Wormholes in The Heavens

By MICHAEL D. LEMONICK

Since well before Albert Einstein, physicists have been conjuring up concepts that defy common sense. Consider just a few of the far-out notions now accepted by the scientific community: clocks that tick slower when they ride on rockets, black holes with the mass of a million stars compressed into a volume smaller than that of an atom, and subatomic particles whose behavior depends on whether they are being watched.

But of all the strange ideas in physics, perhaps the strangest is the wormhole. It comes perilously close to science fiction: a wormhole is a hole in the fabric of space and time, a tunnel to a distant part of the universe. While no one has proved that wormholes exist, that does not for a moment keep the more adventurous of thinkers from trying to figure how they might behave. Last fall, for example, three researchers from Caltech floated the notion that in theory at least, wormholes could be time machines.

This week, at the American Astronomical Society's winter meeting in Boston, physicist Alan Guth of M.I.T. will announce the most mind-numbing wormhole- related news yet. Guth and two collaborators have determined, he says, that "it would apparently be possible in principle for some advanced society literally to create an entirely new universe." The wormhole connection: such + a universe would automatically create its own wormhole, squeeze through it, and then draw the hole closed after it.

To many people, such theories may seem useless, if not ridiculous. But to others, the ideas are brain teasers that both challenge and stretch the imagination. While thinking about wormholes has no immediate practical value, Guth insists that it helps scientists explore how flexible the laws of physics are. More important, the theories could shed light on some of the most fundamental questions of cosmology: how the universe began, how it works and how it might end.

The idea of wormholes comes directly from the accepted concepts of general relativity. In that theory, Einstein argued that very massive or dense objects distort space and time around them. One possible distortion is in the form of a tube that can lead anywhere in the universe -- even to a spot billions of light-years away. The name wormhole comes about by analogy: imagine a fly on an apple. The only way the fly can reach the apple's other side is the long way, over the fruit's surface. But a worm could bore a tunnel through the apple, shortening the trip considerably. A wormhole in space is the same sort of tunnel; it is a shortcut from one part of the universe to another that reduces the travel time to just about zero.

Virtually instantaneous travel leads to the idea of wormhole as time machine. If it were somehow possible to move one end of a wormhole at nearly the speed of light, general relativity dictates that time at that end would slow down, and that portion of the tunnel would then be younger than the other end. Anything moving from the faster-aging end of the wormhole to the slower would essentially go backward in time. The mode of travel, however, could be nothing like the mechanical time machine, complete with saddle, envisioned by H.G. Wells. It is hard to conceive how a human being could move through a wormhole, since it would theoretically be narrower than an atom, and it would tend to vanish the instant it formed.

Just as theoretical are Guth's homemade universes. One way to create a cosmos, he says, might be to heat a region of space to about a thousand trillion trillion degrees. Or one might compress some matter to densities far greater than those of a neutron star -- a star that has shrunk to a diameter of only a few miles. "Of course," admits Guth, "this is not only beyond the range of our technology, but beyond the range of any conceivable technology." It is possible only in principle, but that is what matters to explorers on the frontiers of physics.

Guth came to the idea of creating new universes from his influential work on "inflationary" cosmology, which was considered dubious when he proposed it in the early 1980s but is accepted in modified form by most physicists today. The notion is that in the first fraction of a second after the Big Bang, the universe, though expanding, was still far smaller than the smallest particle now known, and made of a peculiar stuff known as "false vacuum." Among other odd attributes, a false vacuum generates negative gravity; it inflates itself rapidly and enormously -- ending up as big as a universe. Odder still, but likely nonetheless, is that everything in our cosmos could have come from a subatomic bubble of false vacuum with a mass of only 20 lbs. or so.

That concept led to the idea that such a bubble could somehow be manufactured. Classical physics says that unless this matter started out with infinite density, it would collapse right away. But Guth and two other physicists, Edward Farhi and Jemal Guven, applied the more modern laws of quantum physics to the problem. Their conclusion: the bubble might not collapse after all. It could just possibly become a brand-new universe. Not that it would be much good, though. Says Guth: "Such a baby universe would form a wormhole and escape, creating its own space and time in the process." From our universe, the new one would be completely inaccessible, since the wormhole would pinch itself off right away.

Such fanciful thinking may skirt the bounds of credibility, but Guth is an intellectual test pilot. His mission is to push the machinery of physics to its logical extremes, in hopes that he can find out just when it will self- destruct.