Introduction to special relativity: Difference between revisions

Revision as of 16:10, 8 November 2014

Revision as of 16:11, 8 November 2014

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The distances between these objects and the passenger observer do not change. Therefore, this observer measures all of the seats to be at rest, since he is stationary from his own perspective.

An observer standing on the platform would see exactly the same objects but interpret them very differently. The distance between the platform observer and the seats on the train car is changing, and so the platform observer concludes that the seats are moving forward, as is the whole train. Thus for one observer the seats are at rest, while for the othersother the seats are moving, and both are correct, since they are using different definitions of "at rest" and "moving". Each observer has a distinct "frame of reference" in which velocities are measured, ''the rest frame of the platform'' and ''the rest frame of the train'' – or simply ''the platform frame'' and ''the train frame''.

Why can't we select one of these frames to be the "correct" one? Or more generally, why is there not a frame we can select to be the basis for all measurements, an "absolutely stationary" frame?