The race for the pole

One of the very first facts you learn about electromagnetism-long before you walk into your first physics class-is that every magnet has two poles. Cut a bar magnet in half and you wind up with two magnets, each of which has its own north and south poles. And that's true for every single object in our experience that boasts a magnetic field-whether it's the entire Earth or an iron atom. There are no solitary poles. Strangely, though, there is no fundamental reason why that has to be the case. In fact, there are a few good reasons to suspect that there might be single-poled magnetic objects- magnetic monopoles-floating about in the universe. If these particles exist, they are probably quite rare, but that hasn't stopped physicists from looking for them. Here's why: If they exist, they could help answer longstanding questions about the nature of the universe, shedding light on the way fundamental forces of nature are tied together. So over the past few decades, physicists have scoured Antarctic ice and lunar dust and scrutinized rocks culled from ocean beds and polar volcanoes. They've tried to create monopoles in particle colliders and have searched for signatures in cosmic rays that collide with Earth.