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Forget GPS: Medieval Compass Guided Vikings After Sunset

Navigation: today we use satellites. “Yesterday” we used magnets. Before that? Researchers are arguing Vikings may have used sunstones.

Sunstones can be used to track the position of the sun, even when it’s behind clouds or below the horizon. Now, researchers have figured out how it works. The theory is interesting.

A certain transparent calcite found commonly in Iceland can be used as a “sunstone.” Discovery News explains: “Light passing through such a crystal…changes in brightness and color as the crystal is rotated. Vikings presumably could have used such crystals to observe polarization patterns and thereby pinpoint the direction of the sun.” “[W]ith the crystal held up to the sky, there is one specific angle of rotation, called the isotropy point, at which the crystal eliminates all polarization of the light passing through it.” “The investigators say that if you look through the crystal in its depolarizing position and then pull it away suddenly from your line of sight, you can catch a glimpse of a faint, elongate yellowish pattern known as a Haidinger’s Brush. The key here is that the ends of that yellow shape point directly toward the sun.”

clear mineral calcite sunstone

When you know where the sun is, you can find your way. Researchers have found that this method of navigating is as accurate as using a magnetic compass, and more accurate than using stars. “Coupled with a second technique observing the changing polarization patterns passing through the crystal, also tested and described for the first time in this study, the Vikings could have established a reference point that could be used even when the sun was fully hidden, upping the sunstone’s accuracy to within 1 degree.”

Now the controversy comes in because no sunstone has been found in Viking villages or near Viking remains, although there are some scraps of art and literature remaining that suggest they may have used this tool.

There is a tendency in popular culture to describe past peoples are stupid, but they just didn’t have the foundation of accumulated knowledge that we have to work with. They were at least as smart as we are today, and discoveries of tools like this prove it.