Also, nearly all formulas used in physics and chemistry that involve temperature use Celsius or Kelvin, and inserting Fahrenheit would throw off the answers completely, which is part of why F is considered arbitrary.

I'm pretty sure that is totally untrue...

Except when it causes space shuttles to explode.

That doesn't mean the formulas don't work, it just means there's a conversion factor that people can forget. That's like saying that the formula for acceleration due to gravity changes depending on whether you're using feet or meters.

Oh yes, it will work if you have a conversion factor. But all that does is convert Fahrenheit to whatever unit is appropriate before running it through the rest of the equation. I you use the ideal gas law to find the temperature of a gas, your answer will always be Kelvin scale.

Only if you're using 8.3144 for

*R* and your pressure and volume are also in (appropriately scaled, i.e. kPa vs L or Pa vs m^3) SI units. SI in, SI out.

If I take pressure in PSI, volume in cubic feet, and quantity in "lbmol" (1 lbmol = 453.59 mol) I can use 10.731 for

*R* and get my answer in the Rankine (degrees fahrenheit vs absolute zero) scale. And this is a consistent unit set (feet, pound-force, lbmol, rankine) no different from the SI being a consistent unit set (metres, newtons, mol, kelvin), and there are no conversion factors - just a physical constant that has a different value in different units.

Or did you think there was something sacred about 8.3144 in particular and therefore the ideal gas law "uses kelvin" (along with meters and pascals) rather than being a system-agnostic formula?

There are also _no_ physics formulas that use the celsius scale directly. The only significant issue with the "american" system

*in isolation* is the fact that there are two different systems based on different interpretations of a "pound" (the metric system used to also have an alternate system using the "kilopond" (9.8 N) as a unit of force, and the "hyl" (9.8 kg) as the unit of mass), and that can be avoided by being specific about which one you use

At the end of the day, there's no REAL superiority to 1/299724258 the distance light travels in a second vs 1/983571056.43 that distance, or to the weight of one lump of metal vs another (though, the pound is nowadays defined as an exact fraction of the kilogram's lump of metal), or 1/273.16 of the temperature of the triple point of standard water vs 1/491.688 of that temperature, or a zero point 1/27316 less than that vs one 32018/491688 less. And of course both share the definition of the second as 9192631770 times the transition between two arbitrarily chosen states of an arbitrarily chosen element. The point is, these are all completely arbitrary numbers (and/or lumps of metal) with no real mathematical basis. Yeah, the nice round decimal number ten million metres from pole to equator through Paris sounds impressive, until you think that it was only chosen as ten million to get a length close to a yard anyway, there's about an extra 2km because they were off in their measurement, and why Paris anyway or Earth for that matter?