[NatureNS] Moon questions

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From: Burkhard Plache <burkhardplache@gmail.com>
Date: Sun, 3 Mar 2019 21:09:25 -0400
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Hi David,

the answer to the first question is: Due to 'Tidal Locking'
(https://en.wikipedia.org/wiki/Tidal_locking),
which occurs over time between gravitationally  close (astronomically
speaking) bodies.

The answer to the second question would be 'coincidence at the current time'.
https://en.wikipedia.org/wiki/Orbit_of_the_Moon#Tidal_evolution
The gravitational interaction between Earth and Moon causes friction
(periodic compression
and decompression of the rocks on both Earth and Moon), which slows
down the rotation of
both bodies (causing the above tidal lock).
This slow down of the bodies' rotations reduces the body internal
orbital momentum of the Earth-Moon-System.
The other part of the orbital momentum is the Moon-around-Earth motion.
Newtonian physics demands that the orbital momentum of a system be conserved.
When (due to the above mentioned friction) the body-internal component
decreases,
the Moon-around-Earth component must increase.
That increase is achieved by the Moon-to-Earth distance increasing,
hence the moon slowly moves away from earth.

So, any millions of years ago, the moon appeared larger in the sky,
and many million years in the future, there would be no more total
solar eclipses.

Glad we are living today?
Burkhard



On Sun, Mar 3, 2019 at 8:37 PM David <dwebster@glinx.com> wrote:
>
> Dear All,
>     Two things about the moon have puzzled me. Is there some reason why the same side of the moon faces earth ? Does the near side have higher density ?
>     And two, Is there some physical reason for the moon being just the right size to cover the sun during an eclipse ?
>     Are both of these just coincidences ? Strange fate indeed.
> YT, DW, Kentville

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