# Temperature gives a measure of the kinectic energy

1. Nov 1, 2004

### OldTee

Hi all, there's something about temperature that I don't understand. My question is as follow: the way I visualize it, microscopically, temperature gives a measure of the kinectic energy of the surrounding particles. But macroscopically, temperature seems to be something that can be felt. For instance, one feels cold on a winter night; is that due to the fact that the particles that made up my body is losing its kinectic energy to the ambient particles?
Another question I have is the temperature of outer space. I remember reading somewhere that the average temperature of the universe is ~3K. I take it as a statement that the temperature in outer space is around that value, does that comes from the kinectic energy of the very tiny number of gas particles in space? In other words, in 'real' vacuum where no particle existed, is it fair to say that temperature is undefined?

2. Nov 1, 2004

### Sirus

Why you feel cold would probably be better answered in the Biology forum, as this is due to the nerve receptors which indicate to the brain that you are cold. You understand correctly that temperature is a measure of the average kinetic energy of particles. I believe you are also correct in your second question by saying temperature is undefined in a perfect vacuum and that the average temperature of the universe encompasses all the matter contained in it spread over its estimated volume.

3. Nov 1, 2004

### mathlete

Tell me, if I show you 5 men - one wealthy person who has $1 billion, 3 average people who have$50,000, and one very poor person who has $0, will you assume that the average net worth of$200,030,000 is due to those 3 people in the middle?

4. Nov 2, 2004

### Mk

If true, though I do not have any idea how they got that figure, yes.

...and also, there are so many more men out there, that we haven't measured, accurate data has not been produced, we've only taken an attoscopic piece of the pie!

5. Nov 2, 2004

### Clausius2

Body skin and internal nervious web only sense the Heat Flux, not the Temperature itself. If your body will be entirely at 1000K and you touch a reddened steel at 1000K you will not sense nothing. Is the difference of Temperatures what we sense.

6. Nov 2, 2004

### Mk

Ahh, that must be why if something is cold enough it feels hot. But why does it burn, physically?

7. Nov 2, 2004

### Clausius2

I don't know how to answer that. But I think the sensations at -100ºC are not equivalent to those at 100ºC, in spite you employ the word <hot> meaning you sense exactly the same as such low temperatures.

8. Nov 2, 2004

### OldTee

Thanks for the responses. As for the temperature of the universe being ~3K, I'd actually managed to find a few links by googling:
http://www.straightdope.com/mailbag/mspacetemp.html [/URL]
[PLAIN] http://cosserv3.fau.edu/~cis/AST2002/Lectures/C18/Trans/Trans.html [/URL]
But seems like I'd understood it incorrectly, as they're actually measuring radiation.

Last edited by a moderator: Apr 21, 2017
9. Nov 2, 2004

### arildno

This is a good question; but it is basically about neurological response, so you will get more accurate answers in the Biology forum.

To hazard a guess, I would think that the rate at which neurons fire off is proportional to a registered temperature difference. We are accustomed to regard "rapid firing" as burning.

10. Nov 2, 2004

### Staff: Mentor

I believe you are confusing "average" (mean) with "middle" (median). Either that, or you are using the word "average" in a completely arbitrary way.
No, you didn't misunderstand - there is more than one way to measure temperature. A mercury-bulb thermometer measures it directly and the temperature of the mercury is changed via convection or conduction. But radiation is another means of energy transfer, and thus another means of measuring temperature. Every frequency of radiation has an associated black-body temperature. By detecting what "color" radiation an object gives off, you can find its temperature. Have a look at http://www.grainger.com/Grainger/productdetail.jsp?xi=xi&ItemId=1612667458&ccitem= [Broken]

Last edited by a moderator: May 1, 2017