Speed of Light in Inertial Ref Frames: Photon Perspective

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Discussion Overview

The discussion centers on the implications of the speed of light in different inertial reference frames, particularly from the hypothetical perspective of a photon. Participants explore the nature of reference frames in relation to the speed of light as stated in the second postulate of Special Relativity.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions what a photon would perceive regarding the motion of other photons in a beam, asking if they would appear stationary or moving at the speed of light.
  • Another participant argues that the concept of a "frame of reference of a single photon" is contradictory, asserting that there cannot be an inertial frame where light is at rest.
  • A summary reiterates that there are no inertial frames moving at the speed of light, emphasizing that one cannot have a reference frame moving along with a beam of photons.
  • One participant illustrates the idea of chasing a photon, stating that no matter how fast one attempts to catch up, the photon will always recede at the speed of light.
  • Another participant reinforces the previous point by noting that observers will always see someone chasing light moving at less than the speed of light, while the light itself moves at that speed.

Areas of Agreement / Disagreement

Participants generally disagree on the feasibility of discussing a reference frame for a photon, with some asserting it is a flawed premise while others explore the implications of such a perspective.

Contextual Notes

The discussion highlights limitations in understanding reference frames at the speed of light, particularly regarding assumptions about motion and perception from a photon's perspective.

Saptarshi Sarkar
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TL;DR
What would be the speed of a photon in a beam of photons wrt another photon in the beam.
According to the 2nd postulate of Special Relativity, speed of light in vacuum is the same in all inertial reference frames.

If I take a beam of photons and see the other photons in the beam from a frame of reference of a single photon, do they look stationary or moving at the speed of light? Also, as the photon is itself moving with the doped how fast would the surrounding seem to move?
 
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As per the second postulate, the speed of light is the same in all inertial reference frames. Therefore an inertial reference frame in which light is at rest is a contradiction in terms. So there is no answer to your question - it is based on a faulty premise, namely that there is such a thing as the "frame of reference of a single photon".
 
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Saptarshi Sarkar said:
Summary:: What would be the speed of a photon in a beam of photons wrt another photon in the beam.

According to the 2nd postulate of Special Relativity, speed of light in vacuum is the same in all inertial reference frames.

If I take a beam of photons and see the other photons in the beam from a frame of reference of a single photon, do they look stationary or moving at the speed of light? Also, as the photon is itself moving with the doped how fast would the surrounding seem to move?

There are no inertial frames moving at ##c## with respect to other inertial frames. In particular, there is no inertial frame moving along with a beam of photons.
 
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Saptarshi Sarkar said:
If I take a beam of photons and see the other photons in the beam from a frame of reference of a single photon,

Imagine chasing that photon in an effort to catch up to it. No matter how fast you chase after it, it will forever recede from you at speed ##c##.
 
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Mister T said:
Imagine chasing that photon in an effort to catch up to it. No matter how fast you chase after it, it will forever recede from you at speed ##c##.
And anyone watching you chase the flash of light, no matter their state of motion, will find that you are moving at less than ##c## while it is moving at ##c##... so no surprise that you can’t catch it.

(Of course @Mister T knows this - the comment is for others reading this thread)
 
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