How images can move faster than light, and what they can tell us.

If you sweep a laser pointer across the moon, will the spot move faster than the speed of light? Every physics major encounters this question at some point, and the answer is yes, it will. If you sweep the laser pointer at it in an arc, the velocity of the spot increases with the distance to the surface you point at. On Earth, you only have to rotate the laser in a full arc within a few seconds, then it will move faster than the speed of light on the lunar surface!

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