2 photons, same starting point/time, same end point

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Discussion Overview

The discussion revolves around the conceptual understanding of how two photons, starting and ending at the same points in space and time, would perceive each other's positions, time, and distance. Participants explore the implications of this scenario within the framework of physics, particularly focusing on the nature of light and reference frames.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions how two photons would view each other's positions and time, acknowledging the complexity of the question.
  • Another participant asserts that photons do not have a "point of view" as they lack a rest frame, which is necessary for such a perspective.
  • Further contributions emphasize the need to specify the paths taken by the photons, questioning whether they follow the same route or interact with other objects.
  • Some participants suggest that if the photons are identical and overlap in all aspects, they would be perceived as a single, more intense flash of light by observers.
  • There is a consensus that the question of how things appear from the perspective of a photon remains ill-formed due to the absence of a valid reference frame for photons.

Areas of Agreement / Disagreement

Participants generally agree on the limitations of discussing a photon's perspective and the necessity of clarifying the paths of the light pulses. However, there remains some uncertainty regarding how to properly frame the original question to address the time and path of the photons.

Contextual Notes

Participants note that the discussion is limited by the inherent properties of light and the definitions of reference frames, which complicate the exploration of the original question.

69911e
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How would 2 photons with the same starting point& time and same end point view each other's positions, time and distance from start to end point. I recognize this is likely a bad question, so any input would be helpful.
 
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69911e said:
I recognize this is likely a bad question
It is. Photons don't have "point of view" like massive objects do. This is because an object's "point of view", in technical terms, is a reference frame in which the object is at rest. However, no such reference frame exists for a photon.

https://www.physicsforums.com/threads/rest-frame-of-a-photon.511170/
 
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Yes, that is why I mentioned likely bad question.
How can this question be changed so the time and path of the 2 photons can be fully addressed?
 
69911e said:
Yes, that is why I mentioned likely bad question.
How can this question be changed so the time and path of the 2 photons can be fully addressed?

It's easy to describe the paths followed by the two flashes of light, and how those paths will appear to any possible observer. That's a complete description of the physical situation.

There is no "point of view" in which either of the flashes is at rest, nor even moving at any speed other than c relative to the observer.
 
Further to Nugatory's comment, you also need to specify something about the path the light pulses follow. If they start at the same point at the same time and arrive at the same point, are they taking the same route? If not, do they arrive at the same point at the same time? Do they bounce off mirrors? Or are you thinking of gravitationally lensing?
 
Ibix said:
Further to Nugatory's comment, you also need to specify something about the path the light pulses follow. If they start at the same point at the same time and arrive at the same point, are they taking the same route?

I was pondering: Same starting point, same end point, same path, simultaneous within allowable uncertainty. Basically identical signals overlapping in all possible aspects.
 
69911e said:
I was pondering: Same starting point, same end point, same path, simultaneous within allowable uncertainty. Basically identical signals overlapping in all possible aspects.
Electromagnetic radiation superimposes, so for all observers this is going to be a single more intense flash of light moving from the starting point to the end point at speed c.

The question about how things would look from the point of view of an observer moving along with that flash of light is still ill-formed, for the the reason that jtbell gave above.
 

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