Astronomy Gottfried Kirch notices that Chi Cygni's brightness varies. 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 May 24 - Gabriel Fahrenheit, physicist, inventor (+ 1736) Deaths Nicolas Steno: pioneer in early-modern geology