A depolarizer as a possible precise sunstone for Viking navigation by polarized skylight
Viking navigation from Norway to America in the northern latitudes remains a mystery for physicists, historians and archaeologists. Polarimetric methods using absorbing dichroic crystals as polarizers to detect a hidden Sun direction using the polarized skylight have led to controversies. Indeed, th...
Published in: | Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences |
---|---|
Main Authors: | , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
The Royal Society
2011
|
Subjects: | |
Online Access: | http://dx.doi.org/10.1098/rspa.2011.0369 https://royalsocietypublishing.org/doi/pdf/10.1098/rspa.2011.0369 https://royalsocietypublishing.org/doi/full-xml/10.1098/rspa.2011.0369 |
id |
crroyalsociety:10.1098/rspa.2011.0369 |
---|---|
record_format |
openpolar |
spelling |
crroyalsociety:10.1098/rspa.2011.0369 2024-09-15T18:13:28+00:00 A depolarizer as a possible precise sunstone for Viking navigation by polarized skylight Ropars, Guy Gorre, Gabriel Le Floch, Albert Enoch, Jay Lakshminarayanan, Vasudevan 2011 http://dx.doi.org/10.1098/rspa.2011.0369 https://royalsocietypublishing.org/doi/pdf/10.1098/rspa.2011.0369 https://royalsocietypublishing.org/doi/full-xml/10.1098/rspa.2011.0369 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 468, issue 2139, page 671-684 ISSN 1364-5021 1471-2946 journal-article 2011 crroyalsociety https://doi.org/10.1098/rspa.2011.0369 2024-09-02T04:21:03Z Viking navigation from Norway to America in the northern latitudes remains a mystery for physicists, historians and archaeologists. Polarimetric methods using absorbing dichroic crystals as polarizers to detect a hidden Sun direction using the polarized skylight have led to controversies. Indeed, these techniques may lack in sensitivity, especially when the degree of polarization is low. Here, we demonstrate theoretically and experimentally that using the transparent common Iceland spar as a depolarizer, the Vikings could have performed a precise navigation under different conditions. Indeed, when simply rotated, such a birefringent crystal can completely depolarize, at the so-called isotropy point, any partially polarized state of light, allowing us to guess the direction of the Sun. By equalizing the intensities of the ordinary and extraordinary beams at the isotropy point, we show that the Sun direction can be determined easily, thanks to a simple sensitive differential two-image observation. A precision of a few degrees could be reached even under dark crepuscular conditions. The exciting recent discovery of such an Iceland spar in the Alderney Elizabethan ship that sank two centuries before the introduction of the polarization of light in optics may support the use of the calcite crystal for navigation purposes. Article in Journal/Newspaper Iceland The Royal Society Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 468 2139 671 684 |
institution |
Open Polar |
collection |
The Royal Society |
op_collection_id |
crroyalsociety |
language |
English |
description |
Viking navigation from Norway to America in the northern latitudes remains a mystery for physicists, historians and archaeologists. Polarimetric methods using absorbing dichroic crystals as polarizers to detect a hidden Sun direction using the polarized skylight have led to controversies. Indeed, these techniques may lack in sensitivity, especially when the degree of polarization is low. Here, we demonstrate theoretically and experimentally that using the transparent common Iceland spar as a depolarizer, the Vikings could have performed a precise navigation under different conditions. Indeed, when simply rotated, such a birefringent crystal can completely depolarize, at the so-called isotropy point, any partially polarized state of light, allowing us to guess the direction of the Sun. By equalizing the intensities of the ordinary and extraordinary beams at the isotropy point, we show that the Sun direction can be determined easily, thanks to a simple sensitive differential two-image observation. A precision of a few degrees could be reached even under dark crepuscular conditions. The exciting recent discovery of such an Iceland spar in the Alderney Elizabethan ship that sank two centuries before the introduction of the polarization of light in optics may support the use of the calcite crystal for navigation purposes. |
format |
Article in Journal/Newspaper |
author |
Ropars, Guy Gorre, Gabriel Le Floch, Albert Enoch, Jay Lakshminarayanan, Vasudevan |
spellingShingle |
Ropars, Guy Gorre, Gabriel Le Floch, Albert Enoch, Jay Lakshminarayanan, Vasudevan A depolarizer as a possible precise sunstone for Viking navigation by polarized skylight |
author_facet |
Ropars, Guy Gorre, Gabriel Le Floch, Albert Enoch, Jay Lakshminarayanan, Vasudevan |
author_sort |
Ropars, Guy |
title |
A depolarizer as a possible precise sunstone for Viking navigation by polarized skylight |
title_short |
A depolarizer as a possible precise sunstone for Viking navigation by polarized skylight |
title_full |
A depolarizer as a possible precise sunstone for Viking navigation by polarized skylight |
title_fullStr |
A depolarizer as a possible precise sunstone for Viking navigation by polarized skylight |
title_full_unstemmed |
A depolarizer as a possible precise sunstone for Viking navigation by polarized skylight |
title_sort |
depolarizer as a possible precise sunstone for viking navigation by polarized skylight |
publisher |
The Royal Society |
publishDate |
2011 |
url |
http://dx.doi.org/10.1098/rspa.2011.0369 https://royalsocietypublishing.org/doi/pdf/10.1098/rspa.2011.0369 https://royalsocietypublishing.org/doi/full-xml/10.1098/rspa.2011.0369 |
genre |
Iceland |
genre_facet |
Iceland |
op_source |
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences volume 468, issue 2139, page 671-684 ISSN 1364-5021 1471-2946 |
op_rights |
https://royalsociety.org/journals/ethics-policies/data-sharing-mining/ |
op_doi |
https://doi.org/10.1098/rspa.2011.0369 |
container_title |
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences |
container_volume |
468 |
container_issue |
2139 |
container_start_page |
671 |
op_container_end_page |
684 |
_version_ |
1810451241832022016 |