Slowing Down a Photon - Does It Make Sense?

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Discussion Overview

The discussion revolves around the behavior of photons, particularly whether they can be said to travel at speeds other than the speed of light (c) in various contexts, such as in different materials or during specific experimental conditions. Participants explore concepts related to the Lorentz transformation, group velocity, and the implications of slowing light in experiments like Electromagnetically Induced Transparency (EIT).

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • One participant questions whether a single photon can ever travel at speeds other than c, suggesting that applying Lorentz transformations to photons may not be physically meaningful.
  • Another participant asserts that a photon always travels at c, regardless of the inertial frame, and that Lorentz transformations will yield c.
  • A participant expresses confusion about reconciling the constant speed of photons with the observed slowing of light in EIT experiments, proposing a connection between the electromagnetic field and the curvature of space-time.
  • It is noted that the speed of light is c only in a vacuum, while in other materials, light can travel slower than c, though the implications for individual photons in quantum mechanics remain unclear.
  • One participant mentions that in superfluid conditions, light can be slowed significantly, while also noting that photons always travel at c in their own frame of reference.
  • Another participant suggests that using Minkowski space may help clarify some of the paradoxes associated with these discussions.
  • It is pointed out that when photons travel through materials, they may take a zigzag path due to interactions with atoms, which can lead to longer travel times without changing their intrinsic speed.

Areas of Agreement / Disagreement

Participants generally agree that photons travel at c in a vacuum and that their behavior in materials can lead to apparent slowing. However, there are competing views on the implications of this slowing and the application of Lorentz transformations to photons, indicating that the discussion remains unresolved.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about the nature of photons in different contexts, the definitions of speed in various media, and the unresolved mathematical implications of the concepts discussed.

karatemonkey
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Slowing down a photon

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Does a single unique photon ever not travel at c in the same inertial frame?
I'm stuck on the apparent problems with applying the Lorentz transformation to a photon. I don't think it makes sense physically to apply them to a photon. Talking about moving photons from rest to c, I don't think happens or even makes sense. When light is slowed down, isn't that really the group velocity of the EM field that gets slowed from which photons are emitted.
Anyway, enough rambling help!
 
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A photon always travels at c.
If you Lorentz transform, you will still get c.
 
Ok, so I got through the photons always have velocity c in any inertial frame part, which includes photons created inside a semi-conductor laser or in some EIT material,
I'm now stuck on how to reconcile photon velocity and the speed light slowing in EIT experiments. More specifically, is it proper to talk of the EM field taking up and giving back mass from the energy of the photons, and that the taking up and giving back by the field acts as a curvature of space-time? Is that even possible?
 
The speed of light* is only equal to c in vacuum. In other materials the speed of light can be less than c.

*Classical Maxwell-type speed of light, I don't know about for individual photons in a QM type analysis.
 
Last edited:
In a superfluid light can be slowed to a few miles per hour. As for if you mean in a vacuum yes in all frames of reference, except of course the photons own frame of reference it will be traveling at c.
 
I have heard physics profs say many a times that using Minkowski's space to understand such things is more profitable. It clears most of the so-called paradoxes.

Cheers
 
the speed of an individual photon is always c. when a photon travels through a material it can take a zig zag path to the other side as its affected by the atoms in the material so it will take longer to get to the other side and is effectively slowed down.
 

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