Lunar Eclipse

    A lunar eclipse occurs when the earth is between the sun and the moon in a direct line, or as observed in the previous image. To witness a total lunar eclipse, you have to be on the night side of the earth, when the moon is full. Because light rays travel in straight line, and all three bodies are lined up in a row, the earth blocks those rays coming directly from the sun. However, some light rays slip past the earth, and taint the outer edges of the umbra (the total shadow), creating the penumbra (the partial shadow). The umbra of the earth is much larger than that of a solar eclipse, because the earth is much larger then the moon, but the size of the penumbra is slightly larger than a solar eclipse. Although you might expect a lunar eclipse every month when the moon is full (the revolution of the moon is 29.5 days), the sun and the moon don't always line up perfectly straight. Below is an image and a diagram of a lunar eclipse.

         

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