Posted on 03/08/2013 11:05:59 AM PST by Red Badger
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.
Read more at: http://phys.org/news/2013-03-fabled-sunstone.html#jCp
“a sunstone, the fabled crystal ....”
The ambiguous meaning (in this context) of “fabled” seems to imply that there is some doubt about the existence of sunstones. The statement is partially accurate, if “fabled” is taken to mean “made famous in fables”. It is completely wrong, if it is supposed to mean “exists only in fables”.
Sunstones do exist — that’s an indisputable fact. There are also accounts of their use by Viking navigators. Now, it seems that these accounts are likely “historical”, and not merely “fables”. The statement should be changed to: “a sunstone, the crystal made famous in historical accounts of Viking navigation”.
Have you read the book Longitude? I really enjoyed it.
Ragnar Lothbrok!
Been reading the Tom Holt, have ye?
I googled him and you are right, the book is “Who’s Afraid of Beowulf?”
It was a fun read and I recommend it to people.
"Sunstone" is a popular current misnomer for other varieties of feldspar, particularly material from India with bright spangles of mica, and for beautiful copper-infused material of many hues from Oregon, USA. Another gem-grade spangled variety occurs in Tanzania.
As used in Viking lore, the word "Sunstone" referred to some kind of stone (believed by some to be the mineral Iolite) that was used to find the sun on cloudy or foggy days. That name has nothing to do with current usage.
Calcite ("Iceland Spar")is an entirely separate mineral. It is also doubly-refractive and splits light into two beams traveling at different angles through it. One of my friends has created this information about it the fabled Viking "Sunstone": The Viking Compass
Yes, I have. Good book.
Can the suns position in the sky not be estimated by the time of day? Therefore an hour glass could track the Sun from daylight to dark? As long as East and West can be defined?Of course. That is what makes navigation by the stars and sun possible. The whole point of the sunstone is to compare the observed elevation of the sun to what it ought to be at any given observation.
The sun's elevation at (for example, high noon) is known for every latitude for every day of the year and that data can be set out in tables to be published for the use of navigators.
Then the navigator can observe the elevation of the sun at its zenith and consult the table to see his latitude.
Longitude is a tougher proposition. For that, you need to have a highly accurate clock (a navigator's marine chronometer) and a much more complex set of tables to set out elevations for the major stars in your hemisphere, again in relation to the time of day and the day of the year.
The clock would be set for an exact time at a known reference point on the earth (for example at Greenwich Observatory) and the clock must maintain its accuracy throughout the voyage.
The accuracy of the position fix will depend on the accuracy of the clock and the accuracy of the sextant that is used to obtain several stars elevations and the skill of the navigator to take accurate measurements.
Observing three stars wull produce curves lines on a chart of the surface of the globe together they make a "cocked hat" within which is the navigator's calculated position.
The greater the accuracy of the clock and the sextant and the accuracy of the navigator's obseravation, the smaller is the cocked hat.
Latitude was not a major problem for the Vikings. Longitude was a problem.
Caveat: I am grossly over-simplifying here
I guess the main observation for me was From Norway you sail west till you see land and visa versa, or north and south! They weren’t looking for a needle in a haystack! Just land fall! IDK!
Sun Stone Ping
I hope theirs were more useful that ours.
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| GGG managers are SunkenCiv, StayAt HomeMother & Ernest_at_the_Beach | |
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Thanks Red Badger. |
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That is a very pretty rock.
I didn’t expect that!
haha that’s a great line
Interesting reading in fact. I have coursed the Northern Meadows of Newfoundland, and they are a lot more hospitable than Greenland or Iceland.
But the last 20 years of solar driven warming shows us that the medieval warming period may have put the Vikings into contact with native Canadians a long time ago.There are also oral tradition legends about blond haired , blue eyed native Canadians.
great link, thanks.
There is also the historical record...
When Lewis & Clark wintered in North Dakota, they were hosted by blond haired, blue-eyed Mandan "indians".
I suspect this particular remnant would be associated with Minnesota's Kensington Runestone, but they likely would've originated in Greenland or Newfoundland.
Probably from Snorre Sturlasson. He was very accurate.
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