September 1 (1881, 1976, 1979, 1985, 2002) The Colors of Shadows

September 1, 1881

Incident at Cape Horn

[Watch for more about this incident in upcoming posts.]

9/1/76 ~ morning in canyonland. tim is here, we spent last night here and plan to work on the floor of my cabaƱita today. two boulders left to set in the center of the ring, then we get to pound some nails. [...]

tim's dog taffy is with us, and i am very pleased that, regardless of the many animalitos scurrying about in the darkness, she hasn't barked once. a dog i could live with... ”

[Russell Towle's journal]

9/1/79   work, work, work. but today is saturday. last weekend i bought a chainsaw and cleared some brush up in the meadow. muscles growing. a little rain came through. [...]

[Russell Towle's journal]

September 1, 1985

Mid-morning; a strong breeze stirs the trees. [...]

Went to Lovers Leap yesterday for the sunset, but didn't stay; clouds massed in the west prevented light from reaching the Sierra, and no wrens could be enticed near. (I worry that the people I have seen at the Leap on occasion, with pistols etc., might have made the wrens targets.); I left and drove into town. A spectacular sunset from the railroad tracks on Depot Hill rewarded my wandering. Then I went to the McClung's for some TV, which was a washout. Saturday night.

While at the Leap I pondered again the light within the shadows. It shows quite a variation, and in times past, I figured it out. Some shadows are red, some blue, some dark, some light. The ratios of blueness and redness and darkness and lightness were once understood by me; last night, trying to recall, I couldn't; trying to re-understand, I lacked the will and lost the light to boot. One thing was obvious: the darkest shadows were nearest the anti-solar point, which, since I was at the Leap, I could see near the Leap's shadow in Green Valley. Shadows away from the anti-solar point were increasingly washed out by scattered light; more surfaces exist on foliage and rocks to scatter light to the side, rather than back to its source (in fact, no surface exists—except hypothetically, which reflects light back to its source, i.e. no mirror is perfect); there is, I suppose, an optimal angle at which the maximum light is scattered—perhaps 45°—but at this point I waiver. Shadows near the anti-solar point, but made by ridges across the canyon, that is, not the Leap or anything near, showed the most light and the most blueness, if I recall—a very light blue. But shadows both up-and down-canyon showed lots of red. While there was a wide range of angular positions to examine, there was not a complete range. I was not surrounded on all sides by canyons and ravines. I could not see all possible configurations of shadow. I could, however, see half. Half may be enough: one side of a vertical plane connecting the sun and an observer may be the mirror image of the other. Unless polarization plays some role.

I will look into the matter further; the colors of the shadows do not seem to follow the usual rule of increasing blueness with distance, which one sees every day in the mountains. A grove of pine trees near at hand may be green; in the middle distance, blue-green, and in the distance, blue. This is easily observed. But the redness or blueness of shadows—a thicker section of atmosphere near sunset or sunrise causes more extreme scattering of light by the atmosphere, and blue scatters easiest. So red is selected, reaches the eye of the observer. More red light exists for ground-scattering, in proportion to blue, then usual. And the angles of incidence during scattering will cause the amount of light thus scattered to vary over a given surface—that is, the amount of light per square centimeter—as the angles of incidence approach 0 degrees, the rays are more widely spread—as they approach 90°, most tightly bunched. Assume the aggregate of all reflecting surfaces to behave like a sphere. Or a multitude of spherelets. So the optimal angle is 90 degrees to the plane of the sphere-tops. Perhaps; oh, I've got it—shadows closest to the anti-solar point, but not made by the observer, show the most blue light and the most light because they are closest to the optimal angle. More distant shadows show read because of atmospheric editing of the blue light, and darker because of less optimal angles.

[Russell Towle's journal]

Date: Sun, 1 Sep 2002 12:05:18 -0800
To: North_Fork_Trails
From: Russell Towle
Subject: Royal Gorge

Hi all,

Evan Jones, legendary hiker and physics teacher, reports from a recent visit to the Royal Gorge:
>Yesterday we hiked down the Palisades Ck Tr to the
>wash, and then down to the river. Then downstream to
>Wabena Ck Tr and return. All were thankful for your
>brush clearing on Wabena. We did some too. Many
>ouzels on the river, bear scat so prevalent and fresh
>that one felt like looking over one's shoulder,
>kingfisher, canyon wrens, and 2 rattlers. One too
>close for comfort; I stepped down off of a ledge and
>got the warning buzz. I looked carefully around me,
>but no snake. Finally it was mollified, and no doubt
>under an overhang near my left ankle, and I backed off
>with apologies to it. The other, a magnificent 4'
>specimen, was relaxing by the water.
>It was a strenuous day!
The Wabena Trail needs a lot more clearing, maybe this fall we can get a group together and make a big dent in it.


Russell Towle

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