Anders Celsius (1701-1744), a Swedish astronomer who invented the Celsius thermometer scale (often called the centigrade scale) in 1742. Celsius gained early fame when he participated in the French expedition to northern Sweden, which confirmed Isaac Newton's belief that the shape of the Earth is an ellipsoid flattened at the poles, rather than perfectly spherical. In those days, geographical measurements, meteorological observations, and other studies outside of today's astronomy field were included in the work of an astronomer. For his meteorological observations, he constructed the widely-used Celsius thermometer, with 0° indicating the boiling point of water and 100° the freezing point. However, after his death in 1744, the scale was reversed. In 1733, Celsius published a collection of 316 observations of the aurora borealis, or northern lights, that he and others had made from 1716 to 1732. He supervised the building of an observatory at Uppsala, Sweden in 1740 and became its Director. Celsius was also a pioneer in measuring the magnitude of stars using photometric methods.

Further Reading
Anders Celsius (1701-1744) (Uppsala Astronomical Observatory)
Metric system temperature (kelvin and degree Celsius) (U. S. Metric Association)
Fahrenheit to Celsius Converter (NOAA National Weather Service)