Retrograde Motion
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31-05-2011, 01:48 AM
 
Retrograde Motion
Help! This creationist asked me why some planets spin awkwardly than others if we all started in an explosion. I don't really know what a retrograde motion is. Please school me on this one.
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31-05-2011, 02:29 AM
RE: Retrograde Motion
I guess the creationist is asking why stars and planets are seen moving west to east AND east to west across the sky if we're all just projectiles moving in the same direction away from the Big Bang. There are a plethora of reason with a simple understanding of physics (seems to be the missing element in most creationist arguments).

There are the gravitational pull of different celestial masses that alter trajectory. There are the illusions of west or east perception when we are in the middle of the expansion (see bottom video), and then there's this explanation of perception video:






I know this video has been suggested to you before, but this time just watch starting at 10:20 for a few seconds to see how being inside the expansion is perceived different than if we were outside the expansion.






I think the creationist just heard a scientific term, got excited and ran with it without taking the time to understand it, as in common (cough 2nd Law of Thermodynamics cough).

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31-05-2011, 09:10 AM
RE: Retrograde Motion
I met a creationist once how asked why are there planets that move clockwise and others that move counter-clockwise, if all came from the same explosion.
I think that's what SumAtheosMagnus's creationist asked. IF so, the answer is easy.
In the big bang planets were not yet formed, so the direction of the rotation of the planets, were not determined by it.

..."we can be truly free - not because we can rebel against the the tyranny of the selfish replicators but because we know that there is no one to rebel."
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03-06-2011, 11:06 PM
RE: Retrograde Motion
The sun rotates anti-clockwise when viewed from above the north pole, the planets and asteroids orbit in the same direction. Most planets rotate anti-clockwise on their axis. This would be expected (conservation of angular momentum) if the planets coalesced out of a disk of matter left over as the sun formed. (nothing at all to do with the big bang)

Venus rotates clockwise. Uranus's and Pluto's axes lie nearly in the solar plane.

The creationist argument is that this contradicts the idea that the solar system coalesced out of a rotating disk of matter and that Venus, et al were individually created.

The rebuttal is that "something must have happened" like a collision with an asteroid or other external influence.

The whole argument seems pointless since I don't see how any scientific evidence can be adduced to prove whether such influence did or did not occur.

He was part of my dream, of course--but then I was part of his dream, too!
--Alice
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04-06-2011, 04:35 AM
RE: Retrograde Motion
(03-06-2011 11:06 PM)pilgrim Wrote:  The creationist argument is that this contradicts the idea that the solar system coalesced out of a rotating disk of matter and that Venus, et al were individually created.

The rebuttal is that "something must have happened" like a collision with an asteroid or other external influence.

The whole argument seems pointless since I don't see how any scientific evidence can be adduced to prove whether such influence did or did not occur.

Our current physics models match what we see in this solar system very well.
Venus rotates once every 243 Earth days—by far the slowest rotation period of any of the major planets. If you view this from the perspective of the whole solar system Venus doesn't even account for 0.1% of our solar systems total angular momentum. There are other explanations as to how Venus' rotation was slowed over time - like tidal forces. Our planets rotation is being slowed by the moon. Dragging the earths oceans around does work!

It would be stupid to point at Venus and say ha! see! God did it!
Venus does nothing to disprove our current understanding of how solar systems form.

“Forget Jesus, the stars died so you could be born.” - Lawrence M. Krauss
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