A Gedanken Experiment - Continued
The time measured (in each object’s rest frame) to travel a fixed ? distance must be the same (since problem is the same for both A and B).
But A and B each think the others clock is running slow ! Therefore each says that the other is moving at a slower ? velocity !
From the point of view of B, the time measured for A to travel that distance is larger by the factor of ?. Thus, the ? velocity of A must be smaller than the ? velocity of B by a factor of ?
Similarly, from point of view of A, B moves slower.