What do the Earth, electric motors, and your computer all have in common?
These things are all influenced by magnets.
The Earth has a liquid metal core that acts like a bar magnet. It gets its magnetism from being near electrical currents beneath the surface. Because the Earth is not perfectly shaped, every so often the direction of the field will change. Scientists have found evidence that this has occurred at least 171 times over the past 71 million years. How do they know that? Magnets!