| MadSci Network: Science History |
Dear Michele:
This question is interesting. The Fahrenheit scale is not based on the
boiling and freezing points of water. Rather, it is based on the
temperature of an ice/salt mixture and human body temperature. In 1714,
the German-Dutch instrument maker, Gabriel Daniel Fahrenheit (that's where
we get the name from) invented a thermometer which used mercury in a
sealed glass tube.
Using that new (at the time), more accurate thermometer, he came up with
the system by starting with the coldest thing he knew, a mixture of ice
and salt, which he marked off as zero. He then measured his body
temperature. Originally intending that to be 12 degrees Fahrenheit, he
realized that they were too wide, so he multiplied everything by eight and
body temperature was now 96 degrees. The current value is 98.6, because
Fahrenheit's thermometer wasn't really accurate, though it was very good
for his time.
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Admin note: The temperature of a saturated salt and ice bath is about -5.2
degrees Fahrenheit instead of 0.0 degrees, as well.
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Therefore, the boiling and freezing temperatures of water come out to be
32 and 212 on the Fahrenheit scale. The Celsius scale, which is part of the
metric system used by scientists nowadays was developed in 1724 and has 0
degrees for the freezing point of water and 100 degrees for its boiling
point, very much unlike the Fahrenheit scale.
Some great sites to visit are:
About
Temperature
Fahrenhei
t and Celsius
Hope this helps!
Thiam Hock
Try the links in the MadSci Library for more information on Science History.