November 27, 1701 – Birthdate of Anders Celsius, Swedish astronomer, physicist, and mathematician.
Celsius was a professor of astronomy at Uppsala University from 1730 to 1744, but traveled from 1732 to 1735 visiting notable observatories in Germany, Italy and France. He founded the Uppsala Astronomical Observatory in 1741, and in 1742 proposed the Celsius temperature scale which bears his name.
Celsius was the first to perform and publish careful experiments aiming at the definition of an international temperature scale on scientific grounds. In his Swedish paper “Observations of two persistent degrees on a thermometer” he reports on experiments to check that the freezing point is independent of latitude (and of atmospheric pressure). He determined the dependence of the boiling of water with atmospheric pressure which was accurate even by modern day standards. He further gave a rule for the determination of the boiling point if the barometric pressure deviates from a certain standard pressure. He proposed the Celsius temperature scale in a paper to the Royal Society of Sciences in Uppsala, the oldest Swedish scientific society, founded in 1710. His thermometer was calibrated with a value of 100° for the freezing point of water and 0° for the boiling point. In 1745, a year after Celsius’ death, the scale was reversed by Carl Linnaeus to facilitate more practical measurement. Celsius originally called his scale centigrade derived from the Latin for “hundred steps”. For years it was simply referred to as the Swedish thermometer.
In 1982 PostNord, the Swedish postal service, issued a stamp honoring Anders Celsius.