The Hottest Thing in Theoretical Physics

The Unraveling of String Theory — Michael D. Lemonick— — August 2006— (Time Magazine)     Everyone knows that string theory is the hottest thing in theoretical physics. But string theory hasn't been embraced by everyone.     Physicists Peter Woit in Not Even Wrong and Lee Smolin in The Trouble with Physics both argue that string theory is largely a fad propped up by practitioners who tend to be arrogantly dismissive of anyone who dare suggest that the emperor has no clothes.       The two most important ideas of 20th century physics, relativity and quantum theory, were known to be fundamentally incompatible.         Quantum theory describes the universe as intrinsically discontinuous: energy, for example, can come in bits just so small, but no smaller. Relativity treats time and space and gravity as a smooth, unbroken continuum.             The solution: to think of the basic units of matter and energy not as particles but as minuscule, vibrating loops and snippets of stuff resembling string, which turn out to exist not just in our familiar four dimensions of space and time but in 10 or more dimensions.         This bizarre-seeming scheme appeared on first blush to explain why particles have the characteristics they do. It also included a quantum version of gravity and thus of relativity.         But: superstrings have proved a lot more complex than anyone expected. The mathematics is excruciatingly tough, and when problems arise, the solutions often introduce yet another layer of complexity.         The new, improved theory posits a nearly infinite number of different possible universes, with no way of showing that ours is more likely than any of the others.                The string theory’s idea of infinite universes is currently in vogue among some astronomers as well.           String theorists seem ready to abandon the essential definition of science. Is string theory too important to be hampered by old-fashioned notions of experimental proof?       In science, slow accretion of data and evidence eventually eliminates reasonable doubt, but not so with strings.       Nobody has any good idea of how to test string theory. Woit says, 'proposing speculative ideas is fine, but if they can't be tested, they're not science'.