How do Vikings go to sea in cloudy days?

The Vikings navigate the sea with sundial clocks. But in the gloomy days, the sundial is also useless. Many researchers wonder how they overcome it? One theory is that they looked up at the sky with stone crystals (called sun stones) to find their way.

Nobody tested this hypothesis until recently. A research group has set sail on the Arctic Sea on Sweden's icebreaker Oden, and found that solar rocks can indeed illuminate the path in cloudy or misty conditions.

Crystals like cordierite, calcite or turmaline act like polarizing, glowing and radiant filters when sun angles are detected. Based on these changes, the Vikings were able to pinpoint the destination of polarized light, and point out the direction of the sun, said Gabor Horvath, from the University of Eotvos in Budapest.

The top series shows the Arctic sky on a foggy day (a), sunny (b) and cloudy (c).The series of df images shows the degree of light polarization.The series of images shows the polarization angle.(Photo: LiveScience)

In previous works, Horvath and his colleagues demonstrated that Vikings may have used some kind of device, not just with the naked eye, to accurately assess the direction of the sun during cloudy days.

Lack of evidence

However, unlike the sundial, archaeologists have not found any remnants of solar stones. The theory of this type of stone was first introduced in 1966 by a Danish archaeologist. The only suggestion is that the Vikings who used that stone came from a legend of this nation, known as the saga.

Along with the Vikings, birds and butterflies are also thought to have used polarized light to navigate, besides other traces such as the earth's magnetic field.

Picture of Viking boats. (Photo: LiveScience)

T. An