Gary wrote:thus it may be possible to someday demonstrate that the multiverse of parallel quantum worlds exist by building a quantum computer that can outperform all of the matter in the visible universe.

You know...it's hard to put my finger on. But there's just *something* about reading something, and you get this gut feel like it's not very good science, or shaky logic...then you read something else and you think "wow...now that's amazing..."

The article below, to me, reads like that. Really amazing stuff.

A Great NewScientist article on Superstring Theory - and the latest and most promising TheoriesSuperstring theory was a stunning breakthrough. It became one of the fastest growing and most exciting areas of theoretical physics, generating a feverish outpouring of thousands of papers. Then, in the early 1990s, progress seemed to grind to a halt. People became discouraged when they failed to find the answers to two key questions: where do strings come from, and is our Universe among the many solutions of superstring theory? But now the Internet is buzzing again as papers pour in to the bulletin board at Los Alamos National Laboratory in New Mexico, the official clearing house for superstring papers.

The trigger for this excitement was the discovery of "M-theory", which may answer those two vital questions about superstrings. "I may be biased on this one, but I think it is perhaps the most important development not only in string theory, but also in theoretical physics at least in the past two decades," says Harvard physicist Cumrun Vafa. M-theory led John Schwarz of Caltech, one of the founders of superstring theory, to proclaim a "second superstring revolution". And it inspired a spellbinding three-hour lecture by another leading exponent, Edward Witten of the Institute for Advanced Study at Princeton, New Jersey. The aftershocks of the breakthrough have spread to other disciplines, too. "The excitement I sense in the people in the field and the spin-offs into my own field of mathematics...have really been quite extraordinary," says Phillip Griffiths, director of the Institute for Advanced Study. "I feel I've been very privileged to witness this first hand."

In one dazzling stroke, M-theory has come close to solving superstring theory's two long-standing questions, leaving many theoretical physicists (myself included) gasping at its power. M-theory, moreover, may even force string theory to change its name because, although many features of M-theory are still unknown, it does not seem to be a theory purely of strings. Other strange beasts seem to emerge, including various types of membranes. Michael Duff of Texas A&M University is already giving talks with the title "The theory formerly known as strings".

Today, however, physicists are following a different trail-the one leading to superstring theory. Unlike previous proposals, it has survived every blistering mathematical challenge ever hurled at it. Not surprisingly, the theory is a radical-some might say crazy-departure from the past, being based on tiny strings vibrating in 10-dimensional space-time.

To understand how going to higher dimensions can help to unify lower dimensions, think back to how the Romans used to fight wars. Without radio communications and spy planes, battles were horribly confused, raging on many fronts at the same time. That's why the Romans always leapt into "hyperspace"-the third dimension-by seizing a hilltop. From this vantage point, they were able to survey the two-dimensional battlefield as a single, unified whole.

Leaping to higher dimensions can also simplify the laws of nature. In 1915, Einstein changed completely our notion of gravity by leaping to the extra dimension of time. In 1919, the German mathematician Theodor Kaluza added a fifth dimension and in so doing unified space-time with Maxwell's equations for electromagnetism. This triumph was largely forgotten amid the frenzy of interest generated by quantum mechanics. Only in the 1980s did physicists return to this idea to create superstring theory.

Likewise, the laws of physics-the forces between charged particles, for example-are the harmonies of the strings; the Universe is a symphony of vibrating strings. And when strings move in 10-dimensional space-time, they warp the space-time surrounding them in precisely the way predicted by general relativity. So strings simply and elegantly unify the quantum theory of particles and general relativity. Better still, gravity is not an inconvenient add-on. "Unlike conventional quantum field theory, string theory requires gravity," Witten has said. "I regard this fact as one of the greatest insights in science ever made."

Duality in Maxwell's theory is rather trivial. But in M-theory, we find another duality: g1/g. This relationship, though simpler, turns out to be incredibly powerful. When I first saw it, I could hardly believe my eyes. It meant that a string theory defined for large g, which is usually impossible to describe using present-day mathematics, can be shown to be equivalent to another type of string theory for small g, which is easily described using perturbation theory.

Thus, two different string theories can be dual to each other. In the non-perturbative region of string theory was another string theory! This is how, in fact, we prove the equivalence of all five string theories.

Altogether, three different types of duality called S, T and U have been discovered, which yield an intricate web of dualities linking string theories of various dimensions and types. At an incredible pace, physicists have now mapped almost all the solutions and dualities that exist in 10, 8 and 6 dimensions.

Wild stuff...

-Ry