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Regfries 路 M
Action and reaction are equal and opposite馃
Sharon 路 F
@Regfries The question arises in Relativity. When two things ('A' and 'B') move apart, which of the two is moving depends on your view point. As an example, imagine being in a stationary train carriage. Suddenly you see the platform moving relative to the train - is the train moving or is it the platform (and the rest of the universe)?
smiler2012 路 56-60
@Regfries a bit of a deep question really 馃