Tuesday, November 08, 2005

Potential break-through in physics?

I wanted to capture this before it went down the memory hole, so to speak:

There used to be an ice cream parlor in the student center at the Massachusetts Institute of Technology. And it was there, in the summer of 1998, that Lisa Randall, now a professor of physics at Harvard and a bit of a chocoholic, and Raman Sundrum, a professor at Johns Hopkins, took an imaginary trip right out of this earthly plane into a science fiction realm of parallel universes, warped space and otherworldly laws of physics.

They came back with a possible answer to a question that has tormented scientists for decades, namely why gravity is so weak compared with the other forces of nature: in effect, we are borrowing it from another universe. In so doing, Dr. Randall and Dr. Sundrum helped foment a revolution in the way scientists think about string theory - the vaunted "theory of everything" - raising a glimmer of hope that coming experiments may actually test some of its ineffable sounding concepts.

[Several years before, when Randall was in high school] were heady times in physics. Fired by the dream of a unified theory of everything, theorists flocked to string theory, which envisioned the fundamental elements of nature as tiny wriggling strings.

Dr. Randall, however, resisted this siren call, at least for a while. For one thing, physicists thought it would take a particle accelerator 10 million billion times as powerful as anything on earth to produce an actual string and test the theory.

String theory also stubbornly requires space-time to have 10 dimensions, not the 4 (3 of space and 1 of time) that we experience. Preferring to stay closer to testable reality, Dr. Randall was drawn to a bottom-up approach to theoretical physics, trying to build models that explain observed phenomena and hoping to discover principles with wider application. But Dr. Randall and string theory had their own kismet.

In the mid-90's, theorists discovered that the theory was even richer than its founders had thought, describing not just strings but so-called branes, as in membranes, of all dimensions. Our own universe could be such a brane, an island of three dimensions floating in a sea of higher dimension, like a bubble in the sea. But there could be membranes with five, six, seven or more dimensions coexisting and mingling like weird cosmic soap bubbles in what theorists sometimes call the multiverse.

That theory, known as supersymmetry, was invented in turn to solve another problem - the enormous gulf known as the hierarchy problem between gravity and the other forces. Naïve calculations from first principles suggest, Dr. Randall said, that gravity should be 10 million billion times as strong as it is. You might find it hard to imagine gravity as a weak force, but consider, says Dr. Randall, that a small magnet can hold up a paper clip, even though the entire earth is pulling down on it...

But there was a hitch with the way the theory worked out in our universe. It predicted reactions that are not observed.

Dr. Randall wondered if the missing reactions could be explained by positing that some aspects of the theory were quarantined in a separate universe...

When Dr. Randall and Dr. Sundrum published their first paper, describing the two-brane scheme, in 1999, she said that many physicists did not recognize it as a new idea and not just an elaboration on the large extra dimensions of the A.D.D. group. In fact, she said, the extra dimensions don't have to be very large in the two-brane theory, less than a millionth of a trillionth of a trillionth of an inch.

When they published their second paper, about the infinite dimension, she said, even some of their best friends, reserved judgment.

But by the time a long-planned workshop on strings and particle physics at the Kavli Institute for Theoretical Physics in Santa Barbara rolled around that fall, string theorists were excited about the Randall-Sundrum work and the earlier A.D.D. proposal.

The reason was simple: If they were very lucky and one of these versions of string theory was the one that nature had adopted, it could actually be tested in the Large Hadron Collider, the giant particle accelerator due to go into operation at CERN near Geneva in 2007. Colliding beams of protons with a combined energy of 14 trillion electron volts, the collider could produce particles like gravitons going off into the fifth dimension like billiard balls hopping off the table, black holes or even the illusive strings themselves.

"If this is the way gravity works in high-energy physics, we'll know about it," Dr. Randall said.

I do wish the Times would spare us more of the "human interest" stuff that comes lamely across the printed page like the local news story about the lost dog. And I'm really not feeling that misanthropic/misogynistic this morning.

But this is potentially a really cool result- it would be amazing if the multiple universies or branes could be indirectly observed.

It would also lend less credence to the "Intelligent" "Design" folks' argument that "theoretical physicists' theories can't be observed either," although, in fact it's a false argument because an experiment that would falsify the theory could at least be constructed as an idea, something "Intelligent" "Design" cannot do.

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