[Avodah] Geocentrism

[Eliyahu Grossman]

Micha: 
>> But the error I was trying to disabuse people of was that RMMS didn't
deny heliocentrism. He was defending Chazal's saying that the sun, moon,
planets and stars go around the earth. It wasn't an error.

To defend Chazal on a point that they were mistaken is the same as accepting
it, otherwise it is pretending. So if he was promoting that they were not
wrong when they were, whether he believed them or not, it would be an error,
since it would mislead others.

>> I don't believe Chazal knew more astronomy than their contemporaries did.
But I also don't believe in misconstruing RMMS in a way that causes people
to underestimate his subtlety of thought.

IMHO, it wasn't subtle. But let's leave Rav Shneerson out of this, since
that might lead us to places we do not want to go.


>> The sun rises daily, not annually. Each were thought to revolve around
the earth roughly daily: the sun was actually daily, the moon was roughly
daily, plus a one month epicycle. I don't know details, but Saturn also had
epicycles.

Do you realize the impossibility of the sun spinning around the still earth
every 24 hours? The result, because of the 23.5 degree tilt of the
non-moving Earth would be 6 hours of Summer, 6 hours of Fall, and so forth.
You could sleep through whatever season that you didn't care for! I used the
365 day rotation in my example since it was the least extreme.

>> The Pythagorians believed the earth spin, but then, a number of them were
heliocentrists! So we're not talking about them.
>> The epicycles are actually a Fourier approximation of their actual orbits
as seen from earth. But that's not geocentrism, that's specifically
Aristotle or Ptolmy. And AFAIK, Chazal doesn't mention them one way or the
other. And your whole notion about which particular geocentric map they
subscribed to is >> not RMMS's topic -- Chazal don't say anything about what
form of geocentrism they switched to in Rebbe's day.

It appears that they didn't switch to geocentrism, but denied it, and based
on mesechtot Pesachim and Sanhedrin, they used the non-moving earth and
objects rolling over the rakia model, which was uniquely theirs. A sixth
century Bishop forced the church to adopt the flat Earth rakia model, but
eventually the Church dropped the rakia part all together but maintained a
flat  earth geocentric model (just without the dome).

>> My point is, geocentrism replaces the earth's spin with an orbit around
the earth. Their heliocentric orbits are approximated by epicycles, not
replaced by orbits around the earth.

If you could take out a paper and pencil, and draw our solar system (you can
stop at Jupiter), in the way that you see it, and upload that picture, I
would be interested in seeing your model, since I have tried a number of
different possibilities and they all fail based on what I know. (fail in
maintaining a specific distance from the sun as well as a range of distance
from the earth).

>> Tir'u baTov!
>> -Micha

Thanks!

Chesky: 
>> At this point, it's not "wrong" to assert that this force actually
exists; or that (as Chazal believed) the universe revolves around the Earth.
It's just not a very productive way to calculate anything.

Thanks!

Zev Sero:
>> He was actually championing the Rambam's Ptolemaic view, not Chazal's.

"He", meaning Rav Shneerson?

Eliyahu Grossman