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Viking Compass (XI century AD)
Seafaring in the past was incredibly difficult and required reading the stars, the sun, and other unreliable landmarks in order to figure out where to sail. Scientists were puzzled by how the Vikings managed to travel between Norway and Greenland in the Middle Ages until they discovered the Uunartoq disc, a complex sundial used by the Vikings. The texts from the same era mentioned the disk having a “magic crystal” inside it. The researchers believe that certain crystals could help focus dim light on the compass, which was perceived as magic back then.
