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Subject: Info on Full Moon of 12/22/99 (brightest in 100 years).

Date: Sun Dec 19 15:48:08 1999
Posted by John P. Jones
Grade level: grad (science) School: No school entered.
City: Fairmont State/Province: West Virginia Country: USA
Area of science: Astronomy
ID: 945640088.As

There has been an email circulating the 'net recently claiming that the full moon of December 22, 1999 is the brightest in 133 years. That's not true; the one in December 1912 was actually the brightest. The brightness changes due to the varying distance of the Moon to the Earth (when it's closest, the Moon appears brightest) and the varying distance of the Earth/Moon system to the Sun (when closest to the Sun, again the Moon appears brightest). While the full moon of December 1999 is happening near in time to both the Moon's closest approiach to the Earth and the Earth's closest approach to the Sun, the full moon of December 1912 was actually closer in time to both these events, so it was marginally brighter. To be honest, if no one had sent up an alarm I doubt anyone would have noticed; the Moon will only be about 15% brighter than normal. That's not enough for your eye to pick out easily.

I have details about this event including info about the actual brightest full moons of the past 100 years at my Bitesize Astronomy pages.

©2008 Phil Plait. All Rights Reserved.

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