In the last two posts I’ve explained how Special Relativity concerns relative motion between two frames of reference, and that the motion involved is constant, straight-line motion that allows us to view either frame as the “moving” one or the “standing still” one.

Today I’m going to dig a little bit deeper into the idea of relative motion and what that involves for actions within a constantly moving frame of reference versus what observers in a different frame perceive. In other words: trains, planes, and automobiles.

(Warning: this gets a little math-y, but you can ignore those bits.)

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