Using a compass: magnets that point north
Physics · Key Stage 1 · The School
What is inside a compass
A compass has a needle that spins freely. That needle is a tiny magnet. It is not glued in place. It is not controlled by anything. It is free to turn, and it always settles pointing the same way.
The Earth is a giant magnet
The whole Earth behaves like an enormous magnet, with a north end and a south end, deep inside it. A compass needle is far too small to feel a fridge magnet from across a room. But the Earth's whole magnetism is enough to turn it.
Lining up like any two magnets
Two small magnets near each other line up, north end to south end. A compass needle does the exact same thing, except one of the magnets is the entire Earth. That is the whole trick. It is ordinary magnet behaviour, at a huge scale.
Testing that a compass always agrees with itself
Hold a compass flat and let the needle settle. Note which way it points. Now spin your whole body around in a circle, holding the compass the same way. Stop and check the needle again. It has swung back to point the exact same real direction as before, even though you turned. Walk to a different room and check again. Same direction again. The needle is not confused by you moving. It is locked onto the Earth itself.
Using a compass to find your way
Once you know which way is north, you can work out the rest. South is directly opposite. East and west are at right angles to north. Walkers and sailors have used this simple free-spinning magnet, for hundreds of years, to find their way.