Fahrenheit
Fahrenheit is a temperature scale named after the german physicist Gabriel Fahrenheit, 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 melting points of water 180 degrees apart. Thus the unit of this scale, a degree Fahrenheit, is 5/9ths of a kelvin (or of a degree Celsius), and -40 degrees Fahrenheit is equal to -40 degrees Celsius.
The name was also borrowed in computer science for a software standard: see Fahrenheit graphics API.
Fahrenheit established the zero of his scale (0°F) as the temperature at which an equal mixture of ice and salt melts (some say he took that fixed mixture of ice and salt that produced the lowest temperature); and ninety-six degrees as the temperature of blood (he initially used horse's blood to calibrate his scale). Initially, his scale had only contained 12 equal subdivisions, but then later he subdivided each division into 8 equal degrees ending up with 96. He then observed that plain water would freeze at 32 degrees and boil at 212 degrees.
His measurements were not entirely accurate, though; by his original scale, the actual freezing and boiling points would have been noticeably different from 32°F and 212°F. Some time after his death, it was decided to recalibrate the scale with 32°F and 212°F being the actual freezing and boiling points of plain water. This resulted in the healthy human body temperature being 98.6°F degrees rather than 96°F.
The Fahrenheit scale was widely used in Europe and in many English-speaking countries until the Celsius (formerly centigrade) scale was adopted in the late 1960s and 1970s. In the United States and Jamaica, Fahrenheit continues to be used by the general population for everyday, non-scientific temperature measurement. Conversion between the two scales is given by the formula °C = (5/9)(°F-32), where °C and °F are the Celsius and Fahrenheit temperatures, respectively.
History
| Conversion from | to | Formula |
|---|---|---|
| Fahrenheit | Celsius | °C = (°F - 32) / 1.8 |
| Celsius | Fahrenheit | °F = °C × 1.8 + 32 |
| Fahrenheit | kelvin | K = (°F + 459.67) / 1.8 |
| kelvin | Fahrenheit | °F = K × 1.8 - 459.67 |
| Fahrenheit | Rankine | °Ra = °F + 459.67 |
| Rankine | Fahrenheit | °F = °Ra - 459.67 |
| Fahrenheit | Réaumur | °Ré = (°F - 32) / 2.25 |
| Réaumur | Fahrenheit | °F = °Ré × 2.25 + 32 |
Other temperature scales include the Newton (~1700), Rømer (1701), Réaumur (1731), Delisle (1738), Celsius (1742), Rankine (1859), kelvin (1862) and Leyden (ca. 1894?). (Note that "kelvin" is lower-cased because it is an SI unit, even though it is named after a person).
Other scales
External links