Smart Skin

How Do Earthworms Stay So Clean?

 

Materials

• long, skinny balloon
• sink

Try This

1. Blow up the balloon and tie it off.
2. Turn on a pencil-thin stream of water in the sink.
3. Move the side of the balloon up next to the stream of water, without touching it. Does the stream of water do anything?
4. Now rub the balloon vigorously on your hair.
5. Once again, move the side of the balloon up next to the stream of water, without touching it. What happens to the stream of water?

What's Going On?

By rubbing the balloon on your head, you added a bunch of small particles to it (called “electrons”) from your hair, which gave the balloon a negative charge, making it act temporarily almost like a magnet. Water molecules are attracted to these small particles, so the stream of water now bends toward the balloon. This is the same way that earthworms never take a bath but manage to stay so clean, even while they crawl through the dirt all day. When an earthworm starts moving, friction makes electrons from the soil collect on the worm's skin. Water in the soil is then attracted toward the earthworm, cleaning the worm as it travels, and also making the earthworm's journey through the soil more slippery and easier.