Centuries ago, a group of people from Northern Europe called the Vikings sailed great distances without modern technology. How? They may have used sunstones. These are types of minerals—solid substances that form in rocks—that filter sunlight.
Scientists think that the sailors held the crystals to the sky. By checking how the stones’ brightness changed, the sailors could have pinpointed the sun on cloudy days. Because the sun rises in the east and sets in the west, locating it in the sky would have helped the Vikings steer their ships in the right direction.
Researchers recently calculated that if Vikings checked the sunstones regularly, they would have had more than an 80 percent chance of reaching Greenland from today’s Norway. That journey involves sailing more than 1,000 miles!