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On This Day

  • 6-22-1389

    Giovanni Dondi died. In 1381 he built one of the earliest geared equatoria driven by clockwork. There is a model of it in the Smithsonian. It has a heptagonal frame with a planet on each face. Dials show the time of sunrise, sunset, moveable feasts, and the nodes of the moon orbit.

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    Giovanni Dondi
    Dondi's Astrarium
  • 6-22-1633

    Galileo recanted Copernicanism. Under the threat of torture, he was forced by the Inquisition to recant.

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    Galileo Galilei
  • 6-22-1837

    Paul Gustav Heinrich Bachmann born. He wrote (1892-1923) a five volume survey of the state of number theory, including an evaluation of the various methods of proof. He also devoted time to composing, playing the piano, and serving as a music critic for various newspapers.

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    Paul Bachmann
    Number Theory
  • 6-22-1925

    Felix Klein died. In 1905 the famous geometer recommended the teaching of calculus in German secondary schools.

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    Felix Klein