He reaches for the pouch hanging from his waist and takes out his Sunstone. Through the crystal he looks at the small patch of blue sky. He turns the rock until it becomes yellow. Next he shouts to the helmsman with his stretched arm pointing starboard . . . towards Home. Bees do it.
Ants do it.
The Icelandic sagas tell the story of how the Vikings sailed from Bergen on the coast of Norway to Iceland, continuing to Greenland and, likely, Newfoundland in the American continent. In 1967, a Danish archaeologist, Thorkild Ramskou, suggested that the Vikings might have used the polarization of the skylight for orientation when clouds hid the sun position. They would have used as polarizers natural crystals available to them, the famous sunstones described in the sagas. To find the location of the sun they only needed a clear patch of sky close to the zenith to determine the great circle passing through the sun. The pros and the cons of this theory are the following.