CELESTIAL MECHANICS is the grand old lady of science—reliable, precise, unfaltering. Ever since Newton drafted his laws of gravity and mechanics, scientists have used them to predict conjunctions and eclipses, to discover new planets on the basis of tiny gravitational disturbances, and to send spacecraft to the ends of the Solar System. It's all so predictable that we know where the planets and their moons will be thousands of years from now.
But two tiny satellites of Saturn seem intent on being the naughty children in the class. Between 1981 and 1995, these two moons changed speed, apparently defying the laws of gravity. Last summer, they misbehaved again, and no one knows why. Could this mean there's something about celestial mechanics that we're missing?
The two satellites were discovered on photographs snapped by NASA's Voyager 1 spacecraft when it flew past Saturn more than 20 years ago. Called Prometheus and ...
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