

Measuring Angle and Distance with your Thumb - hhm
http://www.vendian.org/mncharity/dir3/bodyruler_angle/

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auferstehung
The width of your thumb at arms length is a very natural unit of measure. As
the article states, it is approximately 2 degrees of solid angle. If you ray
trace your thumb at arms length back into your eyeballs, the image of your
thumb will cover the fovea <http://en.wikipedia.org/wiki/Fovea> The fovea is
the little dimple on your retina responsible for sharp vision. This happens to
be the solid angle that is used to define the CIE color charts
<http://en.wikipedia.org/wiki/CIE_1931_color_space>

If I am not misremembering, two degrees solid angle (your thumb at arms
length) also covers the angular width of the sun and moon.

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s_baar
Now that's cool. This seems like one of those things they should teach recon
soldiers.

