Magnets always have two poles, and nobody knows why

If you snap a bar magnet in half, you don't get a separate north and south pole; you simply get two smaller magnets, each with its own north and south. This is because magnetism is caused by loops of electric current. However, in 1931, physicist Paul Dirac proved that a 'magnetic monopole'—a particle with only one magnetic charge—is mathematically possible and would actually explain why electric charge comes in discrete packets.