Interval vs. Ratio
this post was submitted on 12 Nov 2025
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Kelvin and degrees Celsius are friends, though.
Not according to the meme. 0 K is -273(.15) C.
I think one is supposed to be radians, not sure why they both have the ° though, cause radians aren’t a degree. Should be just R the way Kelvin is just K.
It is clearly the Rankine scale, which is an absolute temperature scale just like Kelvin. Which means that 0 K and 0 °R is exactly the same.
From John Bazell “In metric, one milliliter of water occupies one cubic centimeter, weighs one gram, and requires one calorie of energy to heat up by one degree centigrade—which is 1 percent of the difference between its freezing point and its boiling point. An amount of hydrogen weighing the same amount has exactly one mole of atoms in it. Whereas in the American system, the answer to ‘How much energy does it take to boil a room-temperature gallon of water?’ is ‘Go fuck yourself,’ because you can’t directly relate any of those quantities.”
I was in a situation similar to this one in real life: having to adjust the salt level in a pool.
In metric:
The pool is 8*4 m long and 2m deep on average, the current salt level is 2g/l and the salt comes in 20kg bags.
How many bags of salts do I need to pour in the pool to adjust the salt level to at least 3g/l ?
Answer:
! The pool contains 8m4m2m= 64m³ or 64000l of water, I need an extra 1g/l of salt per litres so 64000l*1g/l = 64000g or 64 kg. So with 4 bags I'll have enough salt.
In imperial:
The pool is 20*10ft long and 5ft deep on average, the current salt level is 2000ppm and the salt comes in 40lbs bags.
How many bags of salts do I need to pour in the pool to adjust the salt level to at least 3000ppm?
Answer:
! I'm just gonna drive to the store with my truck to pick up 2 bags at the time and see if it's enough, no way I'm doing the calculation.
Home pools here are almost never saltwater.
We simply add chlorine tabs until the pH is the correct color on the strips. Even if we knew it would be 62.4 lbs of salt, it's not like you can buy a 62.4 lb bag of salt.
But yeah, it is a lot harder to do applied math in the US, which is why science here went metric :)
It's a shame because salt water pools are honestly so much better and I think overall it was cheaper for us as well.
Instead of adding chlorine every week the salt system just keeps the chlorine level at the right minimal level all the time. So no chlorine smell in the pool and the pool was much cleaner.
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(6 replies)
0 Kelvin = 0 Rankine
Also, both °R and °Ra are Rankine. So 3 of the 5 people in the bottom picture also agree.
And the other two can shake at -40
They shake under the table, but try to keep up appearances.
I think none of K, R, and Ra may be pointing at each other.
Hmm. To my eye, K is obviously pointing at either R or Ra (and F), R has to be pointing at Ra (and K or F), and Ra is pointing at R or K (and C).
K is obviously pointing at R because Rankine is an abomination in the same vein as pound-mole and thousands of an inch.
Motherfuckers, metric is right there, get your disgusting units out of here.
Anyone who uses either of these units in the last 40 or 50 years, I would like to physically fight with you. I have never thrown hands.
°RA sound like the sun's temperature
1°RA = 5500°C / joking
As far as equations go, "one degree RA equals 5500 degree Celsius divided by joking" is unusually abstract 🤔
I know the F C and K, but what are the others?
R is to F what K is to C. Ra is used sometimes because there are other R meanings.
there's a whole host of temperature scales, some of which look similar, some look different, some scale the same at the same temperature difference but have different zeroes, and at least one works backwards. Thank goodness there's only three you're likely to see in the wild these days, I'd hate to have to keep in mind whether or not those degrees are not Celsius or Fahreheit, but... idk, Newton? Réamur? Rømer? Delisle?
More like only 4 than 3, at least in the us, I unfortunately run into Rankine at my job on occasion.
Welp, it is like Kelvin, just with Fahrenheit step.
-40C = -40F
Also 0lbs does not equal 0kg when there’s no gravity.
huh?
Mass doesnt change with gravity
Typically, lbs is not mass, it's weight/force.
isn't that lbf?
The pund itself is defined as 0.45359237 Kg
Lbs can be lbf or lbm, but usually is referring to lbf, which is 0.4536 kg at 1g.
when comparing to kg I will assume the mass unit, since comparing a mass value to a force has no meaning.
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(2 replies)
no mass multiplied with gravity still results in no force, 0 Lb = 0 Kg; 0 Lbf = 0 N
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(1 replies)
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(8 replies)
Would be better ordered like F° C° K° R°
You mean K° F° C° R°epeat
Found the Americans.
I kid, but it's °C, not C°
And K had no degrees at all.
The other two units are not mentioned in this household.
Kelvin is objectively the most accurate. Celsius fans cope.
Er... every system of measurement is accurate, tautologically.
0°F = 0°F because 0°F = 0°F, by definition.
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(7 replies)
For some reason my brain dropped the 'L'.
Sitting here wondering how Kevin does it...
Depends on your measuring tool. A thermometer that measures in K but has an error margin of +2 to -2 K is less accurate than a thermometer that measures in F and has an error margin van -0.1 and +0.1 F
It's a nice day today. Can't be more than 300 degrees
I'm not so sure
I'm coping, Celsius is just as accurate as Kelvin, because it based on it.
Kelvin - 273.15 = Celsius
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(2 replies)
Use molecular wiggles mw
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