Speed of Light Questions

[shades171]

First, I am not an astrophysicist. So please answer as best you can in plain English.

Here are my questions:

1. If I were to travel away from Earth at light speed, and then used a telescope to look back at the earth (yes, all hypothetical questions), would everything appeared to have stopped? What is I was traveling twice the speed of light away - would everything speed up 2x?

2. Sort of same question. If I were to travel toward the earth at light speed would everything double in speed according to my observations?

3. If a particle could look backwards from the direction it's traveling in the Cherenkov radiation effect, would it see itself?

4. If you could send a particle from point "A" to point "B" and it arrives at point "B" before it left (time travel), could you stop the particle at Junction "A"?

[antoniseb]

1. If you were traveling away from Earth at the speed of light (not possible), and looked back with a telescope, all of the photons from Earth would be red-shifted to oblivion, and all you could see is darkness when you look back.

If you were going twice the speed of light, you'd be catching up with photons that left before you did, and so you'd see things moving backwards, to the degree that imaging was possible at all.

2. If you traveled toward the Earth at near the speed of light, photons coming from the Earth toward you would be blue-shifted possibly up to xrays or gammarays, but the images (if you had equipement to see them) would show things moving on Earth very quickly.

3. Not until it slowed down below the speed of light in that medium (and anthropomorphising the particle to have vision and a sense of self).

4. I'm not sure what you mean.