Swedish astronomer/inventor/physicist Anders Celsius (1701—1744), inventor of the eponymous Celsius scale and a mind of great consequence from the time of the Enlightenment, was born on November 27, 1701, in Uppsala, Sweden, north of Stockholm. In fact, an inverted form of Celsius' original design (also known as the centigrade scale) reaped such high praise from the scientific community for its accuracy, that it would go on to become the standard measure of temperature used in nearly all scientific endeavors.

Early Life and Career in Astronomy

Raised a Lutheran, Celsius was educated in his home town. Both of his grandfathers were professors: Magnus Celsius was a mathematician and Anders Spole was an astronomer. From his early childhood, Celsius excelled in mathematics. He went on to study at Uppsala University where, in 1725, he became the secretary of the Royal Society of Sciences (a title he retained until his death). In 1730, he succeeded his father, Nils Celsius, as professor of astronomy.

By the early 1730s, Celsius became determined to build a world-class astronomical observatory in Sweden and from 1732 to 1734, he embarked on a grand tour of Europe, visiting notable astronomical sites, and working alongside many leading 18th-century astronomers. At about this same time (1733), he published a collection of 316 observations on the Aurora Borealis. Celsius published the bulk of his research in at the Royal Society of Sciences in Uppsala which was founded in 1710. In addition, he published papers at the Royal Swedish Academy of Sciences, founded in 1739, and presided over approximately 20 dissertations in astronomy, of which he was primarily the main author. He also authored a popular book, “Arithmetics for the Swedish Youth.”

Celsius made numerous astrological observations over the course of his career, including eclipses and a variety of astronomical objects. Celsius devised own photometric system of measurement, which relied on viewing the light from a star or other celestial object through a series of identical transparent glass plates and then comparing their magnitudes by calculating the number of glass plates it took for the light to be extinguished. (Sirius, the brightest star in the sky, required 25 plates.) Using this system, he cataloged the magnitude of 300 stars.

Celsius is considered to be the first astronomer to analyze the changes of the earth’s magnetic field during the northern lights and to measure the brightness of stars. It was Celsius, along with his assistant, who discovered that the Aurora Borealis had an influence on compass needles.

Determining the Shape of the Earth

One of the major scientific questions being debated during Celsius's lifetime was the shape of the planet we live on. Isaac Newton had proposed that the Earth was not completely spherical but rather flattened at the poles. Meanwhile, cartographic measurements taken by the French suggested that the Earth was, instead, elongated at the poles.

To find a resolution to the dispute, two expeditions tasked with measuring one degree of the meridian in each of the polar regions were dispatched. The first, in 1735, traveled to Ecuador in South America. The second, headed by Pierre Louis de Maupertuis sailed north in 1736 to Torneå, the northernmost area in Sweden, in what was known as "the Lapland Expedition." Celsius, who signed on as de Maupertuis's assistant, was the only professional astronomer to take part in the adventure. The data collected eventually corroborated Newton's hypothesis that the Earth was indeed flattened at the poles.

The Uppsala Astronomical Observatory and Later Life

After the Lapland Expedition returned, Celsius went home to Uppsala, where his exploits earned him the fame and notoriety that were key to securing the funding he needed to build a modern observatory in Uppsala. Celsius commissioned the building of the Uppsala Observatory, Sweden's first, in 1741, and was appointed its director.

The following year, he devised his eponymous "Celsius scale" of temperature. Thanks to its detailed measuring environment and methodology, the Celsius scale was deemed to be more precise than those created by Gabriel Daniel Fahrenheit (Fahrenheit scale) or Rene-Antoine Ferchault de Réaumur (Réaumur scale).

Fast Facts: The Celsius (Centigrade) Scale Anders Celsius invented his temperature scale in 1742.

Using a mercury thermometer, the Celsius scale consists of 100 degrees between the freezing point (0° C) and boiling point (100° C) of pure water at sea level air pressure.

The definition of centigrade: Consisting of or divided into 100 degrees.

Celsius's original scale was reversed to create the centigrade scale.

The term "Celsius" was adopted in 1948 by an international conference on weights and measures.

Celsius was also noted for his promotion of the Gregorian calendar, which was adopted in Sweden nine years after the astronomer's death. In addition, he created a series of geographical measurements for the Swedish General Map and was one of the first to realize that the Nordic countries are slowly rising above sea level. (While the process had been going on since the end of the last ice age, Celsius mistakenly concluded that the phenomenon was the result of evaporation.)

Celsius died of tuberculosis in 1744 at the age of 42. While he had started numerous research projects, he actually finished very few of them. A draft of a science fiction novel, situated partly on the star Sirius, was found among the papers he left behind.