New: Osmosis Desalination and Carnot
The Sun and the Moon a Riddle in the Sky
Uri Lachish, guma science
The following two images show the sun and full-moon:
The sun photo shows uniform distribution of light intensity within the image from end to end.
There are some details of mountains and dry lakes in the moon photo, but apart from that, the light distribution is also uniform within the moon image.
The light density at the sun surface is uniform, but this is not the case with the full-moon. The sunlight that falls on the moon surface is reflected back,
nearly 180 degrees, and observed on the earth. The sunlight density at the center of the moon is maximal since the moon surface is perpendicular to
the coming light. The density drops when moving toward the moon periphery because the moon surface becomes more and more inclined to the incoming light.
A unit area of falling sunlight will be distributed over a larger area of a moon surface. Considering the angle between the sun's line of sight to the moon,
and a line perpendicular to the moon surface, the light density on the surface will be proportional to the cosine of this angle. Thus it will vary from one at the middle
of the moon toward zero at the periphery .
One would expect then that the distribution of light intensity in the moon image will be different from that of the sun.
Nevertheless, the two photos show similar uniform light distribution for both the sun and the moon. Why?
One may speculate that the moon surface has some special property. However, photos of all the planets, taken from space with the sun at the back,
show similar image uniformity.
My Spin on Lunacy,
On the net: July, 2011.
By the author:
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