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Sunstone Unearthed From Sixteenth Century Shipwreck
sciencehabit writes "In 1592, a British ship sank near the island of Alderney in the English Channel carrying an odd piece of cargo: a small, angular crystal. Once it was brought back to land, a few European scientists began to suspect the mysterious object might be a calcite crystal, a powerful 'sunstone' referred to in Norse legends which they believe Vikings and other European seafarers used to navigate before the introduction of the magnetic compass. Now, after subjecting the object to a battery of mechanical and chemical tests, the team has determined that the Alderman crystal is indeed a calcite and, therefore, could have been the ship's optical compass. Today, similar calcite crystals are used by astronomers to analyze the atmospheres of exoplanets—perhaps setting the stage for a whole new age of exploration."
I hope that by "battery of mechanical and chemical tests", they meant "showed it to a geologist for five minutes". There are a number of minerals which can mimic calcite to the untrained eye, but they're easy for the specialist to distinguish.
This interested the hell out of me, I'd never heard of it before. Wikipedia says it was used to find the sun on a cloudy day, which would indeed be very useful to navigators with no compasses.
I find the timing of this story rather interesting, because the History Channel's newest special miniseries Vikings just started up this past Sunday. In it, the main character reveals to his brother a sunstone that a wanderer had given him. He then proceeds to find the sun through the clouds for his brother, who did not believe that the stone would work.
The only thing necessary for evil to triumph is for it to be pitted against a slightly greater evil
I've done a lot of sailing on the Great Lakes and Irish Sea and I can tell you that cold water often brings a kind of dense low fog. There are times when we can see the tops of masts and blue sky above but because the sun is often low at these latitudes, we can't see where the sun is. But sometimes the fog was so bright, I'd wear sun glasses and then I did notice that the zenith blue sky was polarized. What's more, the digital watch we used for sailing was an LCD watch-- which means it polarized display. And the display did darken noticeably when turned at certain angles, so the reflected sky polarization was also discernible. At the time I wondered whether it could be used as a practical form of navigation, but we had a compass. A few years later Loran-C became popular addition to the compass as and then GPS. But when I heard about the theory that an Iceland spar sunstone might have been used for navigation in the high arctic, I'd give it the nod of plausibility. No it isn't as good as a compass, unless you're above 70 degrees magnetic latitude. No it wouldn't work well under conditions of total cloud cover or rain, might not work at all. But I'm sure this kind of low fog is at least as common in the arctic as it is at my latitude and if I were lost without a compass, GPS, Loran-C on a foggy day, you'd better believe I'd break out the sunstone if I had one.