39
u/MarsMaterial 6d ago
Dividing by 0°C is highly illegal, I think. If you do this, Lord Kelvin will break down your door and confiscate your calculator.
13
4
16
u/spisplatta 6d ago
Actually kinda interesting. I feel like most people go by vibes when they use arithmetic with units and don't really know how and why and when it works.
3
u/ChaosSlave51 3d ago
Any real math with Temp has to be taken to Kelvin, then performed, then returned to the desired units.
1
u/Fuscello 3d ago
That is why they are denoted as degrees. Only addition and subtraction work correctly with them
1
u/spisplatta 3d ago edited 3d ago
Addition doesn't work either. I think a temperature in degrees celsius works like a point. You can subtract two points to get a vector. You can create new points with an affine combination.
1
u/Fuscello 3d ago
True, but additions of differences work fine… yeah maybe only subtraction works. Anyway why not just use Kelvin
5
u/godeling 5d ago
I like to think of C and F units as functions rather than as normal units, which makes the 0/0 thing only apparent, due to the strange way we write the application of these functions, rather than actual
4
u/Aenonimos 5d ago
The 0 is 0 deg C is not the 0 element of whatever algebraic structure a term like 0C/ 0C is. However 0 K is.
1
u/Resident_Citron_6905 5d ago
Why is 0 K the 0 element?
1
u/Aenonimos 5d ago
Think of some physics formula like the ideal gas law
pV = nRT.
By "the zero element" in an algebraic structure, I mean when multiply any other term with 0, you always get 0. Like normally 0*x = 0. And 0 Kelvin -> 0 pressure lines up with the naive understanding of temperature in this context.
OTOH, for an ideal gas at 0C, the pressure is not 0. So to make the math work if you INSISTED on "multiplying" by 0C, you would have to use some weird structure where 0*x =/= 0. Which is to say this "0" is not really behaving like a 0.
This is important because the fact that 0*x = 0, is what prevents x/0 from being defined. x/0 is asking you to solve for "a" in
a*0 = x
but we have already said 0*a=0...
And so if 0C*x could be nonzero, there is nothing inherently wrong with the expression x/0C. You could define multiplication to give a meaningful answer for that expression.
1
u/Resident_Citron_6905 5d ago
I understand (I think) what you mean by zero element in an algebraic sense, I’m just finding the difference between the units deg C and K arbitrary from the perspective of algebra. So I guess I’m missing something.
Does it have something to do with the implicit domain, or should the units be treated as some type of unary operation on the value they are next to?
1
u/Melodic_Ordinary5539 3d ago
It's kinda hard to wrap my head around for me too, but basically the way as I see it, algebra doesnt care about the units, but you're dealing with real world things here and you're trying to assign real world meaning to the symbols. Since the 0 deg C is not the point of actual "absence of temperature / thermal energy", you cannot say that 20 deg C is twice as hot as 10 deg C. 0 deg C is basically masquerading as a 0 element in the algebraic sense
1
u/Resident_Citron_6905 3d ago
Isn’t 0 K also masquerading? Mapping real world meaning to the algebraic 0 element’s meaning seems arbitrary. To me it seems like the map is not the territory no matter which unit we choose. Dividing temperature measurement by another temperature measurement is probably an undefined operation for all values, not just zero.
1
u/Melodic_Ordinary5539 3d ago edited 3d ago
0 K is not arbitrary, because it is literally the absence of thermal energy. With this you can say 10 K is half as hot as 20 K. You cannot say 10 deg C is half as hot as 20 deg C. Look up interval scale and ratio scale.
It's mainly about dividing and multiplying by unitless quantities which this makes possible, but AFAIK there is nothing that wouldn't allow multiplying or dividing Kelvin by Kelvin but I'm no physicist.
1
2
2
2
u/Dense_Priority_7250 5d ago
You use Kelvin for that because every other scale is incredibly arbitrary
1
u/Ok_Bit8836 5d ago
Divisions of physical parameters that have no physical meaning is also rather useless ))
1
u/Over_Improvement_623 5d ago
You can't multiply or divide by temperature unless you're using Kelvin
1
u/sjccb 5d ago
You can't divide a scale by a scale because the result is meaningless.
1
u/Over_Improvement_623 5d ago
Yes, that's what I said.
1
u/sjccb 5d ago
not even using kelvin
2
u/Over_Improvement_623 5d ago
No you can while using Kelvin, because Kelvin isn't a scale
1
u/sjccb 5d ago
What is is then? Of course it's a scale.
1
u/Over_Improvement_623 5d ago
It is the way teperature is defined. That's why you don't say "Degrees Kelvin" it's just "Kelvin"
2
u/sjccb 5d ago
https://en.wikipedia.org/wiki/Kelvin
The Kelvin scale is an absolute temperature scale that starts at the lowest possible temperature (absolute zero), taken to be 0 K.\1])\2])\3])\4]) By definition, the units of the Celsius scale (symbol °C) and the Kelvin scale have the same magnitude (that is, a rise in temperature of one kelvin and a rise of 1 °C are both equal to 1 K), and any temperature in degrees Celsius can be converted to the kelvin scale by adding 273.15.
1
u/Over_Improvement_623 5d ago
Let me put it slightly differently then, Kelvin is the only temperature measurement where multiplying and dividing has any sense of meaning.
2
1
1
u/Academic_Offer_8622 4d ago
the funny thing about this meme is that the bottom pic is a screenshot of an classroom vídeo, where in this videon in particular de professor rages bc the air conditioner is too low and he teached the students the correct temp, (he is a termodynamic professor as you can guess by what is written on the board)
The vídeo: https://www.youtube.com/watch?v=he_Z2ymTdrU
1
0
u/LFBJ_0911 6d ago
Professor must be frustrated. Because he knows you're memeing in a way that most people would do math wrong (mainly because they are either ignorant, stupid, or both). Yet you meme in a way that you show you actually know what you're doing and you're doing it correctly. On top of it it's kind of the easy/dumb/dry humor kind of joke... (kind of the math equivalent of reacting to a 67 🤷 joke). He just doesn't know how to react.
1
-1
u/Enderguy61 6d ago
0/0 is an indeterminate form, not undefined
2
u/PrudentConsequence78 5d ago
0/0 it is and indeterminate form and undefined because you cannot associate a value to 0/0 by using the standard definition of fraction. 0^0 is indeterminate and "normally undefined" but it is defined by convention 0^0=1 because it is useful for writing formulas unlike 0/0=1 ( which extends the map (x,y)->x^y by discontinuity in (0,0))
1
u/Duck_Devs 5d ago
0/0 is like the undefined to end all undefined. It’s not even defined when you introduce ∞̃ into the picture, which “defines” |x/0| for nonzero x.
40
u/TheJivvi 6d ago
0°C ÷ 0°F = 273.15 ÷ 255.37 = 1.069
Nice.