Earth's magnetic field and compasses
The earth is one gigantic magnet.
MN = Magnetic north
MS = Magnetic south
The earth acts like a giant magnet. Its invisible magnetism helps animals such as birds, bats, sharks and mice find their way around.
A compass contains a small bar magnet that can rotate. When a compass is held at rest in your hand, the needle always settles in the north-south direction.
The needle in red points towards the magnetic north of the earth.
LIKE POLES REPEL
So how come the compass needle which shows north directs you to the magnetic north?
That's because the magnetic north of the earth is actually a south pole: the scientific convention is to call it magnetic north (when it really isn't).
Note: In the top diagram of the Earth, we show what really happens with the direction arrows but the convention is always to think of the top of the world as North and the arrows travelling the other way. We have used this convention on our mnemonics too.