Transcription: The lack of an absolute standard of rest means that one cannot determine whether two events that take place at different times occur in the same position in space. Suppose our ping pong ball on the tram bounces straight up and down, hitting the table twice on the same spot, one second apart. To someone on the track, the two bounces would seem to take place about forty meters apart because the tram would have traveled that far down the track between the bounces.
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