What is the analogy for EM waves traveling in vacuum?

In summary: Electron as a thing vs. mass of an electron.Electron is not mass in the same way that a rock is not mass. Electron has mass because it has a property that makes it have mass, in this case its charge.Electron is not mass in the same way that a rock is not mass.
  • #36
Well, the difference between this example and the question, where the mass of the nucleon comes from, is that the latter question is not completely answered yet. It's the notorious problem to understand "confinement" from first principles (in this case quantum chromodynamics, QCD). We are pretty sure about the statement that the nucleon mass (and the masses of the other hadrons) is due to the strong interaction is from lattice-QCD calculations, i.e., numerical evaluations of QCD, leading to a satisfactory description of the hadronic mass spectrum.
 
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  • #37
@vanhees71 One final question, the mass that generates the gravitational field is the one due to Higgs field coupling, the one due to color confinement or both? Or we don't know yet?
 
  • #38
Delta2 said:
@vanhees71 One final question, the mass that generates the gravitational field is the one due to Higgs field coupling, the one due to color confinement or both? Or we don't know yet?
The source in Einstein’s field equations (that govern spacetime curvature) is the stress-energy tensor. What generates gravity is therefore not only mass but energy, momentum, and stresses.
 
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  • #39
Orodruin said:
The source in Einstein’s field equations (that govern spacetime curvature) is the stress-energy tensor. What generates gravity is therefore not only mass but energy, momentum, and stresses.
Yes ok, relativity says there are other sources of gravitational field as well, I am just interested to know regarding the mass as source.
 
  • #40
Delta2 said:
Yes ok, relativity says there are other sources of gravitational field as well, I am just interested to know regarding the mass as source.
You cannot decouple mass as a source. It is part of the stress energy tensor.

(Also: I finally did it! When I write ”str” on my phone it suggests ”stress energy tensor” for completion)
 
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  • #41
Delta2 said:
@vanhees71 One final question, the mass that generates the gravitational field is the one due to Higgs field coupling, the one due to color confinement or both? Or we don't know yet?
The source of the gravitational field is not mass but the energy-momentum-stress tensor of matter and radiation.
 
  • #42
weirdoguy said:
This equation states that there is a form of energy connected with mass, namely rest energy. And mass is not the same thing as matter, mass is yet another property of matter.
Yet nothing is at rest. Everything is in motion.
 
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  • #43
Hillbillychemist said:
Yet nothing is at rest. Everything is in motion.

Nonsense. There are infinitely many reference frames in which you are at rest.
 

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