Daily Reveille

Issue date: 2/23/07 Section: News

Media Credit: Adam Rogers Subhash Kak, professor of electrical and computer engineering, checks his e-mail while he explains his resolution to Einstein's twin paradox in his office Thursday afternoon. Using probabilistic relationships, Kak has solved one of the most enduring puzzles of modern-day physics.

Q&A with Stachel and Finkelstein [Click to enlarge]

Months after having a flash of inspiration under the summer heat, Subhash Kak has resolved one of physics' most famous puzzles - Einstein's twin paradox.

The International Journal of Theoretical Physics, a peer-reviewed journal that focuses on original research and reviews in theoretical physics and neighboring fields, published Kak's findings.

The paradox, which is based on a thought experiment, involves two twins, one of whom sets out on a journey into space and returns to Earth.

Stanford Encyclopedia of Philosophy defines a thought experiment as a device of the imagination used to investigate the nature of things.

According to the theory of general relativity, the twin who leaves Earth will experience a slowing down of time because of acceleration. This means the twin on Earth will appear to have aged a lot more than the one in space.

This phenomenon is considered a paradox because special relativity theory shows that either twin could be taken to be at rest with respect to the other twin.

Kak, distinguished professor of electrical and computer engineering, in his introduction to the article, said the diversity and mutual inconsistency of the offered solutions only reinforces the reality of the paradox within relativity.

"The time appears to have come to look very hard at things that have been taken to be settled," Kak said.

The most popular explanations for the paradox include those based on doppler shifts, spacetime diagrams and general relativity.

Kak said his solution uses an analysis based on probability to determine which of the twins is really moving with respect to the far corners of the universe, that is the distant stars.

Kak said his resolution brings into the problem the idea that motion cannot be spoken of in isolation.

"This is something called Mach's principle, which makes the framework much more sound, logically," Kak said.

Paul Davies, an astrophysicist at Arizona State University, in an article for Guardian online said Mach's principle requires that acceleration can be defined only relative to the distant stars.

Bradley Schaefer, associate physics professor, said there was no paradox in Einstein's special relativity theory if the mathematics were carefully followed through.

Schaefer, who had not read the article by the time of the interview, said experiments using atomic clocks have consistently proved that special relativity is correct: basically, from the point of view of someone at rest moving clocks are slow.

"Suppose a student looked at the time on the Memorial tower clock and his watch, both would read the same time," Schaefer explained. "Now suppose, an alien picked up the clock and started accelerating upward, if the student compared his watch to the clock, the watch would appear to be faster."

Schaefer said doubts about the theory persist because the idea is counterintuitive as effects due to relativity kick in only when an object attains a velocity near the speed of light - a speed which is not experienced under normal circumstances.

"There is no viable alternative to special relativity," Schaefer said.

David Finkelstein, professor emeritus at the Georgia Institute of Technology, in an e-mail said he prefers not to use the term "paradox," but that new resolutions for the observation were needed.

ON THE WEBClick to view David Ritz's Web site.

"Why institutionalize the viewpoint of an inaccurate theory when the better theory is available?" Finkelstein said.

Kak said his article does not dispute special relativity, rather that it was interested only in identifying inertial frames - a frame that moves at constant speed.

Kak's work may impact quantum communications because atomic clocks on board communication satellites rotating around the globe move at speeds that are fast enough so as to have possible effects on their accuracy.

John Stachel, director of Center for Einstein Studies at Boston University, said it takes time for ideas like Kak's to be accepted into the scientific canon.

"But I will say that mere publication in a journal - even a peer-reviewed one - is no guarantee of the accuracy of the results, nor of their significance," Stachel said in an e-mail. "A much longer period of testing and evaluation after publication is needed until these things can be settled."


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Contact Freke Ette at fette@lsureveille.com

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