Legend has it that the great Scandinavian sailors used a “sólarsteinn,” or sunstone, to help them navigate their way around Northern Europe and Britain from around 900 to 1200 AD, and stories mentioning the sunstone include the saga of King Olaf and Sigurd, the Icelandic hero. The king asked Sigurd where the invisible sun lay in the cloudy sky and then used a sunstone to check Sigurd’s answer.
Scientists Gábor Horváth from the Eötvös University in Budapest, Susanne Ĺkesson from Lund University, and colleagues around Europe, have been investigating the hypothesis since 2005 because it had never been tested.
The pair crossed the Arctic Ocean on the Oden, a Swedish icebreaker. During the trip they measured the polarization patterns of the sky under a wide range of weather conditions. They were surprised to learn that polarization patterns were very similar on clear and cloudy days, although the polarization was weaker in overcast conditions. This suggests the Vikings could have used this information if they had polarization crystals.
Horváth and Ĺkesson next plan to see if volunteers can use polarization crystals to determine the sun’s location in a range of weather conditions.
The Vikings and earlier seafarers used a number of navigational aids including using special sundials, the stars, migration paths of birds and whales, coastlines, distant clouds over islands, and so on. The sunstone could have been another important tool in their navigational aids kit.
Read more here Vikings could have steered by polarized light