Until weather forecasters started to talk about "degrees Celsius" some 30 years ago, few people had ever heard the term. Even those familiar with the measure knew it as the "Centigrade" scale, and it took a while for them to realise that this new arrival was the same thing.
But Celsius is not a recent innovation; it has been the correct scientific name for the centigrade scale of temperature measurement since early in the 19th century, and its origins go back even further - to a Swede called Anders Celsius, the tercentenary of whose birth occurs today.
Celsius was born at Uppsala on November 27th, 1701, and by the age of 29 was Professor of Astronomy at Uppsala University. He interpreted his brief widely, and delved deeply into the mysteries of many of the physical sciences of his day.
In 1736 he joined an expedition to Lapland to measure the length of an arc of longitude, and his findings verified Newton's theory that the Earth was flatter at the poles than at the equator. He was also a keen observer of the aurora borealis, and is credited with being the first to associate it with the Earth's magnetic field.
But the immortality of Celsius's name was assured in 1742 when he presented to the Swedish Academy of Sciences a paper entitled "Observations About Two Fixed Degrees on a Thermometer". In his discourse he proposed a temperature scale that was defined by two temperatures that could be identified objectively and without great difficulty: the boiling-point and the freezing-point of water. The interval between them was divided into 100 equal parts, which he referred to as "degrees".
Now, the temperature scale proposed by Anders Celsius had a surprising feature: it was the reverse of the Celsius scale we know today. His suggestion was that 100 degrees should be the freezing-point of water, and zero its boiling point; he justified its topsy-turvy nature on the grounds that it avoided the use of the minus sign in winter.
In the decade following its announcement, somebody turned the Celsius scale the "right" way up, but no one knows for sure just who it was. Some say it was Celsius's colleague, Carl Linnaeus; others that it was his friend and successor, Martin Stroemer; and yet another school attributes the rectification to a Frenchman called Cristin from the town of Lyons.
But quam cito transit gloria mundi : "How quickly passes the glory of this world". Poor Celsius died in his native Uppsala in April 1744, aged only 43, and only two years after he had unveiled the centigrade scale that bears his name today.