Viking navigation: Sunstruck

Viking navigation

Reporting on an article by Guy Ropars in Proc R Soc, postulating that the magic stone referenced in the sagas, which could point to the sun even on cloudy days, was icelandic spar.

Iceland spar is a form of calcite that splits light into two beams. If the light is polarised, there is only one way to orient the crystal to produce beams of equal intensity. Find this orientation by looking through the crystal at the sky at a time when you can see the sun, mark the sun’s direction on the crystal, and your mark will always point towards the sun when you match the beams from even a tiny patch of blue in an otherwise overcast sky. Dr Ropars’s experiments suggest the method is accurate to within 5°.

Got that? Good, let’s get to the boat.


Posted on November 10, 2011, in Uncategorized and tagged . Bookmark the permalink. Leave a comment.

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