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

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Discussion Overview

The discussion centers on the nature of photons, specifically addressing why they have no rest mass and cannot possess electric charge. Participants explore theoretical implications, properties of photons, and comparisons with other particles, including the W bosons and quarks. The conversation includes both conceptual and technical elements.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants suggest that photons are massless because only massless particles can travel at the speed of light.
  • Others mention that the gauge symmetry group of electromagnetism (U(1)) implies that photons cannot have charge.
  • One participant introduces the idea that W bosons, which have mass and charge, are different from photons.
  • There is a discussion about the possibility of photons having mass if they couple to another scalar field, raising questions about charge conservation and U(1) invariance.
  • Some participants argue that photons should be viewed as electromagnetic waves and pure energy, which provides insight into their lack of mass.
  • There is a debate about whether photons can be considered particles in the traditional sense, with some participants questioning the definition of "traditional particle."
  • One participant asserts that since photons have no rest mass, they cannot carry charge, while another points out that confined photons can contribute to the mass of a system.

Areas of Agreement / Disagreement

Participants express a range of views regarding the properties of photons, with no consensus on several points, including the implications of mass and charge, and the definitions of particles. The discussion remains unresolved on many aspects.

Contextual Notes

Some statements rely on specific definitions and assumptions that may not be universally accepted, such as the interpretation of "pure energy" and the implications of gauge symmetry. The discussion includes speculative ideas about the nature of mass and charge in relation to photons.

Who May Find This Useful

Readers interested in particle physics, the properties of light, and the theoretical frameworks surrounding mass and charge in quantum mechanics may find this discussion relevant.

  • #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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