Sunday, December 2, 2012


An Italian friend told me that it is particularly American how we always have a compass set up in our minds. "Go north on Duke Street"--"Go west on 15-501"--but how do we always know what direction that might be?

Two math-loving high school acquaintances once got lost in Manhattan because they thought the streets were set up like a normal x-y graph, so walking east they thought they were going west.

I always used to draw numberlines and charts and so forth with the numbers getting bigger from the right side to the left side. I still think of the left side as the side of the future and positive numbers. Maybe that's why I set up my blog with the contents on the left, when so many blogs put them on the right.

On Lygra I never knew the cardinal directions. The sun, rather than starting in the east and setting in the west, started in one corner of the sky and set nearby, never having risen higher than a quarter of the way up.

The Viking sagas reported the use of magical "sunstones" to solve this problem as they navigated the ocean. (As reported in the medieval Icelandic text Rauðúlfs þáttr: "The weather was thick and snowy as Sigurður had predicted. Then the king summoned Sigurður and Dagur (Rauðúlfur's sons) to him. The king made people look out and they could nowhere see a clear sky. Then he asked Sigurður to tell where the sun was at that time. He gave a clear assertion. Then the king made them fetch the solar stone and held it up and saw where light radiated from the stone and thus directly verified Sigurður’s prediction."

After many years of speculation, scientists determined that the sunstones might have been clear crystals like the calcite Iceland spar. The crystals polarize the light as you look through them, changing the light's brightness/color, except in one specific angle where the polarized effect disappears. If you look through that depolarized angle, then move the crystal away, you can see a pinched yellow line (Haidinger's Brush, see link below) that points to the sun, which is similar to how migrating animals and birds are able to navigate during their migrations. You can use this method even when it's overcast or the sun has gone below the horizon. It's not quite clear that you could really use these on the open sea, and they haven't found hard evidence of Iceland spar in Viking artifacts, but this method allows you to find the sun's location with 5 degrees of error or less.

A fun polarization-spotting DIY. Is it as fun as a Comme des Garcons DIY? Only you can decide.

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