E2=m2c4+p2c2 not simply E=mc2 - Think Atheist2016-08-30T07:34:32Zhttp://www.thinkatheist.com/forum/topics/e2m2c4p2c2-not-simply-emc2?feed=yes&xn_auth=noUnless you already know the r…tag:www.thinkatheist.com,2012-01-28:1982180:Comment:10385732012-01-28T03:46:46.141ZBrad Snowderhttp://www.thinkatheist.com/profile/BradSnowder
<p>Unless you already know the rest mass of the photon, you generally find its energy from the wavelength first. Then you take that and divide by c^2 to get the rest mass (mass equivalence of a photon's energy). To calculate the momentum stored in the EM field; divide E by c. Rest mass by definition has no momentum so equivalence reduces to E=mc^2. So E/c=mc and mc=p for a photon. Or become a theist and just have faith that it all works out.</p>
<p>Unless you already know the rest mass of the photon, you generally find its energy from the wavelength first. Then you take that and divide by c^2 to get the rest mass (mass equivalence of a photon's energy). To calculate the momentum stored in the EM field; divide E by c. Rest mass by definition has no momentum so equivalence reduces to E=mc^2. So E/c=mc and mc=p for a photon. Or become a theist and just have faith that it all works out.</p> But isn't it really that when…tag:www.thinkatheist.com,2012-01-28:1982180:Comment:10387032012-01-28T02:55:02.649ZBrad Snowderhttp://www.thinkatheist.com/profile/BradSnowder
<p>But isn't it really that when doing relativistic calculations you are almost always allowed to choose the frame of reference? If you choose the FoR with the same vector as the momentum then the momentum is zero and the whole second term is zero so E=mc^2. When doing real stuff it isn't always that simple but reducing it makes it fit on a t-shirt better.</p>
<p>But isn't it really that when doing relativistic calculations you are almost always allowed to choose the frame of reference? If you choose the FoR with the same vector as the momentum then the momentum is zero and the whole second term is zero so E=mc^2. When doing real stuff it isn't always that simple but reducing it makes it fit on a t-shirt better.</p>