Those tiny loops of string whose harmonics were thought to breathe form into every particle and force known to nature (including elusive gravity) hardly even appear anymore on chalkboards at conferences. The upshot is that string theory today includes much that no longer seems stringy. Some dig deep into particular crevices others zoom out to try to make sense of grander patterns. The more closely people explore any one corner, the more structure they find. String theory today looks almost fractal. “Nobody knows whether to say they’re a string theorist anymore,” said Chris Beem, a mathematical physicist at the University of Oxford. “It’s hard to say really where you should draw the boundary around and say: This is string theory this is not string theory,” said Douglas Stanford, a physicist at the IAS. It’s so ubiquitous that “even if you shut down all the string theory groups, people in condensed matter, people in cosmology, people in quantum gravity will do it,” Dijkgraaf said. The mathematics that have come out of string theory have been put to use in fields such as cosmology and condensed matter physics - the study of materials and their properties. “Things have gotten almost postmodern,” said Dijkgraaf, who is a painter as well as mathematical physicist. Its tentacles have reached so deeply into so many areas in theoretical physics, it’s become almost unrecognizable, even to string theorists. Like many a maturing beauty, string theory has gotten rich in relationships, complicated, hard to handle and widely influential. “We’ve been trying to aim for the successes of the past where we had a very simple equation that captured everything,” said Robbert Dijkgraaf, the director of the Institute for Advanced Study in Princeton, New Jersey. Coming off the momentum of completing the solid and powerful “standard model” of particle physics in the 1970s, they hoped the story would repeat - only this time on a mammoth, all-embracing scale. Many, in retrospect, realized they had raised the bar too high. “The last 20 years have really been a great extension of theoretical tools, but very little progress on understanding what’s actually out there.” “After a certain point in the early ’90s, people gave up on trying to connect to the real world,” Gross said. The complexities of string theory, all the possible permutations, refused to reduce to a single one that described our world. “We even thought for a while in the mid-’80s that it was a unique theory.”Īnd then physicists began to realize that the dream of one singular theory was an illusion. A moment,” said David Gross, an original player in the so-called Princeton String Quartet, a Nobel Prize winner and permanent member of the Kavli Institute for Theoretical Physics at the University of California, Santa Barbara. No one knew just how the dimensions were compactified - the possibilities for doing so appeared to be endless - but surely some configuration would turn out to be just what was needed to produce familiar forces and particles.įor a time, many physicists believed that string theory would yield a unique way to combine quantum mechanics and gravity. These dimensions were folded in on themselves - or “compactified” - into complex origami shapes. The strings were too small to be probed by experiment and lived in as many as 11 dimensions of space. To be sure, the theory came with unsettling implications. At last, it seemed, here was a workable theory of quantum gravity.Įven more beautiful than the story told in words was the elegance of the math behind it, which had the power to make some physicists ecstatic. For one, quantum uncertainty couldn’t rip space-time to shreds. Avoiding the infinitely small meant avoiding a variety of catastrophes. The vibrations would sing out quarks, electrons, gluons and photons, as well as their extended families, producing in harmony every ingredient needed to cook up the knowable world. It seemed, to paraphrase Michael Faraday, much too wonderful not to be true: Simply replace infinitely small particles with tiny (but finite) vibrating loops of string. String theory strutted onto the scene some 30 years ago as perfection itself, a promise of elegant simplicity that would solve knotty problems in fundamental physics - including the notoriously intractable mismatch between Einstein’s smoothly warped space-time and the inherently jittery, quantized bits of stuff that made up everything in it.
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