At the time I am writing this my thermometer shows 98 degrees Fahrenheit. I do not have to venture outside to know this is code red hot by any human standard. So in my search for hidden value in this instrument I thought I struck out. Its value was quite obvious and immediate. But then I began to wonder how this simple Dollar Store device could so accurately predict how my body would react to the temperature. It knows that anything in the upper 60's and 70's is comfortable but extremes above or below that range are uncomfortable to most humans. I also recall having to replace my old refrigerator when the Appliance Service Representative told me it could not maintain a temperature of 32 degrees or less. Seems bacteria and other nasty stuff cannot tolerate temperature ranges below 32 degrees. I can empathize with them.
But none of this knowledge got me to the value I suspected was hidden in this simple device. I did know that German instrument maker Gabriel Fahrenheit made the first reliable alcohol thermometers in 1714. That is why this temperature scale he created is named after him. So I surfed the Web further and learned that the human reaction to hot and cold ranges on the Fahrenheit scale is not coincidental.
The Danish astronomer Rømer (1644–1710) is assumed to be the first to build reproducible
thermometers. In 1702 he proposed using two fixed points. The lower
fixed
point, corresponding to the temperature of an artificial mixture of
salt,
water, and ice, was assigned the value 0 °, while the steam point was
the upper
fixed point and marked as 60 °. The resulting scale was divided into
equal
increments of volume, numbered from 8 to 59. The Rømer scale placed the melting point of ice at
7.5 °(changed later to 8 °). Because Rømer seldom used the upper part of
the
scale for his meteorological observations, he changed its upper
reference
temperature to that of blood heat, labeling it 22.5 ° Rømer’s scale is important because it became the basis
of the
one proposed by Fahrenheit.
Gabriel Daniel Fahrenheit was born in Danzig but lived most of his life in Holland. In 1708 he visited Rømer and borrowed from him the idea of calibrating thermometers using the melting point of ice and the heat of blood [body temperature] as fixed points. The original thermometers of Fahrenheit used alcohol as the thermometric fluid, but later he switched to mercury. At the beginning Fahrenheit used the scale of Rømer, except that he added four more divisions to each degree. Later on, he decided that the values of the fixed points in the Rømer scale were inconvenient and awkward, and he multiplied them by four to give 30 ° for the normal ice point and 90 ° for body temperature. Later, he decided that 96 ° would be a more suitable body temperature because it would be divisible by 12 (and by 32). Soon afterwards, Fahrenheit developed a thermometer to measure boiling points at atmospheric pressure and found the boiling point of water to be 212 °. He, therefore, modified his scale to include the boiling point of water as the upper fixed point at 212 °. In order to give a more rational 180 ° interval between the two fixed points, he made the ice point 32 ° at 1 atm pressure. Body temperature is around 98.4 ° on this final version of the Fahrenheit scale. In 1724 he constructed thermometers in which he had fixed 32 °F as the freezing point of water and 96 °F as normal body temperature. In this way he used a much finer scale than Rømer’s original. It is interesting to note that, although the boiling point of water is 212 °F, it was not originally taken as a fundamental reference point, but it was widely adopted as such by about 1740.
In the world of the 18th century, the focus of science and industry was not concerned with human comfort but with industrial processes. For many of these evolving processes, the ability to measure temperature accurately and consistently was crucial. Although the alcohol thermometers developed by Fahrenheit could determine when water was about to freeze, they exploded when he tried to determine when water would boil. And the value of knowing exactly when water boils or alcohol evaporates was not lost on the steam engine developers and brew masters of that day. Nor is the reason my blood seems to boil when the temp touches the 100 °F So anymore when my back yard thermometer tells me its code red outside I can toast Herr Fahrenheit with a cold glass of beer. And when the thermometer says it is code blue outside, I can toast him with a steaming hot cup of joe... ez does it!
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