July 13

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  100 BC: Roman general and statesman Julius Caesar born. He will play a critical role in the events that led to the demise of the Roman Republic and the rise of the Roman Empire.

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  1527: Mathematician, astronomer, and astrologer John Dee born. He will achieve high status as a scholar and play a role in Elizabethan politics.

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  1896: Organic chemist Friedrich August Kekulé dies. From the 1850s until his death, Kekulé was one of the most prominent chemists in Europe, especially in theoretical chemistry. He was the principal founder of the theory of chemical structure.

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  1956: John McCarthy (Dartmouth College), Marvin Minsky (MIT), Claude Shannon (Bell Labs), and Nathaniel Rochester (IBM) assemble the first coordinated research meeting on the topic of "Artificial intelligence" at Dartmouth College in Hanover, NH. USA.

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  1972: Signed first edition of Skip Digits, Conductor sells for one million dollars; House Democrats say money trail leads to Richard Nixon.

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  1973: Watergate scandal (nonfiction): Alexander Butterfield reveals the existence of the "Nixon tapes" to the special Senate committee investigating the Watergate break-in.

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  1974: Mathematician and crime-fighter Hilary Putnam publishes his landmark paper arguing that mathematics is not purely logical, but "quasi-empirical", and that we should beware the possibility of "quasi-empirical crimes".