Relativity 101: Near speed of light travel

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Discussion Overview

The discussion revolves around the visual effects experienced by an observer traveling near the speed of light, particularly focusing on the apparent positions of stars and the concept of relativistic aberration. Participants explore how the universe might appear compressed in the direction of travel and the implications of photon trajectories in this context.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants propose that at speeds close to the speed of light, all stars would appear to be concentrated in a cone in front of the observer's ship.
  • There is a suggestion that from a non-moving frame, fewer stars would be visible in the forward direction because photons would need to "lead" the ship, resulting in them arriving from behind.
  • A participant introduces a pinhole camera analogy to illustrate how the motion of the observer affects the perceived angles of incoming photons, suggesting that this effect would also apply to human vision.
  • Links to external resources on relativistic aberration are provided for further exploration of the topic.

Areas of Agreement / Disagreement

Participants express uncertainty about how to fully conceptualize the visual effects in the ship's frame and do not reach a consensus on the implications of these effects.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about the observer's frame of reference and the complexities of photon behavior at relativistic speeds, which remain unresolved.

Chuck37
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I thought I read that if you were in a ship near the speed of light, all the stars would appear to be in front of you. The closer to c you are, the more everything will be collapsed to a cone facing forward. Is that right?

Thinking about it a little from the non-moving frame, it seems like there would be fewer visible stars from forward since photons from stars would have to "lead" the ship by so much that they would always end up coming in nearly from behind. I'm not sure how to think about this in the ship frame though. I think the universe would appear compressed in the direction of flight, but I'm not sure what to do with that.
 
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Chuck37 said:
I thought I read that if you were in a ship near the speed of light, all the stars would appear to be in front of you. The closer to c you are, the more everything will be collapsed to a cone facing forward. Is that right?

Thinking about it a little from the non-moving frame, it seems like there would be fewer visible stars from forward since photons from stars would have to "lead" the ship by so much that they would always end up coming in nearly from behind. I'm not sure how to think about this in the ship frame though. I think the universe would appear compressed in the direction of flight, but I'm not sure what to do with that.

Here's a construct that might be helpful.

Imagine a pinhole camera facing straight ahead.

A photon enters at a 45 deg. angle. As it travels to the film plane, the camera is moving forward so it actually intersects the film closer to the center than it would if the camera was not moving. So it appears in the image as if it was coming from an angle closer to straight ahead.
The same effect takes place with photons from positions behind , except the effect is reversed. The motion of the camera while the photon moves from the aperture to the film means the point it hits will be farther from the center than the actual angle so it will appear to be coming from a position more towards the front of the system.
This will of course also take place within an eye ;-)
 
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