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The sun shines light on both the moon and the Earth. When it shines light on one side of either one, they cast a shadow in space. During an eclipse, the shadow of either the moon or the earth gets cast on the other one. For example, during a solar eclipse the sun, moon, and earth have to be aligned Sun - Moon- Earth. The sun shines light on the moon and the moon's shadow gets cast on the Earth. The middle of the shadow where an observer can't see any light is the umbra. The sides of the shadow where you can see partial light is the preumbra.
What else can I help you with?
Why doesn't a lunar eclipse occur once a month?
The phase of the moon (new, half, full, etc) is a function of how much of its lit surface we can see from the earth. Half the moon is always sunlit, half is dark, but as the moon orbits the earth, more or less of the lit face is pointed towards us here on earth. The moon's orbital period around the earth is 28 days, which more or less coincides with the length of a month. Once in each of its orbits, its lit face is directly oriented towards earth -- a full moon. Because the 28-day orbital period is less than a full month, on relatively rare occasions we can have two full moons within one calendar month. The second of those full moons is referred to as a "blue moon" -- thus the phrase, once in a blue moon, which means "rarely."
Why does the moon look red or yellow at times?
Possibly you're looking at a lunar eclipse. I don't see any on the schedule but that's normally what causes it. The moon goes into the Earth's shadow first the preumbra and then the umbra. When it does only the red part of the sun's spectrum of light is bent by the Earth's gravity enough to hit the moon. So the moon looks red.
How do penumbra and umbra relate to eclipses?
The umbra is the portion of a shadow from within which none of the light source is visible. The penumbra is the portion of a shadow from within which part but not all of the light source is visible. ______________________________ "Umbra" is the area of total shadow, while "penumbra" is the area of partial shadow.
