Roslund, C. – Thirslund, S. - Pasztor, E. 2003. A mathematical Search for Viking Navigational Practices (original) (raw)
Related papers
The sunstone and polarised skylight: ancient Viking navigational tools?
Contemporary Physics, 2014
Although the polarisation of the light was discovered at the beginning of the nineteenth century, the Vikings could have used the polarised light around the tenth century in their navigation to America, using a 'sunstone' evoked in the Icelandic Sagas. Indeed, the birefringence of the Iceland spar (calcite), a common crystal in Scandinavia, permits a simple observation of the axis of polarisation of the skylight at the zenith. From this, it is possible to guess the azimuth of a hidden Sun below the horizon, for instance. The high sensitivity of the differential method provided by the ordinary and extraordinary beams of calcite at its so-called isotropy point is about two orders higher than that of the best dichroic polariser and permits to reach an accuracy of ±1°for the Sun azimuth (at sunrise and sunset). Unfortunately, due to the relative fragility of calcite, only the so-called Alderney crystal was discovered on board a 16th ancient ship. Curiously, beyond its use as a sunstone by the Vikings, during these last millennia calcite has led to the discovery of the polarisation of the light itself by Malus and is currently being used to detect the atmospheres of exoplanets. Moreover, the differential method for the light polarisation detection is widely used in the animal world.
Journal of the Optical Society of America A, 2014
It is a widely discussed hypothesis that Viking seafarers might have been able to locate the position of the occluded sun by means of dichroic or birefringent crystals, the mysterious sunstones, with which they could analyze skylight polarization. Although the atmospheric optical prerequisites and certain aspects of the efficiency of this sky-polarimetric Viking navigation have been investigated, the accuracy of the main steps of this method has not been quantitatively examined. To fill in this gap, we present here the results of a planetarium experiment in which we measured the azimuth and elevation errors of localization of the invisible sun. In the planetarium sun localization was performed in two selected celestial points on the basis of the alignments of two small sections of two celestial great circles passing through the sun. In the second step of sky-polarimetric Viking navigation the navigator needed to determine the intersection of two such celestial circles. We found that the position of the sun (solar elevation θ S , solar azimuth φ S ) was estimated with an average error of 0.6°≤ Δθ ≤ 8.8°and −3.9°≤ Δφ ≤ 2.0°. We also calculated the compass direction error when the estimated sun position is used for orienting with a Viking sun-compass. The northern direction (ω North ) was determined with an error of −3.34°≤ Δω North ≤ 6.29°. The inaccuracy of the second step of this navigation method was high (Δω North −16.3°) when the solar elevation was 5°≤ θ S ≤ 25°, and the two selected celestial points were far from the sun (at angular distances 95°≤ γ 1 , γ 2 ≤ 115°) and each other (125°≤ δ ≤ 145°). Considering only this second step, the sky-polarimetric navigation could be more accurate in the mid-summer period (June and July), when in the daytime the sun is high above the horizon for long periods. In the spring (and autumn) equinoctial period, alternative methods (using a twilight board, for example) might be more appropriate. Since Viking navigators surely also committed further errors in the first and third steps, the orientation errors presented here underestimate the net error of the whole sky-polarimetric navigation.
Norse Navigation in the Northern Isles
Journal of the North Atlantic, 2024
This article explores the navigation and seafaring strategies used by Norse mariners in and around the Northern Isles of Scotland. To do so we draw upon a diverse range of sources including saga accounts, placenames, archaeological remains, early historic maps as well as logistical considerations. This diachronic perspective is inspired by Christer Westerdahl’s “maritime cultural landscapes” methodology as well as recent studies of prehistoric seafaring. It is demonstrated, through close examination of the available evidence, that the Norse mariners had very well-developed strategies to avoid dangers as well as maximize their efficiency at sea to ensure that journeys were as safe and fast as possible. Topics explored include navigation markers, naming strategies, landing places, portages, beacons, anchorages and pilots.
Viking Sun Compass ?. The Uunatoq Disc vs the Astrolabe of Al_Sahli
Viking Sun Compass ? The Uunatoq Disc vs the Astrolabe of Al_Sahli, 2023
The Uunatoq Disc, is an artefact that the Vikings used for Navigation? The Uunatoq fragment of a wooden disc that can be seen in the Danish National Museum, dated in the 1200 A.D., compared with the Astrolabe made by Al-Sahlî in Toledo, in the year 1067 A.D.which can be seen in the Museo Arqueologico Nacional. Madrid. Spain. This article is a scholium to the papers written by Alfonso Pastor-Moreno, about Astrolabes and about Sun Compasses,
Applied Optics, 2013
It is widely accepted that Vikings used sun-compasses to derive true directions from the cast shadow of a gnomon. It has been hypothesized that when a cast shadow was not formed, Viking navigators relied on crude skylight polarimetry with the aid of dichroic or birefringent crystals, called "sunstones." We demonstrate here that a simple tool, that we call "shadow-stick," could have allowed orientation by a sun-compass with satisfying accuracy when shadows were not formed, but the sun position could have reliably been estimated. In field tests, we performed orientation trials with a set composed of a sun-compass, two calcite sunstones, and a shadow-stick. We show here that such a set could have been an effective orientation tool for Vikings only when clear, blue patches of the sky were visible.
An analysis of navigational instruments in the Age of Exploration: 15th century to mid-17th century
2006
Australia), and Mel Fisher Maritime Heritage Society and Museum (Key West, Florida, United States). To those professionals and enthusiasts who developed websites on excavations, artifacts, shipping, and navigation, I extend my sincere appreciation for their hard work. Special thanks to Andy Elkerton of the Mary Rose Trust for the information on Mary Rose and Tudor navigation. I would like to thank the Texas Historical Commission, particularly Jim Bruseth, Jeff Durst, and Steve Hoyt for their consistent support and permission to study and use photographs of the navigation artifacts recovered from LaBelle. Special thanks to Texas A&M University, specifically, the Department of Animal Science for use of their digital camera, Don Carona (Department of Physics) for generously sharing his time and knowledge, as well as Dr. C. Wayne Smith (Department of Anthropology) for the use of his equipment. I would also like to thank Helen Dewolf and Amy Borgens at the Conservation Research Laboratory vii (College Station, Texas, United States) for providing conservation records and their careful preservation of the LaBelle artifact. While many authors provided valuable information, for his research into scientific instruments in this period, as well as his personal support for this research, I would like to thank Gerard L'E Turner. I owe a debt of gratitude to Lord High Admiral D. W. Waters and E. G. R. Taylor for their extensive writings on the history of navigation and mathematics in England. Without contest, their texts defined the science and history of navigation in this early period. I wish to acknowledge the invaluable contributions of my committee, particularly Dr. C. Wayne Smith, who served as chair. Their contributions have greatly improved this thesis. Special thanks to the staff of the Evans Library Interlibrary Loan Office. Their unflagging efforts to obtain obscure documents and books, often in foreign languages, were extraordinary. I also wish to thank the Museum of the History of Science for permission to reproduce their photos of navigational instruments. This thesis would not have been possible without the consistent support and encouragement of my parents, Ed Behrle and Gayle Behrle, who encouraged me every step of the way and believed in me. I would like to extend my eternal gratitude to Daren Swanick for his endless enthusiasm, support, and understanding. Specifically, thanks for his tireless efforts on the LaBelle planisphere. And last, but never least, thanks to my sweet Charlie for his support when the going got rough. You're the best! viii