On 17/02/2021 11:26, NY wrote:
"nightjar" wrote in message
...

I never had a feel for Fahrenheit. It didn't really matter to me as a
kid what the outside temperature was beyond whether I needed to wrap
up warm or not. It was only when I started science at school that
exact temperatures mattered and we used the cgs system for that.

Fahrenheit has to be the most hare-brained temperature scale ever
devised - apart from the one which used an inverse scale so a higher
temperature was a lower number. It seems very obvious that you devise a
temperature scale that is based on (and is easily compared with) the
properties of the most abundant liquid on Earth: water. Make 0 the
freezing point of water and some larger number the boiling point. given
that we count in base 10,...

Fahrenheit used two fixed points that were available to him at the time.

Zero is the freezing point of saturated brine, which makes more sense
than that of water in an era when you can't be sure how pure the water
you have is. By deliberately contaminating it with a known substance, he
got a repeatable temperature.

He set 100 at something else readily available to him at the time - the
temperature of the human body. Today, we know it can vary between 97F
and 99F, but it has been suggested that the prevalence of mild
infections would have made 100F more likely in his time.



--
Colin Bignell