Wednesday, March 7, 2007

The universe just might be hanging together by strings. Many scientists think that string theory, a unified theory of the universe, could unite quantum mechanics and general relativity.

Albert Einstein worked for many years to find such a theory but came up empty-handed, says Brian Greene, professor of physics and professor of mathematics at Columbia University in New York City. He holds a doctorate in physics.

“He articulated that it would be a single framework that could talk about things that are small, things that are big and so on,” Mr. Greene says. “Try as he might, he couldn’t come up with a theory that would do that. String theory seems to do just want he wanted, to describe things that are big, fast, small, slow. The issue is that we don’t know if it’s right.”

“String Theory: Brian Greene and Lawrence Krauss Debate” will take place at 7 p.m. March 28 at the National Museum of Natural History’s Baird Auditorium in Northwest. The event is co-sponsored by the Smithsonian Associates and the Department of Energy’s Office of Science, both in Southwest.

In string theory, tiny filaments that look like strings are the ingredient that make up everything in the world, Mr. Greene says. The old picture of existence consisted of atoms, electrons, protons, neutrons, nuclei and then quarks.

“In the new picture, you cut even further, and you get something else inside the quarks, a tiny vibrating string,” Mr. Green says. “When you introduce the ingredient, the hurdles that Einstein couldn’t surmount seem to go away. You can finish the equations that he couldn’t finish.”

Without a unified theory, it is hard to analyze what happened at the beginning of time, Mr. Greene says. With string theory, scientists hope to peer back to the beginning of the universe using equations.

“It would mean that we might answer questions that people have wrested with for centuries,” Mr. Greene says. “Why is there a universe, and how did it come to be?”

For string theory to work, the equations demand up to 10 dimensions of space, not just the three dimensions of space that scientists currently know exist, he says.

“Einstein was too early,” Mr. Greene says. “There wasn’t enough known about the nature of quantum mechanics and matter and so forth. It was pretty much impossible to take that kind of a leap, as much as a genius as he was.”

If the strings exist, they are too small to be seen with today’s technology. In 2008, a new atom smasher should be ready at CERN, the European Council for Nuclear Research, an international collaboration for science experiments in Geneva. At this point, the data from the collisions between particles is the best hope to distinguish if string theory is correct, he says.

Currently, when scientists weigh electrons, they are very light. However, no one has been able to explain the results.

“If it was made up of strings, there is a chance that you might be able to explain the electrons’ weight, and it would be a profound step forward in our understanding of the world,” Mr. Greene says. “We want to understand things as deeply as possible, from the tiniest bits of matter to the far reaches of the cosmos.”

Although Mr. Greene has a positive attitude regarding string theory, he does have many reservations about it, he says.

“I’d like to reserve judgment until the data forces us one way or the other,” Mr. Greene says. “That’s what science is. You search in the unknown and wait to see if your ideas are right.”

Even though string theory solves mathematical ideas on paper, it hasn’t solved any problems in physics, says Lawrence Krauss, Ambrose Swasey professor of physics and a professor of astronomy at Case Western Reserve University in Cleveland. He holds a doctorate in physics.

String theory is worth exploring, but it hasn’t shown any evidence in the real world, he says.

“It has, in fact, turned out to be progressively more complicated,” Mr. Krauss says. “We don’t even know what the theory is. It’s probably not even a theory of strings. We don’t know how many dimensions it exists in. We don’t know the fundamental objects of the theory.”

It’s like talking about matter without knowing what atoms are, Mr. Krauss says. He says most new ideas are wrong, including good ones. Otherwise, it would be easy to do physics. String theory has been researched for about 25 years so far.

“It’s just shooting around in the dark,” Mr. Krauss. “It hasn’t panned out. There are lots of interesting theories that have nothing to do with nature. This may be one of them.”

There have been a lot of strong words said regarding string theory, says Michael Turner, the Rauner Distinguished Service professor in the Kavli Institute for Cosmological Physics at the University of Chicago. He is the moderator of the debate. He holds a doctorate in physics.

String theory has bold aims, Mr. Turner says. Not only does it suggest unifying the two towering achievements of physics of the last century, but it also anticipates defining space and time.

“Some people have gone out on a limb and said it’s not even science or testable,” Mr. Turner says. “Brian needs to convince us it’s science. In doing so, he needs to say how we can test this theory.”

On the other hand, Mr. Krauss needs to present evidence as to why the idea of additional dimensions is wrong and why the theory is untestable, he says.

“As with many good debates, there isn’t going to be a winner,” Mr. Turner says. “I hope people come away with a sense of excitement of the big questions. It’s an exciting time to ask big questions. Although there is no guarantee to answer the big questions, we have a good chance.”

It’s still very early in the days of researching string theory, says Jonathan Bagger, a professor of physics and chairman of the Department of Physics and Astronomy at Johns Hopkins University in Baltimore. He holds a doctorate in physics.

Because physics is a fairly mature subject, there isn’t a lot of room to pull quantum mechanics and general relativity together, he says. Most attempts break something else that scientists already understand.

“If string theory was correct, it explains properties predicted for black holes,” Mr. Bagger says. “This is theoretical because we don’t have black holes sitting around our laboratories, but it’s a major advance for string theory to have done that.”

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