author_facet Hegedüs, Ramón
Åkesson, Susanne
Wehner, Rüdiger
Horváth, Gábor
Hegedüs, Ramón
Åkesson, Susanne
Wehner, Rüdiger
Horváth, Gábor
author Hegedüs, Ramón
Åkesson, Susanne
Wehner, Rüdiger
Horváth, Gábor
spellingShingle Hegedüs, Ramón
Åkesson, Susanne
Wehner, Rüdiger
Horváth, Gábor
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences
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
General Physics and Astronomy
General Engineering
General Mathematics
author_sort hegedüs, ramón
spelling Hegedüs, Ramón Åkesson, Susanne Wehner, Rüdiger Horváth, Gábor 1364-5021 1471-2946 The Royal Society General Physics and Astronomy General Engineering General Mathematics http://dx.doi.org/10.1098/rspa.2007.1811 <jats:p> 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 <jats:italic>p</jats:italic> of skylight should be high enough and (2) at a given Sun position, the pattern of the angle of polarization <jats:italic>α</jats:italic> 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 <jats:italic>p</jats:italic> - and <jats:italic>α</jats:italic> -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 <jats:italic>p</jats:italic> of light from the foggy sky was sufficiently high. </jats:p> 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 Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences
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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_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_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_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_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
topic General Physics and Astronomy
General Engineering
General Mathematics
url http://dx.doi.org/10.1098/rspa.2007.1811
publishDate 2007
physical 1081-1095
description <jats:p> 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 <jats:italic>p</jats:italic> of skylight should be high enough and (2) at a given Sun position, the pattern of the angle of polarization <jats:italic>α</jats:italic> 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 <jats:italic>p</jats:italic> - and <jats:italic>α</jats:italic> -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 <jats:italic>p</jats:italic> of light from the foggy sky was sufficiently high. </jats:p>
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author Hegedüs, Ramón, Åkesson, Susanne, Wehner, Rüdiger, Horváth, Gábor
author_facet Hegedüs, Ramón, Åkesson, Susanne, Wehner, Rüdiger, Horváth, Gábor, Hegedüs, Ramón, Åkesson, Susanne, Wehner, Rüdiger, Horváth, Gábor
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description <jats:p> 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 <jats:italic>p</jats:italic> of skylight should be high enough and (2) at a given Sun position, the pattern of the angle of polarization <jats:italic>α</jats:italic> 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 <jats:italic>p</jats:italic> - and <jats:italic>α</jats:italic> -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 <jats:italic>p</jats:italic> of light from the foggy sky was sufficiently high. </jats:p>
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spelling Hegedüs, Ramón Åkesson, Susanne Wehner, Rüdiger Horváth, Gábor 1364-5021 1471-2946 The Royal Society General Physics and Astronomy General Engineering General Mathematics http://dx.doi.org/10.1098/rspa.2007.1811 <jats:p> 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 <jats:italic>p</jats:italic> of skylight should be high enough and (2) at a given Sun position, the pattern of the angle of polarization <jats:italic>α</jats:italic> 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 <jats:italic>p</jats:italic> - and <jats:italic>α</jats:italic> -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 <jats:italic>p</jats:italic> of light from the foggy sky was sufficiently high. </jats:p> 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 Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences
spellingShingle Hegedüs, Ramón, Åkesson, Susanne, Wehner, Rüdiger, Horváth, Gábor, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 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, General Physics and Astronomy, General Engineering, General Mathematics
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_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_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_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
title_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
topic General Physics and Astronomy, General Engineering, General Mathematics
url http://dx.doi.org/10.1098/rspa.2007.1811