Gamma Ray Delay May Be Sign of 'New Physics'

October 1, 2007

Delayed gamma rays from deep space may provide the first evidence for physics beyond current theories.

The MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov) telescope found that high-energy photons of gamma radiation from a distant galaxy arrived at Earth four minutes after lower-energy photons, although they were apparently emitted at the same time. If correct, that would contradict Einstein's theory of relativity, which says that all photons (particles of light) must move at the speed of light.

"Everybody's very excited," about this result, said Daniel Ferenc, a physics professor at UC Davis and a member of the MAGIC collaboration. Ferenc cautioned that the results need to be repeated with other gamma-ray sources and that a simpler explanation had not been ruled out. But, "it shows that such measurements are possible," he said.

The researchers propose that the delay could be caused by photons interacting with "quantum foam," a type of structure of space itself. Quantum foam is predicted by quantum gravity theory, an attempt to unite quantum physics and relativity at cosmic scales.

The astronomers pointed the telescope at Markarian 501, a galaxy half a billion light-years away that contains a "blazar" -- a massive black hole that gives off bursts of gamma rays. Some of the material falling toward the black hole gets squeezed into jets that burst from the poles of the object at close to the speed of light. These jets fire off flares of gamma rays a few minutes long.

The researchers sorted high- and low-energy gamma-ray photons coming from the object with each flare. Joined by a group of theoretical physicists led by John Ellis from CERN, the MAGIC team showed that the high- and low-energy photons appeared to have been emitted at the same time. But the high-energy photons arrived four minutes late after traveling through space for about 500 million years.

The work has been submitted for publication in Physics Review Letters.

Source: UC Davis

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not rated yet Oct 03, 2007
I've always wondered if higher energy photons were affected by gravity more than lower energy ones. After all the equivalent masses of their energies differ (via E=mc**2) by the same amount as their energies. While the effect of gravitation may not be much on such small equivalent masses, its conceivable that the difference of 4 minutes out of 500 million years is reasonable.
not rated yet Mar 18, 2009
If there was some interaction with gravity, it would produce doppler effects also. Don't know if any such effect was noticed, maybe too small to be measured.
not rated yet Mar 18, 2009
Maybe a development of new detectors like this will help in that search:
not rated yet Mar 19, 2009
Is this effect not to be expected from standard theory? I mean that photons of a higher frequency should travel more slowly in any given medium. Interstellar space is not a vacuum. It is a medium, albeit a very thin one.

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