[Avodah] Geocentrism

[Micha Berger]

I recently wrote on the thread "Traditional Methodologies"

On Wed, Jul 24, 2013 at 12:28:10PM -0400, Micha Berger wrote:
: On Wed, Jul 24, 2013 at 06:41:38PM +0300, Eliyahu Grossman wrote:
...
:: You even had the Lubavitcher Rebbe who preferred to deny provable cosmology
:: and accepted the geocentric model of the Universe as Chazal did (I do not
:: know if the Lubavitcher Rebbe held that the world was flat or if the sun
:: went around a "rakia" dome as Chazal did). 
...
: RMMS noted that under general relativity, the universe could be analyzed
: from a geocentric frame of reference. And therefore geocentrism vs
: heliocentrism. (And vs the sun also revolving around the center of
: the galaxy which is revolving around the center of a galaxy cluster,
: which is...)

... are not mutually exclusive, just different ways of describing the same
thing. (Never finished that thought!)

: However, General Relativity is based on the identity between acceleration
: and gravity. So the effects we see because the earth spins would in this
: frame of reference would be the product of a universal gravitational
: field centered in the middle of the earth...

IOW, geocentrism is just as true in principle, but a way of looking at
reality that makes computing anything much harder.

Well, I found someone who did a better job explaining it, the author
of Discovery Magazine's "Bad Astronomy" column
http://blogs.discovermagazine.com/badastronomy/2010/09/14/geocentrism-seriously

    Geocentrism is a valid frame, but not the only one

    I have two things to say that might surprise you: first, geocentrism
    is a valid frame of reference, and second, heliocentrism is not any
    more or less correct.

    Surprise! Of course, the details are important.

    Look, I'm human: I say "The Sun rose in the east today", and not "the
    rotation of the Earth relative to the rest of the Universe carried me
    around to a geometric vantage point where the horizon as seen from my
    location dropped below the Sun's apparent position in space." To us,
    sitting here on the surface of a planet, geocentrism is a perfectly
    valid frame of reference. Heck, astronomers use it all the time to
    point our telescopes. We map the sky using a projected latitude and
    longitude, and we talk about things rising and setting. That's not
    only natural, but a very easy way to do those sorts of things. In
    that case, thinking geocentrically makes sense.

    However, as soon as you want to send a space probe to another planet,
    geocentrism becomes cumbersome. In that case, it's far easier to use
    the Sun as the center of the Universe and measure the rotating and
    revolving Earth as just another planet. The math works out better,
    and in fact it makes more common sense.

    However, this frame of reference, called heliocentrism, still is not
    the best frame for everything. Astronomers who study other galaxies
    use a galactic coordinate system based on our Milky Way galaxy, and
    the Sun is just another star inside it. Call it galactocentrism,
    if you want, and it's just as useful as geo -- or heliocentrism
    in its limited way. And none of those systems work if I want to
    know turn-by-turn directions while driving; in that case I use a
    carcentric system (specifically a Volvocentric one).

    You use coordinate systems depending on what you need.

    So really, there is no one true center to anything. I suppose
    you could say the Universe is polycentric, or more realistically
    acentric. You picks your frame of reference and you takes your
    chances.

    Relatively speaking, you're still wrong

    So geocentrism is valid, but so is every other frame. This is the very
    basis of relativity! One of the guiding principles used by Einstein
    in formulating it is that there is no One True Frame. If there were,
    the Universe would behave very, very differently.

    That's where Geocentrism trips up. Note the upper case G there;
    I use that to distinguish it from little-g geocentrism, which is
    just another frame of reference among many. Capital-G Geocentrism
    is the belief that geocentrism is the only frame, the real one.

    Geocentrists, at this point, fall into two cases: those who use
    relativity to bolster their claim, and those who deny it.

    Those who use relativity say that geocentrism can be right and
    is just as valid as heliocentrism or any other centrism. That's
    correct! But the problem is that using relativity by definition
    means that there is no One True Frame. So if you use relativity
    to say geocentrism can really be Geocentrism, you're wrong. You're
    using self-contradictory arguments.
    ...

But RMMS was only defending what he calls lower-case-g geocentrism.
That Chazal were not wrong, not that they were more right than today's
scientific theory.

Tir'u baTov!
-Micha

-- 
Micha Berger             People were created to be loved.
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