H.G. Wells, call your office

JustOneMinute points to a NYTimes online (free registration may be required, or you might check out www.bugmenot.com) article, intended for non-physicist types, on the physics of time travel, in part concerned with the debate over whether it will ever be possible.

"No law of physics that we know of prohibits time travel," said Dr. J. Richard Gott, a Princeton astrophysicist.

Dr. Gott, author of the 2001 book "Time Travel in Einstein's Universe: The Physical Possibilities of Travel Through Time," is one of a small breed of physicists who spend part of their time (and their research grants) thinking about wormholes in space, warp drives and other cosmic constructions, that "absurdly advanced civilizations" might use to travel through time.

It's not that physicists expect to be able to go back and attend Woodstock, drop by the Bern patent office to take Einstein to lunch, see the dinosaurs or investigate John F. Kennedy's assassination.

In fact, they're pretty sure those are absurd dreams and are all bemused by the fact that they can't say why.

...In his recent book "The Universe in a Nutshell," Dr. Stephen W. Hawking wrote, "Even if it turns out that time travel is impossible, it is important that we understand why it is impossible."

...somewhat to Einstein's surprise, in general relativity it is possible to beat a light beam across space. That theory, which Einstein finished in 1916, said that gravity resulted from the warping of space-time geometry by matter and energy, the way a bowling ball sags a trampoline. And all this warping and sagging can create shortcuts through space-time.

...Most scientists, including Einstein, resisted the idea of time travel until 1988 when Dr. Kip Thorne, a gravitational theorist at the California Institute of Technology, and two of his graduate students, Dr. Mike Morris and Dr. Ulvi Yurtsever, published a pair of papers concluding that the laws of physics may allow you to use wormholes, which are like tunnels through space connecting distant points, to travel in time.

These holes, technically called Einstein-Rosen bridges, have long been predicted as a solution of Einstein's equations. But physicists dismissed them because calculations predicted that gravity would slam them shut.

...These speculations have been bolstered (not that time machine architects lack imagination) with the unsettling discovery that the universe may be full of exactly the kind of antigravity stuff needed to grow and prop open a wormhole. Some mysterious "dark energy," astronomers say, is pushing space apart and accelerating the expansion of the universe. The race is on to measure this energy precisely and find out what it is.

I don't have nearly the mathematics background I would need to even begin to understand the cutting edge of theoretical physics today, but the issues never fail to fascinate me. 

Quantum mechanics, theoretical methods of propulsion...yeah, I guess I'm a Star Trek geek.  I had a charter membership in Voyager's "Exotic Theoretical Sub-atomic Particle and Fruit of the Month" club.  The transporter of "beam me up, Scotty" fame may be, to put it kindly, implausible from an engineer's point of view, but some other aspects of Gene Rodenberry's fictional universe aren't quite as far-fetched.  Well, at least with a little imagination...

Besides, as soon as I get my prototype time-travel machine finished, I can go back and remember to unplug my router and all from the wall before the thunderstorm earlier this week.