Question about Orbital planes, debris rings and whatnot

[skrap1r0n]

This may seem like a silly question, but why do the planets have rings of debris as opposed to a spherical cloud of debris around them? Also, why do planets seem to orbit in a similar plane around the sun as opposed to orbiting in completely seperate planes, making a sort of sphere? I understand the orbital planes are roughly equal to the equator of the sun and planets, but what is it that causes this? If it's centripital force causing this then why do planets and debris wind up in roughly the same plane? Does the spin of the parent body effect gravitational attraction and orbit in some way that causes child bodies to naturally want to seek the same plane?

[man on the moon]

probably the most common reason given is that way back when the solar system was a big thing of dust and such that started spinning, and as a result flattened out. eventually this dust collected around some of the larger items in the cloud (or heavier elements...someone correct me) and started forming planets. (mayb the heavier elements collected first and formed the larger objects.) and the planets now are in roughly a similar plane due to this. it's not the only explanation i'm sure but it fits well.

i can think of a couple others but i won't throw them in since this is not the against the mainstream forum.

[skrap1r0n]

ok I can buy that, I was thinking that maybe things got caught in a gravity well of the parent body and began swirling like water going down a drain.

[tofu]

It's because of tidal forces and angular momentum. As "man on the moon" said, the cloud of gas from which our solar system formed had a certain angular momentum, and as it collapsed that momentum was conserved and is still evident today in the plane of the solar system, and the orbital direction of the planets. So that explains why the planets are in a similar plane.

As to the orbits of moons (or rings), they are affected by tidal forces from their parent planet. It's a complicated subject, but the gist of it is that every time a planet completes a rotation (so, every day), it gives its moon a little nudge. Over hundreds of millions of years, the nudges add up to alter the orbital inclination of the moon.

This is most evident on Neptune. A long time ago, something big slammed into Neptune and tipped it almost 90 degrees. Whatever it was, it had no affect on the moons. They continued to orbit in the plane of the ecliptic. But over millions of years, their orbits were nudged and today they all orbit pretty close to Neptune's equator.

[Kaptain K]

This is most evident on Neptune. A long time ago, something big slammed into Neptune and tipped it almost 90 degrees. Whatever it was, it had no affect on the moons. They continued to orbit in the plane of the ecliptic. But over millions of years, their orbits were nudged and today they all orbit pretty close to Neptune's equator.

Replace Neptune with Uranus, and you got it right!

[skrap1r0n]

As to the orbits of moons, they are affected by tidal forces from their parent planet. It's a complicated subject, but the gist of it is that every time a planet completes a rotation (so, every day), it gives its moon a little nudge. Over hundreds of millions of years, the nudges add up to alter the orbital inclination of the moon.

ok then that leads me to 2 more questions, First what specifically is this nudge and second, why is an equitorial orbit the natural point the child object seeks?

I could understand it if it was centrifugal force acting on the child object, but gravity is the centripital force acting on the child object. Wouldn't that mean that the child object would remain in an orbit regardless of the plane since it's acting on the center of the parent object, regasrdless of the parents rotation?

Again, I am not trying to be obtuse, just trying to understand.

[Ut]

ok then that leads me to 2 more questions, First what specifically is this nudge and second, why is an equitorial orbit the natural point the child object seeks?

The nudge force is gravity. Interactions between planets and their satellites are tidal, just like the interaction between the Moon and the Earth's oceans. It all has to do with the transfer of angular momentum from the planet to its satellites.

The Earth/Moon system is a good example. Every time the Earth spins once on its axis, it slows down a little bit. Since the Earth/Moon approximate a closed system, the angular momentum of the system must be conserved. That which is lost by the Earth is transfered to the Moon. As a result, the Moons orbit changes ever so slightly. It gets larger.
This is a result of there being slighly more mass in one half of the Earth (and Moon) than in the other. The force of gravity between the two bodies is slightly stronger when the more massive sides face each other. They want to become tidally locked. Currently, the Moon is tidally locked to the Earth. Eventually, the Earth will also be locked to the Moon.
Aside: Do we officially become a double planet, then?

This tidal nudge is what forces a planets satellites to stay in line, so to speak. Larger planets, especially, have a LOT of angular momentum, so they can push their moons around pretty much however they please. It's sort of like they're hitting them with a giant, invisible baseball bat.

[skrap1r0n]

ok that clears things up, somewhat

/scuttles off to look into gravitational tides and whatnot

[Kaptain K]

Remember that the Earth is not a perfect sphere. It has an equatorial bulge. When the Moon is north of the equator, the bulge on the side facing the Moon pulls the Moon south more than the bulge on the opposite side pulls it north. Conversely, when the Moon is south of the equator, it gets a little nudge to the north . Although these forces are miniscule, they add up over time to very gradually pull the Moon into an equatorial orbit.