Anders Celsius was a Swedish astronomer, physicist, and mathematician. He was born on November 27, 1701, and died on April 25, 1744. From 1730 to 1744, he was a professor of astronomy at Uppsala University. Between 1732 and 1735, he visited important observatories in Germany, Italy, and France. In 1741, he founded the Uppsala Astronomical Observatory. In 1742, he proposed a reversed version of the centigrade temperature scale. This scale was later renamed the Celsius scale in his honor.

Early life and education

Anders Celsius was born in Uppsala, Sweden, on 27 November 1701. His family came from Ovanåker in the province of Hälsingland. Their family estate was located at Doma, also called Höjen or Högen (known locally as Högen 2). The name Celsius comes from the Latin word for the estate's name, which means "mound."

As the son of Nils Celsius, an astronomy professor, Anders was related to several scientists. His uncle was Olof Celsius, a botanist, and his grandfather was Magnus Celsius, a mathematician, and Anders Spole, an astronomer. Anders chose to work in science, showing talent in mathematics from a young age. He studied at Uppsala University, where his father taught, and in 1730, he became a professor of astronomy there. Johan Celsius, a well-known Swedish poet and actor, was also his uncle.

Career

In 1730, Celsius published a scientific paper titled New Method for Determining the Distance from the Earth to the Sun. His research also included studying auroras, which he explored with his assistant, Olof Hiorter. He was the first to suggest a link between the aurora borealis and changes in Earth's magnetic field. By observing how a compass needle moved, he found that stronger auroras caused larger deflections. In 1733, he published a collection of 316 aurora borealis observations made between 1716 and 1732.

Celsius traveled widely in the early 1730s, visiting Germany, Italy, and France to study major European observatories. In Paris, he promoted measuring a section of Earth's meridian in Lapland. In 1736, he joined a French expedition led by Pierre Louis Maupertuis to measure the length of a degree of latitude near the North Pole. This mission aimed to compare measurements from Lapland with those from Peru (now in Ecuador) near the equator. The results supported Isaac Newton’s idea that Earth is an ellipsoid, flattened at the poles.

In 1738, Celsius published Observations on Determining the Shape of the Earth. His work on the Lapland expedition earned him respect in Sweden and helped secure funding for a new observatory in Uppsala. He founded the Uppsala Astronomical Observatory in 1741, using instruments he acquired during his travels.

Celsius observed eclipses and cataloged the brightness of about 300 stars using his own system (with an average error of 0.4 magnitudes). In 1742, he introduced the Celsius temperature scale in a paper to the Royal Society of Sciences in Uppsala. His original scale set 0 as the boiling point of water and 100 as the freezing point. After his death in 1744, Carl Linnaeus reversed the scale for practical use.

Celsius conducted geographical surveys for Sweden’s national map and noted that much of Scandinavia is slowly rising above sea level, a process that began after the last ice age. However, he incorrectly believed the rising was caused by water evaporation.

In 1725, Celsius became secretary of the Royal Society of Sciences in Uppsala, a role he held until his death from tuberculosis in 1744. He helped establish the Royal Swedish Academy of Sciences in Stockholm in 1739 and was elected as one of its first members. Celsius proposed the academy’s name.

Works

• "A new way of fishing in the rivers of the Norlandians" (in Latin). Uppsala: Johan Höjer, widow. 1738.
• "Observations about two stable degrees on a thermometer." Proceedings of the Royal Swedish Academy of Sciences (in Swedish). 3: 171–180. 1742.