The Opposite of Boiling Water

Here’s something to think about if you’re in Chicago like me, and you’re thinking of going outside:

Go to your kitchen and fill a pot with water. Put it on the stove and turn the burner up to high. Bring it to a boil. That water is now at about 212°F. Given that your internal body temperature is just under 99°F, the boiling water is about 113°F hotter than your body.

As I post this, the weather station at O’Hare airport is reporting a (non-windchill) air temperature of -14°F, which is about 113°F colder than your body. In other words, the difference in temperature between the outside air and your body is the same as the difference in temperature between your body and a pot of boiling water.

(For those of you of the metric persuasion, water boils at 100°C, normal body temperature is 37°C, and the outside air is at -26°C, for a difference of 63°C.)

So if you wouldn’t stick your hand into that pot of boiling water, you might want to think carefully before going outside today.

(Technically, of course, they’re not equivalent situations, because air has only about 1/4 the heat capacity of water and is about 800 times less dense, meaning that it won’t sap heat from your skin anywhere near as fast as boiling water will scald you. On the other hand, you’re probably going to be exposed to the cold air for a lot longer than you would be likely to touch boiling water, and with a 15 mph (24 km/h) wind, you could easily find yourself in the frostbite zone that will damage your skin in about 10 minutes. Also, every unheated object outside is also at -14°F, and touching some of them could freeze your skin as fast as boiling water would scald it — a metal post being the canonical example. Finally, don’t forget that cooling your skin will make it numb to pain, so you might not notice the damage until it’s too late.)

And if you do go out — like my crazy wife, who had the option to work from home today — be careful out there.