Re: [Embedded troll] Easy Questions

From: Dave Hansen (iddw_at_hotmail.com)
Date: 05/10/04 

Date: Mon, 10 May 2004 14:02:40 GMT

On Fri, 07 May 2004 19:57:36 GMT, Darin Johnson <darin_@_usa_._net>
wrote:

>"Paul E. Bennett" <peb@amleth.demon.co.uk> writes:
>
>> The True North Pole is a fixed single point which I understand is on
>> the axis centre.
>
>Which is my question. Is it a "point", and is it "fixed"? Spin a
>billiard ball, and it is mostly fixed and a single point (that will
>change as the ball slows perhaps). But spin a water balloon, which is
>more like the Earth than a billiard ball, and I don't think you'll
>have a single line that can be considered the axis of rotation. Ie,
>will the point be in exactly the same place a year from now? The
>Earth wobbles on its axis as I've heard.

The axis of the earth's rotation does move a small amount (roughly a
circle 21.6 m or 70.9 ft. over a 14 month period) on the surface, due
to internal motions and shape deformations. The change isn't entirely
predictable, and must be monitored by observation.

There is also the matter of precession. The angle of precession is
about 23.5 degrees and a full rotation takes about 26,000 years. In
13,000 years, Polaris (how did it get that name? ;-) will no longer be
the north star, but Vega will.

For more than you really wanted to know, see
http://www.gb.nrao.edu/~rfisher/Ephemerides/earth_rot.html

Regards,

                               -=Dave 

-- 
Change is inevitable, progress is not.

Relevant Pages

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