Roxann Ross, age 10, of Santa Maria, Calif., for her question:

WHY DOES THE COLD MAKE MY TEETH CHATTER?

Believe it not, your body has its own built in thermostat. Like the thermostat in a home, it tries to keep things at a comfortable temperature. When you get too hot, it causes you to perspire. Sweaty moisture oozes out onto your skin. As it dries in the air, it uses up some of the heat and makes your skin a little bit cooler.

On a chilly day, you can warm up with a fast run. This is because moving muscles give off heat and exercising makes you warmer. So when your body gets very chilly, it tries to exercise  without your permission. Shivering muscles are trying to exercise to create warmth. Teeth chatter when you get so cold that the muscles of your face try to exercise and warm themselves. This is not necessary when you bundle up and go play a fast game in the snow.