“Nobody knows whether the Vikings really used this method,” wrote Horvath and his colleagues. “However, if they did, they could navigate with it precisely.”
But if the navigator took a sighting every four hours, the ship made it to Greenland only 32.1 to 58.7 percent of the time. With sightings every six hours, the success rate dropped below 10 percent. Clearly, Viking navigators couldn’t afford to slack off. Veering too far north might put a ship on some unsettled part of the northern Greenland coast, where they ran the risk of running out of food or water before reaching port. The alternative could be even worse.
“In cases when the sailing routes tended considerably southwards, Viking voyages never reached Greenland, but terminated with the death of the whole crew in the Atlantic Ocean or reached North America,” wrote Horvath and his colleagues. That kind of navigational error might be what brought Viking settlers to the coast of Newfoundland around the year 1000.
Of course, like all simulations, this one tests a very simple version of reality. Ships sailing across the North Atlantic encounter storms, strong winds, and ocean currents, and a ship with its sails furled for the night could still drift off course by morning.
“All these will be studied by us in the future,” Horvath told Ars. He wants to find the environmental conditions that cause successful sunstone navigation to break down. “If it could be consistently shown that the breakdown of successful navigation only occurs for simulated conditions [which are] far from, or rare in, reality, then this would well demonstrate the robustness of our findings presented here,” he said.
Nothing new under the Sun
Archaeologists and historians now have good reason to think that calcite or other minerals could have been the sunstones from medieval texts; what they still don’t have is archaeological evidence that Vikings actually did use these minerals as navigational instruments. No calcite, cordierite, or tourmaline crystal has turned up at a Viking archaeological site so far. But archaeologists found a piece of calcite on the wreck of a British warship, Alderney, which went down off the Channel Islands in 1592—and the crystal was near some navigational instruments.