- #1
Happiness
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- 30
Suppose planet X is so far away from Earth that due to the expansion of the universe, it is moving at a velocity ##v > c## away from us. Xavier stands on planet X and points a torch away from us. To Xavier, the light emitted from the torch is in front of him. But to us, the light emitted from the torch is behind him (since the velocity of light in our frame is also ##c < v##). How can this be?