Why do photons have no rest mass and cannot have a charge?

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Photons are massless particles that travel at the speed of light, which is only possible for entities without rest mass. They do not carry an electric charge due to the U(1) gauge symmetry of electromagnetism. While photons can interact with charged particles, they do not interact with each other in a vacuum, adhering to the principle of superposition of electric fields. The concept of mass in relation to photons is linked to the Higgs mechanism, which explains why other particles have mass while photons remain massless. Understanding photons as electromagnetic waves and pure energy provides insight into their lack of mass and charge.
  • #31
gonegahgah said:
My understanding was that - light traveling @ <c through materials due to photon absorption/re-emission - was not the accepted explanation.
I saw someone say this same explanation without comment another time so I'm starting to wonder if I got that wrong too?
I thought it was due to other factors? Was it something to do with space-time or was it magnetic interaction? I can't remember? Or is absorption/re-emission it?

The speed of light is determined by the permittivity and permeability of a material.
 
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  • #32
Thanks malawi. Hopefully that will put the 'absorption/re-emission' idea to rest.
 

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