Make Your Own Simple Compass
Earth itself behaves like a giant magnet. Rub a needle against a magnet, let it float freely on water, and it will turn to line up with that field and point North.
Estimated time: 20–30 minutes. Difficulty: Easy
- A small needle
- A magnet (from a fridge magnet or a toy)
- A bowl or cup of water
- A small piece of cork, foam, or paper
- Scissors
- Cut a small circle or square from the cork, foam, or paper. This is your float. Ask an adult to help with the scissors.
- Rub the needle along the magnet 30 to 50 times, always in the same direction. Lift the needle away at the end of each stroke instead of dragging it back. This is what makes the needle magnetic.
- Lay the needle carefully on top of your float.
- Gently set the float on the water, in the middle of the bowl.
- Watch. The needle will slowly turn until it points North, then stop.
Why This Works
The Earth is like a giant magnet. Rubbing the needle with your magnet turns the needle into a tiny magnet of its own. The Earth's magnetic field then pulls on it, swinging it round until it lines up pointing North.
The float is the important part. A needle lying on a table is held still by friction, so it cannot turn. Floating on water it is free to spin, and a pull that weak is finally strong enough to move it.
Why does the needle need to float on water instead of resting on the table?
- Water makes the needle more magnetic
- Floating lets the needle turn freely, so the Earth's weak pull is enough to move it
- The water points North and the needle follows it
If It Goes Wrong
- The needle isn't pointing North. Rub it again, and check you are stroking it the same way every time. Rubbing back and forth undoes your own work.
- The needle is sinking. Your float is too small. Cut a bigger one.
- The needle sticks to the side of the bowl. The bowl is metal. Use a plastic or glass one instead.
Try This Next
Try different needles, and floats of different shapes. Does a bigger magnet make the needle settle faster? Once it is pointing North, gently spin the float and watch it find North again — a real compass does exactly the same thing every time you turn.