How could the Viking Sun compass be used with sunstones before and after sunset? Twilight board as a new interpretation of the Uunartoq artefact fragment
Vikings routinely crossed the North Atlantic without amagnetic compass and left their mark on lands as far away as Greenland, Newfoundland and Baffin Island. Based on an eleventh-century dial fragment artefact, found at Uunartoq in Greenland, it is widely accepted that they sailed along chosen latit...
Published in: | Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences |
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Language: | English |
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Royal Society Publishing
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Online Access: | https://lup.lub.lu.se/record/4482319 https://doi.org/10.1098/rspa.2013.0787 |
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ftulundlup:oai:lup.lub.lu.se:b2ba7d7f-3398-4742-9ad0-fbd6828db77c 2023-05-15T15:35:28+02:00 How could the Viking Sun compass be used with sunstones before and after sunset? Twilight board as a new interpretation of the Uunartoq artefact fragment Bernath, Balazs Farkas, Alexandra Szaz, Denes Blaho, Miklos Egri, Adam Barta, Andras Åkesson, Susanne Horvath, Gabor 2014 https://lup.lub.lu.se/record/4482319 https://doi.org/10.1098/rspa.2013.0787 eng eng Royal Society Publishing https://lup.lub.lu.se/record/4482319 http://dx.doi.org/10.1098/rspa.2013.0787 wos:000335326400006 pmid:24910520 scopus:84899798488 Royal Society of London. Proceedings A. Mathematical, Physical and Engineering Sciences; 470(2166), no 20130787 (2014) ISSN: 1364-5021 Biological Sciences Viking navigation sunstone horizon board twilight board skylight compass sky polarization contributiontojournal/article info:eu-repo/semantics/article text 2014 ftulundlup https://doi.org/10.1098/rspa.2013.0787 2023-02-01T23:35:36Z Vikings routinely crossed the North Atlantic without amagnetic compass and left their mark on lands as far away as Greenland, Newfoundland and Baffin Island. Based on an eleventh-century dial fragment artefact, found at Uunartoq in Greenland, it is widely accepted that they sailed along chosen latitudes using primitive Sun compasses. Such instruments were tested on sea and proved to be efficient hand-held navigation tools, but the dimensions and incisions of the Uunartoq find are far from optimal in this role. On the basis of the sagasmentioning sunstones, incompatible hypotheses were formed for Viking solar navigation procedures and primitive skylight polarimetry with dichroic or birefringent crystals. We describe here a previously unconceived method of navigation based on the Uunartoq artefact functioning as a 'twilight board', which is a combination of a horizon board and a Sun compass optimized for use when the Sun is close to the horizon. We deduced an appropriate solar navigation procedure using a twilight board, a shadow-stick and birefringent crystals, which bring together earlier suggested methods in harmony and provide a true skylight compass function. This could have allowed Vikings to navigate around the clock, to use the artefact dial as a Sun compass during long parts of the day and to use skylight polarization patterns in the twilight period. In field tests, we found that true north could be appointed with such a medieval skylight compass with an error of about +/- 4 degrees when the artificially occluded Sun had elevation angles between +10 degrees and -8 degrees relative to the horizon. Our interpretation allows us to assign exact dates to the gnomonic lines on the artefact and outlines the schedule of the merchant ships that sustained the Viking colony in Greenland a millennium ago. Article in Journal/Newspaper Baffin Island Baffin Greenland Newfoundland North Atlantic Lund University Publications (LUP) Baffin Island Greenland Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 470 2166 20130787 |
institution |
Open Polar |
collection |
Lund University Publications (LUP) |
op_collection_id |
ftulundlup |
language |
English |
topic |
Biological Sciences Viking navigation sunstone horizon board twilight board skylight compass sky polarization |
spellingShingle |
Biological Sciences Viking navigation sunstone horizon board twilight board skylight compass sky polarization Bernath, Balazs Farkas, Alexandra Szaz, Denes Blaho, Miklos Egri, Adam Barta, Andras Åkesson, Susanne Horvath, Gabor How could the Viking Sun compass be used with sunstones before and after sunset? Twilight board as a new interpretation of the Uunartoq artefact fragment |
topic_facet |
Biological Sciences Viking navigation sunstone horizon board twilight board skylight compass sky polarization |
description |
Vikings routinely crossed the North Atlantic without amagnetic compass and left their mark on lands as far away as Greenland, Newfoundland and Baffin Island. Based on an eleventh-century dial fragment artefact, found at Uunartoq in Greenland, it is widely accepted that they sailed along chosen latitudes using primitive Sun compasses. Such instruments were tested on sea and proved to be efficient hand-held navigation tools, but the dimensions and incisions of the Uunartoq find are far from optimal in this role. On the basis of the sagasmentioning sunstones, incompatible hypotheses were formed for Viking solar navigation procedures and primitive skylight polarimetry with dichroic or birefringent crystals. We describe here a previously unconceived method of navigation based on the Uunartoq artefact functioning as a 'twilight board', which is a combination of a horizon board and a Sun compass optimized for use when the Sun is close to the horizon. We deduced an appropriate solar navigation procedure using a twilight board, a shadow-stick and birefringent crystals, which bring together earlier suggested methods in harmony and provide a true skylight compass function. This could have allowed Vikings to navigate around the clock, to use the artefact dial as a Sun compass during long parts of the day and to use skylight polarization patterns in the twilight period. In field tests, we found that true north could be appointed with such a medieval skylight compass with an error of about +/- 4 degrees when the artificially occluded Sun had elevation angles between +10 degrees and -8 degrees relative to the horizon. Our interpretation allows us to assign exact dates to the gnomonic lines on the artefact and outlines the schedule of the merchant ships that sustained the Viking colony in Greenland a millennium ago. |
format |
Article in Journal/Newspaper |
author |
Bernath, Balazs Farkas, Alexandra Szaz, Denes Blaho, Miklos Egri, Adam Barta, Andras Åkesson, Susanne Horvath, Gabor |
author_facet |
Bernath, Balazs Farkas, Alexandra Szaz, Denes Blaho, Miklos Egri, Adam Barta, Andras Åkesson, Susanne Horvath, Gabor |
author_sort |
Bernath, Balazs |
title |
How could the Viking Sun compass be used with sunstones before and after sunset? Twilight board as a new interpretation of the Uunartoq artefact fragment |
title_short |
How could the Viking Sun compass be used with sunstones before and after sunset? Twilight board as a new interpretation of the Uunartoq artefact fragment |
title_full |
How could the Viking Sun compass be used with sunstones before and after sunset? Twilight board as a new interpretation of the Uunartoq artefact fragment |
title_fullStr |
How could the Viking Sun compass be used with sunstones before and after sunset? Twilight board as a new interpretation of the Uunartoq artefact fragment |
title_full_unstemmed |
How could the Viking Sun compass be used with sunstones before and after sunset? Twilight board as a new interpretation of the Uunartoq artefact fragment |
title_sort |
how could the viking sun compass be used with sunstones before and after sunset? twilight board as a new interpretation of the uunartoq artefact fragment |
publisher |
Royal Society Publishing |
publishDate |
2014 |
url |
https://lup.lub.lu.se/record/4482319 https://doi.org/10.1098/rspa.2013.0787 |
geographic |
Baffin Island Greenland |
geographic_facet |
Baffin Island Greenland |
genre |
Baffin Island Baffin Greenland Newfoundland North Atlantic |
genre_facet |
Baffin Island Baffin Greenland Newfoundland North Atlantic |
op_source |
Royal Society of London. Proceedings A. Mathematical, Physical and Engineering Sciences; 470(2166), no 20130787 (2014) ISSN: 1364-5021 |
op_relation |
https://lup.lub.lu.se/record/4482319 http://dx.doi.org/10.1098/rspa.2013.0787 wos:000335326400006 pmid:24910520 scopus:84899798488 |
op_doi |
https://doi.org/10.1098/rspa.2013.0787 |
container_title |
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences |
container_volume |
470 |
container_issue |
2166 |
container_start_page |
20130787 |
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1766365803309957120 |