1686 in science
# 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)
