Relativity 101: Near speed of light travel

[Chuck37]

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.

 

[bcrowell]

These may be useful:

http://www.fourmilab.ch/cship/aberration.html
http://en.wikipedia.org/wiki/Relativistic_aberration

 

[Austin0]

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 ;-)

 

[ghwellsjr]

You might find some of the discussion on this thread at post #15 and leading up to it interesting:

https://www.physicsforums.com/showthread.php?p=3946430

 

[sardar]

Your understanding is partially correct. According to Einstein's theory of relativity, as an object approaches the speed of light, its length in the direction of motion will appear to contract from the perspective of an observer at rest. This means that objects in front of the moving ship will appear to be compressed or "squished" in the direction of motion. This is known as length contraction.

In addition, as the ship approaches the speed of light, the light from distant stars will be blueshifted (shifted towards the blue end of the electromagnetic spectrum) due to the Doppler effect. This means that the wavelength of the light will decrease, making it appear more energetic and therefore bluer. This effect increases as the ship gets closer to the speed of light, so the stars will appear to be more concentrated in the direction of motion.

However, it is not accurate to say that all the stars will appear to be in front of the ship. This is because the light from those stars would still need to travel towards the ship, and it would take time for that light to reach the ship. Therefore, the stars would appear to be in front of the ship, but they would also appear to be shifted towards the direction of motion due to the Doppler effect.

It is also important to note that this effect would only be noticeable at extremely high speeds, close to the speed of light. At everyday speeds, the effects of relativity are negligible.

Overall, your understanding is on the right track, but it is important to consider all the factors at play when thinking about how objects and light appear at near-light speeds.