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Name: mike
Status: other
Grade: other
Location: N/A
Country: USA
Date: Summer 2011

I see a cloud and I see its shadow in a field - knowing high sun angles - is there a way of telling how far away the cloud is or how big? - I am thinking if the shadow is 30' wide and the sun is at 2:00 pm- ?

Hi Mike,

Try this, draw a small circle representing the Sun. Somewhere below this circle and maybe to the right, draw an oblong, make this oblong bigger than the circle. Now connect the leftmost edge of the circle with the leftmost edge of the oblong with a straight line. Do the same for the rightmost edges. The oblong now represent the shadow of a cloud on the ground, and the lines represent the rays of the sun passing along the edges of the cloud.

Note that you can draw an oblong anywhere in between these two lines to represent the cloud - and depending on its distance from the shadow, can make the cloud very in size.

In order to determine the size of the cloud, you need one more piece of information - where along these two lines the cloud is.

For this exercise, draw two clouds, one close to the "Sun" and one closer to the "shadow". Draw a line from the leftmost edge of the shadow to the rightmost edges of both clouds. Notice that the angles made by these two lines with the leftmost sunray-line are different.

You now have the minimum information you need. ... I love geometry. :-)

Greg (Roberto Gregorius)
Canisius College

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