Fahrenheit

Daniel Gabriel Fahrenheit was born in Danzig (now Gdańsk, Poland) in 1686 and worked most of his life in the Dutch Republic and the Holy Roman Empire. He was an instrument maker — a manufacturer of thermometers, barometers, and hydrometers. In 1724, he published his temperature scale, which set three reference points: zero was the temperature of a brine solution (the coldest he could reliably produce), 32 was the freezing point of water, and 96 was the approximate temperature of the human body.

The scale was practical, not elegant. Fahrenheit chose his reference points based on what he could reproduce in a laboratory, not on mathematical simplicity. The numbers 32 and 212 (the boiling point of water, determined later) are not round, not intuitive, and not based on natural constants. But the scale worked. Fahrenheit's thermometers were the most accurate in Europe, and his scale became the standard in English-speaking countries.

The Celsius scale, proposed by Anders Celsius in 1742, offered simpler reference points: zero for the freezing point of water, 100 for the boiling point. Most of the world adopted Celsius (along with the broader metric system) during the nineteenth and twentieth centuries. The United States did not. American weather reports, cooking temperatures, and body temperature readings remain in Fahrenheit.

The United States, along with a handful of other territories, is the last significant holdout. Fahrenheit feels natural to Americans: 72°F is a comfortable room, 98.6°F is a healthy body, 32°F is freezing, and 100°F is dangerously hot. These numbers are intuitive to 330 million people and confusing to the other seven billion. A German instrument maker's laboratory calibration became the temperature language of one country.