Anders Celsius (November 27, 1701 - April 25, 1744)

Swedish astronomer and physicist, known for the invention of the Celsius scale for thermometers.

Anders Celsius was born in Uppsala where his father and grandfathers before him worked as professors. The family name is a latinized version of the name of the vicarage they originated from; Högen (= "The Mound") in the province of Hälsingland.

With so many professors already in the family, perhaps it was not too surprising that Celsius too was very talented in mathematics from an early age, learning university level mathematics at the age of 12. Nonetheless, his family first tried to persuade him to study law, as it would be a more certain income than mathematics. He soon abandoned the law studies, however, and in 1730 he was appointed professor of astronomy at Uppsala university. From 1732 to 1735 he travelled in Europe and visited the leading observatories in Germany, Italy, and France.

At Nuremberg he published in 1733 a study of the aurora borealis with more than 300 observations made by himself and others. In Paris he became involved in an expedition that the French Academy of Sciences intended to launch, to measure and compare the length of a degree along a meridian near the equator to one measured near the pole. The expedition to Torneå in the northernmost parts of Sweden was launched in 1736, led by the French astronomer Maupertuis. They worked throughout the autumn and winter with triangulation measurements along the Torneå river, plagued at first by the innumerable mosquitos and then by the severe cold (countered mainly by vodka), but they managed to get results confirming Newton's beliefs that the shape of the earth was ellipsoid, flattened at the poles.

The expedition made him famous, which in turn made it easier for him to raise funds for a new observatory in Uppsala, which was finished in 1741.

Astronomy back in those days could incorporate a bit of everything, and Celsius did research on topics ranging from geographical measurements for the Swedish General map, to measuring the magnetic distortions caused by the aurora borealis. He was among the first to take an interest in the land rise in the nordic countries, due to the land slowly recovering from the last ice age, although he thought it was the water evaporating. Had he but lived a little longer he would have seen another of his pet peeves sorted out; the introduction of the Gregorian calendar in Sweden, which was finally done by dropping 11 days in 1753.

He created the thermometer scale that he's famous for after careful studies of the freezing and boiling points of water to see that they are not dependent on e.g. geographical location. The effect of atmospheric pressure was also accounted for, and he even found a rule for determining how the boiling point of water varies if the barometric pressure changes.

In his astronomical studies, he studied the magnitude of stars by viewing the light from the star through identical slates of glass, and measuring how many slates were needed to extinguish the light. The star Sirius, for example, needed 25 plates. He published catalogues of more than 300 stars measured this way. He studied eclipses and managed to measure the difference in longitude between towns with the eclipses of the moons of Jupiter.

Anders Celsius died in 1744 of tuberculosis, and was buried in the church at Gamla Uppsala (= Old Uppsala) next to his grandfather Magnus Celsius.

Sources, ideas, references: - Svenskt biografiskt handlexikon (1906) Author: Herman Hofberg, Frithiof Heurlin, Viktor Millqvist, Olof Rubenson, from Project Runeberg.

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