- The Washington Times - Thursday, February 28, 2002

Time traveling, which would enable people to get glimpses of the future and the past, and ultimately give them the power over their destiny, has been a popular topic of science, literature and movies for at least 100 years.
"Time travel, like space travel, fascinates us because it opens up a wonderland of speculation," says Paul Davies, an Australia-based physicist who has studied time travel for more than three decades. "The idea that we are free to wander and discover other worlds is very appealing to us."
H.G. Wells wrote the "The Time Machine" in 1895, and in March, his great-grandson, Simon Wells, is coming out with a new movie based on the science fiction saga.
About the same time, Mr. Davies' newest book on time travel, "How to Build a Time Machine" (Viking), will be published, and the author will speak about the topic at the Smithsonian Associates at 6 p.m. on March 14.
So, there are plenty of opportunities for time travel enthusiasts to find out more about the topic, for example that time travel actually is possible at least in theory.
"It may come as a surprise, but travel into the future is an established fact," Mr. Davies says.

Astronauts on the Mir space station have recorded that they have time traveled a millisecond into the future.
"If you move fast enough, you'll move forward, into the future. For a human, this means you have to travel close to the speed of light," says Mr. Davies, who is known as Mr. Time in some circles.
Mr. Davies is the author of 27 books and a professor of natural philosophy (an old term for physics used in Australia and England) at MacQuarie University in Sydney, Australia.
There is no vehicle or propulsion system now that can accomplish velocities that are close to the speed of light, but Mr. Davies says he thinks scientists could come up with a "time machine" that is able to travel to the future. It could possibly happen within his lifetime.
"Traveling into the future is a technological problem, not a physics problem," Mr. Davies says. "If we had the same dedication [to building a time machine] as we did to going to the moon in the 1960s, it might take 100 years."
Traveling into the future, then, is more a question of politics and economics than physics, he says.

A local physicist, Andrew Love, who is a senior engineer of navigation at the Johns Hopkins University Applied Physics Laboratory, agrees with Mr. Davies' theories.
"Everyone understands time travel into the future," Mr. Love says. Simply by traveling 50 percent of the speed of light, he says, you could travel 10 years (into the future) in Earth time, and only seven years would have gone by, according to your own clock and calendar aboard your high-speed time machine.
This means you would take a seven-year journey into space in 2002 in your high-speed rocket, and get back to Earth in the year 2012. You will have leaped three years into the Earth's future.
The speed of light is 300,000 kilometers per second, or 186,000 miles per second.
Using the high-speed method, there is no way to get back to your time of departure. High-speed traveling into the future is a one-way journey.
While high-speed travel theoretically is understood by physicists, it is not feasible in practice, yet. Scientists need to find a power source and build a machine that can reach close to the speed of light velocity and acceleration, Mr. Love says.
The best current spacecraft reaches about 0.01 percent of the speed of light, Mr. Davies says.

Traveling into the past is a different matter altogether, agree Mr. Davies and Mr. Love.
"It's still an open question," Mr. Love says.
While physicists understand the theory of time travel into the future, there is no consensus on how time travel into the past would work.
Albert Einstein showed in the early part of the 20th century that gravitational force slows time, which means that time passes a little quicker at the top of a skyscraper (farther from the center of the Earth) than it does on the ground (which is closer to the center of the Earth), but the difference is so small that we pay no attention to the slight time warp, Mr. Davies says.
Going back in time would most likely entail building a device that would involve using gravitational forces. A neutron star a dense, compact star comprised primarily of neutrons is an example in the universe of a body that has great gravitational force.
A clock on a typical neutron star would tick about 30 percent slower than one on Earth, Mr. Davies says, but using a neutron star for time travel would be impractical, he says, jokingly.
Black holes in space the dark, dense bodies that suck in everything around them have a great gravitational force, but using them in time travel wouldn't be possible because, once you are sucked in, you can't get out. In Mr. Davies' words: "Once inside the black hole, [you are] beyond the end of time."
Physicists are now considering the possibility of so-called wormholes in space. These "holes," as opposed to black holes, might have a point of entry at one part of a galaxy and a point of exit in a completely different part.
It could also be that these wormholes would allow you not only to travel in space but also in time that if you "jumped" one way through the wormhole you would go to the future, and if you jumped in the other direction, you would go to the past.
"But this is all pretty speculative," Mr. Davies says.

Even if scientists were able to build a time machine, it might create an ethical dilemma.
"The idea that you have a chance to correct a mistake is very appealing to us," Mr. Love says, "but it could create problems, too."
For example, if you went back in time and saw that your great-grandmother was a murderer and you took the law into your own hands and killed her, would you not eliminate yourself in the process?
What would happen if you were to find out who would win the World Series in 2003 and then place winning bets on that particular team?
Controlling our destiny is ultimately what we would want, Mr. Davies says.
Could there be conflicts if everyone tried to control their destinies at once?
However, since we haven't time traveled to the past or to the future in any significant way (just that one millisecond), there is no way of knowing whether nature would even allow us to change our pasts.
Maybe we could only be observers without the power of changing things, Mr. Love says.
Mr. Davies offers a theory along the same lines:
"Maybe nature has an inbuilt censor system to prevent you from changing anything," he says.

WHAT: "Paul Davies: Time Travel"
WHERE: S. Dillon Ripley Center, 1100 Jefferson Drive SW.
WHEN:> 6 p.m. March 14
PHONE: 202/357-3030

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