Anders Celsius

Swedish astronomer

• Born: November 27, 1701; Uppsala, Sweden
• Died: April 25, 1744; Uppsala, Sweden

Anders Celsius was an eighteenth-century Swedish astronomer who made significant observations about the North Pole. He is best remembered for inventing the temperature scale that bears his name.

Primary field: Astronomy

Specialties: Observational astronomy; geodesy; meteorology

Early Life

Anders Celsius was born on November 27, 1701, in Uppsala, Sweden. His family came from the province of Hälsingland. Celsius’s father, Nils Celsius, and his mother’s father, Anders Spole, were both astronomers. His father’s father, Magnus Celsius, was a mathematician. Both his grandfathers and his father taught at Uppsala University, one of the oldest universities in Europe. Celsius, who excelled at mathematics in school, studied at Uppsala, where he became the assistant of astronomer Eric Burman. Celsius earned a master’s degree in philosophy in 1728 and started teaching mathematics at the university the following year. In 1730, after Burman retired, Celsius followed the career paths of his father and grandfather, becoming a professor of astronomy. That same year, he published A Dissertation on a New Method of Determining the Distance of the Sun from the Earth.

In 1732, Celsius began his grand tour of European universities and observatories, as was the custom for academics at the time. He travelled for four years, collaborating with other astronomers in France, Italy, and Germany. During his visit to Nuremberg, Bavaria, in 1733, he published observations of the aurora borealis, also known as the northern lights. The observations he compiled had been made by himself and others between 1716 and 1732.

Celsius was a strong advocate for an expedition to measure the arc of the meridian in Lapland, an area located in the northernmost part of Sweden. The goal of the expedition was to prove Newton’s theory that the Earth is flatter at the poles and thus not a perfect sphere. Celsius was part of the expedition to Lapland in 1736, led by French astronomer Pierre-Louis Maupertuis. The expedition helped prove that the arc of a degree of longitude above the arctic circle is longer than it would be farther south. Celsius’s experiences in the harsh climate of Lapland gave him the idea for his temperature scale.

Life’s Work

In Celsius’s time, astronomy professors were also responsible for the geographical and meteorological sciences. It is for this reason that Celsius joined the Lapland expedition and studied the aurora borealis. His publication of 1733 contained 316 observations about the aurora borealis, both from his own research and from other scientists. The compilation was a definitive work for its time. Celsius was the first astronomer to theorize that the lights were connected to fluctuations in the magnetic field of the Earth, when he observed the odd behavior of his compass needle during the lights’ appearance. In the twentieth century, scientists determined that the lights occur when highly charged electrons from solar wind interact with elements from the Earth’s atmosphere. Celsius published his observations with the help of his assistant Olof Petrus Hjorter, who was five years older than Celsius and took over for him when he went on his grand tour in 1732.

After Celsius returned from the expedition to Lapland in 1737, he remained a vocal advocate of the expedition’s findings: measurements that provided strong evidence in favor of Newton’s theory that the Earth is flatter at the poles. The expedition leader, Maupertuis, had many enemies who attacked both the accuracy of his measurements and his personal life, accusing the Frenchman of immorality and taking a mistress. Celsius was one of the few members of the expedition to defend its leader. In his 1738 publication Disquisition on Observations Made in France for Determining the Shape of the Earth, he argued against the views of Jacques Cassini, a French astronomer who disagreed with the Newtonian theory and thus the Lapland expedition’s measurements. When the Newtonian theory was finally accepted by scientists in 1740, Celsius took his share of the credit. With his fame spreading, Celsius used his influence to convince the Swedish government to donate money to build a state-of-the-art observatory at Uppsala University. The structure, named the Celsius Observatory, was completed in 1741 and was used by the school until 1857. The building it was housed in is still preserved at the university.

During his travels, Celsius managed to obtain the latest, most advanced astronomical equipment available at the time, including the first use of glass plates to measure the brightness of stars. Celsius used the plates to collect accurate data on the relative magnitude of stars, which indicates their size. He personally observed three hundred stars with his new instruments, and his findings were published with the Royal Society of Sciences in Uppsala.

Celsius is mainly known for the temperature scale that bears his name. Before his system became official, there was no universally accepted scale for measuring temperatures. Thermometers were generally used to record weather. They measured about as high as 40 degrees Celsius (104 degrees Fahrenheit) and as low as -20 degrees Celsius (-4 degrees Fahrenheit). Different manufacturers used different scales to mark the varying temperatures. The scales ranged from temperatures based on weather, to the human body, to the boiling point of water. Celsius used the boiling and freezing points of water as well, but he was the first to prove that the two points were the same no matter where the observer stood. Latitude does not affect the boiling point of water, as long as the atmospheric pressure is about 1 atmosphere (atm), or the pressure at sea level. For heights far above sea level, which have a lower atmospheric pressure, Celsius found that the boiling point of water is lower. For example, the boiling point of water at 10,000 feet elevation is 90 degrees Celsius instead of 100.

Through observations performed on his travels and in his laboratory, Celsius discovered that the boiling and freezing points of water could be universally fixed for all locations. He also reasoned that these points could be used by scientists as a baseline for all temperature readings. Celsius called his scale centigrade, which is Latin for “one hundred steps.” He presented his findings in 1742 before the Royal Swedish Society of Sciences in Uppsala.

During his life, Celsius made additional scientific contributions, including an observation that the Scandinavian Peninsula is gradually rising above sea level. He also published a popular schoolbook for children, Arithmetics for the Swedish Youth (1741). Celsius died of tuberculosis on April 25, 1744, and was buried next to his grandfather Magnus Celsius.

Impact

Although best known for his namesake temperature scale, Celsius was part of the larger movement known as the European Enlightenment. After the influence of seventeenth-century philosophers such as Francis Bacon and John Locke, scientists were beginning to explore beyond the beliefs of the Middle Ages. Prior to the seventeenth century, many philosophers considered science perfected by the ancient Greeks. In most branches of science, any new published works were credited to an ancient Greek philosopher, with Plato and Aristotle considered the most important.

Celsius and his contemporaries of the Enlightenment believed that they were making new and valuable contributions to knowledge independent of the ancients. Although Celsius became known for his temperature scale, his other projects were significant as well. The Lapland Expedition led to further advances in the measurements of the Earth, and Celsius’s observations about the aurora borealis laid the groundwork for later understanding of the lights.

Initially, Celsius set his temperature scale with the boiling point of water at 0 degrees and the freezing point of water at 100 degrees. This was reversed shortly after his death. The universality of the scale, which worked no matter where a person stood on the planet, eventually helped foster the idea that science is an international collaboration in which everyone can use the same measurements and be understood by scientists across the globe. The Celsius scale eventually became part of the metric system of measurement, which is used by most countries today.

Bibliography

Johannisson, Karin. A Life of Learning: Uppsala University During Five Centuries. Uppsala: Uppsala UP, 1989. Print. A history of Uppsala University, including Celsius’s contributions to the school. Mentions Celsius’s fame after the Lapland expedition and how he used it to obtain funds for an observatory without indebting the university to the state.

Murdin, Paul. Full Meridian of Glory: Perilous Adventures in the Competition to Measure the Earth. New York: Springer, 2009. Print. History of the various expeditions and attempts to establish the Paris Meridian, including an account of the Lapland expedition, detailing the lives of the scientists involved and their disagreements with each other.

Tafel, Rudolph Leonhard. Documents Concerning the Life and Character of Emanuel Swedenborg. Vol. 1. London: Swedenborg Society, British and Foreign, 1875. Print. Contains a brief biography of Celsius. Includes his communications with Swedish scientist Emanuel Swedenborg.