
Elegance, illustrated: heliocentrism vs. geocentrism - Hooke
http://boingboing.net/2016/01/10/elegance-illustrated-helioce.html
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TeMPOraL
My God, I just spent half of the last night debating this on Facebook -.-

My takeaway from that experience - when someone struggles with understanding
why those two views are both equivalent and OK, make sure they understand this
thing: heliocentric and geocentric models have only one purpose. They let you
compute where planets will be at any given time. They do _not_ try to answer
_why_ the planets are moving the way they are. For that, you need at least
Newton's model of gravity, which actually doesn't differentiate between the
Sun and planets at all.

Geocentric models still pop up in real life. When you're using a sky map to
determine where some planet will be visible tonight, you're looking at a
geocentric representation.

~~~
analog31
That was indeed the state of the art in Galileo's time. Heliocentrism wasn't
necessarily more elegant, because it left open problems such as why people
don't fly off the earth, and why the oceans don't slosh around uncontrollably.
From what I've read, the Church was prepared to accept the model of Tycho
Brahe, in which the sun goes around the earth, and the planets around the sun,
which is yet another equivalent view within that conception of reality.

Newton gave us a couple of things. First, as you say, he gave us a model of
gravity. Secondly, he gave us the framework within which to test whether the
earth is rotating or not, e.g., through observations of things like Foucault's
pendulum, and the Coriolis force.

~~~
TeMPOraL
I actually have some sources from my yesterday's discussion handy:

[http://qr.ae/R4iSbs](http://qr.ae/R4iSbs)

[http://lesswrong.com/lw/lq6/the_galileo_affair_who_was_on_th...](http://lesswrong.com/lw/lq6/the_galileo_affair_who_was_on_the_side_of/)

[http://lesswrong.com/lw/lq6/the_galileo_affair_who_was_on_th...](http://lesswrong.com/lw/lq6/the_galileo_affair_who_was_on_the_side_of/bz9v)

They paint a completely different picture of Galileo than the one taught in
schools. TL;DR: Galileo was onto the right idea, but for totally wrong
reasons. His model was worse than existing ones and unsupported by available
empirical data - therefore it was justly rejected by contemporary scientific
community. And the issue with Church was apparently about Galileo being a dick
to the Pope.

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mcphage
Here's the problem with this: the planets' orbits aren't circles. And
scientists had good enough measurements, that they _knew_ circular orbits
didn't match the observed behavior. So neither of those models are very good.
It wasn't until people figured out that orbits are ellipses instead of
circles, that we actually had a model that was simpler _and_ more accurate
than the cycles-and-epicycles of geocentrism.

~~~
terravion
Exactly this. Everyone says oh, it is so much easier to calculate with circles
around the sun--this only true if you want wrong answers to the position of
the planets. So wrong that you can see it with the naked eye. Nobody believed
Copernicus because his model was not predictive--this gets left out when we
want to tell stories about Medieval anti-scientific bias.

When Kepler came along and introduces an elliptical heliocentric model with
the equal areas law, scientifically minded people switch to the heliocentric
view. However, the math for this is really hard. We use elliptical curves in
cryto today. You can calculate the position of a planet with Ptolemy's model
on an abacus with nothing more complex than division.

~~~
jacobolus
Note that an elliptic curve is not at all the same as an ellipse.
[https://en.wikipedia.org/wiki/Elliptic_curve](https://en.wikipedia.org/wiki/Elliptic_curve)

------
elliptic
Perhaps the elegance would be better illustrated if the planets were shown to
move in elliptical rather than circular orbits - this of course was the
primary historical difficulty in understanding planetary motion

~~~
NolF
Most of them are not that elliptical. When put to scale, they difference is
almost negligible. For example Mercury has a 23.8Gm difference (51.7%) which
sounds like a lot but that's 4 times less than Neptune's 80Gm difference
(1.79%) and only 0.5% of Neptune's distance.

* Mercury max 69.8 Gm :: 46.0 Gm :: 51.7%

* Venus max 108.9 Gm :: min 107.5 Gm :: 1.30%

* Earth max 152.1 Gm :: min 147.1 Gm :: 3.40%

* Mars max 249.2 Gm :: min 206.7 Gm :: 20.6%

* Jupiter max 816.0 Gm :: min 740.6 Gm :: 10.2%

* Saturn max 1,509 Gm :: min 1,350 Gm :: 11.8%

* Uranus max 3,008 Gm :: min 2,742 Gm :: 9.70%

* Neptune max 4,540 Gm :: min 4,460 Gm :: 1.79%

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rl3
It's worth noting that the orbital periods on the heliocentric side aren't
even remotely accurate. Otherwise effective visualization though.

