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The magnetic field of the Earth

The shape of the Earth's magnetic field can be explained if you imagine a bar magnet placed at the centre of the Earth.

You can see from the diagram that the Earth's magnetic north pole is not at the same place as the Earth's geographic north pole. At the moment it is to the west of geographic north and moving east but a compass needle will not point to geographic north in London again until around the beginning of the twenty second century. The first records of the position of magnetic north were made in 1659 when it was 11o 15' east. It then moved westwards to be a maximum of 24o 30' west of north in 1820. The magnetic north was about 4oW of geographic north in the year 2002.

The Earth's magnetic pole attracts the north pole of a compass and so it is really a south-seeking pole. This is always confusing when you first study magnets.

We now believe that the Earth's magnetic field is produced by electric currents flowing over 2800 km below us in the outer part of the Earth's core.

Since the north seeking pole (or north pole) of a magnet points to the magnetic north pole of the Earth, the Earth's north pole must be a magnetic south. The earliest use of magnets was as a compass, which used the magnetic field of the Earth to find a direction.

© Keith Gibbs 2020