because of the way the earth rotates
2006-12-05 12:38:20
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answer #1
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answered by Anonymous
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The moon doesn't really change, the perspective that we see is the relationship of the earth to the moon and the moon to the sun and the earth to the sun. The moon revolves around the sun, therefore the earth can block portions of the light reaching the lunar surface. When you look up at the moon and see a half moon, you are actually looking at a shadow of the earth being casted on the moon.
2006-12-05 20:42:39
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answer #2
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answered by Anonymous
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If you are referring to phases of the moon, read on . . . .
The moon is a ball, and so only half is illuminated by the sun. As the moon moves around the Earth in its roughly 1 month orbit, we see different fractions of the ball illuminated vs. dark. When the Earth is more or less in between the sun and moon, we only see the illuminated side, so it looks like a circle. When the moon moves 1/4 further in its orbit, (also known as being in its third quarter) we see half of the illuminated side and half of the dark side, so it looks like a half circle.
Another quarter trip so the moon is more or less between the Earth and Sun and the illuminated side is facing away from Earth and we only see the dark side. This is called the new moon (because it will soon start "growing" bigger as we begin to see more and more of the lit portion as it moves in its orbit back towards being on the other side of the Earth from the sun).
Between the third quarter and new moon, less than half of the illuminated portion is lit, and because the moon is a ball (a curved surface) in projection it looks like a crescent. This is repeated between the new moon and the first quarter. The phase between the full moon and the quarter phases are called "gibbous."
This is a bit difficult to visualize from just words, but there is a great experiment you can do called "moon on a stick".
http://www.marsastro.org/mc/moonstik.pdf
This lab writeup suggests a ping pong ball, but I like the larger styrofoam balls you get at arts and crafts stores. Painting is important; if your "moon" is translucent, the effect is not clear. I found white paint works better than grey or black. Oh, and use a flat paint so specular reflections won't distract you. In a pinch, illuminate an orange impaled on a pencil with a lamp in a dark room.
There is also an illustration of the moons orbit and illuminated side as seen from "above" the moon's and earth's orbits. If you look at that while you read my explanation it will make a little more sense, but it is hard to understand why it looks crescent or gibbous without actually doing the experiment.
2006-12-05 20:41:41
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answer #3
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answered by Mr. Quark 5
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if you mean why it looks different every night, it's because the sun, earth, and moon are at different angles every night. if the earth does not revolve around the sun and stay still along with the moon, the moon would look the same every night, but since everything moves and aims at things at different angles it looks different. the part we see, is struck my the suns light. hope that explained you're question. also, 1 day on the moon = 1 year on the moon, cool huh
2006-12-05 20:44:22
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answer #4
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answered by sk8er4ever 2
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The moon changes shape because we can only see the side that the sun shines on. It changes size slightly because it's orbit is elliptical. It changes location in the sky do to it's orbit and the spin of the earth.
2006-12-05 20:42:29
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answer #5
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answered by Anonymous
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Earth shadow only, otherwise the moon does not change.
full moon means full sun light or full reflection off the earth...1/2 moon means the earth is blocking some of the sun light..etc.
2006-12-05 20:44:20
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answer #6
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answered by Anonymous
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Change how? Try to be more specific
2006-12-05 20:42:07
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answer #7
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answered by Michael B 2
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