A New Slice on Physics

What if everything we hold dear is but a thin slice of some larger, unreachable reality, like a flickering shadow cast on the craggy wall of a cave? What if the moon and stars, your home, your thoughts, your cat, are but projections on this wall -- mere suggestions of unfathomable realms beyond?

In the last few years, a mathematically rigorous version of Plato's 2,000-year-old thought experiment has been refashioning the way physicists think about everything from subatomic particles to the Big Bang. The universe we see, according to this scenario, is stuck on a thin membrane of space-time embedded in a much larger cosmos. And our membrane may be only one of many, all of which may warp, wiggle, connect and collide with one another in as many as 10 dimensions. Physicists call this new frontier the "brane world."

The idea could help solve a long list of outstanding mysteries. Among them: What is the "dark matter" that seems to make up 90% of the universe? And why is gravity trillions of times weaker than electromagnetism?

The revolution was set off in the mid-1990s when UC Santa Barbara physicist Joe Polchinski determined through mathematics that branes were a surface to which things attach, like hair to skin -- except the "things" in this case were the minuscule "strings" that may well be the fundamental ingredients of the universe.

"I was just fiddling around with mathematics

Alan Guth of the Massachusetts Institute of Technology, creator of the currently accepted version of the Big Bang, said recently he felt a little like Rip Van Winkle -- picking up his head from a long sleep only to notice that the landscape of physics he thought he knew had suddenly, drastically, changed.

Stephen Hawking of the University of Cambridge, among others, envisions brane worlds bubbling up out of the void, giving rise to whole new universes. He ends his latest book, "The Universe in a Nutshell," with a call to explore this "brane new world."

One might well wonder why such a seemingly bizarre concept has attracted so many well-established physicists. The short answer is: desperation.

The laws of nature that describe the large-scale universe to an astonishing degree of precision (Einstein's general relativity) are incompatible with the laws that describe the small-scale universe with the same astonishing exactness (quantum theory). This means either that one of these well-tested theories is wrong (all but inconceivable) or that there is some larger, more encompassing theory that somehow accommodates both.