Sólarsteinn

Den siste tiden har det vært debattert om vikingenes sólarsteinn, en krystall som angivelig skal ha vært brukt som navigasjonsinstrument, kunne være en type transparent calcitt, som er vanlig på Island, nemlig Island spar.

Denne krystallen skal ha gjort det mulig for våre forfedre å finne solens posisjon selv om det var helt overskyet, og til og med i storm!

Discovery News publiserte dette 2.november:

Light passing through such a crystal, including the common Iceland spar, changes in brightness and color as the crystal is rotated. Vikings presumably could have used such crystals to observe polarization patterns and thereby pinpoint the direction of the sun. But exactly how this was done was an enigma, until now. Guy Ropars and Albert Le Floch of the University of Rennes’ Laser Physics Laboratory in France, led the latest study, which has solved the mystery of the myth they say by attacking the problem backwards.

“Rather than thinking in term of polarizer, we have deliberately chosen to ‘destroy’ the polarization of the light,” Ropars told Discovery News. “Iceland spar behaves theoretically and experimentally like a perfect depolarizer.” In other words, with the crystal held up to the sky, there is one specific angle of rotation, called the isotropy point, at which the crystal eliminates all polarization of the light passing through it.

Here’s where the “sixth sense” comes in: The investigators say that if you look through the crystal in its depolarizing position and then pull it away suddenly from your line of sight, you can catch a glimpse of a faint, elongate yellowish pattern known as a Haidinger’s Brush. The key here is that the ends of that yellow shape point directly toward the sun.

Les hele artikkelen her.

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