What do I see if I walk forward through a superdense transparent medium?

  • Context: Graduate 
  • Thread starter Thread starter danR
  • Start date Start date
  • Tags Tags
    Medium Transparent
Click For Summary

Discussion Overview

The discussion revolves around the visual perception of light while moving through a superdense transparent medium, specifically considering the effects of light speed and motion on the observer's experience. Participants explore theoretical scenarios involving classical electromagnetism and relativistic concepts.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant proposes that moving at 2 m/s in a medium where light travels at 1 m/s raises questions about visibility of the flashlight and the nature of light encountered.
  • Another participant argues that it is impossible to move faster than light in such a medium, suggesting a fundamental limitation to the scenario.
  • Several participants discuss the classical electromagnetism perspective, suggesting that the observer would see light blue-shifted due to encountering wave crests at a faster rate.
  • There is a challenge regarding how light from behind can be perceived if the observer is moving faster than the light, leading to further clarification that the flashlight has been on for some time.
  • One participant expresses a belief that they would see the light red-shifted due to their relative speed to the wave crests, indicating a nuanced view on the effects of motion on light perception.
  • Another participant mentions the possibility of realizing the experiment using acoustic imaging analogues, suggesting a broader application of the concepts discussed.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the implications of moving through a medium where light travels slowly. There is no consensus on how the observer would perceive the light from the flashlight or the effects of their motion on the light's characteristics.

Contextual Notes

Participants acknowledge the theoretical nature of the discussion, with some emphasizing the classical E&M framework while others introduce relativistic considerations. The discussion remains open to interpretation and lacks definitive conclusions.

danR
Messages
352
Reaction score
4
I am walking at 2 metre/sec and light, from a flashlight behind me, is moving at 1 m/s.

So my eyeballs are catching up with the photons ahead of me. Do I see the flashlight? Do backward photons look strange? Are they red-shifted, blue-shifted? Assume my optics have been replaced with hyperdense refracting material.
 
Science news on Phys.org
If you're in a medium where light effectively travels at 1m/s, there's no chance in hell you're going to be able to move at 2m/s in it.
 
Never mind photons, this is a classical E&M problem, and a nonrelativistic one at that since you're only moving at 2 m/s. No paradoxes involved. There's a changing E&M field in front of you and you're moving through it faster than the fields are advancing. You'll see this "light" blue-shifted, since you're encountering crests at a faster rate. You'll also see the flashlight behind you, but as you move away from it you'll see it with light that left it farther and farther in the past.
 
Bill_K said:
Never mind photons, this is a classical E&M problem, and a nonrelativistic one at that since you're only moving at 2 m/s. No paradoxes involved. There's a changing E&M field in front of you and you're moving through it faster than the fields are advancing. You'll see this "light" blue-shifted, since you're encountering crests at a faster rate. You'll also see the flashlight behind you, but as you move away from it you'll see it with light that left it farther and farther in the past.

Yes it's a classical E&M problem (Heaviside and Cherenkov), but how can you receive the light from behind if you are going faster than the light? Or do you mean that you will receive the light from in front of you?
 
Pengwuino said:
If you're in a medium where light effectively travels at 1m/s, there's no chance in hell you're going to be able to move at 2m/s in it.

It's a gedankenexperiment. I can do whatever the hell I want :biggrin:. Within theoretical reason.o:)
 
Last edited:
harrylin said:
Yes it's a classical E&M problem (Heaviside and Cherenkov), but how can you receive the light from behind if you are going faster than the light? Or do you mean that you will receive the light from in front of you?

I just mean the flashlight's been on for a while.
 
Bill_K said:
Never mind photons, this is a classical E&M problem, and a nonrelativistic one at that since you're only moving at 2 m/s. No paradoxes involved. There's a changing E&M field in front of you and you're moving through it faster than the fields are advancing. You'll see this "light" blue-shifted, since you're encountering crests at a faster rate. You'll also see the flashlight behind you, but as you move away from it you'll see it with light that left it farther and farther in the past.

I should think I'd be seeing it red-shifted. I'm catching up with the wave-crests at a relative speed of half, 1 m/s, what would pertain simply facing the light--2 m/s.

I'm using photons because they are trendy. I don't believe in relativity paradoxes, just used to posting in the relativity section. I'm just curious about what I'd see.

Now that I think of it, the experiment could be realized using acoustic imaging analogues.
 
Last edited:

Similar threads

Graduate What are the unusual absorption features observed in the EIT signal of 85Rb gas?
  • · Replies 1 ·
Replies
1
Views
2K
Graduate What do I see if I was a particle at speed moving by a spaceship?
  • · Replies 4 ·
Replies
4
Views
3K
Graduate Birefringence and Automotive Window Tinting
  • · Replies 9 ·
Replies
9
Views
9K