t opside V olume 120 , I s s u e 2
P a ge 20
An Auxiliarist Explores Sunstone Navigation
by Tim Marks photos and graphic by COMO Joseph Giannattasio
In the annals of seafaring history , the Vikings stand out as legendary navigators , capable of sailing across the vast , treacherous expanses of the North Atlantic a millennium ago . But what made them such skilled mariners ? It was not simply their prowess in boatbuilding , though that was undoubtedly impressive . Rather , it was their ability to navigate the open seas without the benefit of modern tools , such as maps , charts , sextants or compasses .
In those days , navigation was a hazardous enterprise . The sun , which was essential for determining direction and time , was often obscured by clouds or hidden below the horizon . Yet the Vikings had a secret weapon : a mysterious sunstone , or sólarstein , that enabled them to locate the sun even in the most challenging conditions . This crystal , it was said , possessed magical properties that could reveal the position of the sun , even when it was invisible to the naked eye .
Graphic of sunstone use .
Recently , researchers discovered that the sunstone was not a myth , but a real object made of a common calcite crystal , also known as Icelandic spar . This crystal , with its unique property of birefringence , was capable of splitting a beam of light into two paths , creating a double image that could be used to detect the concentric rings of polarization and thus the location of the sun . But could this ancient technology really work in practice , or was it just a fanciful legend ?
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From the experiment , the sunstone indicated the civil twilight sun at approximately 260 °, compared to its actual setting at 262 °.