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Apparent Motion at the Speed of Light

-- | August 29, 2014

Question: If there was a super long empty truck moving half the speed of light and inside it is, lets say a vehicle that also moves half the speed of light, will it go near or at the speed of light on people’s perspective that is outside the truck? — Cyrus

Answer: I believe that the answer to your question is yes, that an external observer would see an apparent speed of the vehicle inside the truck equal to the speed of light. This effect has some similarities to what is called “superluminal motion” in some galaxies which emit jets which are travelling near the speed of light, but appear to be travelling at or above the speed of light.

Jeff Mangum

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