Celsius

Celsius (pronounced sel-see-uhs or sel-shee-us)

(1) As a measure of temperature, pertaining to or noting the Celsius scale of temperature scale in which 0° represents the point (at sea level (ie under normal atmospheric pressure)) where pure water freezes and 100° the point at which it turns to steam.  The Symbol is “C” and the term Centigrade is for most general purposes interchangeable.

(2) In thermodynamics, of or relating to a temperature scale having the same units as the Celsius scale but in which the zero point has been shifted so that the triple point of water has the exact value 0.01°; Celsius temperatures are computed from Kelvin values by subtracting 273.15 from the latter.  The symbol is “CC”.

1742: Named after Swedish astronomer Anders Celsius (1701–1744) who in 1742 proposed the centigrade scale and invented the centigrade thermometer.  The surname Celsius is Latinized from the estate's name, celsus (mound).  The synonyms are centigrade and the rare centesimal.  The term Celsius came into use in 1797 to describe the thermometer and in 1812 in reference to the scale of temperatures.  The companion adjective centigrade (consisting of 100 degrees, divided into 100 equal parts) was a construct of the Latin centi- (from centum (one hundred)) + grade (degree), the second element from Latin gradus (step) & gradi (to walk, go, step), from the primitive Indo-European root ghredh- (to walk, go).  The centigrade thermometer divides the interval between the freezing and boiling points of water into 100 degrees.

It wasn’t until 1948 (at the ninth meeting of the General Conference on Weights and Measures and the Comité International des Poids et Mesures (CIPM)) that the word Celsius (in honor of Anders Celsius) was adopted (by international agreement) as the standard measure of 100^o increment temperatures; prior to that, the unit was known as centigrade and the two terms were for decades in common, interchangeable use.  Most of the world’s population has long used Celsius, the US the only large country still expressing temperature in the old Fahrenheit scale although, even then, Celsius is in wide use in the scientific community and among others dealing with international institutions.  The other widely used scale is kelvin (symbol is “K”), which had a particular applicability in cosmology, physics and other disciplines, 0 K (-273.15 °C) being absolute zero (the lowest possible temperature (thus far something only theoretically described and measured only as “tending to”) at which the motion of particles at a point in time and space cease to move so stopping the generation of heat, the product of energy.  Between 1948 and 2019, through a series of international agreements, the temperature scales were refined and made more precise and the degree Celsius is now precisely equal to the kelvin.

Curiously, the original Celsius was the reverse of the modern practice: Then, the boiling point was 0° C and the freezing point 100° C.  For scientists that was manageable but for most people would have seemed counter-intuitive so in 1743, the scale inversion proposed by French physicist Jean-Pierre Christin (1683–1755) was accepted.  Monsieur Christian was also influential in the development of the mercury thermometer.  For most people, temperature is a well-understood and unconventional measure although, now that climate change is “baked in” and a rise in average global temperature well over 2° C inevitable, a matter in which there is heightened interest.  Temperatures in parts of England exceeding 40° C, something once thought impossible, have focused the minds of many.

Some have however long been aware of the implications.  Mountaineers have long understood how hard it is to get a good cup of tea while climbing because, the higher one climbs, the lower the air pressure and thus the boiling point of water.  Atop Mount Everest (29031.7 feet, 8,848.86 m) water boils at 68° C which is not hot enough to extract the best flavor from the leaves.  The culinary implications go beyond that.  At sea level where water boils at 100° C, the hard-boiled egg is a mundane item but it’s unknown up Mount Everest because the white cooks at 85°C and the yoke at 65°C; up there, the whole of an egg will never cook.  A climber especially fond of hard-boiled eggs could take to the peak a pressure cooker and that would work, the boiling point rising to around 107.5 °C.

Lindsay Lohan and Brittany Byrd (b 1994) emerging from one of Zimmer's cryotherapy cold chambers which run at a temperature as low as -110°C, June 2015.

Although cryotherapy was intended originally as a treatment to hasten an athlete's recovery from injury, cryo-chambers are available for anyone although most presumably don't undertake the treatment wearing a strappy bandage monokini by Moeva London.  That said, the choice was a reminder lime & grey is an underused combination.