See what happens when you get...er..dispersed: you can’t focus and solve this minor problem!

The trick here is that 2 bodies of different tempreture, when brought in contact, tend to cool/heat each other untill their temperature will not equalize.

Like a pot of boiling soup, if you put in on the window sill and open the window, even at 90F outside, will eventually cool down, since it’s temp is much higher than the air’s outside. (OR - I think R.Burns had a poem somewhere, about daughter of a village smith, or something, who was always cold, and some neighbor or other who was feverish. They cured each other, as you might deduce. I think Burns was pondering the same question, Brian)

Anyway, since you
1) raised your body temperature by putting it in hot bath - and don’t tell me you were comfortable - of course you were not; don’t ever overdo it, or you’ll have a stroke, too
2) abruptly brought yourself in contact with much colder air outside of your bathroom,

your skin was cooled by the surrounding ether (and I feel the public gave up on this charming term much too much easily).

If you still not completely satisfied with this explanation, all I can say you get what you paid for.

In anticipation of the photostream,
sincerely yours,

Perhaps you already heard this explanation, but let’s see if this helps:

The key principle is that as a fluid changes from liquid to gas, it absorbs heat.  Thus, refrigerators use a condensor to apply pressure to a refrigerant, turning it into a liquid.  This liquid is then forced through the coils of the refrigeration compartment, where less pressure exists, and the liquid vaporizes, drawing heat from the compartment. The refrigerant then passes back to the compressor, and the cycle is repeated.

I also look forward to your pictures from Lord’s.  It was too bad that England felt it necessary to put up such a high score in the second innings, but clearly Strauss wanted to ensure at least a draw.  However, with such a high target, it sounds like Pakistan didn’t even try for the victory.  Too bad, as it could have been much more exciting.

Regards,
Mike

Put a cool liquid next to something hot. The hot thing transfers its heat to the cool liquid in an attempt to make them both the same temperature. Take away the now warmed up liquid and replace it with more cool liquid.

Repeat as necessary

Thats why if you stand out the other side of an airconditioner, hot air comes out of it?

Best ask at samizdata.

Exactly - heat isn’t lost - it is just moved around.

OK, I’m game for one more attempt.  Following my original post, a compressed liquid refrigerant is forced through the coils of a refrigeration compartment, where less pressure exists, and the liquid vaporizes.  When it vaporizes due to decreased pressure, the refrigerant cools (less pressure = less temperature; fewer molecular collisions) and the coils become colder.  Air within the refrigerator, that is warmer and has higher molecular movement, contacts the colder inner surfaces of the refrigerator (cooled by the coils) and transfers molecular energy from the air to the refrigerator surfaces (equilibrating by cooling the air and warming the inner surfaces of the refrigerator).  Because the refrigerant can be re-compressed electromechanically and can remain a liquid in sub-freezing temperatures, it can be repeatedly compressed/vaporized to extract more and more molecular movement from the air inside the refrigerator, thus cooling it down.  Also, since the refrigerant can remain a liquid below the freezing point of water, and can keep the coils sub-freezing, it can remove enough molecular motion to freeze water (i.e., make ice/ice cubes).

The same process works for the hot bath.  The hot water increases the movement of molecules that make up the tissues in your skin.  When you get out, you’re now in contact with cooler air with less molecular motion, which absorbs energy from the molecular movement in the tissues of your skin.  This decreases your temperature while having a negligible effect on the surrounding air.

Mike

I think I nearly get it now, certainly the mechanical refrigeration bit, which is that the whole process depends on altering pressure.

I still don’t entirely understand the human version, though.  Is it actual refrigeration again, or is it merely that the body sweats when it wants to cool down, but that after a hot bath you are cooling down already, so don’t need to sweat?  Whereas after a cold bath on a hot day, you step out of it and immediately start warming up, and therefore start sweating?  Does the body care about the direction temperature is moving in, rather than its absolute level?  Is that it?

Please don’t bother answering moronic amateur questions like this unless you enjoy it.  But you knew that.

Brian,

Well, to be honest, I just applied the mechanical refrigeration explanation to the human version (in looking back, I didn’t mean to sound so sure of myself for the human version).  The reality is undoubtedly more complex, but I would think that, at least in small part, the same principle as the mechanical example (i.e., molecular transfer of energy) would contribute to cooling.  However, I think you’ve got it:  after a hot bath, you’ve already been sweating (in the tub, unfortunately) and now out you’re cooling down, so you’re body does not give the immediate signal to sweat. 

Also, I think the water from the bath is an important consideration.  That is, after a hot bath, you’ve now got water all over you, which is evaporating, adding to both the cooling effect and negating the need for more sweat.  After all the water evaporates, if you’re still above a “comfortable” temperature range—e.g., if you’re outside in 105 F heat—you’re going to start sweating again after the bath water completely evaporates.  So, in that sense, I would think the absolute temperature is more important than the direction of temperature movement.

Of course, sweating can also be impacted by other, non-heat related things like nervousness and shock.  As mentioned earlier, it probably a bit more complex than all this.

There is still some sinister reason why this is more complex then it should be, I fear.

From a loooong time lurker....normally I have nothing to contribute other than to enjoy your great blog...... but....I hate to be simplistic on this matter; it’s mostly a matter of perception rather than pure science in this case. When you get out of the bath, and until the effect of evaporation kicks in momentarily, you just feel cooler because you were hotter in the bath; that’s why a cool bath doesn’t help except when you’re in it. A cool bath will, however lower your core temperature and help ease the symptoms of heat stress on your body; you just won’t Feel cooler...... but your body will Be cooler.

Once again.... thanks for a most entertaining blog......I followed your recording efforts with great interest. Cheers,

That’s my camera in the picture! I’ll post the original photo, i.e. the one that you can see in the camera viewer, on Flickr.

http://www.flickr.com/photos/adriana-lukas/196023978/in/set-72157594208584280/