– April 25
) was a Swedish astronomer
. He was professor of astronomy at Uppsala University
from 1730 to 1744, but traveled from 1732 to 1735 visiting notable observatories in Germany
. He founded the Uppsala Astronomical Observatory
in 1741, and in 1742 he proposed the Celsius temperature
scale which takes his name. The scale was later reversed in 1745 by Carl Linneaus
, one year after his death.
Anders Celsius was born in Uppsala, Sweden, on November 27, 1701. Born the son of an astronomy professor Nils Celsius and the grandson of a mathematician Magnus Celsius
and an astronomer, Anders Spole, Celsius chose a career in science. His family originated from Ovanåker
in the province of Hälsingland
. The family name is a Latinised version of the name of the vicarage (Högen). His father, Nils Celsius, was also a talented mathematician from an early age, and he had been appointed professor of astronomy in 1730. In 1725 he became a secretary of the Royal Swedish Academy of Sciences
in Uppsala, which he served until his death.
Anders Celsius studied at the University of Uppsala, where his father was a teacher, and in 1730 he, too, became a professor there. His earliest research involved the study of the aurora borealis, and he was the first to suggest a connection between these lights and changes in the magnetic field of the Earth. Together with his student Olof Hjorter he studied auroral phenomena. He observed the variations of a compass needle and found that larger deflections correlated with stronger auroral activity. In 1730 he published the Nova Methodus distantiam solis a terra determinandi.
in 1733 he published a collection of 316 observations of the aurora borealis made by himself and others over the period 1716–1732. Celsius traveled for several years in the early 1730s, particularly during 1732 and he travelled to Germany
in which he visited most of the major European observatories. In Paris
he advocated the measurement of an arc of the meridian in Lapland
, In 1736, he participated in the expedition organized for that purpose by the French Academy of Sciences
, led by the French
mathematician Pierre Louis Maupertuis
(1698–1759) to measure a degree of longitude
. 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 to Peru
, today in Ecuador
near the equator
. The expeditions confirmed Isaac Newton
's belief that the shape of the earth is an ellipsoid
flattened at the poles.
In 1738, he published the De observationibus pro figura telluris determinanda
. Celsius' participation in the Lapland expedition won him much respect in Sweden with the government and his peers, and played a key role in generating interest from the Swedish authorities in donating the resources required to contruct a new modern observatory in Uppsala. He was successful in the request, and Celsius founded the Uppsala Astronomical Observatory
in 1741. The observatory was equipped with instruments purchased during his long voyage abroad, comprising the most modern instrumental technology of the period.
In astronomy, Celsius began a series of observations using colored glass plates to record the magnitude (size) of certain stars. This was the first attempt to measure the intensity of starlight with a tool other than the human eye. He made observations of eclipses and various astronomical objects and published catalogues of carefully determined magnitudes for some 300 stars using his own photometric system (mean error=0.4 mag).
Anders 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 Swedish Academy of Sciences, the oldest Swedish scientific society, founded in 1710. His thermometer had 100 for the freezing point of water and 0 for the boiling point. The scale was later reversed by Carolus Linnaeus in 1745, a year after his death to how it is today. Celsius originally called his scale centigrade derived from the Latin for "hundred steps". For years it was simply referred to as the Swedish thermometer.
Celsius conducted many geographical measurements for the Swedish General map, and was one of earliest to note that much of Scandinavia is slowly rising above sea level, a continuous process which has been occurring since the melting of the ice from the latest ice age. However he wrongly posed the notion that the water was evaporating.
Legacy and death
Celsius wrote about 20 dissertations on astronomy, as well as a well-received book entitled, "Arithmetics for the Swedish Youth," published in 1741. But for all of his accomplishments in his life's work of astronomy, the name Celsius is forever tied to an instrument used every day throughout most of the world. Celsius was a very active supporter of the introduction of the Gregorian calendar
to Sweden. Gregorian calendar reform had earlier been attempted in 1700, but it had been planned to introduce the modifications of the date stepwise by dropping the leap days from 1700 to 1740. When 1704 and 1708 had been revealed to be leap years by error, in 1712 Sweden returned to using the Julian calendar
. The Gregorian calendar wasn't successful until 1753, almost ten years after his death, when the Julian calendar was abandoned by dropping supernumerary 11 days. Celsius was also known to be a writer of poetry
and popular science, and his popular book Arithmetics for the Swedish Youth
published in 1741 was typical of the Enlightenment vibe of the period.
On April 25 1744 he died of tuberculosis in Uppsala, and was buried in the Old Uppsala Church next to his grandfather.
The Celsius crater on the Moon is named after him.