Why do we need different temperature scales?

[Frigus]

I want to know that why we have defined value of temperature of boiling point and melting point of water different on different scales, as I can think we need to know temperature so we have given a certain value to melting point and boiling point of water and we have given them some value but why we need different scales Like Kelvin Celsius e.t.c.

 

[Dale]

We don’t need different temperature scales. They are used because of preference or convenience, not necessity.

 

[Anand Sivaram]

https://www.straightdope.com/column...e-do-0-and-100-have-any-special-significance/
An interesting link about the Fahrenheit scale

 

[tech99]

These scales came about historically when there were no standards to calibrate a thermometer against. The Fahrenheit scale used the temperature of the coldest thing then known for its zero, which was salty ice. It used blood temp, which is quite stable, for 100 degrees. I remember trying to make thermometers when at school aged about 10, as we did not own one and, having an exceptionally cold winter, wanted to find out how cold it actually was.

 

[WWGD]

These scales came about historically when there were no standards to calibrate a thermometer against. The Fahrenheit scale used the temperature of the coldest thing then known for its zero, which was salty ice. It used blood temp, which is quite stable, for 100 degrees. I remember trying to make thermometers when at school aged about 10, as we did not own one and, having an exceptionally cold winter, wanted to find out how cold it actually was.

That's pretty enterprising of you. Did you actually build one.

 

[tech99]

That's pretty enterprising of you. Did you actually build one.

I think I used an inverted bottle over a cup of water to make a gas thermometer.

 

[Andy Resnick]

I want to know that why we have defined value of temperature of boiling point and melting point of water different on different scales, as I can think we need to know temperature so we have given a certain value to melting point and boiling point of water and we have given them some value but why we need different scales Like Kelvin Celsius e.t.c.

The Kelvin and Rankine temperature scales are 'absolute' scales, defined without reference to any specific material. The Celsius and Fahrenheit scales are defined in reference to the phase behavior of water.

 

[kuruman]

https://www.straightdope.com/column...e-do-0-and-100-have-any-special-significance/
An interesting link about the Fahrenheit scale

I found the article rather condescending to old man Fahrenheit. The author states, Then, for reasons nobody has ever been able to fathom, he multiplied all the numbers by 16/15, making 32 freezing and 96 body temperature. Boiling point for the time being he ignored altogether. As I understand it, the numbers were adjusted to make their difference 64. Given the tools of the time, it was easy to bisect a given length into halves, then bisect each half into quarters and so on until you reach 64 equal segments. Think of finding the perpendicular bisector of an arbitrary line segment using compass and ruler. Once technology and instrument-making caught up with the times, we advanced from the Fahrenheit binary subdivision to the decimal Celsius scale.

 

[JT Smith]

The Kelvin and Rankine temperature scales are 'absolute' scales, defined without reference to any specific material. The Celsius and Fahrenheit scales are defined in reference to the phase behavior of water.

They don't have an absolute reference but the scale isn't arbitrary.

I think that speaks to the point of this thread. Suppose you were to devise a temperature scale. How would you decide what the units were?

 

[phyzguy]

I want to know that why we have defined value of temperature of boiling point and melting point of water different on different scales, as I can think we need to know temperature so we have given a certain value to melting point and boiling point of water and we have given them some value but why we need different scales Like Kelvin Celsius e.t.c.

Why do we need different languages? Wouldn't it be simpler if we all spoke the same language?

 

[Frigus]

fixed

Why do we need different languages? Wouldn't it be simpler if we all spoke the same language?

Why do we need different languages? Wouldn't it be simpler if we all spoke the same language?

Because earlier when civilizations were started the transportation was not so developed so people do not travel a lot and therefore different civilizations developed different languages but at the time we have made the scales we almost have all facilities to do communication.

 

[symbolipoint]

https://www.straightdope.com/column...e-do-0-and-100-have-any-special-significance/
An interesting link about the Fahrenheit scale

After reading the article about Fahrenheit, I believe we should completely discard that scale and never use it again. The parts of the world which use this scale may not be so convinced.

 

[Anand Sivaram]

They don't have an absolute reference but the scale isn't arbitrary.

I think that speaks to the point of this thread. Suppose you were to devise a temperature scale. How would you decide what the units were?

Kelvin scale is an absolute scale. The two constant temperatures are Absolute Zero at 0K and the Triple point of water at 273.16K. That is how Kelvin scale was defined in 1968 during CGPM . As Celsius scale was popular, deliberately 1K difference was kept the same as 1C difference.

Anyway, recently a few months ago, the definition of Kelvin has been modified to use Boltzmann's constant.

The kelvin, symbol K, is the SI unit of thermodynamic temperature; its magnitude is set by fixing the numerical value of the Boltzmann constant to be equal to exactly 1.380649 × 10-23…J K-1[joules per kelvin].

Reference:
https://en.wikipedia.org/wiki/Kelvin#History
https://cryogenicsociety.org/36995/news/nist_explains_the_new_kelvin_definition/

 

[phyzguy]

fixed
Because earlier when civilizations were started the transportation was not so developed so people do not travel a lot and therefore different civilizations developed different languages but at the time we have made the scales we almost have all facilities to do communication.

It's not so different from languages. Two different scales were defined and became standards in two different parts of the world. Now the regions that use the Celsius scale and the regions that use the Fahrenheit scale are each happy with their scale and nobody wants to change. Even in the US where we use the Fahrenheit scale for everyday weather, the Celsius scale is used in virtually all scientfic work.

 

[anorlunda]

Regarding personal use, I think it is a matter of memories. Having lived in places that used F and other places with C, I find that my memories do not change scales. I remember a particular day or night, how warm/cold it was, what it felt like and what the thermometer said. If I move from one country to another and change which scale I use daily, my memories do not translate.

Amusingly, I remember playing hockey on the river when it was -40. I remember what -40F feels like. I separately remember what -40C felt like a different year in a different place. But my memories would probably not catch the fact that the temperatures are the same. I think it is one of those enigmas of psychology.

 

[Dale]

After reading the article about Fahrenheit, I believe we should completely discard that scale and never use it again. The parts of the world which use this scale may not be so convinced.

Fahrenheit is simply a rescaling of Celsius. If we get rid of one then we should get rid of both. (Which I support, Kelvin or another absolute scale is preferable)

 

[hutchphd]

When asked to quantify pain or pleasure or any subjective experience the inquisitor will almost always specify "on a scale of 0 to 10" or "on a scale of 1 to 100" tell me what you feel. Seldom will the doctor ask "on a scale of -10 to 40 quantify your pain".
It is for this reason that I am unabashedly in favor of using the Fahrenheit scale for reporting temperatures in our day to day human environment. Seldom (for now at least) does the temperature stray outside the pleasing realm of 0 to 100. A temperature of 70 is copacetic. Above 100 is very hot and below 0 is very cold. And 110 seems about as unreasonably hot as -10 seems unreasonably cold (although this part may be entirely conditioned by my familiarity with Fahrenheit).
So while it is absurd that we in the states refuse to adopt a decimal based system of weights and measures, it would be equally absurd to eliminate F in favor of C. Human beings deserve a human scale. When I do science I use Kelvin (Rankine would be fine with me but that seems unlikely) but when I its really hot out I want it to be 100 and not 38.
Fahrenheit Forever...

 

[phyzguy]

Things that you learn as a child (like language) are difficult to change as an adult. I'm in the US, so I grew up with the Fahrenheit scale. When I see a weather report, I instantly know how to dress for the forecasted temperature. I lived for five years in another country that used the Celsius scale, but even after 5 years I would see the weather report and I would have to convert the temperature in order to know how to dress. It's interesting, because after a while I didn't have to convert meters, liters, or grams, but I always had to convert temperature.

 

[lekh2003]

Rankine is clearly the superior scale. \s

 

[anorlunda]

Building on the idea of memories, I wager that we could invent a non-numeric temperature scale that would work for most people.

A 5 step scale may have cold/grey/pleasant/pink/hot. We could have as many steps as we want, and choose any words as the symbols. My belief is that the meaning of the words is unimportant, but rather the association of a word or a number with a feeling and a memory. Our brains are associative.

 

[WWGD]

Building on the idea of memories, I wager that we could invent a non-numeric temperature scale that would work for most people.

A 5 step scale may have cold/grey/pleasant/pink/hot. We could have as many steps as we want, and choose any words as the symbols. My belief is that the meaning of the words is unimportant, but rather the association of a word or a number with a feeling and a memory. Our brains are associative.

Or maybe the number/type of layers:
3 jackets/2 jackets/1 jacket/light sweater/ t-shirt with maybe a sauna on the right and a " seek shelter" on the left end. Though I wonder if people experience cold similarly-enough to each other for this scale to be helpful.

 

[Vanadium 50]

Or maybe the number/type of layers: 3 jackets/2 jackets/1 jacket/light sweater/ t-shirt

Or Three Dog Night?

 

[WWGD]

Or Three Dog Night?

I had to look it up. It's a band, but I don't see the connection. I am not a hip guy like you , Vanadium ;).

 

[phyzguy]

I had to look it up. It's a band, but I don't see the connection. I am not a hip guy like you , Vanadium ;).

The band got its name from an Inuit term. Sometimes the winter nights were so cold that you had to take three dogs to bed with you in your igloo in order to keep warm.

 

[sophiecentaur]

Fahrenheit Forever...

Hah! Is there anything more arbitrary than using 32° for the melting point of ice - the most recognisable, feelable and safely reproducible fixed point that we could devise?

All unit systems have to be used for them to be accepted by an individual. I think one can get to use and even to love almost any system of measurements unless exposed to unreasonable cultural influences. Why else did we have greengrocers and butchers in the UK offering their goods in pounds and ounces, years after we took the (incomplete) metric step?

I fully expect a 'Resurrect Imperial Measures' movement to emerge if Brexit ever happens. At least the UK never got to drive on the right hand side of the road . . . . . .

 

[phyzguy]

Hah! Is there anything more arbitrary than using 32° for the melting point of ice - the most recognisable, feelable and safely reproducible fixed point that we could devise?

Why are phase changes of water the correct way to set your temperature scale? I think @hutchphd has a good point. If you're talking about reporting the weather, then having 0 being "about as cold as it ever gets" and 100 being "about as hot as it ever gets" makes a lot of sense.

 

[WWGD]

I don't know if it is oversimplification to say that metric is "theoretically nice" and easier to use, with its metric system while English system is more reflective of the real world : feet, yards, etc

 

[sophiecentaur]

Why are phase changes of water the correct way to set your temperature scale?

Nothing in this life is Correct. The point is that the triple point of water is pretty damn easy to work with and we only need to look at a glass of water to tell if it's 0°C outside. Also, pure boiling water is easily obtainable. Both those fixed points are highly practical - same as a lot of other modern measuring standards (Hydrogen wavelength etc.). Dividing that temperature range into 100 degrees also makes a lot of sense. 32 and 212 are not numbers that make a lot of practical sense. Perhaps 100F as the approximate temperature of the human body is the one redeeming feature of the Fahrenheit system. Otherwise it doesn't get my vote - but its easy for me as I was weaned off it when I was in early teens.

 

[JT Smith]

I don't know if it is oversimplification to say that metric is "theoretically nice" and easier to use, with its metric system while English system is more reflective of the real world : feet, yards, etc

The metric system isn't theoretically nice; it's easier to use. But I agree that some of the units are less human-oriented than others. Like with weight, an ounce is something you can feel easily. A gram? Too small. I suppose you could use decagrams instead of ounces but that's kind of clumsy.

I grew up with the Fahrenheit scale and so I'm very comfortable with it. But when I'm overseas I get used using Celsius pretty quickly. It's really not a big deal.

 

[WWGD]

The metric system isn't theoretically nice; it's easier to use. But I agree that some of the units are less human-oriented than others. Like with weight, an ounce is something you can feel easily. A gram? Too small. I suppose you could use decagrams instead of ounces but that's kind of clumsy.

I grew up with the Fahrenheit scale and so I'm very comfortable with it. But when I'm overseas I get used using Celsius pretty quickly. It's really not a big deal.

Yes, it was akward phrasing , I should have said less clunky or akward maybe. Or sanitized; just go from unit to unit by multiplying by powers of 10.

 

[Nugatory]

The parts of the world which use this scale may not be so convinced.

As with the continued use of English units in America - and at this point I must mention member AlephZero's comment about "'English units' (which are no longer used in England in science and engineering, so they really ought to be called 'stupid American units' IMHO)" - it's primarily a matter of economics. The American economy is so large that the cost of switching exceeds the benefits of switching.

 

[symbolipoint]

The metric system isn't theoretically nice; it's easier to use. But I agree that some of the units are less human-oriented than others. Like with weight, an ounce is something you can feel easily. A gram? Too small. I suppose you could use decagrams instead of ounces but that's kind of clumsy.

I grew up with the Fahrenheit scale and so I'm very comfortable with it. But when I'm overseas I get used using Celsius pretty quickly. It's really not a big deal.

One gram weighs what one dollar (bill) weighs.
With that demonstrable comparison, one pound of dollars(the individual paper money bills) would weigh about 454 grams (taking its equivalent in mass, since 'mass' and 'force' are not the same thing). After reviewing all that, be careful about "pounds" in any "pounds" money unit.

 

[hutchphd]

Otherwise it doesn't get my vote - but its easy for me as I was weaned off it when I was in early teens.

But on a scale of, say, -7 to +19 how do you rate each temperature method?...okay I'll stop.
My major point is that there is much to recommend changing the US system to metric but there is no compelling reason to discontinue Fahrenheit and I would argue some reason for keeping it. One need not throw out the baby with the bath water.

 

[Asymptotic]

One good thing about having several different temperature scales is it provides handy, everyday examples when teaching motor drive, and other types of process scaling.

What I wish is Celsius considered "200" the boiling point of water rather than "100". That way, it would have preserved (and somewhat bettered) the integer resolution of the Fahrenheit scale, but without the odd offset of 32 as the freezing point of water.

 

[vanhees71]

They don't have an absolute reference but the scale isn't arbitrary.

I think that speaks to the point of this thread. Suppose you were to devise a temperature scale. How would you decide what the units were?

But the scale is arbitrary, as you see from the use of both the Kelvin and Rankine definitions as the unit for absolute temperature. Today the SI unit K is finally defined by fixing the value of the Boltzmann constant $k_{\text{B}}$.

In natural units you set $k_{\text{B}}=1$ and measure temperatures in, e.g., MeV (in relativistic heavy-ion physics ;-)).