We do not know for sure whether the Vikings actually charted the course with the sunstone, but current experiments show that the hypothesis is physically possible.
About 1000 years ago, the Vikings were known for being good sailors. They traveled from Scandinavia to North America and the Middle East, and all this happened before the advent of the magnetic compass. According to ancient sagas, the Vikings used the sunstone to chart a course through the sun, even when the sky was overcast or the sea was foggy. And in recent decades, many researchers have argued that this was exactly the case.
In 2011, scientists considered proven the use of this method, and three years ago, something that could have been a sun stone was found in the remains of a ship in 1592.
Currently, a group of Hungarian scientists have conducted experiments confirming that this method works, their report was published in the Proceedings of the Royal Society A (Proceedings of the Royal Society A).
The hypothesis is physically possible
Sunstone, which can be, for example, a calcite crystal, acts as a kind of polarization filter. The sun emits light that is polarized in all directions, that is, the tops of the waves go up and down, across, and in all other possible directions.
The structure of calcite causes light to polarize in only two directions, rectangular to each other. Thus, the light comes out in two rays from the other side of the crystal. After "calibrating" the crystal in direct sunlight, Vikings can determine where the sun is behind a layer of clouds by lifting the crystal in two different directions and noticing the distance between the two beams of light and how they overlap. Thus, it was possible to determine the north using the shadow compass.
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Currently, this group of scientists has recruited volunteers who will try to find the sun in the planetarium. 48% of 2,400 experiments ended with the fact that they were able to determine the height of the sun with an accuracy of one degree. Several people were more than three degrees wrong.
Physicist Bjørn Hallvard Samset, who explains the polarization phenomenon more thoroughly with the discovery of the sunstone, says he finds it a lucky experience. “Experience shows that this is possible in principle. The fact that it was done in this way is still based on other facts, but it is brilliant that someone even dared to test the physical possibility of this hypothesis."