Interpretation of Einstein's E=mc2 paper

[bcrowell]

In "Does the inertia of a body depend upon its energy content?," http://fourmilab.ch/etexts/einstein/E_mc2/www/ , Einstein says:

Thus it is clear that the difference H-E can differ from the kinetic energy K of the body, with respect to the other system $(\xi,\eta,\zeta)$, only by an additive constant C, which depends on the choice of the arbitrary additive constants of the energies H and E.

My interpretation of this is that these energies contain both potential and kinetic terms. A potential energy U is only defined up to an additive constant. If, for example, U depends on the distance r between particles, and the distance undergoes a Lorentz contraction, there is no reason to imagine that the constant will stay the same. In nonrelativistic physics, a particular expression for U(r) would give the same result in either frame, so although we would still be free to pick a different C when starting a problem over in a different frame, there would be less physical motivation for doing so.

Am I interpreting this correctly?

At first I thought that the C might refer to the energy equivalent of the rest mass, but Einstein later explicitly states that C has to stay the same before and after emission of the light waves. The rest mass of the emitting body, however, changes.

 

[ZealScience]

In relativity, mass is also relativistic, as energy is different in different reference frames. The idea exactly came from an imaginary experiment of emission of photons.

Most of the rest mass also comes from energy, small proportion is molecular energy and energy of electrons, large proportion is nuclear energy (things like gluons). Only a little bit of the mass is inertial mass that fermions have which associated with Higgs field hypothesis.

If an object emit photons it is losing energy, thus equivalent amount of mass would be lost.

 

[bcrowell]

Hi, ZealScience,

Thanks for the reply, but I was asking about a specific point in the Einstein paper.

Only a little bit of the mass is inertial mass that fermions have which associated with Higgs field hypothesis.

I'm not much of a particle physicist, but I don't think this is right.

-Ben

 

[ApplePion]

The argument Einstein uses is heavily dependent on the relationship between energy and momentum under the Lorentz Transformation. This relationship does not hold up well when a constant is added to the energy. And indeed, one sees this in the final result. If I have a golf ball with the standard mass of a golf ball, I cannot simply have it be a black hole by me adding a huge mass to it by just putting on a large additive constant to the energy.

 

[Matterwave]

I have the same interpretation as you bcrowell.