[Palter]

Vikings, ping.

[GeronL]

interesting

[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.

[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]

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.

[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*

[Monkey Face]

Awesome stuff! Thanks, SC!

[NorwegianViking]

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

[colorado tanker]

Navigational aid: