Does the bending of light by gravity imply that photons have mass?

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Discussion Overview

The discussion revolves around the relationship between gravity and light, specifically whether the bending of light by gravity implies that photons possess mass. Participants explore concepts from general relativity and gravitational lensing, examining the implications of these phenomena on the nature of photons.

Discussion Character

  • Debate/contested

Main Points Raised

  • One participant suggests that the bending of light due to gravity indicates that photons may have a tiny amount of mass, questioning the notion of photons being completely massless.
  • Another participant counters that photons are not "bent" in the conventional sense but follow geodesics in spacetime, implying a different understanding of their interaction with gravity.
  • A third participant clarifies that in general relativity, gravity is determined by energy-momentum rather than mass, allowing light to interact gravitationally despite having zero mass.

Areas of Agreement / Disagreement

Participants express differing views on whether the bending of light implies mass for photons. There is no consensus reached, as some argue for the massless nature of photons while others propose alternative interpretations.

Contextual Notes

The discussion involves assumptions about the nature of mass and energy in the context of general relativity, as well as the interpretation of gravitational lensing. The implications of these concepts on the properties of photons remain unresolved.

Allojubrious
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Because light bends due to gravity, as can be seen in Gravitational Lensing, if gravity responds to mass and light is bent by gravity, does that not imply that the photon is NOT 100% massless?? That the photon indeed has a very tiny amount of mass?? Because if light bends due to gravity, then light must have a some mass right?? If one could explain this phenomenon, that would be great!

Thanks,
Al
 
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Allojubrious said:
Because light bends due to gravity, as can be seen in Gravitational Lensing, if gravity responds to mass and light is bent by gravity, does that not imply that the photon is NOT 100% massless?? That the photon indeed has a very tiny amount of mass?? Because if light bends due to gravity, then light must have a some mass right?? If one could explain this phenomenon, that would be great!

Thanks,
Al

Photons are NOT "bent" in the way you seem to think. Photons follow a spacetime "straight line" (aka "geodesic").
 
No. In general relativity, the strength of gravity is determined not by mass, but energy-momentum. So, light interacts gravitationally even though it has zero mass.
 
Oh ok yeah that makes sense, well thank you!

Thanks,
Al
 

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