Photon Sphere and time travel around a Black Hole?

Click For Summary

Discussion Overview

The discussion revolves around the concept of the photon sphere of a black hole and its implications for time perception and potential time travel. Participants explore the nature of light traveling around a black hole and the effects on an observer positioned at the photon sphere, considering both theoretical and conceptual aspects.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant postulates that an observer at the photon sphere would see themselves in the future due to the light traveling back to them.
  • Another participant argues that the observer would see a past version of themselves, referencing the concept of world lines of photons as discussed in literature.
  • A different viewpoint suggests that the effects of the photon sphere can be replicated with mirrors, emphasizing that everything observed would be from the past without any time travel involved.
  • One participant questions the relationship between time dilation and the perception of past and future, suggesting that seeing one's past could imply being in the future.
  • Another participant counters that the observer would remain in the present, regardless of the light they see from their past.
  • There is a query about whether the behavior of the photon sphere would differ for supermassive black holes, with a suggestion that the size of the photon sphere scales with the mass of the black hole.

Areas of Agreement / Disagreement

Participants express differing views on whether an observer at the photon sphere would see a past or future version of themselves, indicating a lack of consensus on this aspect of the discussion. The relationship between time perception and the effects of black holes remains contested.

Contextual Notes

Participants reference various sources and concepts related to black holes and photon spheres, but the discussion includes assumptions about time perception that are not fully resolved. The implications of time dilation and the nature of light travel around black holes are also not conclusively addressed.

Who May Find This Useful

Individuals interested in theoretical physics, black hole dynamics, and the philosophical implications of time perception in extreme gravitational fields may find this discussion relevant.

infinitebubble
Messages
82
Reaction score
40
Reading the post below on event horizon of a black hole (BH) got me thinking about the photon sphere of the BH. We all know light will travel around this photon sphere and how light from a source would completely travel back to it's source if one could see it real time, we all know this from relativity.

Now I postulate if a vehicle could theoretically be at this photon sphere and travel around it, we know it would see itself from the light traveling back and they would eventually see themselves... would TIME be the same or would as I suspect they would see themselves in the future?
 
Astronomy news on Phys.org
You can reproduce all effects of the photon sphere with mirrors at home (although things like time delays will be too short to notice without sensitive equipment, of course). No time travel involved, and everything you see happened in the past.
 
Last edited:
infinitebubble said:
OK... perhaps I was seeing some time dilation as the light/vehicle traveled around the BH. But if you see your past then you would be in the future would it?

No, you would be here now in the present.
 
jedishrfu said:
No, you would be here now in the present.

Would this be the same for supermassive BH's on the order of millions of Suns?
 
infinitebubble said:
Would this be the same for supermassive BH's on the order of millions of Suns?

The photon sphere would just be larger for larger black holes, right? The light leaves your spaceship and then you see the back of your spaceship. You are in the present and the light you see is from your past.
 
  • Like
Likes   Reactions: infinitebubble

Similar threads

  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 17 ·
Replies
17
Views
6K
  • · Replies 49 ·
2
Replies
49
Views
7K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 87 ·
3
Replies
87
Views
10K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 9 ·
Replies
9
Views
1K