On the trail of Vikings with polarized skylight: experimental study of the atmospheric optical prerequisites allowing polarimetric navigation by Viking seafarers
Författare
Summary, in English
Between AD 900 and AD 1200 Vikings, being able to navigate skillfully across the open sea, were the dominant seafarers of the North Atlantic. When the Sun was shining, geographical north could be determined with a special sundial. However, how the Vikings could have navigated in cloudy or foggy situations, when the Sun's disc was unusable, is still not fully known. A hypothesis was formulated in 1967, which suggested that under foggy or cloudy conditions, Vikings might have been able to determine the azimuth direction of the Sun with the help of skylight polarization, just like some insects. This hypothesis has been widely accepted and is regularly cited by researchers, even though an experimental basis, so far, has not been forthcoming. According to this theory, the Vikings could have determined the direction of the skylight polarization with the help of an enigmatic birefringent crystal, functioning as a linearly polarizing filter. Such a crystal is referred to as 'sunstone' in one of the Viking's sagas, but its exact nature is unknown. Although accepted by many, the hypothesis of polarimetric navigation by Vikings also has numerous sceptics. In this paper, we summarize the results of our own celestial polarization measurements and psychophysical laboratory experiments, in which we studied the atmospheric optical prerequisites of possible sky-polarimetric navigation in Tunisia, Finland, Hungary and the high Arctic.
Avdelning/ar
Publiceringsår
2011
Språk
Engelska
Sidor
772-782
Publikation/Tidskrift/Serie
Philosophical Transactions of the Royal Society B: Biological Sciences
Volym
366
Issue
1565
Dokumenttyp
Artikel i tidskrift
Förlag
Royal Society Publishing
Ämne
- Biological Sciences
Nyckelord
- Viking navigation
- sky polarization
- imaging polarimetry
- atmospheric
- optics
Status
Published
Forskningsgrupp
- Animal Navigation Lab
ISBN/ISSN/Övrigt
- ISSN: 1471-2970