Centigrade

I'm afraid my ingrained intuitions are with the Americans on temperature at least at the top end of the ambient scale.  I know that while 100^o Fahrenheit is only a tad over normal human core temperature, when I was young it got classified in the British tabloid press as "Phew, wot a scorcher!"when it was recorded on a sunny day. Indeed the weather in the WEA is so 'ambient' and unexciting that a mere 80^o was also a 'scorcher' and required men to apply a knotted handkerchief to the top of their bald heads. Fahrenheit was defined with 100^o = normal average human temperature and 0^o = the lowest point that could be reliably achieved with a mixture of salt and ice. The scale was by Daniel Gabriel Fahrenheit (1686–1736) a Northern European instrument-maker and experimentalist who was born in Gdańsk and died in Den Haag but lived and worked in a veritable alphabet of other places including Amsterdam, Berlin, Copenhagen and Dresden. Sometime when I was in school, the British government issued a diktat that we'd all use the Centigrade scale instead because that's what all them foreign johnnies were using. The decision was also driven by the rise in importance of technology and science in our daily lives: scientists had been using centigrade (and grams, metres, litres and hectares) for at least two generations.

We use Celsius as a synonym for centigrade as a tribute to Anders Celsius (1701–1744) a Swedish astronomer who defined 0 as the boiling point of water at sea level and 100 as the freezing point of water ditto.  Yes, you read that correctly, Celsius made his scale upside down.  His compatriot and contemporary Carl von Linné aka Linnaeus, turned it the way we use today the year after Celsius' death. But so did a lot of other people at more or less the same time. Including Jean-Pierre Christin (1683-1755), whose birthday it is today.  Celsius, like Linnaeus, is another Latinised name - derived from the family seat at a place called Högen (pile, mound, heap).  They seem to have come to surnames rather late in Sweden - and haven't got there yet in Iceland.  Because Christin was a founding member of the Académie des sciences, belles-lettres et arts de Lyon, his instrument was known as le thermomètre Lyonnaise in pre-revolutionary France. Much of the rest of Europe called such things Swedish thermometers.

Back then, obsessive precision was not called for because the uses for measurement (smelting, distilling, weather records) of temperature were comfortably fuzzy. Metallurgists, for example, would describe the colour of molten iron to define its temperature.  Possibly Fahrenheit was in a fever of excitement the day he measured his core temperature and called it 100. No chatter about temperature and its measurement would be complete without a hat-tip to  René Antoine de Réaumur of La Rochelle France.  In the 1730s he invented an instrument filled with dilute alcohol and marked it on a scale from 0 to 80 between the freezing and boiling points of water.  Alcohol was unwieldy in its handling (boiling point lower than water etc.) and almost everyone at the cutting edge of calibration switched to mercury filled thermometers.  But the 0-80 scale hung on for at least 100 years in niche areas like cheese making in Italy and Holland when boiling sugar for dropjes and pepernoten. Réaumur scaling was particularly popular in Russia and featured as one of the Y axes in "Probably the  best statistical graphic ever drawn, this map by Charles Joseph Minard portrays the losses suffered by Napoleon's army in the Russian campaign of 1812". As I noted in my analysis of the Battle of Borodino.

It's interesting that the world we inhabit is right down near the bottom of the scale which is defined as being - 273.15^oC.  This is absolute zero when matter is so cold that it is incapable of movement. Temperature seems to be, according to physicists, a product of vibratory movements among atoms, the higher the temperature the more vigorously things vibrate or is it that the vibration causes the increase in temperature??  As my reg'lars know, I failed my physics "O" Level, so I'm stumped on this existential issue but perhaps we can find a physicist in Kiev who would be kind enough to explain in Ukrainian - we'll run it through google-translate afterwards. To complicate matters. modern science measures thermodynamic temperature in Kelvins rather than ^oCs, the units are the same size but start at different places: Ks at absolute zero.  So you can have negative values for Celsius and Fahrenheit but not for Kelvins; heck and by jimminy, it don't get no colder than that absolute zero  Somewhere in the definition of Kelvins is the "triple-point of water" the place where the three phases of that molecule (solid, liquid and vapour) are in dynamic equilibrium. This occurs for water at 0.01^oC and a partial vapour pressure of 611.73 pascals or 6/1000ths of atmospheric pressure. Minute changes of temperature or pressure from this point will tip the water into one or other of its possible states.

At the other end of the temperature scale, the sky is the limit. At the earth's surface under natural weather conditions (i.e. not in the middle of a bush-fire) the hottest recorded temperature is a modest enough 57^oC but in the centre of the earth they think it may be 6000^oC which is pretty close to how hot the surface of the sun is.  In the sun's interior, though, it is 15.7 million K hot.  Astronomers now maintain that there are places which are 20x hotter but can't have much solid ground to stand on there.