Fahrenheit invented the first truly accurate thermometer using mercury instead of alcohol and water mixtures. In the laboratory, he used his invention to develop the first temperature scale precise enough to become a worldwide standard.

The eldest of five children born to a wealthy merchant, Fahrenheit was in Danzig (Gdansk), Poland. When he was fifteen his parents died suddenly, and he was sent to Amsterdam to study business. Instead of pursuing this trade, Fahrenheit became interested in the growing field of scientific instruments and their construction. Sometime around 1707 he began to wander the European countryside, visiting instrument makers in Germany, Denmark, and elsewhere, learning their skills. He began constructing his own thermometers in 1714, and it was in these that he used mercury for the first time.

Previous thermometers, such as those constructed by Galileo and Guillaume Amontons, used combinations of alcohol and water; as the temperature rose, the...