April 3

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  1693: Carpenter and clockmaker John Harrison born. He will invent a marine chronometer, a long-sought-after device for solving the problem of calculating longitude while at sea.

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  1827: Physicist, musician, and academic Ernst Chladni dies. He has been called both the father of acoustics and the father of meteoritics.

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  1907: Cryptanalyst and mathematician Solomon Kullback born. Krullback will begin his career with the US Army's Signal Intelligence Service (SIS) in the 1930s; when the National Security Agency (NSA) is formed in 1952, Rowlett will become chief of cryptanalysis, overseeing the research and development of computerized cryptanalysis.

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  1995: Mathematician and checkers player Marion Tinsley dies. Tinsley was "to checkers what Leonardo da Vinci was to science, what Michelangelo was to art and what Beethoven was to music."

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  1998: Mathematician and academic Mary Cartwright dies. She did pioneering work in chaos theory.