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Did Vikings navigate by polarized light?
Nature ^ | 31 Jan 2011 | Jo Marchant

Posted on 01/31/2011 8:30:21 PM PST by Palter

'Sunstone' crystals may have helped seafarers to find the Sun on cloudy days.

A Viking legend tells of a glowing 'sunstone' that, when held up to the sky, revealed the position of the Sun even on a cloudy day. It sounds like magic, but scientists measuring the properties of light in the sky say that polarizing crystals — which function in the same way as the mythical sunstone — could have helped ancient sailors to cross the northern Atlantic. A review of their evidence is published today in Philosophical Transactions of the Royal Society B1.

The Vikings, seafarers from Scandinavia who travelled widely and settled in swathes of Northern Europe, the British Isles and the northern Atlantic from around 750 to 1050 AD, were skilled navigators, able to cross thousands of kilometres of open sea between Norway, Iceland and Greenland. Perpetual daylight during the summer sailing season in the far north would have prevented them from using the stars as a guide to their positions, and the magnetic compass had yet to be introduced in Europe — in any case, it would have been of limited use so close to the North Pole.

But Viking legends, including an Icelandic saga centring on the hero Sigurd, hint that these sailors had another navigational aid at their disposal: a sólarsteinn, or sunstone.

The saga describes how, during cloudy, snowy weather, King Olaf consulted Sigurd on the location of the Sun. To check Sigurd's answer, Olaf "grabbed a sunstone, looked at the sky and saw from where the light came, from which he guessed the position of the invisible Sun"2.

(Excerpt) Read more at nature.com ...


TOPICS: History
KEYWORDS: ageofsail; crystal; godsgravesglyphs; middleages; navigation; sunstone; sunstones; viking

1 posted on 01/31/2011 8:30:26 PM PST by Palter
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To: SunkenCiv

Vikings, ping.


2 posted on 01/31/2011 8:31:04 PM PST by Palter (If voting made any difference they wouldn't let us do it. ~ Mark Twain)
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To: Palter

interesting


3 posted on 01/31/2011 8:35:01 PM PST by GeronL (http://www.stink-eye.net/forum/index.php)
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To: Palter

The Vikings: Hell’s Angels with boats.


4 posted on 01/31/2011 8:40:25 PM PST by Kenny Bunk (America might survive Obama. It cannot survive those who vote for him)
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To: Palter

Wow, I am not understanding this AT ALL. looking through a polarized lens at a cloudy sky will tell you NOTHING. I’m assuming looking through a polarizing crystal gives the same effect.


5 posted on 01/31/2011 8:41:55 PM PST by mamelukesabre (Si Vis Pacem Para Bellum (If you want peace prepare for war))
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To: Kenny Bunk

Rolf the Granger killed a guy, because his family was in good with the Queen he got exiled instead of killed.

He got some rough customers together and took over “Normandy”, it wasn’t the land of the Northmen until Rolf.

From Normandy they took England, Sicily, Southern Italy, the Crusader Kingdom of Antioch, and twice came within one battle of taking the largest empire of the day, the Byzantines.


6 posted on 01/31/2011 8:46:00 PM PST by allmendream (Tea Party did not send the GOP to D.C. to negotiate the terms of our surrender to socialism.)
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To: Palter
How many of you can see Haidinger's Brush? I read about this years ago in Scientific American, and went outside and saw it right away. It is very distinct on a clear late afternoon with a deep blue sky. I can check for its objectivity by looking straight up and turning around, which causes the hourglass shape of the "brush" to rotate in my field of view.
7 posted on 01/31/2011 8:57:46 PM PST by dr_lew
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To: Palter

If there’s a Viking ping list... I’d love to be on it.


8 posted on 01/31/2011 9:04:00 PM PST by Ramius (Personally, I give us... one chance in three. More tea?)
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To: mamelukesabre

No, this makes sense. And it is very clever.


9 posted on 01/31/2011 9:04:39 PM PST by Kirkwood (Zombie Hunter)
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To: allmendream
From Normandy they took England, Sicily, Southern Italy, the Crusader Kingdom of Antioch, and twice came within one battle of taking the largest empire of the day, the Byzantines.

All this on a diet of lutefisk! But they did hang out around Normandie for a while, enjoying French cuisine, washed down with Calvados, before setting out for England, Italy and points East.

10 posted on 01/31/2011 9:21:15 PM PST by Kenny Bunk (America might survive Obama. It cannot survive those who vote for him)
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To: Palter

I wonder about something here...

I wonder if what they mean by a “sunstone” isn’t an artificial horizon. In the world of celestial navigation, it’s not the stars or the sun or moon that are hard to find in the sky. The problem was that there was no clear horizon to measure them against, due to haze, clouds, or light conditions.

What was developed was the “artificial horizon”. One of the first iterations of this was a broad bowl full of liquid mercury. A large of pool of mercury, even on a ship that is leaning and tipping with the wind, will still be a quite level mirror of the sky. If you measure the angle of star in the sky against its reflection in a pool of mercury, and divide the angle by half... you have a good angle of that star above the horizon even if you don’t have a clear horizon.


11 posted on 01/31/2011 9:27:14 PM PST by Ramius (Personally, I give us... one chance in three. More tea?)
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To: Palter
American Indian DNA In Ancient Iceland

They were taken there by Vikings.


12 posted on 01/31/2011 9:31:49 PM PST by blam
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To: Kenny Bunk
Indeed. Most of the Normans who went on the first Crusade with Tancred and Bohemund grew up in Italy.

The Duke of Normandy Robert Curthose had to hock Normandy to William King of England his brother to afford to go on the first Crusade.

13 posted on 01/31/2011 9:36:54 PM PST by allmendream (Tea Party did not send the GOP to D.C. to negotiate the terms of our surrender to socialism.)
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To: allmendream

But the first Crusade was one of the more effective....


14 posted on 01/31/2011 10:05:40 PM PST by Ramius (Personally, I give us... one chance in three. More tea?)
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To: Palter
This is nothing new. It was reported years ago. The Vikings used a naturally birefringent crystal that polarized the light coming through it. You can do the same thing now with a polarizing filter. If you have one for your camera, give it a try on a cloudy day.
15 posted on 01/31/2011 11:18:06 PM PST by JoeFromSidney (New book: RESISTANCE TO TYRANNY. A primer on armed revolt. Available form Amazon.)
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To: muawiyah

*ping*


16 posted on 02/01/2011 1:00:20 AM PST by hennie pennie
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To: mamelukesabre
No it works http://www.great-landscape-photography.com/polarizing-filter.html

If rotating the polarizing filter darkens the sky (or clouds) you are ponting it at right angles to the sun position.

17 posted on 02/01/2011 4:15:45 AM PST by Oztrich Boy (History repeats itself, first as tragedy, second as farce - Karl Marx)
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To: allmendream
I have always blamed the Normans for not finishing the damn Crusades properly. The entire region would be better off if the present King of Spain, who is the legitimate heir to the Crusader kingdom, were in charge.

And where are the Normans now that we need them to sort the bloody pagans out again? Looking down their long noses as they putter about England, France and Italy? No wonder the world is such a mess. Time to go a-Viking, boys!

18 posted on 02/01/2011 6:33:08 AM PST by Kenny Bunk (America might survive Obama. It cannot survive those who vote for him)
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To: Palter; StayAt HomeMother; Ernest_at_the_Beach; 1010RD; 21twelve; 24Karet; 2ndDivisionVet; 31R1O; ..

· GGG managers are SunkenCiv, StayAt HomeMother, and Ernest_at_the_Beach ·
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Thanks Palter!

To all -- please ping me to other topics which are appropriate for the GGG list.
 

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· Science topic · science keyword · Books/Literature topic · pages keyword ·


19 posted on 02/01/2011 4:11:18 PM PST by SunkenCiv (The 2nd Amendment follows right behind the 1st because some people are hard of hearing.)
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To: Palter; SunkenCiv

Awesome stuff! Thanks, SC!


20 posted on 02/01/2011 4:25:46 PM PST by Monkey Face (Seen on the marquis of local bar and grill: Grave Happy Hour! 4:00 - 7:00 AM)
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To: Monkey Face; Palter

My pleasure, and thanks again to Palter.


21 posted on 02/01/2011 4:52:40 PM PST by SunkenCiv (The 2nd Amendment follows right behind the 1st because some people are hard of hearing.)
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To: Palter
Iolite is the name of the violet-blue gemstone that the Vikings used to help them navigate. It is called the water sapphire. Iolite was used as a polarizing filter to determine the direction of the sun. http://www.docstoc.com/docs/39726618/Gemstone-%E2%80%93-Iolite-the-gem-of-the-Viking-and-Navigation
22 posted on 02/01/2011 5:13:09 PM PST by NorwegianViking
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To: NorwegianViking

You managed to link that back to this thread...


23 posted on 02/01/2011 5:28:39 PM PST by null and void (We are now in day 742 of our national holiday from reality. - 0bama really isn't one of US.)
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To: null and void
Thanks for the message error. I will try again. There is picture of the stone at the link. Hope I get it right this time! Best wishes. iolite Viking navigation gemstone
24 posted on 02/01/2011 5:51:24 PM PST by NorwegianViking
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To: Palter; SunkenCiv

Viking Ray Bans ping!


25 posted on 02/02/2011 9:01:57 AM PST by wildbill (You're just jealous because the Voices talk only to me.)
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To: Kenny Bunk
But they did hang out around Normandie for a while, enjoying French cuisine, washed down with Calvados, before setting out for England, Italy and points East

Trading Coq au Vin for Bangers and Smash. No accounting for some tastes . . . .

26 posted on 02/02/2011 10:30:04 AM PST by colorado tanker
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To: Palter; SunkenCiv
Navigational aid:


27 posted on 02/02/2011 11:09:17 AM PST by colorado tanker
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To: colorado tanker
Apparently, only the dumber Normans stayed in England. The rest had time-shares in Sicily. Anyway, there had to be a big difference between your average Viking and your average Norman, for example Christianity, black hair, no horns on the helmet, plucking and cooking the coq au vin before eating it, etc.
Aye, soft they was by that time.
28 posted on 02/02/2011 12:06:19 PM PST by Kenny Bunk (America might survive Obama. It cannot survive those who vote for him)
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To: colorado tanker

That’ll help ‘em next season, assuming their heads are out where they can use ‘em by then. ;’)


29 posted on 02/03/2011 4:55:12 PM PST by SunkenCiv (The 2nd Amendment follows right behind the 1st because some people are hard of hearing.)
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To: wildbill

Probably they wore Wayfarers. ;’)


30 posted on 02/03/2011 4:55:52 PM PST by SunkenCiv (The 2nd Amendment follows right behind the 1st because some people are hard of hearing.)
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Between AD 750 and AD 1200 the Vikings, were the dominant sailors of the North Atlantic. When the Sun was shining, geographical north could be determined with a special sundial or ‘sundisc’.  However, how the Vikings could have navigated in cloudy or foggy situations, when the Sun’s disc was unusable, is still not fully understood.
Viking sundial navigation device

Viking sundial navigation device

A hypothesis was formulated in 1967, suggested that under foggy or cloudy conditions, Vikings might have been able to determine the azimuth direction of the Sun with the help of skylight polarization, just like some insects.  According to this theory, the Vikings could have determined the direction of the skylight polarization with the help of an enigmatic birefringent crystal (double-refracting crystal), like cordierite, tourmaline, or calcite, which are common in the Scandinavian region and even mentioned in a Viking saga, functioning as a linearly polarizing filter.

The Viking saga tells of a glowing ‘sunstone’ that, when held up to the sky, revealed the position of the Sun even on a cloudy day. It sounds like magic, but scientists measuring the properties of light in the sky say that polarizing crystals – which function in the same way as the mythical sunstone – could have helped ancient sailors to cross the northern Atlantic.

A review of their evidence is published in Philosophical Transactions of the Royal Society B . (Feb 2011)

Viking Sagas

Viking legends, including an Icelandic saga ‘Rauðúlfs þáttr’ with  the hero Sigurður , hint that these sailors had another navigational aid at their disposal: a sólarsteinn, or sunstone.

The saga describes how, during cloudy, snowy weather, King Olaf consulted Sigurður on the location of the Sun.  To check Sigurður‘s answer, Olaf  “made them fetch the solar stone and held it up and saw where light radiated from the stone and thus directly verified Sigurður’ s prediction”.  In 1967, Thorkild Ramskou, a Danish archaeologist, suggested that this stone could have been a polarizing crystal such as Icelandic spar, a transparent form of calcite, which is common in Scandinavia.

Iceland spar, perhaps the medieval sunstone. Image: Wikimedia Commons.

Iceland spar, perhaps the medieval sunstone. Image: Wikimedia Commons.

Light consists of electromagnetic waves that oscillate perpendicular to the direction of the light’s travel. When the oscillations all point in the same direction, the light is polarized. A polarizing crystal such as calcite allows only light polarized in certain directions to pass through it, and can appear bright or dark depending on how it is oriented with respect to the light.

Polarized Light

Air molecules scatter the light in the atmosphere causing sunlight to become polarized, with the line of polarization tangential to circles centred on the Sun. So Ramskou argued that by holding a crystal such as calcite up to the sky and rotating it to check the direction of polarization of the light passing through it, the Vikings could have deduced the position of the Sun, even when it was hidden behind clouds or fog, or was just beneath the horizon.

Historians have debated the possibility ever since, with some arguing that the technique would have been pointless, because it would only work if the crystal was pointed at patches of clear sky, and in such conditions it would be possible to estimate the position of the Sun with the naked eye, for example from the bright lining of cloud tops.

Gábor Horváth, an optics researcher at Eötvös University in Budapest, and Susanne Åkesson, a migration ecologist from Lund University, Sweden, have been testing these assumptions since 2005. The special issue of Philosophical Transactions of the Royal Society B in which their review appears is dedicated to biological research on polarized light.

In one study, the researchers took photographs of partly cloudy or twilight skies in northern Finland through a 180° fisheye lens, and asked test subjects to estimate the position of the Sun. Errors of up to 99° led the researchers to conclude that the Vikings could not have relied on naked-eye guesses of the Sun’s position.

To check whether sunstones would work better, in 2005 they measured the polarization pattern of the entire sky under a range of weather conditions during a crossing of the Arctic Ocean on the Swedish icebreaker Oden.

“Using full-sky imaging polarimetry, we have shown that one of the two atmospheric optical prerequisites of the polarimetric Viking navigation is always fulfilled under both foggy and cloudy conditions,” saidHorváth. “The distribution (pattern) of the direction of polarization of skylight on the foggy or cloudy celestial hemisphere is similar to that of the clear sky, which was a great surprise for us. However, we would like to emphasize that the Dutch meteorologist Guenther P. Koennen has already hypothesized this phenomenon in his famous book Polarized Light in Nature (Cambridge University Press, 1985).”

Through the clouds

Polarimetry images measured by full-sky imaging. Credit: Credit: Gabor Horvath

Polarimetry images measured by full-sky imaging. Credit: Credit: Gabor Horvath

The researchers were surprised to find that in foggy or totally overcast conditions the pattern of light polarization was similar to that of clear skies. The polarization was not as strong, but Åkesson believes that it could still have provided Viking navigators with useful information.

“I tried such a crystal on a rainy overcast day in Sweden,” she says. “The light pattern varied depending on the orientation of the stone.”

She and Horváth are now planning further experiments to determine whether volunteers can accurately work out the Sun’s position using crystals in various weather conditions.

Sean McGrail, who studied ancient seafaring at the University of Oxford, UK, before retiring, says that the studies are interesting but there is no real evidence to indicate that the Vikings actually used such crystals. “You can show how they could be used, but that isn’t proof,” he says. “People were navigating long before this without any instruments.”

Surviving written records indicate that Viking and early medieval sailors crossed the north Atlantic using the Sun’s position on clear days as a guide, in combination with the positions of coastlines, flight patterns of birds, migration paths of whales and distant clouds over islands, says Christian Keller, a specialist in North Atlantic archaeology at the University of Oslo. “You don’t need to be a wizard,” he says. “But you do need to combine a lot of different sorts of observations.”

Keller says he is “totally open” to the idea that the Vikings also used sunstones, but is waiting for archaeological evidence. “If we find a shipwreck with a crystal on board, then I would be happy,” he says.

Faulkes, Anthony. 1966. “Rauðúlfs þáttr: A study”. Studia Islandica 25. Heimspekideild Háskóla Íslands og Bókaútgáfa Menningarsjóðs. Reykjavík. ISSN 0258-3828. 92 pp.

On the trail of Vikings with polarized skylight: experimental study of the atmospheric optical prerequisites allowing polarimetric navigation by Viking seafarers, Gabor Horvath et al., Phil. Trans. R. Soc. B 12 March 2011 vol. 366 no. 1565 772-782. doi:10.1098/rstb.2010.0194

Hegedus, Ramon, Akesson, Susanne, Wehner, Rudiger, and Horvath, Gabor. “Could Vikings have navigated under foggy and cloudy conditions by skylight polarization? On the atmospheric optical prerequisites of polarimetric Viking navigation under foggy and cloudy skies.” Proc. R. Soc. A. 463 : 1081-1095 (2007).

Barta, Andras, Horvath, Gabor, and Meyer-Rochow, Benno. “Psychophysical study of the visual sun location in pictures of cloudy and twilight skies inspired by Viking navigation.” Journal of the Optical Society of America A 22: 1023-1034 (2005).

31 posted on 02/11/2011 7:19:29 PM PST by Palter (If voting made any difference they wouldn't let us do it. ~ Mark Twain)
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