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Author Topic: What is the speed of gamma rays  (Read 7343 times)

another_someone

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What is the speed of gamma rays
« on: 09/02/2008 16:48:33 »
http://www.universetoday.com/2007/10/03/high-energy-gamma-rays-go-slower-than-the-speed-of-light/
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The speed of light is the speed of light, and that's that. Right? Well, maybe not. Try and figure this out. Astronomers studying radiation coming from a distant galaxy found that the high energy gamma rays arrived a few minutes after the lower-energy photons, even though they were emitted at the same time. If true, this result would overturn Einstein's theory of relativity, which says that all photons should move at the speed of light. Uh oh Einstein.

The discovery was made using the new MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov) telescope, located on a mountain top on the Canary island of La Palma. Since gamma rays are blocked by the Earth's atmosphere, astronomers have figured out a clever trick to see them from the ground. When the gamma rays strike the atmosphere, they release a cascade of particles and radiation. The Cherenkov technique detects this cascade, and then works backwards to calculate the direction and energy level of the gamma rays. With a 17-metre detector, MAGIC is the largest telescope of its type.

The international team of researchers pointed the telescope at Markarian 501, a galaxy 500 million light-years away that contains a blazar - a supermassive black hole that periodically releases bursts of gamma rays. More material is falling into the black hole than it can consume, and so it gets squeezed into jets that fire off from the poles of the black hole at close to the speed of light. What astronomers call a "blazar" is when the jets of a supermassive black hole are pointed directly at the Earth.

Researchers sorted high- and low-energy gamma ray photons coming from the blazar with each flareup. Since all the radiation was emitted at the same time, and the speed of light is the speed of light, you would expect the high-energy photons to arrive at the same time. But nope, the high-energy photons showed up around 4 minutes later.

So what's happening? Nobody knows, and this could turn into an entirely new field of physics. The researchers are proposing that maybe the radiation is interacting with "quantum foam". This is a theoretical property of space itself, and predicted by quantum gravity theory - a competitor to string theory.

Original Source: UC Davis News Release

Anybody know anything about this?

The source seems (but I am not sure) credible, but the story seems peculiar.
« Last Edit: 09/03/2008 14:46:09 by ukmicky »


 

Offline DoctorBeaver

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Re: What is the speed of gamma rays
« Reply #1 on: 09/02/2008 17:00:24 »
extract from http://wwwmagic.mppmu.mpg.de/introduction/

Quantum gravity effects might become apparent if subtle time differences can be detected in the arrival of gammas from a given source, at different wavelengths. If they occur in nature, the MAGIC detector has the capability to record such phenomena.
 

Offline Soul Surfer

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Re: What is the speed of gamma rays
« Reply #2 on: 10/02/2008 10:03:24 »
If you had something like a star in orbit around a black hole gradually getting ripped apart as it looses renergy and accelerates into the hole during many orbits you might expect the radiation to start at lower frequencies and head to higher frequencies before it abruptly stops as the material crosses the event horizon so there may be no need to presume that all the photons were emmitted at precisely the same time
 

Offline daveshorts

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Re: What is the speed of gamma rays
« Reply #3 on: 13/02/2008 09:27:15 »
Yes there are various possibilities which may do this without breaking relativity. The two forms of radiation may not have been emitted in the same place or for that matter at the same time, or it could have travelled through some gas which slows down gamma rays more than visible light... Will be interesting to see what happens with it.
 

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Re: What is the speed of gamma rays
« Reply #3 on: 13/02/2008 09:27:15 »

 

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