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Tom Mazanec
2012-Apr-26, 12:28 AM
Assume the OMG cosmic ray particle originated 100 million LY away. How much time did the trip take in the proton's relativistic frame?

antoniseb
2012-Apr-26, 12:51 AM
http://www.fourmilab.ch/documents/OhMyGodParticle/

This guy tabulates it. ... about 3 hours

Tom Mazanec
2012-Apr-26, 11:42 AM
But it says it must have originated close, because of interaction with the cosmic microwave background.
It does not say what the CMB looked like from the OMG proton's view. Blue shifted into soft gamma? Hard gamma, maybe?

antoniseb
2012-Apr-26, 11:53 AM
You asked a specific question. Now you know more. He meant close in this sense as within about 100 Million Light Years. We don't know precisely the limit, but yes, the on-coming CMB microwave photons look like very high energy gamma rays to such a cosmic ray particle, and that's the reason that we don't think the 10^19 eV and higher particles could be coming from anything much further away than M87 or Centaurus A. It is possible that some/most are coming from peculiar situations IN the Milky Way involving strong magnetic fields.