Even the scientific community felt the need to hollow out the Celsius scale, leaving the numerical values of Celsius in tact but otherwise completely decoupling the scale from the properties of water when it created kelvin. It instead moved to measured values, like basically all other SI/metric units.

Celsius is there to describe water. Well, it’s used to describe a mostly pure form of water. Well, it’s used to describe a mostly pure form of water at around sea level. So, why does that make Celsius more relevant or useful for temperatures than Fahrenheit?

Frankly, it feels like Celsius is, to the rest of the world, what the Imperial system is to the US: a vestige of times past that has been supplanted by a better, measurement-based standard, but has yet to be abandoned because it is so entrenched in popular culture.

[–] Umbrias@beehaw.org 1 points 1 year ago (1 children)

Celsius and Kelvin are identical, just shifted scales.

Fahrenheit has an equivalent which is rankine. It's not that one is evidence based over the other, one is just absolute temperature and one shifted to be useful, essentially.

[–] mreiner@beehaw.org 1 points 1 year ago (1 children)

Respectfully, I don’t think you are completely correct.

While you are right that Kelvin is tied to absolute zero, it is also defined in such a way that a change in 1K corresponds to a change of thermal energy kT by 1.380649×10−23 J (the Boltzmann constant).

It is the difference in what 0K describes, along with the fact that a change in temperature equals a specific change in thermal energy (the measured value to which I previously referred), that separate it from Celsius. In Celsius, zero is the freezing point of (mostly pure) water (at sea level), and a change in temperature has no relationship to a specific/prescribed change in thermal energy.

https://en.m.wikipedia.org/wiki/Kelvin

[–] Umbrias@beehaw.org 2 points 1 year ago (1 children)

Celsius is literally Kelvin + 273.15. They measure the same thing.

Fahrenheit is as Celsius is to rankine, which is also a measure of absolute temperature.

I'm not quite clear on where this is confusing you, Celsius is improper in many non relative equations yes but that's due to the math not a fundamental difference in what is being measured.

[–] mreiner@beehaw.org 1 points 1 year ago* (last edited 1 year ago) (1 children)

Ah, I guess I misread (in my own research) or somehow missed that a degree change in Celsius was directly pegged the same degree change in Kelvin (shifted by 273.15 ) when the Kelvin scale was updated to be pegged to the Boltzmann constant. Thank you for helping me understand where my understanding was flawed!

I guess I still don’t understand the utility of Celsius, though. If it’s really just an alias, shifted by 273.15, for Kelvin, what utility does Celsius offer? Why not just use Kelvin?

[–] Umbrias@beehaw.org 1 points 1 year ago

Tradition, culture, etc make Celsius a useful tool. Human perception if temperatures is also not well correlated to Kelvin, where a change in 1 K is less than 0.5%, but to a person it certainly feels more substantial. By relating the scale we use daily to freezing and boiling of water, you at least capture both an okay human sensitivity, and important temperatures to us as humans.

Fahrenheit arguably goes a step further, defining a much narrower range for humans specifically, with some landmarks for water.

No system is objectively better, it's all convention and arbitrary. We could define an absolute temperature scale which puts human temperatures at 1 blorp, 0 as absolute 0. Clearly the resolution is pretty low, you'd have to define the weather with decimals. Oh well, that's fine. Annoying maybe, but valid.