Fahrenheit is a temperature scale named after the German physicist Daniel Gabriel Fahrenheit (1686–1736), who proposed it in 1724. In this scale, the freezing point of water is 32 degrees Fahrenheit (written "32 °F"), and the boiling point is 212 degrees, placing the boiling and freezing points of water exactly 180 degrees apart. On the Celsius scale, the freezing and boiling points of water are exactly 100 degrees apart, thus the unit of this scale, a degree Fahrenheit, is 5/9 of a degree Celsius. Negative 40 degrees Fahrenheit (-40 °F) is equal to negative 40 degrees Celsius (-40 °C).