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Index of Subjects Thanks Both for the explanations. I am a long way from understanding this but at least know the relative roles of physics and coincidence. YT, DW, Kentville ------ Original Message ------ From: "Burkhard Plache" <burkhardplache@gmail.com> To: naturens@chebucto.ns.ca Sent: 3/3/2019 9:09:25 PM Subject: Re: [NatureNS] Moon questions >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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