Re: Reason for Procession of the Equinox?

From: Steve Sherman (smsherm_at_bellsouth.net)
Date: 12/01/04 

Date: Wed, 01 Dec 2004 12:40:09 -0500

Brian Tung wrote:
> Canopus wrote:
>
>>Unlike our spinning top model that contained only one large
>>gravitational attractor, the Earth has two large nearby gravitational
>>sources trying it pull it "downwards" at the same time. The first is
>>the Sun; its gravitational contribution to the Earth's wobble is
>>called precession. The second is the Moon; its gravitational
>>contribution to Earth's wobble is called nutation. Nutation follows
>>approximately a nineteen year cycle.
>
>
> The reading I've had suggests that both the Moon and the Sun are
> responsible for precession; it's the fact that the Moon doesn't quite
> orbit in the ecliptic that is responsible for nutation.
>
> Brian Tung <brian@isi.edu>
> The Astronomy Corner at http://astro.isi.edu/
> Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
> The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
> My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

How about this for a guess. The moon's center of orbit is not the center
of the earth. Thus its pull on the earth is off center and its orbit is
also off center.

Steve

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