PDA

View Full Version : If its 0 degrees centigrade...

sinala1
30th Sep 2005, 19:39
then how cold would it be if it were twice as cold?

:confused:

(this was on Brainiac and I never saw the answer - could go into Faranheit and Kelvin temperatures etc but I cant be f**ked trying to figure it out)

Bre901
30th Sep 2005, 19:54
The only temperature scales for which multiplication makes sense are the Kelvin or Rankine scales as they are both absolute, i.e. they originate at the absolute zero.

If you double the absolute temperature of a given mass of ideal gas at constant volume, the pressure doubles.

:8 :8 :8

sinala1
30th Sep 2005, 20:02
So do you suggest I find out the kelvin value of 0 degrees centigrade, halve that value, then convert that figure back to centigrade?

(in all honesty not that I really care, nor was I expecting a proper answer out of jetblast :O )

flyblue
30th Sep 2005, 20:04
It depends on which scale you are using, if Celsius, Farenheit or Kelvin, since "zero" is a different concept. Celsius "zero" is between -273,17° (absolute zero) and the positive temperatures, Farenheit "absolute zero" is - 459 while on Kelvin "zero" would be what is called "absolute zero" on Celsius and Farenheit= the coldest temperature possible. So I'd say it's not possible to have twice as cold as Kelvin zero, while on C and F it can be discussed (halve it?? :confused: ) .

tony draper
30th Sep 2005, 20:13
One hates to be pedantic but theres no such thing as "cold" what you are seeking is the difference in heat, not cold.
:rolleyes:

G-CPTN
30th Sep 2005, 20:21
We were taught at school that hot air rises, but cold air stinks.

flyblue
30th Sep 2005, 20:24
I agree Drapes, twice as cold as what? What is "cold"? Can you compare a sensation with degrees? :confused:

ShyTorque
30th Sep 2005, 20:45
The Three Degrees were quite a sensation in Herr Draper's younger day ;) Does that help?

Bre901
30th Sep 2005, 21:33
So do you suggest I find out the kelvin value of 0 degrees centigrade, halve that value, then convert that figure back to centigrade? that's provably what I'd do, were I asked such a strange question (twice as cold doesn't really mean anything, whereas twice as hot would, on an absolute scale, as pointed out above by various posters)

My guess would be 273.15 / 2 = 136.575 K or -136.575 deg C

Signora Flyblue Celsius "zero" is between -273,17° (absolute zero) and the positive temperaturesSpent more time looking at the physics teacher's eyes than at the blackboard, haven't you ? ;)

There is only one absolute zero. As temperature is related to atomic or particular motion, it is the temperature at which everyting stops moving, even the tiniest particles. incidentally, you would need an inifite amount of energy to reach it. Lowest temperatures achieved are in the microK range (one millionth).

Initially the Celsius scale was defined as 0 = freezing water, 100 = boiling water at atmospheric pressure.

Nowadays the definition of absolute temperature is the following : the triple point of water (liquid/solid/vapour equilibrium) is at 273.16 K (K stands for Kelvin - there is no such thing as a degree Kelvin). As it is an absolute scale, the origin is at the absolute zero.
The Celsius scale is a relative scale and is defined by 1 degree Celsius = 1 K and the origin of the Celsius scale is at 273.15 K

hence :

TK = Tc + 273.15
Tc = TK - 273.15

Farenheit is a bit more complicated :
initially 0 degrees F = ice/salt brine, 100 degrees F = Farenheit's body temperature (BTW he was a bit feverish)
Nowadays Tc = (5/9)*(Tf-32), Tf = (9/5)*Tc+32
0 deg C = 32 deg F, 0 deg F = -18 deg C, etc

Rankine is an absolute scale where 1 R = 1 degree F = 5/9 K
Absolute zero is indeed at -459 F

:8 :cool: :8 :cool: :8

G-CPTN
30th Sep 2005, 21:55
Twice as cold? Do they mean half as hot?
Twice as anything implies an initial separation from 'the norm' (and then doubling it). AFAICT the attempts at calculation using Absolute temperatures are relying on the separation of 0 deg C from Absolute Zero (which cannot in any way be considered a 'norm' IMHO).
If you were to consider STP (Standard Temperature and Pressure),
"Definition: Standard temperature and pressure. The standard conditions used as a basis for calculations involving quantities that vary with temperature and pressure. These conditions are used when comparing the properties of gases. They are 273.15 K (or 0°C) and 101325 Pa (or 760 mmHg)."
Then there IS no separation from 0 degC, therefore twice (or half) the separation is zero, so the answer is the figure that you first thought of (sort of).
No?

If you want to measure 0 deg C from the average norm ambient temperature, then the world is your lobster . . .

BTW -40 deg F is also -40 deg C (but you knew that anyway . . . )

Avtrician
1st Oct 2005, 00:14
G-Cptn
Was going to say some thing along those lines.

English is a strange language, in that you try to multiply some thing to result in a smaller result.
Does twise as cold mean 1/2 the temperaure, is is the sensation of cold measured on a logerithmic scale?

20 Deg C is warm, 15 is cold, 25 is getting nice (or a heat wave in England) 30 uncomfortable 32 hot 40 dont think about that.

Its all too hard for a Saturday morning, and I'm only on my second coffee.

tinpis
1st Oct 2005, 03:06
Tin never drinks beer in tempuratures below 30C

flyblue
1st Oct 2005, 10:13
Spent more time looking at the physics teacher's eyes than at the blackboard, haven't you
Mr Bre, I avoided looking too much at my Physics teacher to avoid nightmares at night :ugh: so I'm sure I was looking at the blackboard allright when he taught us that in Celsius "absolute zero" was -273,15 and that the negative temperatures went up to 0°, the temperature of water freezing into ice.
Now Physics might have changed since I was in High School, it's true we didn't know about Matrix and the like during the Eighties :E

Bre901
1st Oct 2005, 10:18
flyblue

What bothered me was the "between". Maybe your wording was a bit hasty, you put it correctly the second time :ok: :ok:

tobzalp
1st Oct 2005, 10:20
0 degrees? Well for sure that is warmer than where Jerricho lives.

flyblue
1st Oct 2005, 10:37
Maybe your wording was a bit hasty
I shouldn't post after my headache medication at night :(

planepsycho
1st Oct 2005, 11:28
So what happens when you factor in your body temperature and windchill/heat index? Does that change the answer?:ooh:

Jerricho
1st Oct 2005, 13:33

:E :E

flyblue
1st Oct 2005, 14:17
A very, very senior Captain :E

Noah Zark.
1st Oct 2005, 16:09
Flyblue,
I shouldn't post after my headache medication at night
Were you feeling one degree under? :D

flyblue
1st Oct 2005, 16:37
Were you feeling one degree under?
Cool! :ok: :E

Gouabafla
1st Oct 2005, 16:39
Is cool more or less than cold?:confused:

flyblue
1st Oct 2005, 16:43
Depends which way you turn the scale.

...I better get my coat before someone evicts me from the thread, and it's not a nice precedent for a Mod... ça fait désordre! :E

Gouabafla
1st Oct 2005, 16:47
I better get my coat

You'll need your coat - it isn't half cold outside.

OK, moi aussi, je sors....

PanPanYourself
1st Oct 2005, 20:13
0 degrees Celcius is 273 degrees Kelvin, ie. 273 degrees above absolute zero.

"Twice as cold" would mean half as hot I guess, so 136.5 degrees Kelvin which is -136.5 degrees celcius . This is as close to a "correct" answer as you're gonna get and itsmore than you deserve.

Why? Why for the love of God did you post such a terrible question and why am I trying to answer it?

Shame on you. Shame on us all, there are more important unanswered questions out there.

Bre901
1st Oct 2005, 20:18
PanPanYourself

0°C is 273.15 K, so half as cold is 136.575 K or -136.575 °C

BTW did you read the posts on page 1 ?
:rolleyes: :rolleyes:

tony draper
1st Oct 2005, 20:36
As I understand it absolute zero is unachievable, one can get close, but not yer actual -273.15, hmm just as well, one doesn't think ones Canadian Mounty Fur cap with ear muffs would be enough.
:rolleyes:

Jerricho
1st Oct 2005, 21:05
S'kay Drapes....... you could borrow mine ;)

PanPanYourself
2nd Oct 2005, 10:53
I just thought of another somewhat logical answer while in the shower (don't ask why). I yelled "Eureka" and ran out. I am currently dripping all over the couch and my laptop.

Anyway, here it is. Most humans are most comfortable at around 21°C RTP (Room Temperature & Pressure) or something like that. So 0°C is effectively 21°C too cold. So for it to be "twice as cold" it would have to be -21°C, ie. 42°C too cold.

-21°C is my final answer.

Thats it, I'm done. Damn it all to hell.

sinala1
2nd Oct 2005, 10:59
Why? Why for the love of God did you post such a terrible question and why am I trying to answer it?

Why are you trying to answer it? Because its jetblast and you cant help yourself! :O

And its not my question - I did not come up with it - it was on a TV show called Brainiac which I saw only very very briefly, they asked this question and I did not get to see the answer...

G-CPTN
2nd Oct 2005, 11:09
>Anyway, here it is. Most humans are most comfortable at around 21°C RTP (Room Temperature & Pressure) or something like that. So 0°C is effectively 21°C too cold. So for it to be "twice as cold" it would have to be -21°C, ie. 42°C too cold.
-21°C is my final answer.
Thats it, I'm done. Damn it all to hell.

************************************

As I said in an earlier post, the world is now your lobster . . .
(If you want to measure 0 deg C from the average norm ambient temperature, then the world is your lobster . . . )

BTW, was your shower HOT and did you look like a lobster? There could be a connection with your Eureka moment, though I hope that after a shower it wasn't you that reeked!