University at Buffalo - The State University of New York

Published: December 1, 2005

By KEVIN FRYLING
Reporter Contributor

Brian Greene is interested in the big questions: "What is space? What is time? What are the fundamental laws that govern the universe?"

GREENE

Philosophers, poets and mathematicians are among those who ask these questions, said Greene, a groundbreaking physicist, superstring theorist and the latest speaker in UB's Distinguished Speakers Series.

Greene presented the President's Lecture for Science and Technology on Nov. 16 to a crowd of more than 4,000 packed into Alumni Arena, including more than 1,200 students from 41 schools throughout the Buffalo area who received free tickets to the event.

During the lecture, Greene employed simple language, clear analogies and video graphics to enable his audience to grasp normally daunting physics concepts. An acclaimed science writer known for his wit and talent at communicating complex ideas in straightforward speech, Greene required no advanced knowledge from his listeners.

Greene speculates that string theory could answer the big questions, but to understand where physics is going, he first had to explain where it came from.

He began in the 16th century with Sir Isaac Newton, who, he noted, formulated the laws of gravity while on retreat from Cambridge in the English countryside, where he had fled from an outbreak of plague. Good scientific theory must be grounded in observation, stressed Greene, and Newton's laws enabled scientists to predict the motions of the stars thousands of years into the future. "Think of the power in those numbers," he said, "It's fantastic."

However, at the turn of the 20th century, Albert Einstein "put everything back on the table," Greene explained. Not afraid to question, Einstein turned to Newton's time-tested laws. He found his theories a close approximation of the truth, but not exact, said Greene. One century ago, during his annus mirabilis, Einstein revolutionized physics with the famous equation E=MC2 and his law of special relativity.

Yet even in 1905, Einstein could not fully account for gravity, said Greene. Consulting Newton's "Principia," Einstein discovered Newton never speculated about the mechanism by which gravity operates; he simply wrote, "I leave it to the consideration of the reader."

Unlike most people, Greene said, "Einstein was up to the challenge." After 10 years of labor, his theory of general relativity concluded that gravity transmits through the fabric of time and space. "The answer is stunning, it's beautiful, it's elusive," said Greene. Gravity affects space and time, so larger objects, such as the sun, "warp" the universe as though space were a rubber sheet. The depression is deep enough to attract smaller objects, such as planets, which "slide" toward them in orbit, he said. Gravity travels in the form of "ripples," similar to those formed when a pebble is thrown in a pond.

"Space and time come alive in 1915," Greene said. No longer was the universe an "inert stage on which the events of the universe take place," but a medium responding to its environment in "a wonderful, intertwined dance of space and time and matter and energy," he said.

In the 1920s and '30s, though, physicists developed quantum mechanics because nothing formulated up to that point could explain the behavior of molecules, atoms or subatomic particles, Greene said. Laws that predicted the actions of huge bodies, such as planets and stars, when applied on the molecular scale, determined that "every single atom in the universe should self-destruct in a fraction of a second," according to Greene. "Doesn't happen," he added.

The root of the problem is that the universe seems to act differently on the large scale verses the small scale, as stated in the Heisenberg uncertainty principle, he said. The "surface" of the universe on the scale of planets and stars is as placid and smooth as a sheet, Greene explained, but on the quantum scale, behavior is more difficult to predict. Viewed from that perspective, the surface of space is as violent and turbulent as a pot of boiling water. The effort to reconcile general relativity and quantum mechanics into a unified theory is the central challenge facing physicists today.

Physics currently can use a combination of theories to explain most of the universe, Greene said. Yet thousands of physicists are devoting their lives to solving this problem. The reason, Greene said, is a devotion to the truth. Moreover, a unified theory could enable physicists to examine the origin of the universe.

"We can use the laws of physics to wind back the clock to a split second before the big bang," he said, but physics currently cannot explain what occurred at the moment of the explosion that created the universe because conditions are so extreme. "At some point, the entire universe was tiny," said Greene. "If you want to know how the universe began, you have to come up with laws of physics that do not break down, no matter what."

The 1960s saw the discovery of "quarks," Greene added, but the dizzying array of subatomic particles found since then suggests a more streamlined, "elegant" explanation is out there, he said.

Superstring theory claims that the building blocks of the universe are not subatomic particles, but a more fundamental layer composed of filaments of vibrating energy known as "strings." Greene compared it to a "cosmic symphony."

"It's a beautiful idea," he said.

Superstring theory resolves the "laws of the small with the laws of the big," said Greene. Spreading particles out into strings "dilutes" the turbulent motion of the subatomic world like "ink in water," he noted. Smoothing out the fabric of space enables string theorists to slow down the action at the quantum level to the point at which physicists can again apply general relativity.

One of the strangest features of the theory, said Greene, is that the mathematics involved point to the existence of extremely small dimensions beyond our familiar, three-dimensional world.

"These extra dimensions may answer the deepest questions of experimental physics," said Greene, adding that physicists are working to determine the exact shape of these dimensions.

He compared the manner in which the dimensions curl into themselves as being similar to a three-dimensional sheet of paper wound so tightly that it appears as a two-dimensional line. There are about 20 fundamental properties in the universe, he added, including various atomic masses and gravitational strength, which, were they not exactly as they are, the universe could not exist. Physics can only measure, not explain, these properties, he said. Were the shape of the extra dimensions in string theory known, Greene speculates physicists could extrapolate from the information these fundamental properties. He said this could prove string theory as the crux of any theorem in its ability to make accurate predictions. In addition, Greene has stated the next generation of particle accelerators might enable experiments to test string theory.

Greene's mind-bending journey into the realm of theoretical physics seemed to awake a sense of curiosity in his audience. In a question-and-answer session following the lecture, Greene fielded questions from scientists, as well as average individuals, on such topics as dark matter, time travel and the nature of God. In terms of the physical universe, Greene could not offer definitive answers to these queries, as all remain in the realm of speculation; the more philosophical ones, he suggested, could be forever.