title: 1686 in science
text: # 1686 in science
  
  The year 1686 in science and technology involved some significant events.
  
  ## Astronomy
  
  * Gottfried Kirch notices that Chi Cygni's brightness varies.
  
  ## Biology
  
  * John Ray begins publication of his Historia Plantarum, including the first biological definition of the term species; also his edition of Francis Willughby's Historia Piscum.
  
  ## Geology
  
  * Edmund Halley establishes the relationship between barometric pressure and height above sea level.
  
  ## Meteorology
  
  * Edmund Halley presents a systematic study of the trade winds and monsoons and identifies solar heating as the cause of atmospheric motions.
  
  ## Physics
  
  * Isaac Newton uses a fixed length pendulum with weights of varying composition to test the weak equivalence principle to 1 part in 1000.
  
  ## Births
  
  * February 10 – Jan Frederik Gronovius, Dutch botanist (died 1762)
  * May 24 – Gabriel Fahrenheit, physicist and inventor (died 1736)
  * July 6 – Antoine de Jussieu, French naturalist (died 1758)
  * October (possible date) – John Machin, English mathematician (died 1751)
  
  ## Deaths
  
  * May 11 – Otto von Guericke, German physicist (born 1602)
  * November 25 (NS December 5) – Nicolas Steno, Danish pioneer geologist (born 1638)
  