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Time Travel Machine Outlined

2007-08-21 10:10:00

Charles Q. Choi

Special to LiveScience

LiveScience.comMon Aug 20, 11:55 AM ET

A new concept for a time machine could possibly enable distant future

generations to travel into the past, research now suggests.

Unlike past ideas for time machines, this new concept does not require exotic,

theoretical forms of matter. Still, this new idea requires technology far more

advanced than anything existing today, and major questions remain as to whether

any time machine would ever prove stable enough to enable actual travel back in

time.

Time machine researchers often investigate gravity, which essentially arises

when matter bends space and time. Time travel research is based on bending

space-time so far that time lines actually turn back on themselves to form a

loop, technically known as a "closed time-like curve."

"We know that bending does happen all the time, but we want the bending to be

strong enough and to take a special form where the lines of time make closed

loops," said theoretical physicist Amos Ori at the Technion-Israel Institute of

Technology in Haifa. "We are trying to find out if it is possible to manipulate

space-time to develop in such a way."

Many scientists are skeptical as to whether or not time travel is possible. For

instance, time machines often are thought to need an exotic form of matter with

so-called "negative energy density." Such exotic matter has bizarre properties,

including moving in the opposite direction of normal matter when pushed. Such

matter could theoretically exist, but if it did, it might be present only in

quantities too small for the construction of a time machine.

Ori's latest research suggests time machines are possible without exotic

matter, eliminating a barrier to time travel. His work begins with a

donut-shaped hole enveloped within a sphere of normal matter.

"We're talking about these closed loops of time, and the simplest kind of

closed loops are circles, which is why we have this ring-shaped hole," Ori

explained.

Inside this donut-shaped vacuum, space-time could get bent upon itself using

focused gravitational fields to form a closed time-like curve. To go back in

time, a traveler would race around inside the donut, going further back into

the past with each lap.

"The machine is space-time itself," Ori said. "If we were to create an area

with a warp like this in space that would enable time lines to close on

themselves, it might enable future generations to return to visit our time."

Ori emphasized one significant limitation of this time machine "it can't be

used to travel to a time before the time machine was constructed." His findings

are detailed in the Aug. 3 issue of the journal Physical Review D.

A number of obstacles remain, however. The gravitational fields required to

make such a closed time-like curve would have to be very strong, "on the order

of what you might find close to a black hole," Ori told LiveScience. "We don't

have any way of creating such strong gravitational fields today, and we

certainly have no way of manipulating any such gravitational fields."

Even if time machines were technically feasible, the gravitational fields

involved need to be manipulated in very specific, accurate ways, and Ori said

his calculations suggest any time machine could be very unstable, meaning "the

tiniest deviations might keep one from working. We need to explore the problem

of stability of time machines further."

Theoretical physicist Ken Olum of Tufts University in Medford, Mass., who did

not participate in this study, was skeptical concerning how this new model

claimed to sidestep prior theoretical objections to time travel.

Still, Olum noted, "It's important if it's right that there really is some kind

of loophole. So this should be scrutinized very closely." The point of such

work, he added, was to "expand the bounds of what's possible, what kind of

things we can have and what kinds of things we cannot have."

Top 10 Time Travel Tales You Can't Travel Back in Time, Scientists Say Video:

Can You Time Travel? Original Story: Time Travel Machine Outlined

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