No, it’s not your dry hair, it’s the dry weather, says Walter H.G. Lewin, a physics professor at the Massachusetts Institute of Technology who demonstrates this static electricity phenomenon every year in class.
What happens as you move around a room or sit on a chair, he says, is that you often rub against something, which causes you to become electrically charged. “If the air is humid, this charge leaks off you very rapidly,” he says. “If the air is dry, that does not happen.” You may also hear crackling sounds when you comb your hair in the winter. These are sparks flying from your hair to the comb and from hair to hair.
If you are charged, you get a shock when you touch a metal door or your car. Walking barefoot will prevent these shocks because you keep discharging all the time through your feet. (When you wear shoes, the soles prevent this discharge from occurring.)
To avoid shocks when the air is dry, try touching the doorknob with a wooden pencil in your hand before you turn it. This will discharge the static electricity in your body –the current will be much lower than if you touch the doorknob with your bare hands.
For some truly shocking fun, Lewin suggests the following experiment. (Yes, you CAN try this at home.) Stand in front of a mirror in a darkened room, wearing a nylon shirt. Take the shirt off. “You will see light sparks in the mirror. Your whole shirt may glow. I have done it many times, ” says Lewin. But do it now because this doesn’t work in the summer.