Viking Sunstones: Possibility or Just a Myth?

The Vikings are one of the most impressive navigators in our world’s history. Many hypotheses have been made regarding what methods or tools they used to navigate, but this paper will specifically dive into the possibility of the use of “Viking Sunstones,” the nickname given to the calcite crystal that the Vikings may have used to navigate the seas. The Viking Sunstone is thought to have been the Vikings’ way of locating the sun in the sky when weather conditions did not allow for it to be seen with the naked eye. While it cannot be experimentally proven whether or not the Vikings actually used this sunstone, it can be proved experimentally whether or not the use of the sunstone for navigation was at least possible. We demonstrate the principles used to locate the sun with this Viking Sunstone, a birefringent calcite crystal, by modeling incoming sunlight with a polarized laser beam and demonstrating how it responds to being passed through the crystal. We find that two light beams emerge out the other side of the crystal, and they are of equal intensity when there is a 45 degree angle between the optic axis of the crystal and the polarization direction of the light. This is then applied to a different method used to locate the sun. By drawing a dot on one side of the crystal and holding it up to a location in the sky such that the two resulting dots are of equal intensity, we find two possible lines that the sun must be located on. By repeating this process multiple times for different locations in the sky, a fix is made, and the exact location of the sun is found.