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From: leichter@yale-com.UUCP (Jerry Leichter)
Newsgroups: net.physics
Subject: Re: what is the voltage (EARTH based) of ground on the MOON?
Message-ID: <2503@yale-com.UUCP>
Date: Fri, 2-Dec-83 12:42:59 EST
Article-I.D.: yale-com.2503
Posted: Fri Dec  2 12:42:59 1983
Date-Received: Sun, 4-Dec-83 03:19:19 EST
References: sri-arpa.14160
Lines: 33

"In particular, two nonpolarizable insulators in an intense electric
field..."  True, but it sort of begs the original question.  If you assume
both Earth and moon are truely non-polarizable insulators, then the external
electric field has no effect on "the charge on the Moon" relative to Earth,
whatever that means.  We have to stand back a bit and try to make sense
of the question:

If the question is:  If I consider the Earth and Moon to be more-or-less
conducting objects - implicit in the notion of "ground" in the electrical
sense, then what I'm asking is:  What will a voltmeter read, if one side
is attached to the Moon, the other to Earth?  In this case, an external
xxx (not relevant).  Two components contribute to the reading:  An Earth-
Moon difference in charge - which must be small, by my previous argument -
and an outside potential, which would also have to be small, since a
conductor placed in such a field WOULD become polarized.

If I consider the Earth and Moon to be non-polarizable insulators - which
is definitly false, by the way; the Earth's core, at least, is a conductor,
and most rocks are quite polarizable crystals - I then have the interesting
question:  Where is this external field coming from?  SOMETHING is alleged
to be generating a field between Earth and Moon - but both are moving.
So any field would have to be very variable.  In fact, such a field probably
does exist, centered at the Sun, due to the solar wind, which consists of
a lot of charged particles.  However, since the Earth and Moon ARE quite
polarizable, the field must be pretty small.  In this case, you probably
don't get nearly as sharp a bound, since you have to figure in the polariza-
bility - capacitive constant?  Permitivity? - It's been a while - but this
is balanced out by the fact that the field must be changing - you would
see an attraction whenever the Earth-Moon line was pointing toward the Sun,
no effect when it was normal to a solar radius (cosine curve variation).
The resulting wavering of the Moon's orbit would be pretty noticable.
							-- Jerry
					decvax!yale-comix!leichter leichter@yale