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Volume 14, Issue 19 ~ May 11 - May 17, 2006

Sky Watch

by J. Alex Knoll

Lunar Projections

Sunlight illuminates the full moon like a projection machine lights a movie screen

A beautiful pairing of the moon and Jupiter cross our night skies Thursday and Friday. Saturday the moon rises between the claws of Scorpius.

Friday is the full moon, called the Flower Moon, The Corn Planting Moon and the Milk Moon. It rises in the southeast at 8pm, just as the sun sets in the northwest. This synchronicity is tied to the moon’s 28-day cycle and specifically to its place in relation to the earth and the sun.

Each full moon, the moon floats in space opposite the sun in relation to earth. As darkness descends and the moon rises, sunlight cascades around earth, illuminating the surface of the moon much like the light from a projection machine hitting the screen at a movie theater. Move the screen behind or to the side of the projection machine, turn around in your seat and you could still see it — until the movie began, and then you would be blinded to the screen by the light hitting your face.

Perhaps you’ve wondered what someone on the opposite side of the world sees during full moon hereabouts. If we’re seeing a full moon, are the people in China experiencing a new moon?

No. As the moon sets for us, it rises on the opposite side of the world, yet it remains in between the earth and sun. In a sense, those in China are watching an earlier or later showing on the same screen.

Given the moon’s own rotation, are those people in China seeing the same visage of the moon as we did 12 hours earlier, or are they seeing the opposite side?

Everyone, all over the globe, witnesses the same side of the moon, which rotates 360 degrees on its axis every 271⁄2 days — the same time it takes for the moon to circle the earth. Called captured rotation, this is why no one has ever seen the dark side of the moon from earth, just as if we had turned our backs to the movie screen.

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