Face off.
Brian Greene (left) and Lawrence Krauss debated the merits of string theory.

Credit: (left, Greene) Lumidek: (right, Krauss) Lawrence Livermore National Laboratories

String Theory, With No Holds Barred

By John Simpson
ScienceNOW Daily News
29 March 2007

String theory assumes that elementary particles are tiny vibrating strings that exist in multiple dimensions. In trying to unite Einstein's theory of gravity with quantum mechanics, it hopes to answer mysteries about the beginning of the universe and the very nature of matter, energy, and time. The claims are deep, and opponents of the theory say the findings so far have been shallow, even nonexistent. Last night's debate did little to settle the argument, but a packed house of academics, physics geeks, and just-curious laypeople seemed to enjoy themselves nonetheless.

Krauss threw the first punch. A professor at Case Western Reserve University in Cleveland, Ohio, and an expert on black holes, dark matter, and dark energy, Krauss said he has grown tired of string theory's hyped but hollow antics. In 37 years, he noted, the hypothesis has explained little while confusing a lot. "It doesn't make predictions," he said. "It usually makes excuses."

Greene shot back: Although string theory's successes can't be experimentally verified at the moment, that doesn't mean they aren't there. Mathematically, the hypothesis appears to resolve a decades-old problem of merging the "two pillars" of physics: gravity and quantum mechanics. And, noted the Columbia University theoretical physicist, mathematician, and darling of public television, string theory might also account for the origin of disorder in black holes, which has stumped physicists for decades. String theorists are eagerly awaiting the results of the Large Hadron Collider, as it might show subtle details about the strings themselves. Like any great masterpiece, Greene explained, string theory will take time to be completed--and fully understood. After all, it's a lofty goal: "trying to answer the most profound, difficult question in science."

Krauss wasn't impressed. "I don't want it to answer a profound question," he said. "I want it to answer one question." The audience erupted in laughter, but Krauss wasn't through. "Some of my students have gone on to be relatively well-known string theorists," he continued. "Of course, I wouldn't want my daughter to marry one."

Susan Isaacs's teenage daughter is unlikely to become one of those brides. A home-schooled student who's also an intern at NASA's Goddard Space Flight Center in Greenbelt, Maryland, Alex Isaacs always circles debates like this on her calendar. The burgeoning physicist was impressed with Greene's charisma, but she wasn't impressed with his strings. "When I first heard of [string theory], I thought it was the next coming," she said. "But anything that's been around this long and has had this much intellectual talent that hasn't shown anything, it must not be it."

The master of ceremonies was less decisive. Although famous for coining the term "dark energy," Turner was at a loss for words when it came to picking a winner. In the end, he awarded the prize--a long piece of orange string--to both Greene and Krauss. The pair playfully began fighting over the string, tugging it back and forth as the audience clapped. It was a fitting end to the evening: both a microcosm of the debate and of the world of string theory, in which the winner is still unknown and the whole thing is still over just about everyone's heads.

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