Another basic question

[goodabouthood]

A stationary observer sees a moving train going at .6c.

Does the moving train see the stationary observer going .6c from his frame of reference as well?

I want to say yes but I'm not sure.

[ghwellsjr]

Yes, but if we want to use the standard configuration for the Lorentz Transform, we say that the train sees the observer moving at -0.6c.

[HallsofIvy]

Yes in terms of "velocity". In terms of the "speed", which is what relativity normally deals with, each sees the other as moving at 0.6c.

[ghwellsjr]

The Lorentz Transform which is so very important in Special Relativity will not be reciprocal if you use 0.6c when transforming from one frame to the other and back again. If you use 0.6c when transforming an event from the first frame into the second frame then you must use -0.6c when you transform that event back into the first frame if you expect to get the same event you started with.