Do Photons Have Mass? - Debate & Questions

  • Context: Graduate 
  • Thread starter Thread starter duu57f
  • Start date Start date
  • Tags Tags
    Mass Photons
Click For Summary

Discussion Overview

The discussion revolves around the question of whether photons have mass, exploring theoretical implications, definitions of mass, and the effects of gravity on light, particularly in the context of black holes. Participants engage in a debate that touches on concepts from general relativity and quantum physics.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Exploratory

Main Points Raised

  • Some participants argue that if photons had mass, it would contradict established theories, yet they question how light can be affected by gravity if it has no mass.
  • Others point out that there is an experimental upper limit on photon mass, suggesting it is very small, but not definitively zero.
  • One participant explains that general relativity describes gravity as the curvature of spacetime, which affects all particles, including massless ones like photons.
  • Another participant challenges the assertion that gravity only acts on mass, arguing that gravity affects all objects due to spacetime curvature, regardless of their mass.
  • Some participants discuss the definitions of mass, distinguishing between rest mass, inertial mass, and gravitational mass, and how these definitions influence the debate.
  • There is mention of the possibility that an object with high energy density could have zero active gravitational mass, which would affect spacetime curvature.
  • Several participants emphasize that gravity is described by the stress-energy tensor in general relativity, rather than solely by mass.

Areas of Agreement / Disagreement

Participants express differing views on the nature of mass and its relation to gravity, with no consensus reached on whether photons have mass or how gravity operates on massless particles. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Participants highlight the complexity of definitions surrounding mass and gravity, noting that the debate involves nuanced interpretations of physical concepts and the implications of general relativity.

  • #91
georgir said:
tl;dr
But the idea that something needs mass to be affected by gravity is obviously false - all things that have mass are affected absolutely identically by gravity, they receive exactly the same acceleration, regardless of their mass. So even if they had zero mass, it would be normal to assume they will still be affected in the same manner and get the same acceleration.

Do you mean that light can be accelerated overcoming its constant speed,or simply follows the space curvature? But curvating motion also means acceleration.
 
Physics news on Phys.org
  • #92
harve said:
Do you mean that light can be accelerated overcoming its constant speed,or simply follows the space curvature? But curvating motion also means acceleration.

The velocity of light is always c, yet it is affected by gravity and will change its direction of propagation.
 
  • #93
One thing should be clarified. The velocity of light is always "c" using local clocks and rulers, which means that in a coordinate independent sense, it's always "c".

The rate of change of the distance coordinate with respect to the time coordinate isn't always "c". So it's important to know how you are defining velocity before you talk about it. If you define it as being measured by local clocks and rulers, then it's always constant.

It's a separate argument about why that's the best way to define velocity - I find that it's mostly a waste of time. it may be worth mentioning - errr repeating - that the issue is one of coordinate independence.
 

Similar threads

High School Photon Energy Without Rest Mass – How?
  • · Replies 19 ·
Replies
19
Views
3K
High School How Can Photons Contribute Mass to a Container?
  • · Replies 16 ·
Replies
16
Views
2K
High School Does a hot coffee have bigger mass than a cold coffee?
  • · Replies 102 ·
4
Replies
102
Views
7K
High School What if we use a non physical reference point to measure an object's mass?
  • · Replies 5 ·
Replies
5
Views
1K
High School Photon Mass: Does Light Have Direction?
  • · Replies 6 ·
Replies
6
Views
1K
High School Photon Frequency: How Special Relativity Affects Light
  • · Replies 23 ·
Replies
23
Views
3K
High School Does Spacetime Have Physical Existence?
  • · Replies 58 ·
2
Replies
58
Views
4K
Graduate Exact meaning of the mass M in the Kerr metric event horizon formula?
  • · Replies 4 ·
Replies
4
Views
1K
Undergrad Still have questions about photon mass
  • · Replies 22 ·
Replies
22
Views
2K
Undergrad What if a body loses 86,6% of its mass as couples of gamma photons?
  • · Replies 9 ·
Replies
9
Views
2K