Presumed mass content of photon as gravitational source

Click For Summary

Discussion Overview

The discussion revolves around the gravitational influence of photons, particularly in relation to their presumed mass content as described by the equation m_0 = hf/c². Participants explore whether photons can be associated with gravitational effects when near a mass, despite the concept of rest mass not being applicable.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions the validity of associating a gravitational influence to a photon based on its "mass content," suggesting that this approach may not be correct.
  • Another participant argues that the effects of a photon in a gravitational field are more akin to an object with twice the mass, but notes that the fast motion of the photon complicates the application of Newton's laws.
  • A different viewpoint suggests that in a gravitational field, such as near the Earth's surface, photons should behave similarly to other masses, implying they would fall with the same acceleration as other objects.
  • A reference to an exercise by Paul Hewitt is made, which compares the behavior of a falling ball and a beam of laser light in a reflective environment, indicating an interest in exploring the conceptual parallels between light and mass in gravitational contexts.

Areas of Agreement / Disagreement

Participants express differing views on the gravitational behavior of photons, with no consensus reached on the validity of associating gravitational effects with their mass content.

Contextual Notes

The discussion highlights the complexity of applying classical mechanics to photons and the potential limitations of the assumptions made regarding their mass and gravitational influence.

DaTario
Messages
1,097
Reaction score
46
Hello,

I have read some of the posts which discuss the meaning and mistakes involving the equation:
## m_0 = \frac{h f }{c^2}.##

My question has to do with gravitation. I would like to know if it is correct to associate to a photon with frequency f, crossing a region near a mass M, a gravitational influence based on the "photon's mass content" above described (even if the concept of rest mass is not applicable).

Best wishes,

DaTario
 
Science news on Phys.org
That doesn't work. The effect is more similar to an object with twice the mass, but you still have non-negligible effects from the fast motion that doesn't allow to apply Newton's formula for example.
 
But near the surface of the earth, for example, being a region where we can approximate de gravitational force on a mass m to mg, and which implies that all bodies will fall with the same acceleration g, the photon will also behave like this, isn´t it?
I recall an interesting exercise proposed by Paul Hewitt in Physics Teacher magazine, in which he asks for a comparison between the fall of a ball and a beam of laser light, both bouncing back and forth in perfectly reflecive walls.
ball and light drop hewitt.jpg
 
Just for the sake of good references, in the previous post (#3) I attached an illustration by Paul Hewitt, relative to the very problem I cited.
 

Similar threads

  • · Replies 21 ·
Replies
21
Views
9K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 78 ·
3
Replies
78
Views
6K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 27 ·
Replies
27
Views
6K
  • · Replies 23 ·
Replies
23
Views
3K
  • · Replies 7 ·
Replies
7
Views
2K
Replies
1
Views
256