Why does a balloon make your hair stand up?

The longer answer

Everything is made of tiny particles, and some of them carry electric charge. Usually the charges are balanced, so nothing happens. Rubbing two things together can move some charge from one to the other, and that is when things start to stick, spark and stand on end.

This kind of electricity is called static because it stays put on the surface instead of flowing along a wire. It builds up until it finds a way to escape, which is the little zap you feel from a door handle after walking on a carpet.

Static works best when the air is dry. On a damp day, the charge leaks away into the moist air, so the balloon trick is harder to do.

Three things to know

• Lightning is static electricity, only gigantic. Inside a storm cloud, ice and water rub together and build charge until it jumps all at once. That jump is the flash.
• That little zap off a door handle is the same spark. Walking on a carpet builds charge all over you, and it leaps the last small gap when you reach for metal.
• A charged balloon can bend a trickle of water. Hold a rubbed balloon beside a thin stream from a faucet and the water leans toward it, without anything touching it.

Try it at home: Two balloon tricks

1. Tear some tissue paper into tiny bits and spread them on a table.
2. Rub a balloon on your hair or a wool sweater for a few seconds.
3. Hold the balloon just above the paper and watch the bits jump up to it.
4. Rub the balloon again, turn on a faucet to a thin trickle, and hold the balloon close to the stream without touching it.

Keep pieces of a burst balloon away from little ones, and an adult should handle the faucet.