Why are mountain shadows always triangles?

I mean big mountain near daybreak or sunset. If you don't believe me, here are some pictures:

http://i125.photobucket.com/albums/p53/mkvispics/MountainShadowCaptioned.jpg
http://epod.usra.edu/blog/2007/12/mountain-shadow-in-southern-greece.html
http://www.alpinestateofmind.com/gallery/6496951_Gt5VK#534265336_vBbEZ
http://www.exo.net/~pauld/lectures/patternscostarica/patternsnature2004.htm (scroll down a little)

2010-11-23T08:02:41Z

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My take is that this is similar to a picture of railroad tracks. ( http://farm3.static.flickr.com/2118/2203250246_af06cddc67.jpg )
Parallel lines when mapped on to a 3D sphere converge

Here, it is the light rays going around the mountain that appear to converge. And most of the details of the mountain get wiped out. The general shape of the mountain only magnifies this effect.

The convergence of the sun's rays at the horizon are called anticrepuscular rays. Here is a good picture of this effect: http://antwrp.gsfc.nasa.gov/apod/ap060917.html . The big difference is when on a mountain, you are looking down on the anticrepuscular rays, not up at them.

Scythian19502010-11-22T21:46:40Z

Favorite Answer

The 2nd picture unfortunately gives away the answer, so I can't take credit for a brilliantly insightful answer. It's a consequence of perspective, which "sharpens" peaks of mountains, even if their summits aren't necessarily very peak like. Let's say we have a "sloppy summit" mountain, like an asymmetrical pyramid with the top lopped off. It casts a shadow far into the horizon, and perhaps even beyond the horizon where it reduces light backscatter in the air in the distance. The summit irregularity by that time, in the great distance, will look very small to one standing on the summit. Hence, it's as if the silhouette of the mountain has been "pinched" at the top, so that such shadows of all mountains look about the same. You don't see this effect if the shadow is not far away, like, say, across a canyon.

You can make anyone look like a pinhead by same means of stretching the silhouette.

shaka2010-11-23T13:32:12Z

because mountains are cone shaped which in a flat surface world look triangle i wont knock you for asking that question but its too easy lol.

gintable2010-11-23T05:31:36Z

Um...mountains are "triangles"...triangular in frontal shape.

Objects tend to cast shadows of their shape in some regards.

Q2010-11-23T14:16:26Z

'Cause mountains are conical in shape .