Crystals 'helped Viking sailors' (For Viking fans....and others, of course).

BBC ^ | Wednesday, February 7, 2007

[Jedi Master Pikachu]

The sun was not necessary for Vikings to navigate, say researchers

Vikings may have used a special crystal called a sunstone to help navigate the seas even when the sun was obscured by fog or cloud, a study has suggested.

Researchers from Hungary ran a test with sunstones in the Arctic ocean, and found that the crystals can reveal the sun's position even in bad weather.

This would have allowed the Vikings to navigate successfully, they say.

The sunstone theory has been around for 40 years, but some academics have treated it with extreme scepticism.

Researcher Gabor Horvath from Eotvos University in Budapest led a team that spent a month recording polarisation - how rays of light display different properties in different directions - in the Arctic.

Polarisation cannot be seen with the naked eye, but it can be viewed with what are known as birefringent crystals, or sunstones.

Birefringence, or double refraction, is the splitting of a light wave into two different components - an ordinary and an extraordinary ray.

The researchers found that the crystals could be used to find out where the sun was in the sky in certain foggy or cloudy conditions.

It is already thought that Vikings used sundials aboard ships to navigate.

Vikings were a seafaring race from Scandinavia who used their longboats to explore and conquer parts of Europe, Greenland, Iceland and Russia.

[Ramius]

The sun will ~sometimes~ be visible through thin clouds and/or fog. But if the cloud cover is very thick at all, the disc of the sun doesn't always come through.

You also need a clear and sharp horizon to do local apparent noon, and weather conditions will foul that up as well.

Sure there are artificial horizon devices, but they're not very reliable. They work, sort of, but aren't to be relied on unless you've got no choice.

[Ramius]

I'd like to see this in action. I'm having a hard time believing that when light is completely diffused there's some refractive principle that can un-diffuse it. An estimate of where the sun sits is possible through an overcast, but its really approximate and subject to easy mis-direction.

[Cold Heart]

The sun will be South of you, when in the Northern hemisphere, your latitude is greater than the suns declination. If you are on the equator and the sun is on the Tropic of Cancer the sun will be to the North.

I have crossed the North Pacific and never saw the sun the entire crossing on numerous crossings. We dead reckoned all the way across. Later we got Sat Nav and then GPS but we still couldn't always see the sun.

Lower latitudes we generally could always get the sun.

[Sam Cree]

My daughter lived in Syracuse, NY for awhile...they don't see the sun up there too often in winter! 'Course, I don't suppose you really need celestial nav on Lake Ontario, probably DR works well enough.

Thanks for your input. I do a fair amount of sailing too, but coastal, although that includes extended Bahamas cruises from FL. But you don't need celestial for that, the distances are small enought that dead reckoning works very well, though nowadays we've got GPS. I still do the DR plot anyway, nice to have a "second opinion."

I'm curious about your N Pacific crossings and type of boat, etc.?

[Sam Cree]

I'm definitely not the expert navigator, but have figured out the sun is to the south, and travels between the Tropics of Cancer and Capricorn during June 21 and December 21, and ought to be due south at local noon for those north of it, I believe. Still, all input is welcome, since my piloting skills, while I like to think I understand them, are fairly rudimentary by many people's standards.

[Ramius]

Yes, to confirm... at Local Apparent Noon the sun is due South (true south, of course). It's used mainly to find Latitude.

[ASOC]

In Barrow Alaska, they don't see any sun for 66 days (mid winter). A cheerful place to live and visit.

[Bernard Marx]

The crystal in question was iolite, aka cordierite after the name of the mineralogist who first described it. This mineral is trichroic (offering 3 different colors when viewed in different orientations). Two of them, blue and yellow, are very distinct.

The modern usage of the word “sunstone” refers to an entirely different mineral, varieties of feldspar.

Here are two links that give more detail about how early seafarers might have used iolite crystals as a navigation aid.

Navigation and Iolite

[Cold Heart]

I sailed on merchant ships for 30 years. Started out with celestial and finished up with a company which was used as pre-market testing for electronic navigation equipment.

Back to the sunstone, there is a compass called a Sky Compass which detects the location of the sun by polarization even if the sun is just below the horizon.

There is a sun compass which reads the suns location by shadow and is afixed to a compass.

There is another called the Astro Compass, similar to the Sun Compass but used for other celestial bodies.

All three are museum grade now. I never saw one, they were mainly for polar navigation.

My favorite form of navigation was radar & visual along
coastal waters. Radar was my forte.

[lepton]

Not sure how it'd work on a moving object like a boat...but if you throw a pointed shadow and mark the point, and then several minutes later see where the mark is, the shadow point will have moved directly to the east.

My guess as to the "sunstone" would be that you'd use two...both in-line and one on each polarization axis, and where the second one went "dark", then they'd be in line with the sun for whatever frequency they were polarizing for.

[lepton]

Apparently my idea would work but is more complicated and less reliable. :)

[R. Scott]

...then that might imply the Vikings assumed the earth was round.

Why wouldn’t they? They were a sea faring people, and the round earth would be obvious to them.

[Rudder]

Why wouldn’t they? They were a sea faring people, and the round earth would be obvious to them.

Well, that's what I thought. But it wasn't until 1492 and later, even, that the world was thought, by Europeans, to be flat.

Looks like the Vikings, as long-distance sea travelers in general, had based their navigational procedures upon the assumption of sailing a globe-shaped surface. I should read more about this, since I'm studying for my Captain's license, and navigation is a big part of that.

[R. Scott]

I believe the “World is Flat” was pretty much relegated to churchmen and people who had never been to sea.
People weren’t stupid. If you are near the ocean stand and look at it from the shore. You will see a noticeable curve to the horizon. Board a boat and head out to sea. First the shoreline will drop below your horizon, than the higher land and finally the hills.
Watch an approaching boat. The first thing you se is the mast, then the hull and finally the waterline.
Head back toward shore. The first thing you see will be the tops of the hills, followed by the lower hills and finally the shoreline.
The only explanation is that you are on a curved surface. The Greek Erastothenes measured the circumference of a spherical Earth over 2,000 years ago

[Valin]

Vikings may have used a special crystal called a sunstone to help navigate the seas even when the sun was obscured by fog or cloud, a study has suggested.

What it can't do is help them find the End Zone.

[Jedi Master Pikachu]

The Greeks did have the opinion of an Earth with a circuference--but that idea fell out of mainstream later, and then came back even later than that.

As for the "churchmen" part, do try to lay off of the snide comments about "religious folk," if that was your intent. The geocentric universe was not a Christian theory (it was Ptolemy's--from A.D. Alexandria), and there is mention of the world being round in the Bible.

[Jedi Master Pikachu]

Appreciated.

[R. Scott]

The geocentric universe was not a Christian theory (it was Ptolemy's--from A.D. Alexandria), and there is mention of the world being round in the Bible.

The Geocentric Universe had nothing to do with the shape of the earth - round or flat. It was a system that placed the Earth in the center of everything. While not strictly Biblical, there are passages in Genesis 1:9 that hint at a flat Earth, as do passages in Psalms (75:3), and at least half a dozen other passages. It was endorsed by many members of the early Church, as were other ancient philosophies (philosophy and science were synonymous back then). There was no attempt to put down religion nor religionists in my post.
The Church has seldom spoken with one voice. While the Pope was the final authority, there have always been those who disagreed with him - and were usually branded heretic. Copernicus’ De Revolutionibus was placed on the Index in 1616 and only removed in 1835. This paper espoused the idea that the Earth was not the center of the universe. In 1633 the Inquisition convicted Galileo of heresy and forced him to recant his support of Copernicus.

[WesternCulture]

Leif Eriksson discovered America, speaking from a West European perspective.

This has been proved time after time.

Furthermore, for several years it has been known that evidence strongly indicate Vikings also used advanced navigation techniques like actual compasses.

Though being of Viking descent, my mission is not to boast.

But to hallow truth.

[GATOR NAVY]

At High Noon, the sun will be at its highest point and no matter how bad the cloud cover is, the sun will ALWAYS be visible at the noon hour, briefly perhaps, slightly dimmed by clouds, but still with enough resolution to make a sighting. Ask a sailor.

Okay, I was a sailor. In fact, my job was navigation. Since you asked, I'll tell you. You have no idea what you're talking about.