OK, This question probably has an easy answer, But it escapes me. Someone asked me this recently and I couldnt come up with a convincing answer.

 

Why is it, That on a cold day, Say 20 degrees, Clear skies, That while in your car you can feel the heat of the sun on your face, Yet the window is very cold?

First of all you must realize that skin is a poor thermometer. It is a much better measure of heat transfer, which is why a piece of metal feels colder than a piece of wood at the same temperature (below body temperature) - the metal conducts heat better away from your skin.

 

There are three types of heat transfer - conduction, convection and radiation. The sun radiates a lot of energy - more than a kW per square meter - and you feel that on your face inside the car. But there is little convection, since there is no wind, and minimal conduction, since air is a gas and doesn't have a large heat capacity.

 

So what you feel is the radiation heat transfer, as the other forms have been reduced.

Thanx, I knew it was something similar to that. What a cool site Ive found. Ill have to check in each day for interesting topics.