This is fascinating.
In a paper published earlier this week, a Franco-British group argued that the Alderney Crystal — a chunk of Icelandic calcite found amid a 16th century wreck at the bottom of the English Channel — worked as a kind of solar compass, allowing sailors to determine the position of the sun even when it was hidden by heavy cloud, masked by fog, or below the horizon.
That’s because of a property known as birefringence, which splits light beams in a way that can reveal the direction of their source with a high degree of accuracy. Vikings may not have grasped the physics behind the phenomenon, but that wouldn’t present a problem.
“You don’t have to understand how it works,” said Albert Le Floch, of the University in Rennes in western France. “Using it is basically easy.”
Some persons are skeptical, with reason, given that the Vikings left little evidence of how they managed to navigate across wide stretches of the Atlantic.
Read the rest.