If I remember correctly, it's not the freezing point. Fahrenheit used a brine that included ammonium chloride to set 0 on his scale since it was the closest thing he could make in his lab that was a consistent temperature. The other end was body temperature, which he set at 96 if I'm remembering right since it's more easily divisible than 100. He was a little off on his body temperature measurements so it's considered a little higher than that now.

[–] ricecake@sh.itjust.works 26 points 7 months ago (1 children)

It's more chaotic than that.

He started with the Romer scale (brine freezes at zero, water 7.5, boils at 60, body temperature 22.5), which he tweaked to not need fractions for plain water freezing and body temperature by fudging some numbers and multiplying by four.

This made water freeze at 30 and human body temperature 90. He recalibrated it so that it was 32 and 96 so that there were 64 degrees between them, so he could draw the markings by dividing the interval between them in half six times.

He then saw that water boiled at about 212 on this scale, so he tweaked it again so that water froze at 32 and boiled at 212, since they're 180 degrees apart, which is desirable because it puts them on opposite sides of a temperature gauge.

Because of these tweaks, the original brine temperature is now about 4F, and body temperature is 98.6.

The tweaks make sense if you know that Fahrenheit was making and selling temperature gauges, so taking the Romer scale and marking every quarter degree gets you the first Fahrenheit scale.
Then he tweaked it to make it easier to produce, and then again to fit in the dial better.

[–] BallsandBayonets@lemmy.world 5 points 7 months ago (3 children)

So he fudged the science so the product would be easier/cheaper to make? Why does this feel like such a common story?

[–] ricecake@sh.itjust.works 20 points 7 months ago (1 children)

Because it wasn't science. :) keep in mind it was before there was a notion that a temperature scale was part of science, it was part of a tool.
"My thermometer is easier to read and the scale is more likely to line up with what you want to measure".

It's kinda like how a CD having 700mb of storage is a product of engineering choices and compatibility with older tape/record formats that usually had less than 80 minutes of audio, and not some fundamental measurement about the world.

The science he did was in making methods of consistently measuring temperature, not the numbers he assigned to those temperatures.

[–] kbotc@lemmy.world 4 points 7 months ago

CDs have ~700 mb storage because that’s how many bytes it took to store 74 minutes, which was how long a CD needed to be to store Wilhelm Furtwängler's 1951 recording of Beethoven’s 9th Symphony. That was the longest copy of the Symphony they could find and so that’s what set the standard.

[–] zephr_c@lemm.ee 4 points 7 months ago

How is changing a number fudging the science? Dude just liked powers of 2 so he set arbitrary things to be slightly different numbers. Heck, even Celsius is pretty arbitrary. The triple point of Hydrogen Hydroxide isn't actually some magical mystical temperature that's more important than all other temperatures, and the boiling point of one particular chemical at our best estimate of the average atmospheric pressure on the surface of this one particular rock is almost completely meaningless.

[–] saltesc@lemmy.world 0 points 7 months ago

https://youtu.be/7qxTKtlvaVE?si=2sTunmM5aAeKzxK8

[–] Paraneoptera@sopuli.xyz 2 points 7 months ago

It's debated. One source points to the lower end of the scale established as the freezing point of a brine made by dissolving ammonium chloride in water.