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## Main Question or Discussion Point

I've read many explanations of time dilation and relativity, that describe things from the point of an observer, and then some other object moves away from it at some fraction of light speed. i.e. say a spacecraft moves away from an observer at 0.1c for 1 year ship time. Then presumably, to an observer, it really appears to take 1.1 years, and presumably appears to have a speed of 0.1/1.1 (I know some of this maths, is possibly slightly off - I'm trying to state this in general).

But, then I always wonder, what happens when it comes back. I'm really unsure of how to describe the maths of this, but wouldn't it look faster coming back, somewhat like the doppler effect. It seems symmetric, if total ship time for ship occupant's is 2 years, and it seemed like it took 1.1 to go out, it seems like it would - from the observers point of view - that it would take 0.9 to come back.

What am I missing?

But, then I always wonder, what happens when it comes back. I'm really unsure of how to describe the maths of this, but wouldn't it look faster coming back, somewhat like the doppler effect. It seems symmetric, if total ship time for ship occupant's is 2 years, and it seemed like it took 1.1 to go out, it seems like it would - from the observers point of view - that it would take 0.9 to come back.

What am I missing?