The study published by the Royal Society
says legends of Vikings using so-called “sunstones” to navigate in occluded conditions could well be true.
An article in the New Scientist
says calcite crystals could have had a polarizing effect and might have been what the Sagas called “sunstones”. The Royal Society article
pointed out that earlier, critics of the “sunstone” idea said too little polarized light makes it through heavy overcast to allow accurate readings. Gábor Horváth and his team write in their report:
To our great surprise, the patterns of the direction of polarisation under totally overcast skies were very similar to those of the clear skies.
In other words, the Viking sagas could in fact be correct and Viking seafarers would have had enough light to use a polarizing crystal to find the position of the sun in overcast conditions.
Normally, the Vikings would have used a sun shadow board, or “sun compass”
to observe the position of the sun and deduce where North was. At night, they would have used the North Star for the same purpose.
Scandinavian seafarers during the Viking Era
(Ninth to Twelth Centuries) made great voyages in which they raided Ireland, Britain and France as well founding the nation of Iceland and travelling as far across the open ocean as Greenland and North America.
The Vikings founded the capital city of Ireland, Dublin and another of their towns, Linn Duchaill
, was discovered last year.