On Nov. 27, 1701, Anders Celsius was born in Uppsala, Sweden; the astronomer proposed the Celsius temperature scale, which has become, after a flop and some tweeks, the standard measurement for temperature in almost every nation of the world.

The United States (and for some reason, Belize) clings to the Fahrenheit temperature scale in all but scientific uses.

Celsius was the son of an astronomy professor; one of his grandfathers was mathematician Magnus Celsius, who was more famous for his work in translating the “staveless” runic alphabet that were used in the 2nd through the 8th centuries by Germanic tribes in Scandinavia; his other grandfather was an astronomer. Anders Celsius followed in the family business of scholarship and teaching.

In his early career, Celsius focused on astronomy and measurement. His first major paper, in 1730, was on determining the distance from the Sun to Earth; and later he became interested in accurately determining the distance of meridians of latitude. His work, published in 1738, confirmed Isaac Newton’s theory that the earth is flattened at the poles.

He became well known in scientific circles and persuaded the Swedish government to fund the new Uppsala Astronomical Observatory in 1741, under his supervision. With his interest in measurement and measuring devices, Celsius began documenting the magnitude (brightness) of stars using colored plates to create a photometric standard; he measured and catalogued more than 300 stars.

He turned his attention to temperature, performing experiments to determine a temperature scale that could be used for scientific purposes, and was particularly interested in the effect of atmospheric pressure on the freezing and boiling points of water; his experiments yielded a rule on how much effect atmospheric pressure had on the temperature at which water boiling. He presented his scale and thermometer to the Royal Society of Uppsala, Sweden’s oldest, with the boiling point set at 0 degrees and freezing point set at 100 degrees. He called his scale “centigrade,” from Latin, “centum,” a hundred, and “gradus,” step.

About a year after Celsius died, on April 25, 1744, the acclaimed Swedish scientist Carl Linnaeus flipped the scale on the thermometer, 0 degrees centigrade for freezing, 100 degrees centigrade for boiling.

Until 1948, the temperature scale was in degrees centigrade, but the term was ambiguous. The 1948 general conference of the International Bureau of Weights and Measures defined the international unit of temperature to be degree Celsius. A degree Celsius is equal to one degree Kelvin, and the temperature scale is based on absolute zero, (zero degrees Kelvin, -273.15 degrees Celsius), and the triple point of water, where the three phases of water, liquid, gas and solid, coexist in balance (precisely 273.16 degrees Kelvin and 0.01 degrees Celsius, with the water specified as Vienna Standard Mean Ocean Water (VSMOW). VSMOW is not saltwater; it is purified water with specific isotopes as defined by the International Atomic Energy Agency in 1968).

In 1724, the Dutch-German inventor of the mercury thermometer, Daniel Gabriel Fahrenheit, devised the temperature scale commonly used in the United States. Fahrenheit used several common points to fix his scale: the freezing point of brined water (zero degrees), the melting point of water (32 degrees), human body temperature (98 degrees), and the boiling point of water (212 degrees).

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