A physicist from the University of California, Santa Barbara, has taken what scientists are calling a major step toward finding a long-sought unified theory of nature. If it works, such a theory would explain everything from subatomic particles to supernovas as different aspects of the same fundamental stuff.
Ever since Isaac Newton discovered that falling apples and orbiting planets are both pulled by gravity, physicists have been hooked on finding unity in nature.
Since Newton’s time, physicists have made great progress bringing pieces of the puzzle together: They found that the lightning that crashes from the clouds is just a different aspect of the magnetism that makes compass needles point north. They learned that undulating waves of light can act like pellets of matter.
But they have been stumped in their search for a “grand unified theory” that would unite gravity with the other forces and particles. The only theory that comes close is “string theory.”
String theory suggests that everything in nature is made of tiny vibrating strings. Depending on the way the string squirmed and twisted in space, it would become an electron, or a quark, or a graviton or some other fundamental building block of nature.
Until now, even string theory could not encompass all of nature. When physicist Stephen Hawking figured out almost 20 years ago that black holes can evaporate, leaving only particle-like dregs, he left physics with a number of pesky problems. One was that the dregs of black holes just wouldn’t go away.
While physicists were confident these black holes were an essential ingredient of nature, they were incompatible with string theory.
But now, they’ve discovered that black holes can transform into strings and vice versa, in the same way as ice changes into water.
But, the theory only works when the strings vibrate in 10-dimensional space. Three of those dimensions are the familiar north/south; east/ west; up/down. The fourth is time.
That leaves six “extra” dimensions to worry about. To get to reality, says Andrew Strominger, the physicist who made the discovery along with colleagues Brian Green and Dave Morrison at Cornell, “we have to get rid of those extra dimensions.”
So far, physicists have done this by imagining that the six extra dimensions are so tightly curled in on themselves that they disappear. “If you look at a garden hose from very far away, it looks like a straight line,” said Greene.
“But if you look at it from close up, you can see that it has another dimension curled up around it.”