Calculating Arrival Time Difference for Particles Produced in a Distant Galaxy

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Maybe its because my exams are close and I'm starting to panic but there is a question that has been bustin' my balls all day and was hoping any of you could help...

A particle with mass 10eV and a photon are produced simultaneously in a galaxy 150,000 light yrs away. The energy for both particles is 10MeV. Estimate the difference in arrival time between the particles.

My question really is: Is the energy for the photon a red herring because surely this travels at speed c and you don't need this info?!

Thanks in advance people cleverer than me
 
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So the photon has 10MeV (ignoring GR effects),and that is not a useful piece of information.It should arrive in exactly 150,000 years.

What about the electron...?The time that is needed is in the Earth's reference frame...

Daniel.
 
you are going to need the relativistic formula for energy. you know, the Einstein-formula(E² =p²c² + m²c^4). Also be sure to know wether the given mass is restmass or not...

For a photon E =pc since the restmass is ZERO

marlon
 
You needn't momentum & stuff.

The gamma factor is 1000.That should give you the velocity,which is all u need.

Daniel.
 
cheers for your help guys.
Once again much appreciated
 
dextercioby said: "The gamma factor is 1000."

How do you get that?
 

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