The Vikings liked to see the world. For a couple of centuries, they plied northern oceans, exploring much of Europe, establishing colonies in Greenland, and even reaching North America. They did so with a good sense of the natural world, including the sky. But they might’ve had a little help. They might have pinpointed the Sun’s position through fog and light cloud cover using crystals — sunstones.

Sunstones are mentioned in the Norse Sagas — accounts written a couple of centuries after the peak of Viking exploration. No one has found such a stone in any Viking sites. But scientists have explored the possibility that ancient navigators could have used them. And some of the results suggest that it’s plausible.

Most studies have focused on a crystal known as calcite. Researchers paint a black dot on one face of the crystal, then aim the stone at the sky. The crystal splits a beam of sunlight into two beams. That creates two images of the dot. The observer turns the crystal until the dots are the same brightness. At that point, the angle of the crystal reveals the direction of the Sun — a big help when navigating through skies that obscure the Sun. Computer simulations back up that possibility.

None of the experiments prove that Vikings actually used sunstones — scientists need better evidence for that. Still, it’s at least possible that these master navigators used the stones to help them see the world.

Script by Damond Benningfield