The very early configuration of our solar system was a lot of random loose matter colliding with each other, in a three dimensional space. The situation was like those three dimensional indications of electrons around a nucleus that one often sees, for example in the logos for nuclear organizations. The effect of the Sun and Jupiter soon started to flatten this three-dimensional grouping, and bring the matter close to the ecliptic plane.

As the different planets were formed out of the agglomeration of matter, the spin of that planet came about as the net effect of all the impacts of material, but in the three dimensional picture, this meant that the planet spin and the direction of orbit were coupled. Hence, for example, Uranus, whose orbit was initially close to right angles to the final plane of the ecliptic, has a planet spin that was related to that initial orbit in the three dimensional array of matter in the proto Solar System.

While the spin of a planet in the vacuum of space is a very robust characteristic, the orbit is not, and is affected over time by the Sun/Jupiter dynamic. Hence Uranus spins as it always did, but is now entrained to the ecliptic. I do not believe that a passing gravitational presence can simply rock the planet spin over by 90 degrees and stop there. Rings of matter, and moons for the large planets are also evidence of the longevity of the spin, since they are always aligned with the spin axis of the planet.

The initial period for the Solar System was very exciting for another reason. The three dimensional birthplace of the planets meant that a minority of planets had retrograde orbits, and spins associated with that direction, and the action of Sun/Jupiter entrained them to the ecliptic as well, if one studies the gravitational interactions carefully. An analogous effect is seen in the coexistence of prograde and retrograde moons for Saturn at the present time, in the same plane.

These doomed retrograde planets suffered one of three possible fates:

a) They would collide with prograde planets and create asteroids, as in the region between Jupiter and Mars.

b) Because they would be fighting and losing to the larger gravity field of the prograde planets, they would spiral into the Sun, and upon impact, their retrograde momentum vectors would actually decrease the Sun's angular momentum, as is the case to this day. The Sun's angular momentum is less than one would expect for the solar system we have. In fact, the difference in momentum would provide a means to estimate the total mass of the retrograde planets.

c) They could spiral in toward the Sun, but by chance interaction with the larger planets, narrowly miss the Sun, and get swung around to prograde orbit.

In the last case c), the only way one could detect this, is if one checked the planet spin and found it to reflect such a retrograde-orbit past. I believe that this is the case with regard to Venus. Of course, I would only have a strong case if Venus' spin actually was retrograde.

So Venus presently is a planet that was initially in a retrograde orbit, probably quite a bit further from the Sun than its present orbit position. There was probably an extended period of highly elliptical orbits for Venus, bringing it close to Earth, in the distant past.

swanee.


“The initial period for the Solar System was very exciting”


Yes. The early solar system was certainly very exciting. However, your model for retrograde planets has some serious problems. If they were minor problems, you might save the model by revising it. But these are large problems and you are better off abandoning the model and returning to the drawing board.


Here is the first problem;

“The situation was like those three dimensional indications of electrons around a nucleus”


That’s not what we see when we look at the nearby star systems in their infancy. We see mostly disks. There are thin halos of material to be found out of the disk proper, but this amounts to very little when compared to the mass within the disk.


http://www.ast.cam.ac.uk/HST/press/o...tent/9905c.jpg

http://astronomy.swin.edu.au/staff/m..._disks2_sm.gif


Close encounters may lead to high inclinations (>20 degrees), but more often than not, the object is now traveling so rapidly that it will be ejected from the solar system entirely.


“Uranus, whose orbit was initially close to right angles to the final plane of the ecliptic, has a planet spin that was related to that initial orbit in the three dimensional array of matter in the proto Solar System.”


No swanee, this can not be the case. Here’s why. You are suggesting an orbital inclination of over 90 degrees for a gas (or ice) giant planet of at least 14 earth masses. That’s a tall order by itself. Then you require another unlikely encounter to bring it back to the plane of the ecliptic. Remember, whatever obstacle course you put the planet through, it has to end up the way we see it today.


You did not specify what stage in the accretion era these extreme encounters took place, so let’s look at both the early and late accretion era. If you lob Uranus out of the disk too early, while it is still little more than 5 or 6 earth masses, it’s growth stops because it is no longer in the feeding zone. In fact, the young wayward planet is spending ~90% of it’s time out of the feeding zone while the other giant planets are grabbing all the mass in their path. The clock is ticking (accretion disks thin out over time through absorption by the proto-planets or ejection out of the system) so the longer it spends out of the feeding zone, the less likely it becomes that it can end up as we see it today; a giant planet.


Now, let’s look at the late accretion era. You start with a nearly complete giant planet within the disk and shoot it by another giant planet (nothing else could change its orbit so drastically). Then you have to do it again to bring it back to the ecliptic. Why bother? Well, you did leave a clue here;


“I do not believe that a passing gravitational presence can simply rock the planet spin over by 90 degrees and stop there.”


Why not? We know from the impact record on the solid bodies of the solar system that bombardment was common in the early solar system. It’s not as if a gas giant planet will just continue to rock pass 90 degrees, 180, 270, etc. It’s not some wooden top of low mass; it’s a massive giant. In terms of probability, it’s a lot easier to rock a planet’s spin 90 degrees than it is to lob it into a halo orbit and then lob it back to the plane of the ecliptic with a second encounter. Two encounters with two different giant planets is going to great lengths just to avoid the standard model. It’s called “ad hoc”. Invoking a very unlikely set of events to salvage a model you like or to avoid a model you don’t like. BTW. The majority of recognized models employ an impact to rock the planet over rather than “a passing gravitational presense”.

“The three dimensional birthplace of the planets meant that a minority of planets had retrograde orbits”


This does not compute. Nor has it been demonstrated. Your science teacher needs to be horse-whipped. Perhaps tarred and feathered.


“An analogous effect is seen in the coexistence of prograde and retrograde moons for Saturn at the present time, in the same plane.”


No swanee. This analogy does not work. The irregular retrograde moons of Saturn are almost certainly captured objects. There is no evidence that they formed in situ concurrent with the regular prograde moons.


“They could spiral in toward the Sun, but by chance interaction with the larger planets, narrowly miss the Sun, and get swung around to prograde orbit.”


Extremely unlikely. Impossible to prove.


“So Venus presently is a planet that was initially in a retrograde orbit”


Very dubious conclusion and impossible to demonstrate.


“There was probably an extended period of highly elliptical orbits for Venus, bringing it close to Earth, in the distant past.”


If you are one of those people trying to revive Velikovsky’s wonk-melon theories, then there is nothing to discuss until you’ve done some homework on the actual history of the solar system. Seriously. A couple of links to get you started.


http://zebu.uoregon.edu/~js/ast122/lectures/lec09.html




http://www.astro.lsa.umich.edu/users/cowley/lecture28/

Ah! But when we see disks around these stars, are we actually seeing embryonic star systems in the process of forming planets, or are we merely speculating that the systems are in their planet-forming phase because of the existence of the disks?

tracer.

“Ah! But when we see disks around these stars, are we actually seeing embryonic star systems in the process of forming planets,”


Yes. That’s exactly what we’re seeing. The evidence is overwhelming and built on a solid foundation of observation backed up by the numerous predictions which have been confirmed.


“or are we merely speculating that the systems are in their planet-forming phase because of the existence of the disks?”


No. We’re not. The time for speculation came and went decades ago. This is yesteryear’s news and pretty basic stuff.


The cause for the paradigm shift came from the other side of the iron curtain in the early 1970’s with the translation into English of a monograph authored by V.S. Safronov. “Preplanetary cloud evolution and the formation of Earth and the planets.” Nauka, Moscow. 1969.


Nebular cloud models were common enough but fudged over the crucial transition period of cloud to planets. With a disk model in hand, old pix of unidentified fuzzy objects now made sense. We now knew not only what we were looking at but what to look for. As imaging technology improved, so did the certainty that young stars have a telltale signature distinct from all other objects. A crash course on some of the basics; the temperature-luminosity relationship,

http://www.physics.gmu.edu/~rms/astr.../L7/l07X56.GIF and,

http://www.chelt.ac.uk/gdn/origins/images/hrannot.gif


Main sequence stars are readily discerned from pre-main sequence stars.

http://casa.colorado.edu/~kachun/res.../yso_class.gif


There is very close agreement with computer simulations and what we see all around us.

http://www.astro.su.se/~pawel/blois/talk_3.3.1.html

http://ast.star.rl.ac.uk/symp202/talks/stapelfeldt.html

http://www.exn.ca/Stories/1999/02/09/57.asp

Review the material and get back to me if you have further questions.

We even have actual evidence of planets forming in these dust rings now.

http://antwrp.gsfc.nasa.gov/apod/ap021011.html

__________________
...And that, my liege, is how we know the Earth to be banana-shaped. --Sir Bedevere

Have I not read in this BBS that Venus's retrograde rotation may be the result of tidal interaction with Earth? It was written that only about 60% of Venus's surface is visible from Earth due to its rotation. Not perfect, but close enough to suggest a possible link, is it not?

The retrograde spin of Venus is most likely the result of a tidal coupling between the solar torque (which drive Venus towards synchronous rotation) and atmospheric tourque (which drives venus away from synchronous rotation). Its current slightly retrograde spin evidently fits an equilibrium between these two torques. It was once though that there was a tidal resonance with Earth, but that now seems unlikely. See Venus II: Geology, Geophysics, Atmosphere, and Solar Wind Environment, University of Arizona Press, 1997, the chapter Venus Spin Dynamics by C.F. Yoder, pp. 1087-1124. All the gory details are there.

It is highly unlikely that Venus, or any of the other 9 planets, ever had a retrograde orbital motion around the sun. Such a system is wildly unstable, and the retrograde planet would be ejected from the system (most likely), or perhaps suffer a collision (less likely I think). It certainly would not re-enter the solar system on a prograde orbit without the benefit of divine intervention.

More disks, courtesy of STIS. I worked on these images, and others.

So what do planetary systems forming around other stars do to the geocentrists? Make them balk?

How are planetary systems around other stars different from, for instance, the moons around Jupiter? In regards to geocentrism, I mean.

I just noticed, as near as I can tell, this is the first mention of geocentrism in this topic. Was this posted to the right topic? If not, I'll move the discussion to the other topic.

The general creationist position is that NO new star formation is taking place.

http://www.answersingenesis.org/docs/1384.asp

Grapes--

I was simply curious. As we witness the birth of stellar systems in other parts of the galaxy that seem to mimic the mainstream model of the solar system, it seems that the only thing for the geocentrist to do is go into denial as Karl pointed out (from an admittedly non-geocentrist website).

Denial of what? Are they all denying that we do not see evidence of planets or planetary formation?

Denial that our planetary system might behave dynamically as others do, with a star at the fiducial center and a system that orbits it via the laws of Kepler.

I'm still trying to figure out why that would be any different than Jupiter's moons. The extra-solar planets wouldn't seem to cause any additional anxiety.

The problem here is that you are looking at this in a logical way.

"With the Lord, all things are possible."

That is not logical, but belief. With belief, all things are possible. You can't argue with belief, regardless of the actual facts.

I guess it is my contention that Geocentrists are all believers in some (generally a Christian) supreme being. You won't find any atheist G/geocentrists, because that doesn't make any sense.

Fair enough for you and me, Grapes, but here's where it gets interesting:

1)We expect that the sun is at the fiducial center of the solar system and NOT the Earth.
2)We see other planetary systems that form and if we were to model what the universe would look like from a planet in one of those planetary systems is would look pretty darn similar to what we experience on Earth.
3)Why should we expect that the Earth is still the center of the universe since a given person sent to that planetary system would see the same evidence and be equally compelled to conclude that their stationary planet is the center of the universe?

The only viable alternatives are that either a)there's something that makes us special (what is it, scientifically?) or b)these systems aren't there so it's a non-issue.

Are there alternatives, Grapes?

I guess we could be in denial. [img]/phpBB/images/smiles/icon_smile.gif[/img]

I don't know why this question just popped into my mind, but it did. Why do the rings around Uranus vary from the plane of the ecliptic so much? Is it possible to have polar rings (by this, I mean rings that orbit around the poles instead of around the equator)? Just a couple questions.

__________________
"Some see the glass half full, some see it half empty, and some see it crawling with toxic alien parasites who want to devour your pancreas." - Sgt Aarhus, from the book Ascending by James Alan Gardner

Uranus's rings are on equatorial, the poles are of kilter 98 degrees

Jetmech0417.

“Why do the rings around Uranus vary from the plane of the ecliptic so much?”


The short answer……because the rotation of the planet varies from the plane of the ecliptic. Three major dynamic characteristics are “slaved” one to the other.

(a) The rotation of the primary. (Uranus)
(b) The plane of revolution of the secondary bodies. (moons)
(c) The plane of the rings will consistently match (a) and (b).


“Is it possible to have polar rings (by this, I mean rings that orbit around the poles instead of around the equator)?”


I don’t see why not. I also would not expect a polar orbit ring system to have the longevity of an equatorial ring system. In other words, it’s possible but they wouldn’t last long. Relatively speaking. I suppose it ultimately depends on the source of the rings. If rings represent the shattered remains of former moons, then the ring plane will be equatorial rather than polar. If rings are the shattered remains of intruders (comets, asteroids, etc) then perhaps a short term polar ring system is possible. Just not very likely.

What would make a polar system so unstable? Tidal forces? I've always understood that planets, moons, even stars, etc. orbited around the parent's center of mass/the system's barycenter.

__________________
"Some see the glass half full, some see it half empty, and some see it crawling with toxic alien parasites who want to devour your pancreas." - Sgt Aarhus, from the book Ascending by James Alan Gardner

Do you mean that they are actually close to the ecliptic?

Jetmech0417.

“What would make a polar system so unstable? Tidal forces? I've always understood that planets, moons, even stars, etc. orbited around the parent's center of mass/the system's barycenter.”


Tidal forces would be one influence toward instability. Within the Roche limit, tidal forces exceed gravitational influences. (All ring systems reside within their planet’s Roche limit.) Interestingly, the Roche limit is also known as the tidal stability limit.

http://pegasus.phast.umass.edu/a101/...he_diagram.jpg


Within this limit, no large moons can form. Beyond this limit, they can and do form.


The gravitational attractions of the planet and its moons are still present as a secondary influence. The gas giant itself is slightly oblate (squashed looking) rather than a perfect sphere. The moons of the giant planets tug, ever so slightly upon the particles of the rings.


Quote from the following link;


“The model includes the perturbations from the major satellites, the sun and Saturn’s oblateness.”

http://www.lpi.usra.edu/science/hahn...2DPSposter.pdf


Any influence which pulls the ring particles out of a circular orbit will act to destabilize and therefore destroy the ring. Polar orbit ring systems would experience more perturbations and therefore more instability than an equatorial ring system.

No, Uranus's poles are not aligned with the ecliptic. The rings are equatorial relative to Uranus. Sorry, I should have been clearer.

No, now that I look back, that's what you said. I just needed to clarify to make sure, I guess.

How do you like my new sekret identity? I took it from my friend ToSeek.

Actually, while we're on polar alignments, are all the magnetic poles oriented relative to each other? Is there a difference in the North Magnetic Pole to the South Magnetic Pole? If a planet cannot be retrograde, can it be upside down, magnetically speaking?

If I understand what you're asking, the answer is "yes." There's evidence that Earth's magnetic field has reversed (north-south) many times in its existence.

__________________
Everything I need to know I learned through Googling.

I see, you understood me. Are there any indications as to why the poles flip? (forgive me while i cringe, I do not mean that in the sense of the PX pole switch)

I'd like to chime in on the subject of planetary ring systems in polar orbit.

As I understand orbital dynamics, the rotation of the planet on its' axis would prohibit a polar ring sytem. Due to the tidal forces caused by the surface of the planet below, the part of the ring over the equator would be deflected more than the ring at the poles (and everywhere in between) so, assuming a polar ring could form in the first place, it would not last more than a few month or years at most.

Plus you'd have total angular momentum working against you. Some fraction of the total for the system would be applying force 90 degrees to the planet's angular momentum. In the physics world, "Mass Wins" every time. In short, the planet would rip up the ring and either consume the mass or fling it out of the system.

Anybody have a different take on this?

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