BUDAPEST, HUNGARY—Science Magazine reports that Gábor Horváth and Dénes Száz of Eötvös Loránd University created computer simulations of 3,600 Viking sea voyages from Bergen, Norway, westward to Hvarf, Greenland, in order to test the possible use of sunstones in navigation. Scholars speculate the Vikings may have used ultrapure crystals of calcite, cordierite, and tourmaline to split sunlight and spot the rings of polarized light around the sun. This would make navigation possible on a cloudy day, when the sun is otherwise hidden. Sunstones are mentioned in Viking literature, but no such crystal has been found at any Viking shipwreck site. The simulation tested travel between the spring equinox and the summer solstice, and varied in the amount of cloud coverage, the type of crystal, and how often a navigator might have used a sunstone to find the sun and adjust the ship’s course. The simulations suggest that if the Vikings had checked the position of the sun every three hours or less, in an equal number of morning and afternoon readings, they could have successfully navigated to their destinations more than 90 percent of the time. Slight differences were found in the performance of the different minerals as well. Cordierite was found to be the most reliable overall. For more, go to “The Viking Great Army.”