January 31: Joost Bürgi

Joost Bürgi

February 28, 1552 - January 31, 1632

Joost Bürgi, or Jobst Bürgi, was a Swiss clockmaker, a maker of astronomical instruments and a mathematician. He is widely considered one of the most innovative and most skillful 'mechanics' of his era. It has been suggested that he should also be counted among the leading astronomers of his time because his unprecedented ability to design and construct mechanical models of the movement of heavenly bodies proves an advanced level of insight into celestial mechanics. He worked closely with the astronomer Tycho Brahe at the court of Rudolf II. He also worked with the astronomer and cosmologist Johannes Kepler.

Bürgi became the most innovative clock and scientific instrument maker of his time. Among his major horological inventions were the cross-beat escapement, and the remontoire, two mechanisms which improved the accuracy of mechanical clocks of the time by orders of magnitude. This allowed for the first time clocks to be used as scientific instruments, with enough accuracy to time the passing of stars (and other heavenly bodies) in the crosshairs of telescopes to start accurately charting stellar positions.

Working as an instrument maker for the court of the Margraf Wilhelm in Kassel he played a pivotal role in developing the first astronomical charts. He invented logarithms as a working tool for himself for his astronomical calculations, but as a "craftsman/scholar" rather than a "book scholar" he failed to publish his invention for a long time.

The most significant artifacts designed and built by Burgi surviving in museums are:

• Several mechanized celestial globes (now in Paris, Zuerich (Schweizerisches Landesmuseum), Stuttgart)
  
• Several clocks in Kassel, Dresden (Mathematisch Physikalischer Salon) and Vienna (Kunsthistorisches Museum)
  
• Sextants made for Keppler (at the National Technical Museum in Prag)
  
• The Mond-Anomalien-Uhr (a mechanical model of the irregularities of the motion of the Moon around the Earth)
  

The Lunar crater Byrgius is named in his honor.