Re: Moon hopping around?

Edward Green wrote:
Sam Wormley wrote:

donnaboo wrote:

I have heard thru the rumor mill about the moon hopping around in the
sky the last few weeks.
The moon is following a Keplerian orbit about the earth-moon
barycenter--the moon's position being confirmed by laser ranging
to an accuracy of better than a centimeter.

Hah! You and Greg Neil have no imagination, and no poetry. There is
something exceptional about the current state of the moon's orbit, and
it goes beyond my minor observations about the length of the lunar
Earth day -- I didn't guess the half of it:

http://www.umass.edu/sunwheel/pages/moonteaching.html

*****************************************************

"With the culmination of the 18.6 year cycle of the Moon in 2006, also
called the Major Lunar Standstill, we are afforded the unique
opportunity to teach the public about the monthly, annual, and
18.6-year wanderings of the Moon. The 18.6 year cycle is caused by the
precession of the plane of the lunar orbit, while this orbit maintains
a 5° tilt relative to the ecliptic. At the peak of this cycle, the
Moon's declination swings from -28.8° to +28.8° each month. And even
though we are more than one year away from the peak of the 18.6-year
cycle, already the Moon's declination ranges each month between -28°
and +28°. What this means is that each month for the years 2005-2007,
the Moon can be seen rising and setting more northerly and also more
southerly than the solar extremes, and will transit monthly with
altitudes which are higher in the sky than the summer Sun and lower in
the sky than the winter Sun."

*******************************************************

That was written in 2005, so we are on the other side of this event,
but the moon is still jumping. _That's_ something I didn't notice
through my casual observations of "huh... moon". I didn't know about
the 18.6 year lunar cycle, the inclination of the lunar orbit, the
precession, the swings in declination. I didn't know squat diddly.
This is _great_ :-)

This must have fascinated the bejesus out of ancients who had nothing
to do at night with energy left over from animal appetites but to stare
at the sky until they knew it so well, they could errect huge stone
blocks to charts its changes.



Saros (18 years 11 days 8 hours)--They come and go.

NASA - Eclipses and the Saros
http://sunearth.gsfc.nasa.gov/eclipse/SEsaros/SEsaros.html

.

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