Researchers: We may have found a fabled sunstone (Update)

Mar 08, 2013 by Raphael Satter
This photo taken in Alderney, one of the Channel Islands, dated June 2012 and released on Friday March 8, 2013 by scientist Guy Ropars shows the Alderney Crystal, a piece of calcite. Researchers say the rough, whitish crystal recovered from the wreckage of 16th century English warship may be a sunstone, a special kind of mineral believed by some to have helped medieval seafarers navigate the high seas. (AP Photo/Guy Ropars)

A rough, whitish block recovered from an Elizabethan shipwreck may be a sunstone, the fabled crystal believed by some to have helped Vikings and other medieval seafarers navigate the high seas, researchers say.

In a paper published earlier this week, a Franco-British group argued that the Alderney Crystal—a chunk of Icelandic calcite found amid a 16th century wreck at the bottom of the English Channel—worked as a kind of solar compass, allowing sailors to determine the position of the sun even when it was hidden by heavy cloud, masked by fog, or below the horizon.

That's because of a property known as birefringence, which splits light beams in a way that can reveal the direction of their source with a high degree of accuracy. Vikings may not have grasped the physics behind the phenomenon, but that wouldn't present a problem.

"You don't have to understand how it works," said Albert Le Floch, of the University in Rennes in western France. "Using it is basically easy."

Vikings were expert navigators—using the sun, stars, mountains and even migratory whales to help guide them across the sea—but some have wondered at their ability to travel the long stretches of open water between Greenland, Iceland, and Newfoundland in modern-day Canada.

Le Floch is one of several who've suggested that calcite crystals were used as navigational aids for long summer days in which the sun might be hidden behind the clouds. He said the use of such crystals may have persisted into the 16th century, by which time magnetic compasses were widely used but often malfunctioned.

Le Floch noted that one Icelandic legend—the Saga of St. Olaf—appears to refer to such a crystal when it says that Olaf used a "sunstone" to verify the position of the sun on a snowy day.

But that's it. Few other medieval references to sunstones have been found, and no such crystals have ever been recovered from Viking tombs or ships. Until the Alderney Crystal was recovered in 2002, there had been little if any hard evidence to back the theory.

Many specialists are still skeptical. Donna Heddle, the director of the Center for Nordic Studies at Scotland's University of the Highlands and Islands, described the solar compass hypothesis as speculative.

"There's no solid evidence that that device was used by Norse navigators," she said Friday. "There's never been one found in a Viking boat. One cannot help but feel that if there were such things they would be found in graves."

She acknowledged that the crystal came from Iceland and was found near a navigation tool, but said it might just as easily have been used as a magnifying device as a solar compass.

Le Floch argued that one of the reasons why no stones have been found before is that calcite degrades quickly—it's vulnerable to acid, sea salts, and to heat. The Alderney Crystal was originally transparent, but the sea water had turned it a milky white.

Le Floch's paper—written with Guy Ropars, Jacques Lucas, and a group of Britons from the Alderney Maritime Trust—appeared Wednesday in the Proceedings of the Royal Society A.

Explore further: Radar search to find lost Aboriginal burial site

More information: The paper: rspa.royalsocietypublishing.or… .1098/rspa.2012.0651

A video tutorial on how birefringence works: www.sixtysymbols.com/videos/birefringence.htm

4.9 /5 (20 votes)
add to favorites email to friend print save as pdf

Related Stories

Vikings could have steered by polarized light

Feb 03, 2011

(PhysOrg.com) -- The Vikings are said to have been able to navigate with the aid of "sunstones" that allowed them to see the sun on cloudy or foggy days. Now scientists in Hungary and Sweden say the sunstones ...

Shipwreck find could be legendary 'sunstone'

Mar 06, 2013

An oblong crystal found in the wreck of a 16th-century English warship is a sunstone, a near-mythical navigational aid said to have been used by Viking mariners, researchers said on Wednesday.

Viking 'sunstone' more than a myth

Nov 02, 2011

Ancient tales of Norse mariners using mysterious sunstones to navigate the ocean when clouds obscured the Sun and stars are more than just legend, according to a study published Wednesday.

Was St. Edmund killed by the Vikings in Essex?

Dec 19, 2011

Keith Briggs, a visiting research fellow in linguistics at the University of the West of England, has proposed a new site for the battle in which King Edmund of East Anglia was killed in 869. If confirmed, the new proposal ...

Vikings in English grave had filed teeth

Jul 08, 2011

(PhysOrg.com) -- In what is believed to be a gravesite filled with thousand year old Viking bodies along with separated heads, in southern Britain, a new artifact has been discovered; one of the slain Vikings ...

Recommended for you

Radar search to find lost Aboriginal burial site

4 hours ago

Scientists said Tuesday they hope that radar technology will help them find a century-old Aboriginal burial ground on an Australian island, bringing some closure to the local indigenous population.

Archaeologists excavate NY Colonial battleground

Jul 19, 2014

Archaeologists are excavating an 18th-century battleground in upstate New York that was the site of a desperate stand by Colonial American troops, the flashpoint of an infamous massacre and the location of the era's largest ...

User comments : 5

Adjust slider to filter visible comments by rank

Display comments: newest first

Husky
2.9 / 5 (8) Mar 08, 2013
At the Corona Institute we have deciphered parts of the rune inscription and it reads:
ma.e .n ch..a , still working on the complete translation...
Dr_toad
2.3 / 5 (3) Mar 08, 2013
What inscription? Surely you must mean the one not mentioned anywhere in the stub of an article above?

Wow.
frajo
3.4 / 5 (5) Mar 08, 2013
made in china
sstritt
1.7 / 5 (6) Mar 08, 2013
What inscription? Surely you must mean the one not mentioned anywhere in the stub of an article above?

Wow.

It was a joke!
Tektrix
5 / 5 (4) Mar 08, 2013
Finding the sun via birefringent media works in part due to the way the eye works as well as the way the atmosphere polarizes sunlight. We humans have the ability to sense atmospheric polarization of sunlight with the unaided eye, but polarizing materials can enhance the effect, making it a lot easier to see. The visual effect is called Haidinger's Brush: http://www.polari...ger.html