Temperature scale devised by Gabriel Fahrenheit in the 1700's. Using this scale, at sea level the boiling point of water is 212 degrees fahrenheit and the freezing point of water is 32 degrees fahrenheit. Seems pretty arbitrary to me, but what do I know?

Other temperature scales include celsius AKA centigrade and kelvin.

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On the Fahrenheit scale, the freezing point of water is 32 degrees and the boiling point is 212 degrees. Zero Fahrenheit was the coldest temperature that the German-born scientist Gabriel Daniel Fahrenheit could create with a mixture of ice and ordinary salt. He invented the mercury thermometer and introduced it and his scale in 1714 in Holland, where he lived most of his life.

Supposedly 100 degrees Fahrenheit is the approximate rectal temperature of a healthy cow, according to Grzcyrgba, but I think that's just serendipity.

Fahrenheit originally wanted the scale to be as 0 the coldest temperature he could get, and 100 degrees as the temperature of a healthy human. His calculations were off, maybe because the temperature in your mouth and ears and armpits and rectum is a few degrees off from your core temperature, and the average temperature of a human is actually at 98.6 degrees.

F approximation
One day the weather person on TV said one can get F from C by "doubling the number and adding 30." This turns out to be an easy and reasonably accurate approximation for temperatures around 10°C, because the 30 offset results in an F approximation within ±1 of actual °F for the range 5-15°C. More generally,
  • 32 for -5 - 5°C
  • 31 for 0-10°C
  • 30 for 5-15°C
  • 29 for 10-20°C
  • 28 for 15-25°C
offsets results in ±1°F approximations.

As you may have guessed, there is a point where Fahrenheit and Celsius coincide: -40°C = -40°F. Mathematically, this can be shown thus: since C = (5/9) * (F - 32), and since F = -40, then:
C = (5/9) * (-40 - 32)
C = (5/9) * (-72)
C = -360/9
C = -40

Since Celsius and Fahrenheit converge at one point, surely Fahrenheit and Kelvin do too? Well, yes. Since K=C + 273.15 (and hence C=K - 273.15), then:
K - 273.15 = (5/9) * (F - 32)
K = F ∴ K - 273.15 = (5/9) * (K - 32)
K = (5K/9) - (32*5)/9 + 273.15
4K/9 = 273.15 - 160/9
4K = 9(273.15) - 160
K = 2458.35/4 - 40
K = 614.5875 - 40
K = 574.5875
Hence, 574.5875K = 574.5875°F

Thanks to rootbeer277 for pointing out my error to me, and to Wntrmute, krimson, AspieDad and jrn for letting me know where I went wrong.

PS: 1Amidala24601Fan has sent me this little bit of trivia regarding the Celsius and Rankine scales (where Rankine is to Fahrenheit as Kelvin is to Celsius, i.e. 0°Ra = 0K = absolute zero):
C = (Ra - 491.67) * (5/9) (the proof, given only what I've already written about, is trivial but messy and will not be shown here)
C = Ra ∴ C = (C - 491.67) * (5/9)
C = (5C/9) - (2458.35)/9
4C/9 = -(2458.35/9)
4C = -2458.35
C = -614.5875

This is, of course, impossible.

Fah"ren*heit (?) a. [G.]

Conforming to the scale used by Gabriel Daniel Fahrenheit in the graduation of his thermometer; of or relating to Fahrenheit's thermometric scale.



The Fahrenheit thermometer or scale.

⇒ The Fahrenheit thermometer is so graduated that the freezing point of water is at 32 degrees above the zero of its scale, and the boiling point at 212 degrees above. It is commonly used in the United States and in England.


© Webster 1913.

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