
'Viking sunstone' found in shipwreck? - cwan
http://www.bbc.co.uk/news/world-europe-21693140#TWEET647219
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SiVal
The BBC article mentioned refraction, but Iceland Spar makes it possible to
see the direction of polarization of skylight, which means it could be used on
small, clear patches of sky on an otherwise overcast day to find the direction
to the sun. This is another way it could act as a "sunstone" for navigation.
Whether it actually was used this way is unfortunately not known.

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Gustomaximus
I love when believed 'mythology' is shown to be fact. We write off our
ancestors too often and they were great hackers in their own right.

Now the Mythbusters just need to get Archimedes mirror working one day!

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martey
I do not think that this paper proves anything about _Viking_ navigation.

While the researchers seem to have been able to prove that the found crystal
is Iceland spar, it was recovered from a Elizabethan shipwreck in the English
channel from 1592, centuries after the magnetic compass started being used in
Europe. While other articles on the topic claim that they suggest that
sunstones would have been destroyed in Viking burials, I think that the lack
of similar crystals from known Viking ruins is troublesome.

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contingencies
Fair concerns. An interesting and not entirely unrelated tangent is that of
the nearby Basques. In _Salt: A World History_ , Mark Kurlansky presents a
theory that the Basques preserved their ancient and linguistically
disconnected culture by bartering salt-preserved fish gained from the vast
stocks on the Atlantic coast as protein stocks to neighbouring peoples during
the European winters. Evidence of such tools may lend some further support to
this theory.

(Edit: I just noticed he has also written _The Basque History of the World:
The Story of a Nation_... that's definitely on my list now!)

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rodelrod
Even if you concede that the basques did have an early start on exploiting the
Newfoundland fisheries, that would have given them an edge for a few centuries
after the year 1000 (more like 1400 if you wait for the necessary navigation
technology). By the 3rd century AD, all of Iberia except for the Basque was
speaking a romance language.

So, this theory -- very poorly documented in itself -- fails to explain at the
very least these mere 7 to 10 centuries of preservation of Basque identity.

EDIT: by the way, I totally buy that Europeans were fishing for cod in
Newfoundland before Columbus, and that at least some of those were basques.
15th century Portuguese maps calling those waters "Mare Baccalearum" are proof
enough for me.

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Luc
In the book 'Emergency Navigation' by David Burch (
[http://www.amazon.com/Emergency-Navigation-Improvised-No-
Ins...](http://www.amazon.com/Emergency-Navigation-Improvised-No-Instrument-
Methods/dp/0071481842) ), the method is explained more clearly. With a clear
Iceland spar crystal 1 to 2 inches on a side, the direction of the sun can be
pinpointed to within a few degrees. You can also get the same effect using a
piece of cellophane and the lens of a pair op polarized sunglasses. You do
need a patch of clear sky at a 90 degrees angle from the sun direction to
observe the change in intensity.

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qwertzlcoatl
This is kind of old news. This Ouest-France article from November 5th, 2011
even has two pictures of the 'Viking sunstone'

[http://www.ouest-france.fr/actu/actuLocale_-Des-
physiciens-p...](http://www.ouest-france.fr/actu/actuLocale_-Des-physiciens-
percent-le-secret-des-Vikings-_-2007955------35238-aud_actu.Htm)

~~~
JoeAltmaier
Yeah, the op was lame - a picture of some sailing ship, and not the sunstone.
Why do bloggers to that?

Your link also does not seem to have a picture?

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anthonyb
page 2

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rexreed
Exactly how would this work when the sun has set?

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defrost
The sun below the horizon is still a source of diffuse light, the crystal is
used to find the angle to a source of light and in northern latitudes with
long twilights the sun produces a glow long after it has set.

See: [http://www.livescience.com/16831-viking-sunstone-crystal-
com...](http://www.livescience.com/16831-viking-sunstone-crystal-compass.html)

~~~
contingencies
Nice. First 3D-printed replica wins my vote as a teaching aid and generally
cool retro hack. We need more of this offline tech stuff.

Combine a compass and other navigational tools, and I see an interesting
evolution as a sort of retro, creative-commons, git-forkable hacker-army
object.

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jff
When you figure out how to 3d print a birefringent material, let me know. In
fact, when you get a hobby-grade 3d printer to print something you can
actually see through, let me know.

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contingencies
Sure. Obviously not everything comes from a machine. One can probably rely on
people finding some crystal separately and/or if feasible order bulk-printed
3D transparent material (no idea of light properties of those, though I know
they exist... just saw some this morning!).

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jff
If you find the crystal separately, there's nothing left to print. The tool is
fully functional as nothing more than a lump of crystal.

~~~
contingencies
My understanding from the image is that the operation is based upon the
combination of two directional light beams through holes driven by an opaque
piece with a rotating disc. Whether this was used at the time or not, it still
seems a clear way to demonstrate the concepts.

At the very least the operation could perhaps be usefully modelled three
dimensionally using raytracing, perhaps also with the capacity to vary basic
optical properties of the transparent crystal feature such as reflectiveness,
refractiveness and average opacity, as well as atmospheric conditions
encountered in the seas ancient European seafaring peoples are known to have
sailed.

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k2enemy
A little off topic, but Iceland Spar features prominently in Pynchon's
"Against the Day"[1]. It is a pretty amazing book that might appeal to this
audience.

[1] <http://en.wikipedia.org/wiki/Against_the_Day#Doubling>

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koala_advert
And of course, no image is available.

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eford1
I can't wait to evolve my Sunkern!

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sampsonjs
This sounds like the MacGuffin from a video game.

