M

When viewing string theory from four-, five-, or 10-dimensional perspectives, it appears to be fragmented. When looked at from inside the littlest, 11th dimension, all the string theories become a whole: M-theory.

Physicists around the world gasped when Witten posted M-theory on the Los Alamos Web site four years ago. The discovery of the 11th dimension unleashed hundreds of new ideas and revelations.

Steve Shenker, Leonard Susskind, Tom Banks, and Willy Fischler were inspired to invent an offshoot of M-theory -- what they call Matrix Theory -- in 1996. Shenker simplifies the discovery by comparing it to a chart in which cities are listed in relation to mileage. To find the miles between two cities you follow the lines inside the matrix to a coordinate. Only, in this case, there are multiple coordinates, because there are multiple dimensions, or multiple ways to measure where and when a string is.

(The theorists carry these matrices around in their heads -- massaging the numbers without benefit of computers. For purposes of discovery, they tend not to use the powerful computers at their command, because machines are stupid; they have no intuition, no art.)

For a short while, Shenker and his collaborators were the toast of the high-energy physics world. Then, a new theory of "p-branes" burst upon the scene. The physicists gasped again.

The newest fad in M-theory says that a string is fashioned from a kind of membrane -- a p-brane -- wrapped around the previously hidden 11th dimension. Nobody is prepared to say what the difference is between a brane and a string, but, it seems that some strings are built from branes that are actually tiny black holes -- that is, black branes.

Is M Real?
Inside her normal four dimensions, Eva Silverstein relaxes by playing soccer, running, and reading fiction -- but not science fiction. Who needs science fiction, she snorts, when you have M-theory?

As she talks strings, words spill out of Silverstein's mouth, but their meanings are not always obvious. She says that she tries to talk shop with her family -- her father is a professor of philosophy at Washington State University -- and they all end up laughing at the absurdity of the communication gap.

But Silverstein is serious about finding a way to experimentally validate M-theory (short of building a galaxy-sized particle collider). She is concerned about symmetry. Indeed, all scientists are stuck on symmetry.

As an example of perfect spatial symmetry, consider a sphere, such as a beach ball. No matter how you rotate it in space, it always looks the same. Now consider a very unsymmetrical object, such as a tree. It looks different from different angles of viewing: It is asymmetrical and, therefore, ugly to a physicist (until reaching symmetries at the molecular level, of course).

Mathematics is moved along by internal symmetry -- by equations that balance. And the symmetry of simple geometrical objects is analogous to a "supersymmetry" between elementary subatomic particles. In a supersymmetric universe, every subatomic particle in existence will have a matching partner called a superpartner. Particle-colliding machines have yet to detect superpartners. But M-theorists claim that when they do spot them -- when machines powerful enough to do so come online sometime in the next decade -- the superpartners will not be exactly symmetrical to their mates. M-theorists desire to find what they call a "broken" symmetry, because according to M-theory the universe is not exactly symmetrical.

Finding these previously unseen, slightly asymmetrical superpartners would partially -- and very indirectly -- validate some of the claims of M-theory.

And how will Silverstein feel if she is the one to "break" supersymmetry? "I feel important when I understand how the world works," she grins.

Egg or Chicken?
Back in the cafeteria, Leonard Susskind and Steve Shenker discuss supersymmetry and p-branes. Three wide-eyed graduate students memorize their every word.

Yet, studied nonchalance seems to be the party line for most string theorists when asked about personal motivation. They do it because it is a puzzle, because it is interesting. A few spout off about the beauty of the universe and knowing the mind of God.

Shenker, a lifelong atheist, is more down to earth. He says that most people are selfish and act only upon material incentive. He also says that most physicists care more about the opinions of the world of science than they care about the opinions of the general public. They seek emotional satisfaction from the approval of their peers -- that incredibly small circle of people who speak M-theory and make awards.