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Treebeard's Stumper
21 January 2000

More Lunacy

Right or wrong, the moon is often associated with lunacy (luna-see!) and illusion. Here are two moon illusions to explain. I've long noticed that many kids at school are surprised to see the moon in daytime. But in fact, the moon is out during the day just as much as it's out at night. It must be, since the moon orbits the turning earth once a month! Why do so many people think otherwise? The full moon looks extra large when it rises over the mountains as the sun sets. It's not so impressive high in the sky, but it's really just the same size. Explain!

Full moon rising over Isla Vista as viewed from Devereux Point on the night of the winter solstice on December 22, 1999, when the moon is closest to the earth (near perigee) and the earth is closest to the sun (near perihelion). This combination of circumstances was said to make the moon appear larger and brighter than it's been for 133 years. We didn't notice any difference, but it was a beautiful moonrise and the -1.7 low tide was spectacular.


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