The accurate measurement of temperature is vital across a broad spectrum of human activities, including industrial processes (e.g. making steel), manufacturing; monitoring (in food transport and storage), and in health and safety. In fact, in almost every sector, temperature is one of the key parameters to be measured.

Thermoscopes, the ancestors of modern thermometers, have been around since about 200 BC. The first recognizable, modern thermometers were made in the 16th century by both the Italian Galileo Galilei and Santorio Santorio, a physician to the King of Poland.

The two temperature scales commonly in use today date from the eighteenth century and are named after Gabriel Daniel Fahrenheit and the Swedish astronomy professor Anders Celsius.
Fahrenheit ____ Anders Celsius
Fahrenheit designed his scale to have two reference points that could be set up in his workshop. He originally chose the melting point of pure ice and the temperature of a normal human body, which he took as being 32 and 96 respectively.

Celsius also used the ice and steam points, but took them to be 0 C and 100 C respectively.

Lord Kelvin

A third, fundamental, temperature scale was proposed in 1854 by the Scottish physicist William Thomson, Lord Kelvin. It is based on the idea of the absolute zero, the point of no discernible energy, which is independent of any particular material substance.

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