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As one of the shakers of string theory, Shenker helped create a theory group at New Jersey's Rutgers University in the early 1990s. The group was a bit revolutionary in its approach to collaboration, says Silverstein, who did postdoctoral work with Shenker. "It was kind of like a Quaker meeting," she remembers.
Instead of sitting through "snobby" lectures, Shenker and his colleagues gathered and spoke whatever was on their minds, even when it came out as stream-of-consciousness rambling. Silverstein says that the Rutgers collective approach to thinking is being copied at string theory centers around the world, including Stanford.
The open discourse that has fueled advances in string theory seems, at times, dangerously self-sacrificing. The price of hearing the new ideas of others is to risk having your own new ideas ... appropriated. The art of physics is no longer an individualistic pursuit, as it was for Sir Isaac Newton, or Albert Einstein. Twenty-first-century string theory is a problem-solving game, and to play, group participants need to know a little bit about all the realms of math and physics. Most important, they need to listen to one another.
Listening to the conversation flowing from the Stanford physics couches is anything but relaxing. Trying not to drown in a sea of jargon, at one point I ask what I fervently hope to be an intelligent question. After an embarrassed silence, Shenker takes pity and whispers, "We stopped talking about that an hour ago."
Later, Shenker confides that he was sad to leave the Rutgers theory group, which had significantly advanced the frontiers of string theory. But the world of physics requires cross-pollination of minds, and one of string theory's founders was, and still is, at Stanford.
At age 58, Leonard Susskind claims elder status in the string revolution; he was, after all, a midwife to string theory at its birth in 1969. Neither he nor Shenker has any truck with the scientists who try to popularize their ideas with talk of worm holes and time machines and Star Trek-ian warp drives. But both physicists are eager to translate, into mundane language that the general public might grasp, the sheer natural beauty they have glimpsed through the looking glass of their mathematics. Today, for example, over cheap lunch in a student cafeteria, they are chewing over one of string theory's odder postulations: that black holes exist at both ends of the universe.
In the large -- cosmological -- scale, black holes are ancient stars that have collapsed in on themselves until all of their matter becomes condensed -- so condensed and heavy, in fact, that not even light can escape their massive gravitational fields. All of known physics falls apart at the entrance to a black hole. It is a realm from which no visitor can return -- even in the "thought experiments" that characterize theoretical physics. These type of black holes have been described well enough in the popular press to be known to many nonscientists.
Now, Susskind explains, some of the smallest objects in the universe also are being described as black holes -- black holes so small that they compare to an atom, in the same proportion that an atom would compare to the size of the solar system. In fact, explains the scruffy visionary, tiny black holes may be a basic building block of nature.
In a string-related sort of way.
Stringing the Large to the Small
Twentieth-century physics devoted itself to exploring two great scientific principles: gravity and quantum mechanics. The laws of gravity govern the motion of very large objects, such as planets. The rules of quantum mechanics describe the motion of unimaginably small things: the components of atoms.
Albert Einstein showed that gravity -- acting over tremendous distances -- actually shapes the geometry of the universe. Along the way, Einstein proved that nothing can travel faster than the speed of light, and that time itself slows down as objects approach that 186,000-miles-per-second limit.
But Einstein's theories -- known generally as relativity -- don't work for describing the motion of very small objects moving around each other at extremely small distances. For this type of subatomic calculation, Max Planck invented the science of quantum mechanics during the Roaring '20s. Radio, radiation therapy, and hydrogen bombs are all practical offshoots of quantum mechanics.
Quantum mechanics also injected a systemic uncertainty into the observation of elementary particles, from protons and electrons down to the almost chimerical quarks. To the disgust of Einstein -- who believed in a God-ordered universe -- quantum mechanics was based on probability, on chance. And its rules were not compatible with the rules of Einstein's relativity.
Einstein died still trying to think up the "unified field theory" that could combine the laws of the big with the rules of the ineffably small.
In the late 1960s, government-subsidized physicists were trying to explain the mysterious force that binds together certain particles at the center of the atom called protons. Fragmentary evidence indicated that the protons might themselves result from the movement of infinitesimally small, stringlike objects: little loops of energy that vibrate through 25 dimensions of space. Oops, said the scientists. We can't deal with the four dimensions we already have -- three of space and one of time -- so forget these strange string things.