Physicist and instrument maker Daniel Gabriel Fahrenheit dies. He will live on, to a degree.
Galileo (see here) had created a water-based thermoscope as early as 1593, and Santorio Santorio introduced a numerically graduated model in Florence in the mid-seventeenth century. The Florentine instruments used the expansion of an alcohol solution to register changes in temperature. But no two instruments were exactly alike. They were usually marked only with the high and low temps for Florence in the year they were made.
You could compare the temperature in the same place from day to day, or even year to year, but not place to place. Isaac Newton (see here) had considered standardizing thermometers by marking universal points that didn’t vary. But Newton had other things on his mind that he didn’t want to drop, and he never followed up.
Fahrenheit wanted to standardize the thermometer. In 1714, he produced two thermometers that gave identical readings, a major accomplishment. Next, he substituted mercury for alcohol as the measuring medium, and he introduced the cylindrical shape, replacing a spherical bulb.
He developed the scale that bears his name and that’s still used in the metric-averse United States. Folklorically, the coldest day of that winter was 0 degrees, and 32 degrees was the freezing point of water, which resulted in 212 degrees for the boiling point of water at sea level. In fact, 0 degrees was the coldest he could make a concentrated solution of ice, water, and salt, and 96 degrees was supposed to be human body temperature. He was low, but striving for mathematical convenience: 96 = 3 × 32.
Fahrenheit also invented a hygrometer for measuring the moisture content of air. Remember that the next time you say “It’s not the heat, it’s the humidity.”—RA