Friday, June 25, 2010

The Lunar Eclipse and the Large Moon

Something rare and extremely cool is happening tonight/early tomorrow morning: a partial lunar eclipse. For about three hours, beginning around 3:15 AM Pacific Time, the earth's shadow will cover part of the Full Moon. A sunset-colored shadow will overtake approximately 54% of the moon during one point. It should certainly be an amazing sight.

But what makes it all the more amazing is that the moon will appear abnormally large to observers. As this excellent piece explains, the reasons for it aren't understood by scientists, but when the moon is close to the horizon it appears much larger than it actually is. It's completely an illusion, a weird natural trick of the mind, because what we're seeing is exactly the same size glowing disc that we usually see in the sky.

The first time I witnessed and heard about this effect was an evening in October of 2006, sitting in the second to last row of Shea Stadium with my brother John. We were behind (or, rather, far above) home plate watching Game Two of the NLCS between the Mets and the Cardinals.* So Taguchi had smacked a home run to win the game for the Cardinals, the game was over, Mets fans had departed through the cold autumn air. John and I sat there at the very top of Shea Stadium letting the masses below us clear out. Directly behind us, through the chainlink fence that held top row observers from jumping out of the stadium, we could see the glittering New York City skyline. In front of us, past the left field fence and above the Whitestone Bridge we saw a huge yellow moon, partially shadowed (it was a waxing moon, no lunar eclipse) and tilted. John explained to me the phenomenon and its mystery and we chatted for another fifteen minutes or so about the earth's angle being visible in the slanted moon, Stephen King's post-apocalyptic novel The Stand, and the Mets. Then we went home.

*You can read one of my earliest, albeit sloppy, pieces entitled "Say it Ain't So...Taguchi" --- a guest column I wrote for Jay Jaffe's Futility Infielder blog about that Mets-Cardinals game back in 2006.

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