Viking navigation: From speculative history to laboratory exercise on polarization

Although the actual techniques used by Viking navigators remain uncertain, some historical and optical hypotheses suggest they may have relied on the polarization of skylight to estimate the Sun's position under cloudy conditions. While this idea is speculative, it offers a compelling context for a physics laboratory exercise. In this article, we present a hands-on activity designed for undergraduate students in introductory astronomy or optics courses. The activity explores solar geometry using a simplified sun compass and introduces basic polarimetric sky measurements. The activity combines physical modelling with historical curiosity, aiming to stimulate student engagement and critical thinking. Student results indicate that navigation based on polarimetry would be most beneficial under partly cloudy conditions, while polarization of skylight becomes difficult or impossible to observe when the sky is fully obscured.