"How does the human body react to different gravities? What is the maximum gravity the human body can withstand?"
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Question
What causes the phases of the Moon and eclipses?
A lot of people are not sure what causes the lunar phases or eclipses, which is why these topics are explained in so many popular astronomy books and are always taught in the first weeks of an astronomy course. I am sure you can find good explanations (with diagrams to help you visualize the situation) is any of dozens of astronomy books available in your library. Very briefly, the Moon's phases result from the changing angles of illumination of the Moon by the Sun as the Moon orbits around the Earth -- from completely illuminated at full phase to obliquely illuminated at crescent phase. Eclipses take place when the shadow of one object falls on another. Lunar eclipses take place when the Moon moves through the shadow of the Earth, and solar eclipses when the Earth moves through the shadow of the Moon. Shadows have nothing to do with phases, which are just a matter of the angle of illumination.
David Morrison
NAI Senior Scientist
March 1, 2004
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