Your pet peeve, technical or otherwise.

[PlainName]

What's wrong with using centigrade? 150% of 20C is 30C, isn't it?

[Analog Kid]

* Only us who are from there are permitted to call it "IlliNOISE", which of course is wrong ...

Tell that to someone in New Jursee.

You mean "Joisey", of course. Where the balance of "R"s is all out of whack:
Toilet = "terlet"
Jersey = "Joisey"

[Analog Kid]

What's wrong with using centigrade? 150% of 20C is 30C, isn't it?

So you're saying that this can only apply to Centigrade, not Fahrenheit?
Yet another slander against our (N. American) system (which I say is superior as it has greater resolution than °C). And really, who cares about 0°=freezing and 100°=boiling? That's just a round-number fetish.

[PlainName]

You can use Fahrenheit but then you'd need to specifiy your base value: using the logical 0C/32F gives a different change than if you use 0F. By using C you incorporate that automatically.

Yet another slander against our (N. American) system

Not at all. It was refutation of needing to use Kelvin by showing an example that would be easily understood. There are other scales that could be used, but listing all of them, and using examples in each, would just confuse the matter.

That's just a round-number fetish.

Nowt wrong with that. Easy to understand and use - what's not to like?

[Infraviolet]

For both centigrade and fahrenheit, the zero point is arbitrary and when you get cold enough you cross it. This means working in terms of temperature ratios, and therefore percentages, can get confusing. Furthermore, as temperature is a measure of the kinetic energy per molecule, how fast atoms of a gas at that temperature are flying around, the idea of a temperature being 150% of another should be taken as meaning molecules are rushing around 1.5 times as fast, this only works when you use Kelvin where the particles have zero energy (stop moving) at zero kelvin and cannot get any colder (nor technically, can they ever get quite down to zero kelvin, just arbitrarily close to it). 150% of 20 celsius is: 20C = 20C+273=293K then 293K*1.5 gives 439.5K, which converts back to 146.5 C. This really matters when you're using equations which include temperature as a variable, like the thermal radiation emission T^4 law (how much infrared a warm body kicks out, or how much visible light if it gets hot enough to glow), there's a good reason they all work in Kelvin and you have to convert values to other units before and afterwards if you really want to use C or F.

[Analog Kid]

Maybe I'm missing something here, but I can't understand why one can't just treat a temperature, no matter what the scale, as a percentage of some other temp. Nothing special about temp as a quantity that I can see: "X is Y% of Z" seems perfectly valid to me.

We can do it with voltage, current, frequency, etc., etc.; why not temperature?

[Analog Kid]

That's just a round-number fetish.

Nowt wrong with that. Easy to understand and use - what's not to like?

Except that there's really nothing needing to be "understood" here. We're taught from a very early age that 32°=freezing, 212°= boiling and 68°=room temperature, and somehow we manage to retain that and don't have to refer to any cue cards to figure out whether it's hot, cold or balmy. (Same goes, of course, to those who grew up using °C.)

Like knowing that 4 quarts=1 gallon, 12"=1', 1 mile=5,280', etc., etc. Somehow we manage to muddle along here ...

[PlainName]

what's 2/3 the way between freezing and boiling? What is 176F? Fahrenheit is just a horrible scale to do things with, and the only reason we get on with it is because we learn it by rote: 68F is comfortable working, 50F is cold, etc. It is like the time table in that we only know instantly that 7x6 is 42 because it's been drummed into us. We pretty much never work it out. With 0-based scales we can work with unusual values easily, and they tend to be meaningful rather than 'because they are'.

[Analog Kid]

What's 2/3 of the way between freezing and boiling? Welll:

Code: [Select]

(212 - 32) * 2 / 3 = 120Was that so hard? Sure, probly can't do it easily in your head, but who cares? How many times will a problem like that come up?

176°F: pretty damn hot. Hot enough to fry an egg, probly.

Really, what is "meaningful" about 0°=freezing, 100°= boiling? Just round numbers is all. Are we really that stupid that we need that level of "roundness" to remember things?

BTW, do they really use Fahrenheit over there in Vatican City?

[TimFox]

Maybe I'm missing something here, but I can't understand why one can't just treat a temperature, no matter what the scale, as a percentage of some other temp. Nothing special about temp as a quantity that I can see: "X is Y% of Z" seems perfectly valid to me.

We can do it with voltage, current, frequency, etc., etc.; why not temperature?

You can treat temperature as a fraction of another temperature, but only in absolute temperature (Kelvin or Rankine).
Otherwise, Fahrenheit and Celsius are like "utility" in economics or game theory:  you can only compare differences (e.g., 10^o C to 30^o C is twice 15^o C to 25^o C .
The other variables you mention go neatly down to zero, just like absolute temperature.

[PlainName]

you can only compare differences (e.g., 10o C to 30o C is twice 15o C to 25o C

So 30C is 50% difference from 0C than 20C is, right?

I am not seeing the problem.

[PlainName]

What's 2/3 of the way between freezing and boiling? Welll:

Code: [Select]

(212 - 32) * 2 / 3 = 120Was that so hard? Sure, probly can't do it easily in your head, but who cares?

That - the emphasised part - is what it's about. The rest is just deflection to make it seem irrelevant.

[RJSV]

   Yes well my inclination is to view a number, like '156' as having some Xtra implied value,  that of a bottom or zero.

   If you say '156' bunnies,  thats with implied zero as the other end, like you would a length calculation.

   If you wish to increase, say 2%,  it's of the 156.

   But better include the bottom,  if that's Fahrenheit as that's the system.
Putting the '156' minus 32,  gets the bias out.
At that point you can do the 2% increase.   Since it's a percentage increase,  it won't matter how big each 'degree' is,  (so no need to reconcile).

However,  must say my confidence factor,  in my answer here,  is only 39 %.

[TimFox]

you can only compare differences (e.g., 10o C to 30o C is twice 15o C to 25o C

So 30C is 50% difference from 0C than 20C is, right?

I am not seeing the problem.

Yes, compared to 0^o C, except your arithmetic is wrong. 
A 0^o to 15^o increment is 50% of 0^o to 30^o, whether you use Celsius, Fahrenheit, or Réaumur.
However, physics explains the necessity of absolute temperature to say that a given temperature is twice another.

An analogous example:  Chicago has a Cartesian system for street numbers, with 100 numbers = 1 furlong (1/8 statute mile = 220 yards).
The distance from Fullerton Ave (2400 N) to Belmont Avenue (3200 N) is 1 mile, which is half the distance from Fullerton Ave to Irving Park Rd (4000 N).
However, Irving Park Rd is not 1.67 times Fullerton Ave in location.

[Analog Kid]

A 0^o to 15^o increment is 50% of 0^o to 30^o, whether you use Celsius, Fahrenheit, or Réaumur.
However, physics explains the necessity of absolute temperature to say that a given temperature is twice another.

OK, so we can paraphrase the Bible here and say "all temperature scales (save one) have sinned and fallen short of relative comparability". Meaning that neither Centigrade nor Fahrenheit can be so compared: one needs Kelvin for that.

°C no better than °F in this department ...

[TimFox]

A 0^o to 15^o increment is 50% of 0^o to 30^o, whether you use Celsius, Fahrenheit, or Réaumur.
However, physics explains the necessity of absolute temperature to say that a given temperature is twice another.

OK, so we can paraphrase the Bible here and say "all temperature scales (save one) have sinned and fallen short of relative comparability". Meaning that neither Centigrade nor Fahrenheit can be so compared: one needs Kelvin for that.

°C no better than °F in this department ...

Don't forget Rankine (absolute Fahrenheit).  Your paraphrase makes little if any sense in this case, even as an analogy.
This is why the SI unit for temperature is the Kelvin (the "degrees" is redundant and not used in careful writing).

[PlainName]

However, physics explains the necessity of absolute temperature to say that a given temperature is twice another.

Yes, I see the issue. The context, however, is how the temperature feels to a person (that is, TV weather reports), so it's on rather wobbly ground to start with.

[TimFox]

However, physics explains the necessity of absolute temperature to say that a given temperature is twice another.

Yes, I see the issue. The context, however, is how the temperature feels to a person (that is, TV weather reports), so it's on rather wobbly ground to start with.

For judging how one feels (from a weather forecast), Fahrenheit is better suited to human biology and has roughly twice the resolution, so on that grounds I prefer it when deciding on which sweater to wear.
For real physical situations, Kelvins are preferred.

[TimFox]

Once again, XKCD has this covered.
 https://xkcd.com/3001/
(There are actually more scales that have been used than this, but these should cover most applications.)

[RJSV]

I'm more and more convinced:

   Take the physics out of consideration.   Now 32 degrees F is up above zero F,  but neither value needs to be tied to 'zero molecular motion.   You just need a scale that starts at zero,  in whichever format.
   It's the VALUE that increases,  and any percentage change needs a value range,  that starts a zero.
   So,  with Fahrenheit the '32' is just a physics and H2O reference.   The MATH however,  starts at 0° F.   Therefore you can specify the math driven increase.

   So,  150 % of 32 will be 48...naked numbers to slap meaning on as the last step.

[RJSV]

...I mean;   Otherwise you get caught up into trying to multiply X zero,  at 32 F.

[TimFox]

I'm more and more convinced:

   Take the physics out of consideration.   Now 32 degrees F is up above zero F,  but neither value needs to be tied to 'zero molecular motion.   You just need a scale that starts at zero,  in whichever format.
   It's the VALUE that increases,  and any percentage change needs a value range,  that starts a zero.
   So,  with Fahrenheit the '32' is just a physics and H2O reference.   The MATH however,  starts at 0° F.   Therefore you can specify the math driven increase.

   So,  150 % of 32 will be 48...naked numbers to slap meaning on as the last step.

See my analogy above for street addresses.  Increments, differences, or changes can be compared, single values cannot.

[RJSV]

Disagree.
   Any number like '30' will be 30 degree units above zero and so,  if you go up, to 31 that's again relative to your zero,  thus adding a 30th.
All percentage changes would be relative to first value, before the change.

   Centigrade already has that implicit zero as the start,  but the value '32' F hasn't any context or meaning, until later when you identify that as the physics phenomenon.

   You could say,  accurately, that BOTH types of measuring, (C or F) have a scale from 0 to 100 and beyond really, both in the negative direction, and positive direction.
   It's just that the physics makes the distinction of when a value is 'impossible'.

   After you tell 'Fred' that 30 is another half, past 20,  you've then gotten the task of explanation,  and again it's one of physics interpretation.

   You have to say that the answer, '30' isn't a direct moleculer motion LINEAR relation.
Essentially telling poor 'Fred',  that as far as temperature measuring goes,  sometimes the best you can conclude is of which temperature exceeds another temperature.

[vk6zgo]

Central US? Grew up in Illinois*; can't get any more central than that. Never heard even a hint of the "L" in walk, talk, etc. Maybe the somewhat New Yawk/Jewish "tawk", "wauk", but no intrusive "L". Dunno where you might have heard that.

There are always those weirdos who insist on oddball pronunciation, like "of-ten" instead of the standard "offen".

* Only us who are from there are permitted to call it "IlliNOISE", which of course is wrong ...

I wonder if you're as equally ticked off when people say "Arkansas" as "Ar-kan-sus"... even I made that mistake one time

That said, do any Canadians here feel annoyed when anybody says "Etobi-Coke" instead of what it actually is?

Western Australians are freaked out when people from the other states call "Albany" "Orlbany", or "Derby", "Darby".

The "snooty version" of "often" was, when I was younger, "offen".

My answer to that was that the line in Wordsworth's poem "I wandered Lonely as a cloud" wasn't
 
" For off when on my couch I lie."

The "snooties" also liked to pronounce "ate" as "et", like unto Jed Clampett.

[Analog Kid]

The "snooty version" of "often" was, when I was younger, "offen".

My answer to that was that the line in Wordsworth's poem "I wandered Lonely as a cloud" wasn't
 
" For off when on my couch I lie."

But "offen" is the accepted (American) English pronunciation; silent "t". "Often" sounds weird to our ears. (Unlike the poetic "oft".)
(Apologies if you already knew this.)