How Does Relativity Affect Our Perception of Light and Photons?

  • Context: Graduate 
  • Thread starter Thread starter poeteye
  • Start date Start date
  • Tags Tags
    Photons Time
Click For Summary

Discussion Overview

The discussion centers around the nature of photons, particularly how relativity affects their perception in terms of time and space. Participants explore concepts related to the experience of time by photons, their behavior in spacetime, and the implications of their masslessness on their 4-velocity. The conversation includes theoretical considerations and mathematical reasoning.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants assert that photons do not experience time, while others question the appropriateness of this statement, suggesting that it may not be suitable to say photons "don't experience time" as there is no frame of reference for them.
  • There is a discussion about whether photons are "outside" spacetime, with some arguing that they are not outside but rather that their time dilation approaches infinity as they travel at the speed of light.
  • One participant explains that every system in spacetime has a 4-velocity of 1, and that a photon, having no rest mass, allocates all of its 4-velocity to spatial dimensions, leaving none for time.
  • Another participant raises the question of whether there are physical entities that have 100% of their 4-velocity in the time dimension and 0% in the space dimension, noting that in a sublight object's rest frame, this is indeed the case.
  • Some participants discuss the dual nature of photons as both particles and waves, suggesting that coherence length may play a role in this characterization.
  • There is a technical discussion regarding the normalization of 4-velocity for photons, with some confusion about why a normalized 4-velocity for a photon is not Lorentz invariant.

Areas of Agreement / Disagreement

Participants express differing views on whether photons experience time and the implications of their masslessness. There is no consensus on the nature of photons in relation to spacetime, and the discussion remains unresolved regarding several technical aspects, including the normalization of 4-velocity.

Contextual Notes

Limitations include the dependence on definitions of time and spacetime, and the unresolved nature of certain mathematical steps regarding the normalization of vectors in the context of Lorentz transformations.

  • #31
DaveC426913 said:
That's a question better answered by someone more in the know than I.

Essentially, all the light in front of you will be blue-shifted way up the scale to nearly infinite energy, whereas all the light behind you will be red-shifted way down the scale. Think of what an ambulance in front of you and another behind you would sound like if you were traveling at mach .99.

There are other details, such as the fact that your destination would get up all in your face as you virtually immediately arrive there.

So we would not see anything because our eyes can only see in the visible spectrum of light?
 
Physics news on Phys.org
  • #32
jlorda said:
So we would not see anything because our eyes can only see in the visible spectrum of light?
Well... Don't forget that the universe is shot-through with very low frequency radiation as much as anything else; that would be correspondingly blue-shifted up into the visible spectrum.

That is, if you magically lived through the raging storm of hard ultra-high energy cosmic radiation pelting your ship.
 
  • #33
jlorda said:
So we would not see anything because our eyes can only see in the visible spectrum of light?
High energy gamma rays would however excite your retina together with all the other components of your eyes and your vision area in your brain, so I imagine that you would perceive an almost infinitely bright light as if it were coming from all over, at least for an infinitesimal time before your death...
 
Last edited:

Similar threads

  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 32 ·
2
Replies
32
Views
2K
  • · Replies 26 ·
Replies
26
Views
2K
  • · Replies 1 ·
Replies
1
Views
280
  • · Replies 55 ·
2
Replies
55
Views
4K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 41 ·
2
Replies
41
Views
5K
  • · Replies 3 ·
Replies
3
Views
2K