Both sides of the battle over string theory have made it to our shortlistby Philip Ball / March 2, 2015 / Leave a comment
When I met Edward Witten—one of two physicists on Prospect‘s world thinkers list—at CERN in Geneva some years ago he chatted genially enough in his rapid, precise and high-pitched sentences, and yet it was hard to shake off a sense that this was some omniscient demigod doing a reasonable impression of pretending to be an ordinary mortal. His high forehead even seems designed to hold more brain than the rest of us. It’s hard to get past his reputation as the brainiest mathematical physicist on the planet.
The awe with which Witten is regarded among his peers makes Stephen Hawking seem like a bright graduate student. He is the only physicist to have been awarded a Fields Medal, a Nobel equivalent for mathematicians under 40. That was back in 1990, before he had even come up with the theory for which he is most famous: M-theory, which showed that all five of the then-existing versions of string theory were different aspects of the same meta-theory. (Witten never specified what “M” stands for: some say magic, mystery or matrix.) The discovery of this unanticipated unity offered one of the most telling hints that string theorists were on to something.
Yet string theory, first popularised in the 1980s, is one of the most divisive ideas in physics. It represents an attempt to get down to the next layer of reality, after quantum mechanics has explained the behaviour of atoms and their constituent particles, and the theory called quantum chromodynamics explained how subatomic particles within those atoms (protons and neutrons) are themselves made of more fundamental particles called quarks and gluons. String theory posits that the point-like particles of quantum theory are made up of one-dimensional vibrating threads called “strings.”
But string theory is more than that, for its real aim is to reconcile quantum theory with gravity, the force currently described by Einstein’s theory of general relativity (see my blog). The discrepancy between these two descriptions of the physical world—one working primarily at gigantic scales, the other at the scale of the invisibly small—is the most alarming lacuna in modern physics. Resolving it—developing a working theory of quantum gravity—would give us a unified view of physics and would surely be one of the greatest…