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[Tormod]

Here is an article from the AAAS, February 2002:

In search of extra dimensions: Hang on-a new reality may be around the corner

BOSTON, MASS. - "Reality is merely an illusion, albeit a persistent one," according to the late Albert Einstein. But, "if everything is an illusion and nothing exists," humorist Woody Allen has observed, "I definitely overpaid for my carpet."

Hang onto your carpet receipts:

Our understanding of reality - that is, a world where events happen over time within a three-dimensional space - may be turned on its head by the year 2005, scientist Maria Spiropulu said today during the American Association for the Advancement of Science (AAAS) Annual Meeting.

"The way we think about things is about to change completely," said Spiropulu. "This is truly a revolution in the way we understand our world."

Spiropulu, a 32-year-old scientist with the Enrico Fermi Institute at the University of Chicago, is hot on the trail of extra dimensions. She's using new methods to prove, experimentally, whether our reality is more complicated than we previously assumed.

"We are very close" to a new reality, she said. "Right now, we imagine space and time as a static question, and we solve equations as a function of space and time. But, what we're learning is that, at the very large scale or the very small scale, space and time are dynamic. What is happening at those scales, we cannot explain. So we have to wonder, do these scales hold some extra dimensions?"

Traditionally, physicists have mathematically explained all that happens in the world by using a "standard model." In this system, all matter is made of lightweight "leptons" (such as electrons and neutrinos) and quarks. Three forces manipulate these particles: electromagnetism, and strong and weak nuclear reactions.

But, this traditional approach doesn't explain gravity, the fourth force. The conventional rules of quantum mechanics have been successfully married with Einstein's Theory of Special Relativity, which explains the behavior of very fast objects-but not with his Theory of General Relativity, the guidebook to gravitational force. Mathematical gobbledygook usually results from trying to combine quantum mechanics and general relativity. Consequently, we still don't know, for example, what happens to particles sucked into a black hole.

In an effort to uniformly explain all events, physicist Gunnar Nordstrom (1881-1923) first introduced the notion of an extra dimension at the beginning of the 20th century. Perhaps, he thought, gravity happens in a realm we don't understand and can't mathematically define. Some 10 years later, Theodor Kaluza (1885-1954) and Oskar Klein (1894-1977) took Nordstrom's ideas another step forward: An extra dimension may be curled up like an unimaginably small ball, they said, on the order of the Planck scale-the smallest unit of length in the universe (10 to the minus 33 centimeters).

The idea of an extra dimension was resurrected yet again in the late 1990s, as scientists began to ask whether Newton's Law of Universal Gravitation reliably predicts gravity's behavior below the centimeter scale, Spiropulu explained. Physicists were energized in 1997 by the discovery of possible links between the standard model and "superstring theory"-the notion that a series of extremely tiny, vibrating strings may lurk beneath the level of quarks and leptons.

Researchers Nima Arkani-Hamed, Savas Dimopoulos, and Gia Dvali then caused further excitement, by suggesting that at least one of these tiny dimensions might, in fact, be large enough to measure. Still, no one has produced undeniable proof of superstrings, and many questions persist.

Since then, Spiropulu reported to AAAS attendees, experiments have shown that Newton's Law is valid down to the 200-micron level. That is, gravity "follows the rules" at that scale. But, the physical reality below this level remains a mystery. Somewhere within the Planck scale, or at extreme energy