PAST TIME TRAVEL POSSIBLE!!!

University of Washington physicist John Cramer is preparing to perform an experiment to see if time can go backwards.

It's a project that aims to do a conceptually simple bench-top test for evidence of something Albert Einstein called "spooky action at a distance." The test involves using a crystal to split a photon, a light particle, into two reduced-energy photons ( as shown in the figure ) that -- through careful manipulation - University of Washington physicist John Cramer thinks could reveal a flash of time traveling backward.


To begin with, he thinks the celebrated theoretical physicist and author of "A Brief History of Time," Stephen Hawking is wrong. Not about everything. Just time."Hawking has this 'arrow of time' idea in which he argues that time can only advance in one direction, forward," Cramer said. It's appealing, elegant and certainly makes sense intuitively, he noted, because this is the only way we experience time.
Unfortunately, the one-way notion of time doesn't fit all that well with the mathematical and experimental evidence of quantum theory. This is a highly counter-intuitive branch of physics, also known as quantum mechanics, that describes the bizarre behavior of matter at the atomic and subatomic levels.

One of the mysteries of quantum mechanics is the Einstein-Podolsky-Rosen paradox. Quantum theory predicts two subatomic particles derived from a single particle -- like two photons split from a single photon -- will, if not further influenced by other particles, continue to influence each other's behavior no matter how far apart.

This is known as "entanglement." Experiments at the subatomic level tend to support the idea, but there's a conceptual problem. It means the two photons must be able to communicate instantaneously, even if light years apart, which violates the speed of light.

"There's been a lot of interest in this problem over the years," Cramer said. In 1986, he proposed a solution to this paradox that he called the "transactional interpretation" of quantum theory. Some of his approach was based on the ideas of such physics luminaries as Richard Feynman and John Wheeler.

Basically, Cramer showed how entanglement could be explained -- and how the paradox could be explained away -- by assuming some kind of signal that can travel both forward and backward in time between the two photons. His theory, he says, violates no rules of quantum theory and resolves the mystery.

All that's needed now, Cramer said, is some way to provide evidence that it's real.




THE CRAMER'S EXPERIMENT:

In the basement of the UW's Astronomy and Physics building, the UW physicist and his student, Skander Mzali, are making do with what they can find in the lab. At the end of an ultraviolet laser is an array of prisms, filters, splitters and other devices aimed at directing or altering the laser light.

A camera hooked up to a computer monitor sits at the receiving end. On the PC monitor is a grainy screen displaying an interference pattern of photons.

What Cramer hopes to be able to do is split a photon, sending two "entangled" photons down two very different pathways of varying lengths using fiber-optic cables. Photons can exist in either particle or wave forms. The outcome can be manipulated by placement of detectors.

Because the photons are entangled, however one is detected (i.e., whether as a particle or a wave) also will determine the form taken by the other. But by running one photon through a 10-kilometer spool of optic cable, the second photon will be delayed 50 microseconds.

In short, moving the location of the detector for the delayed photon to change it from wave to particle would also change the first photon -- according to standard quantum theory. For this to happen, some kind of signal has to go backward in time.


"In 20 years, nobody has been able to tell me why this can't work," Cramer said. "They just say it can't work like that. It's unacceptable."

Cramer said they first need a more precise crystal prism and a more sensitive camera.To really see if they can pull this off, the UW physicist said, he would rather not have to depend upon what kind of scraps they can cobble together.but as other great scintific works,he is also going out of fundings. .