[meteorite-list] Shielding of the Moon by earth

[Melanie Matthews]

I see, but the other side of the moon does look a lot more heavily cratered than 
that "shielded" by Earth.. 


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-Melanie
IMCA: 2975
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Known on SkyRock Cafe as SpaceCollector09

I eat, sleep and breath meteorites 24/7.



----- Original Message ----
From: Rob Matson <mojave_meteorites at cox.net>
To: meteorite-list at meteoritecentral.com
Sent: Tue, September 7, 2010 10:46:12 PM
Subject: [meteorite-list] Shielding of the Moon by earth

Hi Melanie/List,

The side of the Moon that faces the Earth is only ~barely~ shielded
by the earth compared to the side facing away from Earth. In fact,
I would be surprised if the difference is even detectable as far as
cratering density. From the Moon's surface, the earth subtends
about 1.9 degrees, so a Full Earth looks over 14 times larger (in
"area") than does a Full Moon from earth. While that may seem large,
the amount of angular space shielded by the earth is tiny -- about
one part in 7000 for any portion of the lunar hemisphere with a
view of the earth. In other words, square mile for square mile,
if the earth had the Moon's vacuum, its surface would get hit just
as often as the Moon's.  --Rob

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