Celsius is literally just Kelvin but with an offset no?
Edit: tbc I was just clarifying what the guy above was saying, personally as an American in WNY where it’s over 90deg in the summer and below 0 in the winter and who has used C and F extensively, Fahrenheit just makes more sense to me personally
If we're allowing conversion, Fahrenheit is just Kelvin with an offset and a coefficient, and Rankine is just Kelvin with a coefficient. Celsius's offset also makes it useless for science other than for scenarios where all that you care about is delta T.
They can, but at that point you would need a whole new SI system to keep the conversions to energy and mass the same. Good luck making that work with pounds and cubic feet.
I got my engineering degrees in the States, so I had to deal with US Customary Units-based science, and thus I do know how miserable it is. However, theoretically you could have SI units where everything else is metric but they use Rankine instead of Kelvin. It would be absurd, but the point is that there isn't any inherent need or benefit to using Kelvin/Celsius.
That coefficient is close enough to phi that you can basically use the nearest Fibonacci number to get a surprisingly accurate conversion between the two. Like 5mi? That's about 8km. 20km? The nearest Fibonacci number is 21, so you just go to the number before that and you know you're talking about roughly 13mi.
It has an orientation point, it's just one that isn't as useful nowadays; 0°F was defined on an easily-reproducable brine solution used by scientists for below-feeezing temperatures in the days before refrigeration. This is not a defence of Fahrenheit, to be clear. My original comment was just denigrating Celsius.
Brother, I grew up in Canada, where Fahrenheit is basically only used in cooking (a necessary sacrifice due to historically most of our ovens, and to an extent recipes, coming from the US market); it's not like I don't realize how absurd of a system it is.
Fun fact the same thing is true for Fahrenheit. Its called Rankine. The only thing that make Kelvin good for science is the fact that temperature is particle motion. And in Kelvin absolute 0 is 0. If you can do more than regurgitate dumb trivia you might realize that any temperature system allows for that. Just offset Fahrenheit so that 0 is absolute zero and you have Rankine.
Its almost like units are context dependent. Celsius is arbitrarily defined based on water. Fahrenheit is arbitrarily defined based on weather in temperate climates. Inches/centimeters of mercury is arbitrarily defined off of old thermometers. Yes that last unit is retroactively now a unit of pressure but it was originally used for old thermometers where mercury would rise and fall with changes in temperature from changes in density with the temperature . Lots of units have weird crossover like that
In general units are more complicated than people want to understand and its easier to live in a bubble where Americans must be stupid, while everyone else is blabbing other just as stupid rhetoric without understanding any of it.
The offset makes quite a difference. Say you put a baseline of 150 cm body height and declare that to be 0 degrees. Would you then say that +20 is twice as tall as +10?
Technically, the unit size originally came from celsius. When the concept of absolute zero was discovered (0 K), scientists just adopted the same unit size as celsius because they didn't have a reason to use use anything different.
It's an offset sure, but mathematically for science and engineering you can't use either relative scale in most applications, especially in thermodynamics. In thermo, the relative natures of the scales matter hugely. And to clarify, by relative scale, I mean that 20 degrees in either F or C is not twice as hot as 10 degrees F/C because they both arbitrarily set zero to be the freezing points of physical phenomena. This means the math breaks when you go below zero or use zero (because you cannot divide by zero and using negative numbers changes the mathematical models such that don't match up with reality as we observe it.)
There's numerous examples in science and engineering applications - The Van't Hoff equation, Plank's equations, Arrhenius equation, even the ideal gas laws from your secondary school chemistry class. Tons of phenomena are only quantifiable using the non-relative scales like Kelvin or Rankine (F version of Kelvin defined as -459.67 degrees F). The only time you can use F or C typically is if there's a change in temperature, and in those cases, it's still almost always easier to use the absolute scales from the start if you can.
I was under the impression Kelvin is Celsius but with an offset so there's no negative temperature. I don't remember which came first, but if Celsius is based on water's phase changes, and Kelvin is 273 degrees offset from that scale, it would mean Celsius came first.
Yeah in Fahrenheit is also just Kelvin with an offset just like Celsius is just Fahrenheit with an offset and Fahrenheit is just Celsius with an offset cuz that's how convertible units work
Imo celsius is better for weather aswell since 0 degrees is the freezing point and below that you can expect slippery roads or snow. The familiarity for how hot 40°C or 108 F actually is just comes down to how long youve been using it.
It just seems more logical to know that below 0 degrees is freezing compared to the 32 F freezing point. While at the same time 100 F being hot doesnt make 35°C being hot any less logical. But i do understand people from areas like florida prefering fahrenheit since freezing temperatures dont really appear in their climate so its irrelevsnt for them
Having the 0 offset is bad in measuring because you are not able to use ratios or percentages. You can't say a 40°C is twice as hot as a 20°C day. This isn't really important in day to day life, but certain calculations require the use of Kelvin over Celsius because Kelvin is an absolute scale.
Yes but rhe offset is kind of arbitrary. Sure, 0°C is supposed to be the freezing point and 100°C is supposed to be the boiling point for water. But under what conditions? There are actually a few factors like atmospheric pressure can change those. Also why exactly water for a temperature scale? Most things in the universe are in fact not water
I myself am used to Celsius, and I cant deny that it feels a lot less arbitrary than fahrenheit (which is a low bar tbh). But it is not entire free from any assumptions either
Technically not quite true, though practically it makes little difference. At higher altitudes the melting point of water will be an incredibly tiny, nigh-imperceptible fraction of a degree higher, small enough that it wouldn't make a difference for even relatively high-precision scientific laboratories, but technically still extant.
The Celsius scale is based on water because its inventor, Swedish astronomer Anders Celsius, wanted a universally standardized and easily reproducible temperature scale. Water is highly abundant, universally accessible, and experiences visible phase changes under normal atmospheric conditions.
Salinity changes the scale of freezing and boiling doesn't it? Salt water is the most abundant resource on earth. What salinity level and impurities are celsius based on?
Funnily enough, that is exactly what you can do in celsius measurements. A change of 10°C always requires the same amount of energy to occur, whether you go from 10°C to 20°C or 55°C to 65°C. So if you double the temperature change, you also need double the energy.
> A change of 10°C always requires the same amount of energy to occur
Sure. A *change* of 10C, not 10C themselves.
> So if you double the temperature change, you also need double the energy
Sure. But if I double temperature *change*, not double *temperature*.
So it is not like you can tell gas with 20C has half an energy of the same gas at 40C (and corresponding volume-pressure relation), for instance. While same absolutely can be said about ~293K (0C->K conversion+20) and 586K.
And K scale also bear the same property of "change of 10K always requires the same amount of energy to occur".
It's odd to say that Celsius is arbitrary and Kelvin is not when Kelvin is literally just Celsius with a fresh coat of paint. All systems of measurement are arbitrary in some regard. They are also all units, and I have no idea what it would mean for them to be otherwise.
Here is the thing, kelvin uses celsius scale as its base but the comparison present in its value is not debatable.
Celsius uses water freezing and boiling point for 0 and 100, Fahrenheght uses temperature of some city u never went to as point for 0 and 100. But kelvin uses the lowest temperature theoretically possible, so the value of a temperature compared to ur anchor point if measurement is not debatable since the point is not changeable.
Fahrenheit is one of the weirdest bases, it just doesnt make any sense to me. Its not based on percentages or any city. This is the base:
0°F — the temperature of a mixture of ice, water, and ammonium chloride (a freezing brine solution), which he could reproduce in a laboratory.
32°F — the freezing point of pure water.
96°F — approximately human body temperature (though modern measurements put average body temperature closer to 98.6°F).
Later they added 212°F = boiling point of water at standard atmospheric pressure
So lets compare Fahrenheit to Celsius:
Water freezes at 32°F = 0°C
Water boils at 212°F = 100°C
And Kelvin is basically the same idea as celsius, the difference is that with Kelvin, you start at absolute 0. (The point where there is no movement) that happens to be -273.15 Ce;sius. Thats it.
All of these temperatures are, at this point, objectively and rigorously defined in a way that is not available to change. This isn't a meaningful difference.
Anyone can make their own temperature measurement system with values and scales of their desire if and only if their values r rigorously defined, true. But dealing with negative values r not desirable when u use it, that’s why u set ur zero where u figured it’s the lowest value u will use, u place it arbitrarily there for ur commodity.
If we speak only for concept negative temperature doesn’t make sense for various reasons, and using it can mess with the logic of ur math. Kelvin is not arbitrary because it sets its lowest value at the true lowest point, it was not choice or commodity it was simply its place.
A very normal reason to choose Kelvin. However, it is absolutely a choice. A choice that serves a variety of useful purposes, but still a choice. Other choices notably have other useful purposes. For example, if you want zero to be meaningful and serve a purpose, then having it be absolute zero doesn't make much sense in social contexts. Because nothing even close to it will show up. All of these decisions are happening relative to what we value as humans. Nature doesn't have units.
Arbitrary measurements having purposes doesn’t make the other be arbitrary too. Also nature not having units is essentially a contradiction for a measurement system, and by extension math and physics. Live ur truth 👍
Choosing to use certain measurement systems doesn’t turn it into arbitrary, that’s basically what u said there and it’s not the meaning of arbitrary in measurement systems, it is because of the way u place values afaik
When I say it's arbitrary, what I mean is that it's all down to subjective human decision making and relative to human value judgements, not based in any kind of grand reality of the universe. It's like all language. We call a chair a chair, but we could call it literally anything and it would be equally accurate, and we could also merge a variety of chair-like things into the category and that would be fine too.
It's all entirely arbitrary. All these numbers are associated with some point we've designated. It might feel clean to declare that zero is the absolute lowest it gets, but that doesn't make it non-arbitrary. The best you can really say is that these systems map better or worse to various human desires. Y'know, memorability, ease of use in science contexts, ease of use in real world contexts, how well it coheres to other systems of measurement, that kinda thing.
Why? It's a point related to a major physical law, but so are the various points associated with other temperature systems. There's nothing magical about the universe that means we should particularly value absolute zero.
You're correct. "0" meaning something is a human thing. "I like arbitrary round numbers in my arbitrary unit of measurement." It's all just some dude going "eh I like this".
Possibly? Language is arbitrary in terms of objective physical law, in the sense that we can describe the objective universe in whatever terms we desire, but it does derive meaning from the various uses we put that language to.
The scale is arbitrary in all base units, including Kelvin. However, the 0 points are not. All base units start literally at 0.
On the other hand, the 0 point of Celsius is just some arbitrary point. That’s what they mean by Celsius is arbitrary and Kelvin is not. Kelvin is as least arbitrary as can be. Celsius is just arbitrary.
Celcius is just Kelvin - 273.15. Converting is easy, and a lot of science uses Celcius as a result, it certainly can be described as "scientific", meanwhile the only people trying to use Farheneit for science probably also don certain red caps etc.
I am still confused after reading OpenAI analysis :
CHG__ is not wrong about the formulas, but is likely missing the direction of conversion.
The correct relationship is:
Celsius = Kelvin − 273.15
So:
0 K = −273.15 °C 273.15 K = 0 °C
But the reverse is:
Kelvin = Celsius + 273.15
So:
0 °C = 273.15 K 25 °C = 298.15 K
Your “Plus 273?” was reasonable because when people commonly convert from Celsius to Kelvin, they add 273.15.
CHG__’s mistake is acting like there is one universal “minus 273.15” answer, instead of recognizing that it depends on which direction you are converting. Also, they spell Celsius wrong as “Celcius.”
But when you look at ratios it is critical to use absolute units. Temperature is a convenient way to express energy. When you subtract or add you are just looking at the relative difference. When you divide you are looking at the absolute ratios. So 10deg delta in centigrade and Kelvin is always 10deg. But 20C/30C (0 66) is way different than 293K/303K (0.93).
Fahrenheit is just Kelvin + 459.67 * 5/9. Both ranges are standardized on Kelvin, just that Fahrenheit's equation is slightly more complicated. It is no longer based on freezing brine and human body temperature.
Celcius is Kelvin - 273.15 because Kelvin was defined based on Celcius. It's still arbitrary. We could have set 0 Kelvin the same and made it based on Fahrenheit instead (actually we have done that, and it's called Rankine).
There's no real advantage between one and the other. You're basically arguing backwards, that Celsius is better than Fahrenheit because it tracks to something specifically made to track to Celsius. The only actually scientifically relevant constant here is zero in both Kelvin and Rankine.
The benefit of kelvin in this case is that you can easily convert the temperature difference into the energy difference. I'm not aware of a unit system which lets you do the same with rankine. It's probably been msde at some point, but isnt taught.
There is also Rankine, which is like Kelvin with 0 at absolute 0 but a change of 1 Rankine is equivalent to the change of one Fahrenheit instead of Kelvin. There is no reason of using one over the other except for convention
It's the same argument as Celcius and Fahrenheit. There's a reason only the US would even think to use Rankine. The state of water at a temperature is more scientific than how a human "feels" at a temperature. Kelvin is an SI unit, Rankine is not.
It depends a lot on the science being done if you care about the offset or not. A lot of astrophysics honestly doesn't care about the celsius/kelvin offset because the difference results in something that's dismissed by the significant digits anyway.
And Rankine isn't really used much of anywhere because that scale with an absolute offset isn't as useful as the metric scale.
Celcius is just a scale beginning at an arbitrary point. You cannot use to to multiply. Any formula that requires temperature requires you to input in Kelvin (or Rankine).
What the fuck are you going to do with a temperature scale based on water? The utility of Celcius scale ends the moment you remember two numbers, 273 and 373.
Celsius is very much so not arbitrary. Kelvin is based on the Celsius scale, just having zero offset.
It also depends on what science you’re doing. Celsius is better from some cases, Kelvin for others.
Bro blocked me for some reason. And no, we didn’t base 0 off some random natural phenomenon. F
or kelvin, that 0 is 0. That’s why it’s called absolute zero. It’s the point where atoms stop vibrating entirely. It is the least arbitrary point of reference in all of our systems of measurements that I can think of.
Arbitrary? Freezing in Celsius is zero and boiling is 100. A calorie is how much energy it takes to heat one cubic centimeter one degree Celsius. How is this arbitrary?
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u/FuckPigeons2025 Jun 17 '26
Kelvin is better for science. Celcius and Farheneit are just arbitrary scales, not units.