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Re: [Phys-l] Teaching Special Relativity



Quoting Moses Fayngold <moshfarlan@yahoo.com>:
    On the other hand, one does not have a problem in actually measuring its relativistic mass m(rel) = h*w/c^2.
 Based on this, should we discard the notion of the invariant mass for photons and use only their relativistic mass? 

You may want to include Frank Wilczek's insight (See Below). That is, mass of proton’s mass comes from the relavististic masses of the quarks and gluons. :-)

Modern physics answers Einstein’s question with a resounding "Yes!" Most of the mass of ordinary matter—well over 99%—is concentrated in atomic nuclei. Nuclei are made of protons and neutrons, which in turn are made of quarks and gluons. Our modern fundamental theory of the behavior of quarks and gluons, quantum chromodynamics or QCD, is based on a beautiful mathematical generalization of Maxwell’s electrodynamics. It surely would have given Einstein great pleasure, and it got me a Nobel Prize. According to this theory, the building blocks of protons and neutrons are gluons, which have precisely zero mass, and so-called u (“up”) and d (“down”) quarks, which have masses that are very small—smaller by far than the mass of protons. So where does the mass of the proton come from, if not from adding up the mass of what’s inside it? Most of the proton’s mass arises from the fact that the quarks and gluons inside it are moving around quite vigorously. Therefore they have a lot of energy. It is just that energy, through the magic of m = E/c2, which accounts for most of your mass.

Frank Wilczek's Happy 100th Birthday, Special Relativity


Best regards,
Alphonsus