It may not look like much, but this half of a wooden disc was likely used by the Vikings to navigate the high seas, even after the sun went down.
Archaeologists found this artefact, called an Uunartoq disc, in 1948 in Greenland in an 11th century convent. The Vikings travelled 1,600km to get there and were well-known sea-farers, as they travelled to both England and Greenland in treachorous waters.
Researchers think this wooden tool was used with a blunt object in the middle, which would have given the shadow from the sun, which would have worked as a compass. But how did they use it after dark you ask? Crystals people, crystals known as sunstones, which form patterns after being exposed to UV rays, and when lifted up to the sky, it forms these patterns even after sunset.
Scientists tested the device and discovered there was only 4 degrees of error to it, not bad. It may not have been 100% accurate, but it would have given the Vikings a pretty good estimate which way to go and eventually discover land.
For more, check out Live Science.