Temperature by Degrees

On May 24, 1686, self-taught physicist Daniel Gabriel Fahrenheit was born. He was also a self-taught engineer and, having once worked as a glass blower, became an innovative maker of scientific instruments. At the time, although thermometers were available for trade, no two ever gave the same readings because no two “scales” were alike. Typically, a thermometer’s low and high points represented one year’s coldest and hottest days… at the location the instrument was made! All points between the coldest and hottest days were relative to those temperatures.

Fahrenheit invented an alcohol thermometer and produced two instruments that gave the same readings on the 12-point scale he chose. He was dissatisfied with alcohol as a medium for the temperature extremes he wished to measure. These would be points of absolute temperature that would be most widely and commonly experienced by the greatest number of people. The medium he required inside his thermometer would be sensitive but reliable enough to record the same temperature reading at the same point of the thermometer’s scale in any location.

He turned his attention to mercury and studied its properties of expansion and contraction then invented a mercury thermometer. Realizing he needed fixed and reliable points to deliver a serviceable scale for reading temperature, Fahrenheit chose water as the best and most global candidate for measurement and set about determining its freezing point and its boiling point. For the third calibration point on his scale, Fahrenheit chose the human body temperature normally taken in the mouth or under the arm. With few modifications, Fahrenheit’s temperature scale was used globally for well over 200 years.

Although the Celsius scale eventually became a global standard, fahrenheit is still the commonly used temperature scale in the United States of America.

B Bondar / Real World Content Advantage