proven and can be known, because we're just us and we've got our brains and it's hard for us to think in more dimensions than three?

  • BRIAN GREENE:

    Definitely. I can't think in more than three dimensions, even though I work on them all the time. I just use the mathematics at that point. But, for instance, what we do in the "Nova" program is try to strip away the mathematical details and go as far as we can visually. But you're right, there's no guarantee.

    There's no guarantee that this thing we have inside our heads will be able to fathom the deepest workings of the universe. We might hit a dead end at some point. We haven't yet. That's the amazing and wonderful thing. Every time we've tried to answer a question in physics through thought and experiment, sooner or later we've been able to make that next step. So we haven't hit any walls yet, but we might.

  • RAY SUAREZ:

    Until then, are scientists like particles bumping up against each other and creating new things?

  • BRIAN GREENE:

    Well, certainly the best developments in physics often do come when there is conflict. And in fact, string theory emerged from a conflict between two laws of physics– Einstein's Theory of Gravity on the one hand, and quantum mechanics on the other. They bumped heads and that gave rise to string theory.

    Now not everybody in the physics community is in favor of string theory. It's a somewhat controversial idea, but that's a healthy way for things to be. Until something is proven experimentally, it should be controversial, because we won't believe it until it makes contact with the world as we know it.

  • RAY SUAREZ:

    Professor Greene, thanks for being with us.

  • BRIAN GREENE:

    Thank you.