By Kate Conger
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By Rachel Swan
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By Chris Roberts
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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.
Once admitted to the inner sanctums of the theory groups, a string theorist's material needs are guaranteed -- through academic tenure and a military-scientific umbilical cord -- for life. Most particle physicists receive career-long salaries from the U.S. Departments of Defense and Energy; those grants follow the scientists, no matter where they research. Today's string theorists decry the notion of a "string bomb"; but they have to admit that yesterday's "relativists" did not know that their "pure science" would map the road to nuclear winter. And certainly, the Pentagon and the Energy Department have their collective fingers crossed in hopes that wild-sounding string theories will one day lead to practical military and/or energy-generating devices.
But it is obvious that money is not the main motivation of the string theorists, and practical applications -- military or otherwise -- hold little interest for them. In the self-contained world of extremely talented physicists, it is considered not just fair, but the way of the world to trade insights into the structure of the universe for social privileges.
Whether M-theory is ever "proven," it is no hoax; the alignment of its mathematics with both quantum mechanics and relativity is too elegant for any physicist to ignore. But that does not mean M-theory is intuitive. A recent article in Scientific American put the theory's paradoxical nature this way: "Elementary objects now seem to be made out of the very particles they create."
And not all of Shenker and Susskind's colleagues are thrilled with M-theory. Gerard 't Hooft, a prominent Dutch physicist, complains, "You can't ask anymore what is happening, you have to believe in miraculous outcomes of abstract mathematical procedures." And 't Hooft scoffs at the notion of a Theory of Everything. How can anyone claim to know the answer, he asks, when they don't even know what the question is?
It is possible, the M-theorists admit, that M is a grandly correct theory -- a theory that applies not to our, but to another, universe!