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Magnetism and a scholarly Crusader

The earliest users of magnets may well have been the ancient Egyptians, but the earliest users whose usage spread worldwide were the Chinese. They introduced magnets to others through their trade with both Europe and the Arab world via the Silk Road.

It is probably that Arab merchants obtained lodestone from the Chinese before their European counterparts. However, there was contact between Arabs and Europeans in the unlikeliest of contexts: the crusades. It was on one of these crusades – the seventh – that one Padre Peregrinus (AKA Pierre de Maricourt) saw a compass and wrote about it in great detail.

But Peregrinus did more than just write a superficial description. He studied various shapes of magnets and loadstones, including spherical ones, and he made some interesting observations. For example, he noted how some ends of magnets were attracted to one direction and the other end to the other. He then found that the ends of magnets that were attracted to the north repelled others that were similarly attracted. Ditto for the ends of magnets that were attracted to the south

However, he found that one end that is attracted to the south and another that is attracted to the north have an attraction towards each other. He also discovered that you couldn’t create a magnet that had only one polarity and not the other. If you cut a magnet in two, the part that was the middle and is now at the far end of the original north pole became the south pole of that half of the original magnet.

Meanwhile, on the other half of the original magnet, the part that was the middle at the end furthest from the original south pole became the new north pole. That meant that the middle of a magnet was neither north nor south. Magnetism was not a substance that could be separated into two separate objects. Rather it was a directional feature of each magnetized object.

It was round about this time that a naming convention developed. It was decided to call the pole of the magnet that is attracted to the north, its north pole. Similarly, the end that is attracted to the south is the south pole. Strictly speaking this makes no sense. If one treats the magnet as a kind of miniature version of the earth (which it is) then the end that points north (when floating freely) should be the south pole, because opposite poles attract. However the naming convention stuck.

The interesting thing is that in the world of magnetic bracelets, they do not follow this convention. Instead they call the end that is attracted to the north the biosouth pole and the end that is attracted to the south, the bionorth pole. This can be confusing, but it signifies the fact that people who use magnet therapy are willing to defy convention, yet in some ways they are more logical than those who passively conform.