1 upvotes, 2 direct replies (showing 2)
View submission: Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary Science
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Comment by mfb- at 06/12/2023 at 19:25 UTC
10 upvotes, 1 direct replies
You see the distance between the two trains increase at 1.6 c, but you don't see any train exceed c.
The trains see the other train moving at (0.8+0.8)/(1+0.8*0.8) = 0.976 times the speed of light using the relativistic velocity addition, which is again below c.
Comment by nick_hedp at 06/12/2023 at 18:47 UTC
6 upvotes, 0 direct replies
Yes, but I don't believe there's any relativistic problems with that. Similarly, I could watch a guy walk along the platform to the left and shine a flashlight to the right, and the relative velocity between the two will also exceed c, but nobody in their own frame would measure that.