Freezing @ 500 degrees centigrade

[miss photon]

i found this in a textbook.
at a high altitude the temperature of the atmosphere is 500 degrees centigrade. yet an animal there would freeze to death and not boil. why does this happen?

 

[russ_watters]

Do you have a reference for this? That region of the atmosphere is called the "thermosphere", but I don't see why an animal would freeze there. By then you are basically in space, and what happens in space is a lot more complicated than saying you'd "freeze to death" (you'd suffocate first...).

 

[mgb_phys]

I suppose that although the temperature of the few gas molecules flying around might be 500deg - you are facing a lot of solid angle of 3K space, so radiatively you woul dget pretty cold pretty quickly.

 

[stewartcs]

This explains it rather simply...

http://en.wikipedia.org/wiki/Thermosphere

 

[russ_watters]

The few particles of gas in this area can reach 2,500°C (4500°F) during the day. Even though the temperature is so high, one would not feel warm in the thermosphere, because it is so near vacuum that there is not enough contact with the few atoms of gas to transfer much heat. A normal thermometer would read significantly below 0°C.

That doesn't make any sense to me. You get cold by transferring heat, so while it is true that there is not enough air to gain heat by convection, you can't lose heat by convection either. So how do you (or that thermometer) get cold? Radiation? Well...

temperatures increase with altitude due to absorption of highly energetic solar radiation by the small amount of residual oxygen still present. Temperatures are highly dependent on solar activity, and can rise to 2,000°C.

If the air gets hot by absorbing solar radiation, why wouldn't you? At night, though, you would certainly get cold by radiating heat (though we calculated that once here and found that you could stand it for quite a while - probably indefinitely with a little insulation).

A thermometer doesn't generate its own heat, but we do.