Could Vikings have navigated under foggy and cloudy conditions by skylight polarization? On the atmospheric optical prerequisites of polarimetric Viking navigation under foggy and cloudy skies
In sunshine, the Vikings navigated on the open sea using sundials. According to a widespread hypothesis, when the Sun was occluded by fog or clouds the Vikings might have navigated by skylight polarization detected with an enigmatic birefringent crystal (sunstone). There are two atmospheric optical...
Published in: | Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences |
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Language: | English |
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Online Access: | http://dx.doi.org/10.1098/rspa.2007.1811 https://royalsocietypublishing.org/doi/pdf/10.1098/rspa.2007.1811 https://royalsocietypublishing.org/doi/full-xml/10.1098/rspa.2007.1811 |
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crroyalsociety:10.1098/rspa.2007.1811 2024-10-13T14:05:05+00:00 Could Vikings have navigated under foggy and cloudy conditions by skylight polarization? On the atmospheric optical prerequisites of polarimetric Viking navigation under foggy and cloudy skies Hegedüs, Ramón Åkesson, Susanne Wehner, Rüdiger Horváth, Gábor 2007 http://dx.doi.org/10.1098/rspa.2007.1811 https://royalsocietypublishing.org/doi/pdf/10.1098/rspa.2007.1811 https://royalsocietypublishing.org/doi/full-xml/10.1098/rspa.2007.1811 en eng The Royal Society https://royalsociety.org/journals/ethics-policies/data-sharing-mining/ Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences volume 463, issue 2080, page 1081-1095 ISSN 1364-5021 1471-2946 journal-article 2007 crroyalsociety https://doi.org/10.1098/rspa.2007.1811 2024-09-17T04:34:45Z In sunshine, the Vikings navigated on the open sea using sundials. According to a widespread hypothesis, when the Sun was occluded by fog or clouds the Vikings might have navigated by skylight polarization detected with an enigmatic birefringent crystal (sunstone). There are two atmospheric optical prerequisites for this alleged polarimetric Viking navigation under foggy/cloudy skies: (1) the degree of linear polarization p of skylight should be high enough and (2) at a given Sun position, the pattern of the angle of polarization α of the foggy/cloudy sky should be similar to that of the clear sky. Until now, these prerequisites have not been investigated. Using full-sky imaging polarimetry, we measured the p - and α -patterns of Arctic foggy and cloudy skies when the Sun was invisible. These patterns were compared with the polarization patterns of clear Arctic skies. We show here that although prerequisite (2) is always fulfilled under both foggy and cloudy conditions, if the fog layer is illuminated by direct sunlight, prerequisite (1) is usually satisfied only for cloudy skies. In sunlit fog, the Vikings could have navigated by polarization only, if p of light from the foggy sky was sufficiently high. Article in Journal/Newspaper Arctic The Royal Society Arctic Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 463 2080 1081 1095 |
institution |
Open Polar |
collection |
The Royal Society |
op_collection_id |
crroyalsociety |
language |
English |
description |
In sunshine, the Vikings navigated on the open sea using sundials. According to a widespread hypothesis, when the Sun was occluded by fog or clouds the Vikings might have navigated by skylight polarization detected with an enigmatic birefringent crystal (sunstone). There are two atmospheric optical prerequisites for this alleged polarimetric Viking navigation under foggy/cloudy skies: (1) the degree of linear polarization p of skylight should be high enough and (2) at a given Sun position, the pattern of the angle of polarization α of the foggy/cloudy sky should be similar to that of the clear sky. Until now, these prerequisites have not been investigated. Using full-sky imaging polarimetry, we measured the p - and α -patterns of Arctic foggy and cloudy skies when the Sun was invisible. These patterns were compared with the polarization patterns of clear Arctic skies. We show here that although prerequisite (2) is always fulfilled under both foggy and cloudy conditions, if the fog layer is illuminated by direct sunlight, prerequisite (1) is usually satisfied only for cloudy skies. In sunlit fog, the Vikings could have navigated by polarization only, if p of light from the foggy sky was sufficiently high. |
format |
Article in Journal/Newspaper |
author |
Hegedüs, Ramón Åkesson, Susanne Wehner, Rüdiger Horváth, Gábor |
spellingShingle |
Hegedüs, Ramón Åkesson, Susanne Wehner, Rüdiger Horváth, Gábor Could Vikings have navigated under foggy and cloudy conditions by skylight polarization? On the atmospheric optical prerequisites of polarimetric Viking navigation under foggy and cloudy skies |
author_facet |
Hegedüs, Ramón Åkesson, Susanne Wehner, Rüdiger Horváth, Gábor |
author_sort |
Hegedüs, Ramón |
title |
Could Vikings have navigated under foggy and cloudy conditions by skylight polarization? On the atmospheric optical prerequisites of polarimetric Viking navigation under foggy and cloudy skies |
title_short |
Could Vikings have navigated under foggy and cloudy conditions by skylight polarization? On the atmospheric optical prerequisites of polarimetric Viking navigation under foggy and cloudy skies |
title_full |
Could Vikings have navigated under foggy and cloudy conditions by skylight polarization? On the atmospheric optical prerequisites of polarimetric Viking navigation under foggy and cloudy skies |
title_fullStr |
Could Vikings have navigated under foggy and cloudy conditions by skylight polarization? On the atmospheric optical prerequisites of polarimetric Viking navigation under foggy and cloudy skies |
title_full_unstemmed |
Could Vikings have navigated under foggy and cloudy conditions by skylight polarization? On the atmospheric optical prerequisites of polarimetric Viking navigation under foggy and cloudy skies |
title_sort |
could vikings have navigated under foggy and cloudy conditions by skylight polarization? on the atmospheric optical prerequisites of polarimetric viking navigation under foggy and cloudy skies |
publisher |
The Royal Society |
publishDate |
2007 |
url |
http://dx.doi.org/10.1098/rspa.2007.1811 https://royalsocietypublishing.org/doi/pdf/10.1098/rspa.2007.1811 https://royalsocietypublishing.org/doi/full-xml/10.1098/rspa.2007.1811 |
geographic |
Arctic |
geographic_facet |
Arctic |
genre |
Arctic |
genre_facet |
Arctic |
op_source |
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences volume 463, issue 2080, page 1081-1095 ISSN 1364-5021 1471-2946 |
op_rights |
https://royalsociety.org/journals/ethics-policies/data-sharing-mining/ |
op_doi |
https://doi.org/10.1098/rspa.2007.1811 |
container_title |
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences |
container_volume |
463 |
container_issue |
2080 |
container_start_page |
1081 |
op_container_end_page |
1095 |
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1812810973993500672 |