Did Vikings navigate by polarized light?

Nature ^ | 31 Jan 2011 | Jo Marchant

[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.

[Palter]

Vikings, ping.

[GeronL]

interesting

[Kenny Bunk]

The Vikings: Hell’s Angels with boats.

[mamelukesabre]

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.

[allmendream]

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.

[dr_lew]

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.

[Ramius]

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

[Kirkwood]

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

[Kenny Bunk]

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.

[Ramius]

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.

[blam]

American Indian DNA In Ancient Iceland

They were taken there by Vikings.

[allmendream]

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.

[Ramius]

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

[JoeFromSidney]

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.

[hennie pennie]

*ping*

[Oztrich Boy]

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.

[Kenny Bunk]

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!

[SunkenCiv]

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[Monkey Face]

Awesome stuff! Thanks, SC!