Let's Do the Time Warp Again

I Canna Get No Power, Captain!



If we're all time travelers, the problem is that we can't get very far using current technology. Spending just over two years in Mir's Earth orbit, going 17,500 miles per hour, put Sergei Avdeyev 1/50th of a second into the future, according to Princeton astrophysicist J. Richard Gott III, and "he's the greatest time traveler we have so far."



To move through time at a serious clip, you have to go very fast-say, 99.995 percent of the speed of light. At that rate, if you "go out 500 light-years, then come back at the same speed," Gott notes, "when you arrive back the Earth would be 1,000 years older and you would only have aged 10 years."



But to attain this sort of velocity you have to overcome what Michio Kaku, a professor of theoretical physics at the City University of New York, calls the "gasoline" problem: the need for an almost inconceivably powerful energy source. This problem crops up constantly in time-travel theory, from simple extrapolations of relativity (go really fast so you can travel to the future) to more complex ideas such as the wormhole engineering that Kip Thorne theorized for Carl Sagan.



"Back to the Future is one of my favorite time travel stories," says Kaku. "The DeLorean is energized by plutonium. But that's not enough. To really energize your time machine, you need what's called the Planck energy ... roughly a quadrillion times more powerful than our most powerful atom smasher." Physicist Paul Davies-author of How to Build a Time Machine, which will be released in the United States this month in happy synchronicity with the Wells movie-notes: "At the moment it looks like making a wormhole ... would require something like a particle accelerator bigger than the solar system. So if you just look at current technology, then it looks to be pretty hopeless."



The foundation of time machine physics is Einstein's General Theory of Relativity, completed in 1915, which describes gravity as a warping or curving of space and time by matter. "If," as Gott says, "space and time are curved, you can have a situation where space and time are sufficiently twisted that you can circle back and visit an event in your own past." (Picture an ant crawling along the edge of a piece of paper, trying to get from one corner to the far corner; then fold the paper so that the corners are brought together and the ant's journey is drastically shortened. To travel in time, just fold space and time in the same way; the time machine does the folding.)