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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  3. "The Sun and the Moon a Riddle in the Sky",, July (2011).
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  8. "Optimizing the Efficiency of Reverse Osmosis Seawater Desalination",, May (2002).
  9. "Boltzmann Transport Equation",, May (2002).
  10. "Energy of Seawater Desalination",, April (2000).
  11. "Avogadro's number atomic and molecular weight",, April (2000).
  12. "Vapor Pressure, Boiling and Freezing Temperatures of a Solution",, December (1998).
  13. "Osmosis Reverse Osmosis and Osmotic Pressure what they are",, February (1998).
  14. "Calculation of linear coefficients in irreversible processes by kinetic arguments", American Journal of Physics, Vol 46 (11), pp. 1163-1164, November (1978).
  15. "Derivation of some basic properties of ideal gases and solutions from processes of elastic collisions", Journal of Chemical Education, Vol 55 (6), pp. 369-371, June (1978).


  1. Thermodynamics Research Laboratory,
  2. Thermodynamik - Warmelehre,
  3. The Blind Men and the Elephant
  4. My Spin on Lunacy,
  5. Five Weeks in a Balloon
  6. The first man I saw
  7. "Faster, Faster!"
  8. Perfection can't be rushed
  9. The man higher up
  10. Brains
  11. The First-Class Passenger
  12. other