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## Main Question or Discussion Point

Hello all,

I'm trying to figure out how light from different galaxies gets red shifted. I wonder if I could get some quick answers to a few example situations so I can get a better intuitive understanding of how light moves through space.

Q1. Say two people are moving apart at constant velocity. Person A has a flashlight that person B is observing. Does B see the light as red shiftshifted. I'm pretty sure the answer is "no" to this one.

Q2. Same two people, but they are now accelerating away from each other. Is the light red shifted for B?

Q3. The two observers are out in a portion of expanding space, but are not moving through space (relative to each other). Do they see each other moving apart? I think they will, if the space that each occupy themselves is not expanding (lets assume this, in fact). Will the light from A be redshifted for B?

If anyone can help me out with these, I'd be most appreciative.

Thanks,

Wendy

I'm trying to figure out how light from different galaxies gets red shifted. I wonder if I could get some quick answers to a few example situations so I can get a better intuitive understanding of how light moves through space.

Q1. Say two people are moving apart at constant velocity. Person A has a flashlight that person B is observing. Does B see the light as red shiftshifted. I'm pretty sure the answer is "no" to this one.

Q2. Same two people, but they are now accelerating away from each other. Is the light red shifted for B?

Q3. The two observers are out in a portion of expanding space, but are not moving through space (relative to each other). Do they see each other moving apart? I think they will, if the space that each occupy themselves is not expanding (lets assume this, in fact). Will the light from A be redshifted for B?

If anyone can help me out with these, I'd be most appreciative.

Thanks,

Wendy