Today's interesting fact has to do with magnetic north.

Magnetic north has been moving around a lot lately.

At the moment, it is changing it's position on the earth by more than 40 miles a year.

No one knows why this is occurring and there are many new theories that are being tested and refined at the moment.

But one of the effects of the magnetic pole moving, is that several airports have had to change their signs. The large signs at the ends of the runways, display the degrees off magnetic north that the runway lays on, and pilots rely on these to ensure their on board compasses are working correctly. With recent changes, several of these have had to be changed yearly.