Weather Station

Coriolis Force

What it does

This experiment shows how the Earth's rotation causes the coriolis effect. The coriolis effect determines the direction of major wind and water currents on Earth.

What you need

Thick paper or cardboard
scissors
a pencil
eyedropper

What to do

Cut a six to eight inch wide circle out of the paper or cardboard.
Push the pencil through the center of the circle. Hold the pencil up so that the paper is horizontal.
Put a drop of water on the paper near the center of the circle.
Twirl the pencil between your hands in a counter-clockwise direction.

What it's all about

The water will swirl around the paper in a clockwise direction—opposite the direction of your spinning. This is because the water is thrown forward when you spin the paper. The paper moves out from under the water.

Like the paper in the experiment, the Earth constantly spins. Its motion affects the direction of air and water currents. This phenomena is called the coriolis effect.

In the Northern Hemisphere, the coriolis effect cuases currents to move in a clockwise direction. In the Southern Hemisphere, currents move in a counter-clockwise direction.

Remember, be sure you have a parent, teacher, or other adult help you!