March 9

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  1815: Electrical engineer and inventor Francis Ronalds describes the first battery-operated clock in the Philosophical Magazine.

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  1851: Physicist and chemist Hans Christian Ørsted dies. Ørsted discovered that electric currents create magnetic fields, which was the first connection found between electricity and magnetism.

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  1923: Theoretical physicist, theoretical chemist, and Nobel laureate Walter Kohn born. Kohn will develop density functional theory, which will make it possible to calculate quantum mechanical electronic structure by equations involving the electronic density.

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  1928: Engineer Gerald Bull born. Bull will attempt to build artillery guns capable of launching satellites into orbit.

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  1943: Computer scientist Jef Raskin born. Raskin will conceive and start the Macintosh project for Apple in the late 1970s.