Einstein’s Thought Experiment

  • By Arlo Perez
  • Posted 05.30.18
  • NOVA

Your perception of time depends on how you are moving.

Running Time: 01:49


Einstein’s Thought Experiment

Published May 30, 2018

Narrator: He imagines a man standing on railway platform. Two bolts of lightning strike on either side of him. The man is standing exactly halfway between them, and the light from each strike reaches his eyes at exactly the same moment. For him the two strikes are simultaneous. Then Einstein imagines a woman on a fast moving train. Travelling at close to the speed of light, what would she see?

As the light travels out from the strikes, the train is moving towards one and away from the other. Light from the front strike reaches her eyes first. For the woman on the train, time elapses between the two strikes; for the man on the platform, there is no time between the strikes.

This simple thought has mind-blowing significance. Simultaneity, and the flow of time itself, depends on how you’re moving.



Digital Producer
Arlo Perez
Editorial Review
Julia Cort, Ari Daniel
© WGBH Educational Foundation 2018



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