Consider the usual twin paradox: Person A stays on the earth, while person B flies quickly to a distant star and back. B is younger than A when they meet up again. The paradox is that one might argue that although A will see B??s clock moving slowly, B will also see A??s clock moving slowly, so A should be younger than B. There are many resolutions to this ??paradox??. Perform the following one: Let B??s path to the distant star be lined with a wire that periodically zaps B as he flies along (see Figure). Let this be accomplished by having every point in the wire emit a ??zap?? simultaneously in A??s frame. Let tA be the time between zaps in A??s frame. Find the time between zaps in B??s frame, and then use the fact that both A and B agree on the total number of times B getszapped.

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earth star