Our planet is a magnet
Why Does a Compass Point North?
Molten iron churning deep inside Earth turns the whole planet into a magnet.
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Step 1 of 5
Earth has a liquid metal core.
About 3,000 km down is an ocean of molten iron and nickel, hotter than the Sun's surface and constantly churning.
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Step 2 of 5
Moving molten metal makes magnetism.
Heat from the inner core drives the liquid iron in huge slow loops. Moving electrically conductive metal generates a magnetic field — a planetary dynamo.
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Step 3 of 5
The field wraps the whole planet.
It loops out of one pole, arcs through space, and dives back in at the other. Every point on Earth's surface sits inside that field.
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Step 4 of 5
A compass needle simply lines up with it.
Nothing is pulling it north. It is simply settling. The needle is a small magnet on a near-frictionless pivot. It rotates until it points along the local field lines — roughly north-south.
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Step 5 of 5
Magnetic north is not the true north pole.
The magnetic pole wanders — it has moved over 1,000 km in a century. Maps list the local correction, called declination.
The field has flipped completely hundreds of times. Frozen into old lava, the record of those flips proved plate tectonics.
The short version
Earth's churning liquid iron core generates a magnetic field, and a compass needle just lines up with it.
Try it yourself
Float a magnetised needle on a leaf in a bowl of still water. It will slowly rotate to point north.