Why do we need different temperature scales?

[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 ;-)).

 

[sophiecentaur]

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.

As a Scientist, I should have thought that a system that tracks the Kelvin scale would be very desirable. I am really amazed how people (on PF even!) appear to be so emotionally attached to Fahrenheit.
I have the same problem with the Mile. Why the UK still uses the mile, in amongst all the metric units, is hard to explain. When moving to decimal coinage in the early seventies, we had loads of reaction in the UK but, because they had no option, the public just adopted it. We still ask "what's that in old money?" but for all sorts of different unit comparisons (not just money). That question is used ironically and is often a dig at old fashioned ideas in general.

It's really not a big deal.

That's the most relevant comment in the whole thread.

 

[sophiecentaur]

Suppose you were to devise a temperature scale. How would you decide what the units were?

If I had any sense then I would base it all on convenient fixed points and so would Scientists on the Planet Zog. If they were (sensible) carbon-based life forms then odds are that they would also choose the melting and boiling points of water (OK - local atmospheric pressure etc. could affect their Standard Temperature and Pressure choices). It's unlikely that 0K would have been involved when their temperature scales were invented. The -273 number would just have been 'found' somewhat later. If the Zoggians happened not to have five digits on a hand then they might not be using a decimal system but you can bet they would have used degrees between melting and boiling points, based on their number system. Not "arbitrary" but linked to their arithmetic system - like our 100 degrees.
Interestingly (?) the Zoggian absolute zero would also be at -2.73 times their basic melting / boiling interval.

 

[hutchphd]

I'm with @vanhees71 for my scientific scale...give me eV all the time. The Zoggians could do their derived single point calibration from any fixed energy event (say Hydrogen alpha) assuming they are technically savvy.
This still leaves the problem of the weather guy on the tube. I don't think "tomorrow's high will be 1/40 eV" is likely to catch on. Nor would Celsius ab initio , I contend. This is a very small point but the context is larger. I am a scientist to my very core, but the "natural" unit for measurement are not always the "best for everyone" units.
Now I must get in my car and drive 30 miles per hour to the grocery...I will not drive at 4x10^-8c. Perhaps we would all be better scientists if we did, but it would get tedious!

 

[sophiecentaur]

In the same vein. I just learned something this morning about the good old imperial foot. Apparently, UK cartographers and surveyors use(d) decimal feet in their height measurements. At a talk on old benchmarks, the guy brought out surveying poles with tenths of a foot markings. It's been that way for ages, according to him. I wonder it that's standard practice in the quaintly imperial United States.

 

[hutchphd]

My brother is a land surveyor (retired) and I will ask him. Was there a name for the unit? I have not seen it myself. I have of course seem rulers with the inches delineated in tenths (I even have a set of calipers so delineated and of course micrometers are always in mils). Yes the law was on the books to metrify the US (Jimmy Carter's impetus) but Mr Reagan, in his infinite Republican wisdom, made it go away.
Some time you will need to describe why the British have so damned many different styles of screw threads.

 

[JT Smith]

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).

Demonstrable? I suspect that dollar bills do not weigh 1.000 ± 0.001g, which is how precise their weight would have to be to guarantee that 454 of them weighed 454g.

In any case, my point was that it's too small a weight for humans to detect easily. If you put a dollar bill in your hand you will feel the paper on your skin. But if insulate your hand from the sense of touch you almost certainly will not feel the weight.

But the weight of 28 bills (about an ounce) is much more easily detectable.