Speed of Light Near Black Holes: Explained

Click For Summary

Discussion Overview

The discussion revolves around the behavior of light near black holes, specifically addressing whether the speed of light changes in such extreme gravitational fields. Participants explore concepts related to the speed of light, gravitational effects on photons, and the implications of these effects on frequency and energy.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants assert that the speed of light remains constant at c, both far from and near a black hole.
  • One participant questions the assumption that gravity would increase the speed of a photon, suggesting that the intuition behind this idea may stem from a misunderstanding of gravitational effects.
  • Another participant explains that while the speed of light does not change, gravitational effects can alter the wavelength and frequency of light, which is dependent on the observer's perspective.
  • There is a discussion about the relationship between a photon's energy and its frequency, with references to gravitational attraction affecting the kinetic energy of particles as they approach a massive body.

Areas of Agreement / Disagreement

Participants generally agree that the speed of light does not change near a black hole, but there is disagreement about the implications of gravitational effects on light, particularly regarding frequency and energy. The discussion remains unresolved regarding the intuitive understanding of these concepts.

Contextual Notes

Participants express varying levels of understanding regarding the effects of gravity on light, and there are references to intuitive notions that may not align with established physics. The discussion highlights the complexity of gravitational interactions with light without resolving the underlying assumptions.

Prashan Shan
Messages
31
Reaction score
0
black holes pulls light right,
then when a black hole pulls photon will the speed that photon increase?
 
Physics news on Phys.org
No, the speed of light does not change near a black hole. Why do you think the photon's speed should increase ?
 
As the rabbit said, the speed of light in a vacuum is c.

Far away from a black hole, the speed of light in a vacuum is c.

Near a black hole the speed of light in a vacuum is c.

The speed of light in a vacuum is c.
 
  • Like
Likes   Reactions: Prashan Shan
wabbit said:
No, the speed of light does not change near a black hole. Why do you think the photon's speed should increase ?

lol likely because gravity "pulls" things, pretty easy to intuit the OP is envisioning that "pull" on a photon.

Prashan Shan said:
black holes pulls light right,
then when a black hole pulls photon will the speed that photon increase?

No it will not increase the speed of the photon. The photon is already traveling at an invariant speed, but that doesn't mean nothing happens. That "pull" "stretches" or "compresses" the wavelength of the photon, changing frequencies. Which one depends on your perspective / which way the light is traveling through the "distorted" spacetime.
 
nitsuj said:
lol likely because gravity "pulls" things, pretty easy to intuit the OP is envisioning that "pull" on a photon.
The thing is, it's not really wrong to think that there's a "pull", the issue is, what does a pull do to a photon since it cannot change its speed ? As you mentionned it acts on its frequency, but the intuition as to why it does so is not obvious.

Prashan Shan, perhaps you know than a photon's energy is ## E=h\nu ## where ## \nu ## is its frequency. You can think of that as kinetic energy since the photon does not have a rest mass - now what does gravitational attraction do to the kinetic energy of a particle as it gets closer to the attracting mass?
 
Last edited:

Similar threads

High School A photon always travels in a black hole
  • · Replies 9 ·
Replies
9
Views
1K
High School How can a black hole absorb matter?
  • · Replies 31 ·
2
Replies
31
Views
2K
Undergrad Can light be reflected in a black hole?
  • · Replies 22 ·
Replies
22
Views
2K
Undergrad Is Measuring the One-Way Speed of Light Possible Near a Black Hole?
  • · Replies 10 ·
Replies
10
Views
2K
High School Theories about light and time near a black hole
  • · Replies 20 ·
Replies
20
Views
2K
Undergrad Black Hole Waterfall Analogy & Light Speed
  • · Replies 15 ·
Replies
15
Views
3K
High School Is there a white hole inside every black hole?
  • · Replies 22 ·
Replies
22
Views
2K
Undergrad On the possibility of exploding a black hole
  • · Replies 15 ·
Replies
15
Views
1K
Undergrad Looking closely at the descent into a black hole
  • · Replies 51 ·
2
Replies
51
Views
2K
Undergrad You can't actually enter a blackhole?
  • · Replies 40 ·
2
Replies
40
Views
4K