scholarly journals The sixteenth century Alderney crystal: a calcite as an efficient reference optical compass?

2013 ◽  
Vol 469 (2153) ◽  
pp. 20120651 ◽  
Author(s):  
Albert Le Floch ◽  
Guy Ropars ◽  
Jacques Lucas ◽  
Steve Wright ◽  
Trevor Davenport ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Sixteenth Century ◽  
Crucial Role ◽  
Sea Water ◽  
The Sun ◽  
Calcite Crystal ◽  
Sun Compass ◽  
Sand Abrasion ◽  
Iceland Spar

The crystal recently discovered in the 1592 sunken Elizabethan ship is shown to be an Iceland spar. We report that two main phenomena, with opposite effects, explain the good conservation and the evolution of this relatively fragile calcite crystal. We demonstrate that the Ca 2+ –Mg 2+ ion exchanges in such a crystal immersed in sea water play a crucial role by limiting the solubility, strengthening the mechanical properties of the calcite, while the sand abrasion alters the crystal by inducing roughness of its surface. Although both phenomena have reduced the transparency of the Alderney calcite crystal, we demonstrate that Alderney-like crystals could really have been used as an accurate optical sun compass as an aid to ancient navigation, when the Sun was hidden by clouds or below the horizon. To avoid the possibility of large magnetic errors, not understood before 1600, an optical compass could have helped in providing the sailors with an absolute reference. An Alderney-like crystal permits the observer to follow the azimuth of the Sun, far below the horizon, with an accuracy as great as ±1 ° . The evolution of the Alderney crystal lends hope for identifying other calcite crystals in Viking shipwrecks, burials or settlements.

scholarly journals A depolarizer as a possible precise sunstone for Viking navigation by polarized skylight

2011 ◽  
Vol 468 (2139) ◽  
pp. 671-684 ◽  
Author(s):  
Guy Ropars ◽  
Gabriel Gorre ◽  
Albert Le Floch ◽  
Jay Enoch ◽  
Vasudevan Lakshminarayanan
Keyword(s):  
Degree Of Polarization ◽  
The Sun ◽  
Calcite Crystal ◽  
Birefringent Crystal ◽  
Northern Latitudes ◽  
Polarization Of Light ◽  
Iceland Spar

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.

The Safe Aircraft Competition, The Sun Compass, and more

1930 ◽  
Vol 142 (3) ◽  
pp. 232-234
Author(s):  
Alexander Klemin
Keyword(s):  
The Sun ◽  
Sun Compass

GOD OF METALS: TLATLAUHQUI TEZCATLIPOCA AND THE SACRED SYMBOLISM OF METALLURGY IN MICHOACAN, WEST MEXICO

2010 ◽  
Vol 21 (1) ◽  
pp. 69-78 ◽  
Author(s):  
Hans Roskamp
Keyword(s):  
Sixteenth Century ◽  
Present Article ◽  
Crucial Role ◽  
Metal Artifacts ◽  
Technology Studies ◽  
West Mexico

AbstractIn recent years the development of metallurgy in West Mexico has received increasing attention in the field of archaeological and technology studies. Considering that the latter already include excellent descriptions and analysis of the ritual and sumptuary functions of metal artifacts, the present article focuses on the sacred symbolism of the metal resources and the metalworking process itself according to several indigenous cosmogonical narratives and other additional pictorial and alphabetical sources from sixteenth-century Michoacan and adjacent cultural areas. The available documentation clearly shows that a crucial role was attributed to the native god Tlatlauhqui Tezcatlipoca.

Endless skies and open seas – how birds and fish navigate

Neuroforum ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Lisa Spiecker ◽  
Bo Leberecht ◽  
Corinna Langebrake ◽  
Malien Laurien ◽  
Shambhavi Rajendra Apte ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Magnetic Fields ◽  
Home Range ◽  
Environmental Conditions ◽  
Geomagnetic Field ◽  
Visual Cues ◽  
Quantum Mechanical ◽  
The Sun ◽  
Seasonal Migrations ◽  
Research Questions

Abstract Every year, billions of animals leave their home range and start seasonal migrations in order to find more favorable resources and to escape harsh environmental conditions. These round trips often span thousands of kilometers. To successfully navigate along their route, animals rely on various external references. While landmarks and celestial cues like stars or the sun are easy to imagine as guidance on these journeys, using the geomagnetic field for orientation is more elusive. The geomagnetic field is an omnipresent cue, which can be sensed and relied upon by many animals, even when visual cues are sparse. How magnetic fields can be perceived seems to vary between birds and fish. While birds seem to use a mechanism based on the quantum mechanical properties of electron spins, fish may have evolved a compass similar in its function to the technical devises developed by humans. How these mechanisms work precisely and how they are integrated are research questions addressed in SFB 1372.

scholarly journals Mechanical Properties of Sea Water Sea Sand Coral Concrete Modified withDifferent Cement and Fiber Types

2020 ◽  
Vol 8 (8) ◽  
pp. 915-937
Author(s):  
Xibo Qi ◽  
Yijie Huang ◽  
Xiaowei Li ◽  
Zhenhua Hu ◽  
Jingwei Ying ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Sea Water ◽  
Fiber Types ◽  
Sea Sand

Spaces for Music in Sixteenth-Century Paduan Courts

2012 ◽  
Author(s):  
GUIDO BELTRAMINI
Keyword(s):  
Sixteenth Century ◽  
Crucial Role ◽  
Rare Plants ◽  
Way Of Life ◽  
Pietro Bembo ◽  
Literary Sources ◽  
Hadrian’S Villa ◽  
Hadrian's Villa ◽  
The Ideal ◽  
The Way

This chapter is dedicated to a particular culture relating to the way one might ideally lead one's life in line with ancient practices and views. The trend in question, which developed in Padua in the first half of the Cinquecento, was promoted by such humanists as Pietro Bembo, Alvise Cornaro and Marco Mantova Benavides. Exceptional connoisseurs of the mores and values of antiquity, these intellectuals personally supervised and directed the building of their homes. Following the model of Hadrian's villa at Tivoli, the complexes of these Paduan residences comprised dwelling areas, pavilions, large gardens and the installation of fountains, statues and rare plants. Inspired by literary sources, the ideal of recreating the ‘ancient’ way of life, in which music played a crucial role, was revived.

Encountering Homer through Greek Plays in Sixteenth-Century Europe

2018 ◽  
pp. 63-75
Author(s):  
Tanya Pollard
Keyword(s):  
Sixteenth Century ◽  
Early Modern ◽  
Crucial Role ◽  
Fifth Century ◽  
Literary Texts

Originally received as oral performances, Homer’s epics circulated in sixteenth-century Europe not only as printed literary texts, but also through performances of a different sort. This chapter argues that fifth-century Greek plays on Homeric material played a crucial role in shaping the epics’ early modern reception. In a phrase widely circulated in the sixteenth century, Aeschylus reportedly claimed that all of his tragedies were ‘slices from the great banquets of Homer’. Although Virgil and Ovid were more familiar vehicles for Homeric material, Greek plays made distinctive contributions to perceptions of Troy and its aftermath through their links with performance, and their status as models for dramatic genres. It is proposed that the versions of Homer transmitted through Greek plays had an important role in shaping not only early modern understandings of Homer, but also the development of the early modern popular stage.

The Role of Nanoparticles on the Durability of Lime-Pozzolan Binding System

2019 ◽  
Vol 286 ◽  
pp. 119-132 ◽  
Author(s):  
Eirini Chrysanthi Tsardaka ◽  
Eleni Pavlidou ◽  
Maria Stefanidou
Keyword(s):  
Mechanical Properties ◽  
Research Study ◽  
Sea Water ◽  
The Other ◽  
Binding System ◽  
Water Cycles

The present research study is an effort to evaluate the effect of different nanoparticles in lime-pozzolan system, in time. nanosilica, nanoalumina and nanocalcium oxide were used in different combinations in this traditional binding system. The paper aims to record the durability of the traditional binding system in time, up to 365 days. For that purpose, the samples were subjected to ageing tests, such as wetting-drying cycles, sea water cycles and salt cycles. Up to 90 days, nanosilica benefits the most of the physic-mechanical properties, as well as the microstructure. Though, by studying the systems in time, the behavior of the other nanoparticles seems to favor certain properties more than nanosilica, especially at later ages. The addition of nanocalcium oxide combined with nanoalumina aids the improvement of the microstructure and the system presented great compressive after 40 cycles in ageing tests.

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