Ancient Sunstone Said to be Found

Researchers May Have Found Fabled Sunstone

By: Raphael Satter | Associated Press
Published: March 8, 2013
Britain sunstoneAP Photo/Guy Ropars

This photo 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.

LONDON  — 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.

from:    Associated Press Published: March 8, 2013 Britain sunstone /www.wunderground.com/

The Closer to the Poles, the Larger the Brains

ScienceShot: Brains Grow at Earth’s Poles

by Daniel Strain on 26 July 2011, 7:02 PM
sn-northerners.jpg
Credit: Eiluned Pearce

Underneath those horned helmets, Vikings may have sported big brains. Like other residents of the dark north, however, the Scandinavian pillagers would’ve needed the grandiose noggins to see, not to sack cities. Scientists have long known that polar days tend to be shorter and dimmer, on average, than their equatorial counterparts. Northern and southern peoples seem to compensate much like owls do, scientists report online today in theProceedings of the Royal Society B. The researchers examined 55 skulls dating back to the 1800s and taken from various parts of the world. They discovered that humans living along the tropics tend to have smaller eye sockets than people dwelling at higher and lower latitudes. Since bigger eyes absorb more light, large polar orbs could make up for the twilight conditions there. In fact, high- and low-latitude natives seem to see just as well in low light as tropical people do in bright light, according to the study. Cerebral size seems to grow by a few milliliters with increasing and decreasing latitude, probably because the brain’s visual centers expand as peepers widen.

fr/http://news.sciencemag.org/sciencenow/2011/07/scienceshot-brains-grow-at-earth.html