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| Thorkild Ramskou, in describing how both the Twilight Compass (detail) and the sunstone theory work, explains that the partially polarized light from the low sun vibrates perpendicularly to the plane containing the zenith, the observer (airplane) and the sun. (Thorkild Ramskou Solstenen, Primitiv Navigation i Norden før Kompasset., 1969, page 88). | |