Could a Mass for Photons Change Our Understanding of Relativity?

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Discussion Overview

The discussion centers around the hypothetical implications of photons possessing mass on the theory of relativity. Participants explore various perspectives on how this could alter our understanding of fundamental physics, particularly regarding the speed of light and the nature of massless versus massive particles.

Discussion Character

  • Debate/contested
  • Exploratory
  • Technical explanation

Main Points Raised

  • Some participants propose that if photons were discovered to have a small mass, it could lead to them traveling slightly less than the speed of light, which raises questions about the implications for relativity.
  • Others argue that the concept of photons having mass is irrelevant since current understanding holds that they are massless, and thus travel at the speed of light.
  • One participant mentions that evidence supporting the masslessness of light includes its constant speed across different inertial frames, referencing the Michelson-Morley experiment.
  • Another participant suggests that if photons had mass, the universal speed limit would remain unchanged, as massive particles cannot reach the speed of light.
  • A historical perspective is introduced, noting that de Broglie's theory accommodates the possibility of photons having a small rest mass, and mentioning Proca's modifications to Maxwell's equations regarding massive photons.
  • One participant claims that photons exhibit a rest mass in superconductors, suggesting that this could imply they travel slower than light in such materials and may require acceleration or deceleration during emission or absorption.
  • Another participant questions the validity of claims regarding photon mass in superconductors, noting a lack of citations and stating that no mass has been detected beyond current measurement limits.
  • A later reply references the Anderson-Englert-Brout-Higgs-Guralnik-Hagen-Kibble mechanism, implying a connection to the discussion of mass and photons.

Areas of Agreement / Disagreement

Participants express differing views on the existence of mass for photons and its implications for relativity. There is no consensus on whether photons can have mass or how that would affect established theories.

Contextual Notes

Some claims rely on specific interpretations of experimental evidence, while others depend on theoretical frameworks that may not be universally accepted. The discussion includes unresolved questions about the implications of mass for photons and the nature of light in different contexts.

PlanckShift
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So relativity is defined about the speed of light. The speed of light is what it is because the photon is massless. What if, sometime in the future, it's discovered that the photon has a small mass so that it travels a little less than the speed of light. What does that do to relativity?
 
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Do you hear yourself? You just asked what happens if light travels at less than the speed of light. Actually, light travels at the speed light travels at.

As to what happens if photons have mass, that's irrelevant since they don't.
 
One important piece of evidence that light has no mass is that the speed is constant irrespective of inertial frame (starting with Michelson-Morley). Particles with mass have different speeds when measured in different frames.
 
PlanckShift said:
So relativity is defined about the speed of light.

Better: relativity is about a universal speed limit. Particles with mass can never reach that speed, and particles without mass must always travel at that speed.

What if, sometime in the future, it's discovered that the photon has a small mass so that it travels a little less than the speed of light. What does that do to relativity?

Nothing. The universal speed limit remains unchanged. If photons have a small mass, then they must travel at slightly less than that speed. We went through something similar with neutrinos about ten years ago, when they were discovered to have mass instead of being massless.
 
One of the germinating ideas behind de Broglie's theory is that photons might have a very small rest mass. Obviously his theory accommodates that possibility. Another eminent physicist, Proca, developed a slight modification of the Maxwell equations or even a Lagrangian which bears his name. The homogeneous Maxwell equations are not changed. More detail on that can be found in Jackson's "Classical Electrodynamics". On page 5, Jackson even considers how a massive photon would affect the Inverse Square Law of electrostatics.
 
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Photons have a rest mass in superconductors; about 10^-11 of the proton. See Wiki's Photon page, et al.

I can't find any mention of it, but this would seem to mean the photon must go <c in superconductors, and maybe need a period of acceleration / deceleration when being emitted or absorbed... ?
 
On the wiki page, there is one line stating that photons in superconductor have rest mass. However, there are no citations supporting that statement, and as far as I know, there are no transparent superconductors.

All the wiki page can give is an upper limit for any mass, meaning no mass has been detected to the present limit of measurement.
 
The Anderson-Englert-Brout-Higgs-Guralnik-Hagen-Kibble mechanism, isn't it?
 

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