Significance of equal Sun and Moon apparent sizes?by Loren Booda Tags: apparent, equal, moon, significance, sizes 

#1
Jan904, 11:31 AM

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How has the near equality of the Sun's and Moon's apparent size (as seen from Earth) affected our planetary history (vs transient phenomena like eclipses)?




#2
Jan904, 04:55 PM

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I believe its principal effect has been on mythology. As far as the physics of the earth, unlikely.




#3
Jan904, 09:42 PM

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As the Moon's distance from the Earth has, over our double planet's history, changed quite a lot  and as the Earth's distance from the Sun has been pretty much constant  the apparent nearequality we see today is a curious coincidence in time.
Anyone got a reference (or want to do a calculation) on how the average angular size of the Moon (as seen from the Earth's surface) has changed in the last 500 million to 3 billion years? 



#4
Jan904, 11:55 PM

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Significance of equal Sun and Moon apparent sizes?
I found several values for the rate at which the moon is moving away from the earth. 3.8cm/yr seems to be a good approximate value. However, I'm guessing that this rate hasn't been constant over a period of 500 million years or more.
http://www.lpi.usra.edu/expmoon/Apol...ents_LRRR.html 



#5
Jan1004, 12:25 AM

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If we assume that the moon is receding at a constant rate of .038 m/yr, 1 million years ago, the moon was 38,000 meters closer. Compared to it's present distance of 3.84x10^8 m, the moon was closer only by a factor of 1.00009896. If today, the moons average apparent size is only 30 arc minutes, 1 million years ago, it would have subtended an additional .18 arc seconds.
A billion years ago, it would have been 38 million meters closer. A factor of about 1.1 times closer. It's apparent size would have been larger by about 3 arc minutes. These calculations are probably wildly inaccurate in reality. 



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Jan1604, 12:12 PM

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