From the Universe Today:
“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.”
Read the rest: High Energy Gamma Rays Go Slower Than the Speed of Light?
Dispersion effects in empty space? Weird….
It *is* weird. The article doesn’t mention the energies of the gamma rays, but given the source I’d guess they’re pretty extreme.
I’ll dig around and see if I can find a journal article about this with more information.
Hmm… My guess would be that the radiation traveled through a medium with an index of refraction ever so slightly greater than unity for the gamma rays, which still would be very cool…The only way you could prove this, of course, would be to see the shift in the directionality of the stream…