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Anders CelsiusAnders Celsius

developer of a temperature scale

Anders Celsius was born in Uppsala, Sweden, on November 27, 1701, the son of Nils Celsius, an astronomy professor, and the grandson of mathematician Magnus Celsius and astronomer Anders Spole. He attended Uppsala University, and assumed his father's position as professor of astronomy there in 1730.

In 1730, Celsius published Nova Methodus distantiam solis a terra determinandi (New Method for Determining the Distance from the Earth to the Sun). His research for the work involved the study of auroral phenomena, which he conducted with his assistant Olof Hjorter, and he became the first to suggest a connection between the aurora borealis and changes in the magnetic field of the Earth. He observed the variations of a compass needle and found that larger deflections correlated with stronger auroral activity. In 1733, he published a collection of 316 observations of the aurora borealis made by himself and others over the period 1716–1732.

Wanting to build an astronomical observatory in Sweden, Celsius spent the better part of two years (1732-1734) visiting as many European observatories as possible. During this period, he also became part of the debate concerning the shape of the earth, with one side saying that the Earth was a perfect sphere and the other (led by Isaac Newton) saying it was actually more "ovoid-shaped," with the poles being flatter than the equator. In 1736, Celsius participated in an expedition designed to settle the debate once and for all. Organized by the French Academy of Sciences and led by French mathematician Pierre Louis Maupertuis, the aim of the expedition was to measure the length of a degree along a meridian, close to the pole, and compare the result with a similar expedition near the equator. Newton’s theory about the flattening of the earth at the poles was finally confirmed in 1744, after all measurements had been taken and compared.

Returning to Uppsala upon completion of his role in the expedition, Celsius used his new fame to secure funding for an observatory in Uppsala, which opened in 1741, with Celsius as its director. There, he carried out many geographical measurements for the Swedish General map, and was one of the first to note that the land of the Nordic countries is slowly rising above sea level. In astronomy he made observations of eclipses and various astronomical objects, and published catalogs of carefully determined magnitudes for a total of 300 stars using his own photometric system. That system involved the use of identical transparent glass plates and viewing the ray of light from a star through them. He could then compare the magnitudes of the stars by the number of glass plates needed to extinguish the light. For example, Sirius, the brightest star in the sky, needed 25 of his plates to be extinguished.

Celsius is best known today for the temperature scale that bears his name. That scale divided a mercury thermometer at air pressure of 760mm of mercury into 100 degrees, where 100 was designated the freezing point and 0 the boiling point of water. Celsius proposed the scale in 1742, and by 1745 it had been adopted by much of the scientific community, but with 0 as the freezing point and 100 as the boiling point.

Celsius was also a very active supporter for introducing the Gregorian calender in Sweden, but he wasn't successful until 1753, almost ten years after his death.

Celsius published most of his work in the publications of the Royal Society of Sciences in Uppsala, the oldest Swedish scientific society (founded in 1710), of which he was the secretary from 1725 to 1744, and in the publications of the Royal Swedish Academy of Sciences, founded in 1739. He also presided at about twenty dissertations in astronomy where, as was the general rule in those days, he was the main author.

Anders Celsius died of tuberculosis in Uppsala on April 25, 1744. The term "Celsius" as a unit of temperature was adopted in 1948 by an international conference on weights and measures.

Isaac Newton

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This page was last updated on 05/25/2017.