Today is the birthday of Anders Celsius, a Swedish astronomer with many accomplishments in a short life, most notably the system for measuring temperature on a decimal scale. Born in Uppsala, Sweden (27 November 1701 – 25 April 1744), Celsius had an extremely productive and influential scientific career-traveling Europe to visit observatories and befriending scientists from every field.
The Celsius scale was originally called the centigrade scale, from the Latin words centus for one hundred and gradus meaning degree. The eponym Celsius wasn’t adopted by the scientific community until 1948 and remains the only scientific symbol in the upper case (°C), to distinguish it from the lower case c (constant) famous from Einstein’s energy equation.
Despite his obvious genius, the centigrade scale originally proposed by Anders Celsius had 100 as the freezing point of water and 0 as the boiling point. In 1744 and shortly after his death, the great Swedish scientist Carl Linneaus reversed the scale making hot temperatures have higher numbers than cold temperatures.
Today the Celsius scale is the most widely used scale for measuring and reporting temperature. In addition to his interest in a better scale for measuring temperature, Anders Celsius participated in expeditions to confirm Isaac Newton’s theory that the Earth is not a perfect sphere but rather ellipsoid, and also was the first to use colored glass plates to try to analyse and catalog magnitude and differences in stars. He supported the formation of the Royal Swedish Academy of Sciences (along with Carl Linneaus and several others) and was elected to the Academy in its first meeting. He died of tuberculosis in 1744 at the age of 42.
Image of Anders Celsius from the portrait that hangs in his honor at the Uppsala Astronomical Observatory which he founded shortly before his death. Image in the public domain.