March 28, 2008
Particle Collider May Prove String Theory
One of the most significant moments in the history of science may come after a new particle collider starts work this year beneath the Swiss-French border, according to a renowned physicist, Brian Greene.
The Large Hadron Collider just might prove that the controversial "theory of everything," string theory, is true.
Greene, professor of physics and mathematics at Columbia University, New York City, and author of best-selling books on string theory, spoke Tuesday at Brigham Young University's Marriott Center.
His book, "The Elegant Universe," was developed into a three- part series broadcast by PBS. "The Fabric of the Cosmos: Space, Time and the Texture of Reality," the title of his latest book, also was the name of the lecture.
"Space and time are the most familiar and yet most enigmatic concepts in science today," Greene said, but they are not what our senses would lead us to believe.
"We are learning that reality is not what we think it is. The very basis of existence is not what we think it is," he said.
At the turn of the 20th century, Albert Einstein asked himself how gravity worked. How could the sun reach across 93 million miles and affect the motion of Earth? He struggled with the question for 10 years.
By 1915, Einstein had come up with the General Theory of Relativity as an answer. Einstein pictured space-time as something like a big rubber sheet. When something massive, like the sun, weighs down a portion of the sheet, it causes a distortion in it, and a smaller object will roll around and around the pit.
"Einstein says take that idea and apply it to the cosmos," Greene said. Thus, a planet will circle the sun because the sun causes a deformation, like a pit, in the fabric of space-time.
Rather than static, fixed features, "space and time can actually do something. Space and time push things around," he said. Each person "affects the shape of space; in fact, the shape of time as well."
General Relativity works beautifully on the large scale. But scientists realized that Einstein's ideas were in conflict with another proven theory, that of quantum mechanics, which covers the very small scale.
"Quantum mechanics is a very mysterious, strange, really mind- boggling subject," Greene said.
Quantum effects have been proven in the laboratory. The ideas "are confirmed by experimental observation." A famous feature of quantum mechanics is that one may know one aspect of an electron, such as its speed, without being able to know another, such as its position -- and vice versa.
On the large scale, Einstein's laws show the smooth, predictable actions of relatively big phenomena. But on a tiny scale, things are "chaotic," Greene said.
When Einstein's theories were applied to extremely small things, "the laws made wrong predictions."
String theory accommodates both sets of laws. It holds that each subatomic particle actually is an incredibly minute vibrating filament of energy. The frequency of the vibration determines whether the particle is a quark or an electron, for example.
Vibrating strings define space, time and everything in existence, many scientists believe. The theory "winds up fixing" the conflict between the laws of the large and the small.
But if string theory is correct, "it says something really wild," Greene said. It fails when restricted to our three spacial dimensions -- up and down, left and right, front and back. "If that's all there is in space," he said, "this thing doesn't work."
Not until 10 spacial dimensions are used in the calculations do the equations work. But we perceive only three. Where are the others? They could be curled up within the normal dimensions, he said.
Greene asked the audience to imagine a piece of paper, essentially a two-dimensional object. When it is curled up and seen from a distance, it looks like a one-dimensional line. But if an ant were on it, the insect might find itself going back and forth in one dimension and around the tube of paper in another.
Peering through binoculars, a watcher might see the ant's circular sauntering and realize the paper has another dimension.
Understanding the nature of the paper "escaped you without the right equipment -- the binoculars."
String theory may allow tiny curled-up dimensions to be everywhere, so small that we can't detect them. "We haven't seen them -- yet," he said.
But the Large Hadron Collider being built near Geneva -- an almost 17-mile circular tube built beneath the French-Swiss border, because it was cheaper to use land underground for such a massive structure -- may provide proof of string theory. When it begins smashing rotating streams of protons together, the ideas may be verified.
"There's a chance ... that some of the debris from these collisions will be ejected out of our dimensions," and scientists may be able to discover "these missing energy signatures," he said. "If this is confirmed experimentally in the next few years, to me this would be one of the most significant moments in the history of science."