Fahrenheit is the temperature scale
proposed in 1724 by German physicist Daniel Gabriel Fahrenheit
(1686–1736). In 1717, Fahrenheit became a glassblower, making
barometers, altimeters, and thermometers. After 1718 he was a
lecturer in chemistry. At that time, temperature scales were not
standardized and everybody made up their own scale. He originally
copied another thermometer, but adjusted his scale so that the
melting point of ice would be 32 degrees, body temperature 96
degrees, and water boil at about 212 degrees. 180 degrees made for
even spacing of his scale.
Other scientists later refined it to make the freezing point of
water exactly 32 °F, and the boiling point exactly 212 °F. That is
how normal human oral body temperature became 98.6°.
The Fahrenheit scale was replaced by the Celsius scale in most
countries during the 1960s and 1970s when converting to metrics.
Fahrenheit remains the official scale of the United States, Cayman
Islands, Belize (by Guatemala), Puerto Rico, Guam, and the U.S.
Virgin Islands. Scientists use Celsius in all countries.
The Fahrenheit and Celsius scales intersect at −40° (−40 °F and −40
°C represent the same temperature).