Viking Optics – sun stones and lenses
I recently read an old copy of New scientist from 7 November 1998 which carried a story about viking lenses. It says that the vikings made high quality quartz lenses – aspheric ones which have an elliptical, rather than spherical, shape. These were made on simple lathes and were apparently used for as fire starters or to cauterise wounds. There are examples of such lenses in museums in Munich and Sweden and no doubt elsewhere. There is a web page discussing viking lenses and research into them by Olaf Schmidt of the University of Applied Science in Aalen, Germany.
Rock Crystal Lenses from the Viking Harbor Town of Fröjel, Gotland in Sweden
I was talking to a Dane recently about this, and he told me that the vikings also used things called sun stones for navigation, and he suggested that they somehow lit up when held aloft, even on cloudy days, to enable them to locate the sun and thereby derive a position. I suggested that it might not have been far fetched if, say, some sort of crystalline stone which might act like a polarising lens. This might be able to filter diffuse light and reveal the direction of a non-polarised light source, which would have been the sun. And after a bit of a search online found that my hypothesis might be correct! Indeed Norway is one source of a naturally occurring felspar which had polarising properties – the other major source was Iceland where the vikings had continuous settlements.
Certainly the Vikings were excellent navigators and they had ships well capable of traversing open ocean, rather than just being brown water vessels, so it is quite likely that among their many navigational tools, they might have used a polarising filter.
Cheers
Jerry
