Vikings may have used sunstones as navigational aid during times when the skies were covered with clouds, a new study suggests.
Vikings conducted raids across Europe from the late 790s till 1066, when the Normans famously conquered England. They were also long-distance seafaring travellers, venturing as far as the Middle East and North America, researchers said.
How they found their way across vast stretches of ocean has been a mystery, particularly during times when there were no stars or sun in the sky to guide them.
Some historical evidence such as Icelandic legends have mentioned travel under snowy skies using sunstones and a study of a Viking wreck conducted in 2002 showed that a crystal had been onboard that was found near other implements used for navigation.
Now, a team of researchers from several institutions in Hungary, including Eotvos University, has carried out experiments to test the possibility that such crystals could really have helped Vikings find their way across the ocean, Phys.org reported.
They believe it was a three step process: determining the direction of light from the sky using the sunstone held up to the sky, using that information to determine the direction of sunlight and then using a shadow stick to determine which direction was north.
The team previously conducted tests to measure the accuracy of the first two steps and, have now conducted experiments with the third.
To test the third step, the researchers asked 10 volunteers to try to work out the position of the sun in a digital planetarium using dots to stand in for results of using a sunstone.
After conducting a total of 2,400 trials, the researchers report that 48 per cent resulted in producing an accurate reading to within just one degree.
They also noted that the volunteers did best when the virtual sun was near the horizon, showing that the method worked best at dawn and dusk.
The team suggests their results indicate that it was possible that the Vikings used sunstones to navigate under cloudy skies.
The research was published in the journal Proceedings of the Royal Society A.