[Avodah] Geocentrism

[David Cohen]

R' Eliyahu Grossman, attempting to prove that the geometric model is
objectively incorrect,  wrote:

>> The short of it is that in a Heliocentric model, Mars is correctly *34 MILLION
MILES* away,
>> and so it took the space rover less than a year to get there. That is a
fact.
>> In the Geocentric model, Mars is *226 MILLION MILES* away, which would
mean
>> a travel time of about 6 years. That is a variance of nearly 1000%. That
is a fiction.

One does, in fact, reach such and obviously false conclusion if one
attempts to apply the Kepler / Newton laws of celestial mechanics to a
geocentric model.  Such an attempt leads to many other large problems, not
the least of which is that under Newtonian physics, there is no way to
explain the retrograde motion of the planets in the geocentric model.  The
epicycles used by Ptolemy (and the Rambam) are an elegant *mathematical*
model of what's going on, but nothing in our current *physics* will account
for why such epicycles should exist.

But it's important to remember that laws of physics are descriptive rather
than prescriptive.  The world doesn't "follow" the laws of physics.  We
make certain observations about the universe, and we then attempt to come
up with a consistent set of rules -- a model of physics -- that elegantly
explains it.

Kepler chose to observe the solar system from the heliocentric perspective,
and he came up with a set of consistent rules that explain these
observations.  The mere existence of Kepler's "laws" does not make the
heliocentric any more "correct."  They simply make the heliocentric
perspective much *simpler* to use, since Kepler's laws, which neatly
explain our observations from that perspective, are simple, elegant, and
consistent with Newton's laws of motion and with orbital mechanics as
observed on a smaller scale (e.g. ballistics).

If one were to prefer observing the solar system from the geocentric
perspective, one would need to come up with an alternative model of
physics.  Such a model of physics would need to have some rule explaining
why Mars is moving so slowly around the Earth despite its being only 34
million miles away.  It would need to have a rule explaining the epicyclic
motion of the planets.  Such a model might say that Newton's laws of motion
apply *except* under certain particular circumstances.  Such an alternative
model of physics would undoubtedly have lots of unanswered questions, but
then again, so does classical physics. We can't say *why* the gravitational
force exists, but we can use it as a "law" that consistently explains lots
of our observations.

Personally, I see no theological imperative, or even advantage, to adopting
the geocentric perspective.  As far as having an simple, elegant model of
the laws of physics, the advantages of adopting the heliocentric
perspective are clear.  But I would have to agree with the Lubavitcher
Rebbe zt"l that this doesn't make the geocentric perspective objectively
"wrong."

-- D.C.
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