What is the experience of a photon?

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Discussion Overview

The discussion revolves around the experience of a photon as it travels from one event to another, particularly focusing on the implications of special relativity and quantum mechanics. Participants explore the conceptual understanding of a photon's journey and its implications for perception and reference frames.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant describes an event where an electron in an LED releases a photon, questioning how the photon experiences its journey from the point of emission to the point of observation.
  • This participant suggests that, according to special relativity, a photon would experience zero time and zero distance during its travel, invoking the Lorentz transformation.
  • Another participant counters that a photon does not experience anything and that there is no valid frame of reference for a photon, emphasizing that attempts to ascribe experiences to a photon can lead to confusion.
  • A later reply acknowledges the interest in the concept of a photon but requests the closure of the discussion, suggesting that the topic has been sufficiently addressed.

Areas of Agreement / Disagreement

Participants express differing views on whether a photon can be said to experience its journey. One viewpoint suggests a conceptual framework for understanding this experience, while another firmly states that such an experience is not applicable to photons. The discussion remains unresolved regarding the interpretation of a photon's experience.

Contextual Notes

The discussion highlights the limitations of applying human-like experiences to photons and the challenges in defining a frame of reference for light-speed travel. There is an acknowledgment of the complexities involved in reconciling quantum mechanics with relativistic principles.

Brian Preece
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TL;DR
How does a photon experience its journey from one event to another?
I’m watching TV. An excited electron in an LED in the screen falls back to its normal energy state, releasing a quantum of electromagnetic energy in the form of a photon. Let’s call this event ‘A’ (x1, y1, z1, t1). The wave packet of this photon fills the universe (quantum mechanics). Across the room, after a short time, I observe the photon as its wave packet collapses and transfers its quantum of energy to an electron in my retina. Let’s call this event ‘B’ (x2, y2, z2, t2). This is how I see it, but what about the photon? How does it see the journey?

When the photon travels from ‘A’ to ‘B’ at the speed of light (c), its clock stops; the ultimate twin paradox, (special relativity – simultaneity). It will measure the distance between ‘A’ and ‘B’ using the Lorentz transformation [(x2 – x1)2 + (y2 – y1)2 + (z2 – z1)2 – (t2 – t1)2c2] (general relativity). In simple terms the photon will take zero time to travel zero distance. This is how I imagine the photon experiences the journey.

Am I correct?
 
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Brian Preece said:
Summary: How does a photon experience its journey from one event to another?
A photon does not experience anything. Any attempt to pretend that it does will simply result in confusion.

To state this more formally, there is no such thing as a frame of reference for a photon. This is such a frequently asked question that we have a FAQ on it:

https://www.physicsforums.com/threads/rest-frame-of-a-photon.511170/
 
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Thank you for your reply, I have seen one or two related discussions since posting this one. The concept of a photon is certainly interesting.

Please close this discussion, as the topic has been thoroughly answered.
 
Brian, the way to get a thread of yours closed is to use the "report" button so that a moderator will see that you want to close it.
 
Brian Preece said:
Please close this discussion, as the topic has been thoroughly answered.

Thread closed.
 

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