What is the Fahrenheit system based on?

Answer 1

Fahrenheit is a temperature scale named after Daniel Gabriel Fahrenheit (1686-1736), the German physicist who proposed it in 1724.

He used three reference points. The first, 0 degrees, was the lowest temperature he could obtain using a mixture of ice, water, and salt. The second was that temperature at which snow began to melt. His third point was the normal body temperature of a person, which he placed slightly incorrect at 96 degrees. He was not concerned with the boiling point as he was interested in atmospheric science, and air temperature is never that high. When his scale was adjusted so that the boiling point of water was 212 degrees, the body temperature fell to 98.6.

Answer 2

Fahrenheit set zero as the lowest temperature he could achieve using a saltwater "slurpy". His second reference point, 32 degrees, was the temperature at which ice began to form on still water and the third, 96 degrees, was the human body temperature. Later scientists observed the difference between freezing and boiling was approximately 180 degree and made a slight adjustment to make it exactly that difference. This adjustment is the reason body temperature is no longer Fahrenheit's 96 degrees.

Answer 3

Zero is the freezing point of the saltiest water available and 100 is the internal temperature of a human being. (Note that both are no longer valid and so are arbitrary now, with 32 the melting point of "pure water", 212 the boiling point (at sea level), and 98.6 as human body temp.)