Starship Asterisk*

dougettinger wrote:If one is able to look downward on the moon and Earth from a far place above the Sun's north pole, you should see that the moon takes a wavelike path about the Earth's orbital path. I then suppose the moon's absolute velocity about the Sun should be unchanging.

I suspect the planets in the same way would take planar wavelike paths about the Sun's orbital path around the galaxy. Since the planetary ecliptic plane is more perpendicular to the Sun's path, the planets travel more in a spiral fashion like DNA with respect to the galaxy's center. But the absolute velocity of each planet should remain unchanged regardless of the planetary ecliptic angle to the plane of galaxy disk.

dougettinger wrote:In the case of the ecliptic plane being along the vector of the Sun's travel - then the planets would have to increase their orbital velocities when going against the direction of the Sun's path and decrease their orbital velocity when going with the Sun's direction which is independent of the differences of Keplerian velocities. This is not to say that Keplerian velocity changes would also be a factor. Is this correct ?

dougettinger wrote:I was not trying to establish a relationship between galactic orbit and ecliptic plane. I was checking to confirm any relationship between direction of travel (no matter what the location) and any established ecliptic plane.

So the ecliptic plane for our solar system could have been just as easily laid along the vector of the Sun's travel ?

dougettinger wrote:Allow me to add another question to this discussion after Chris presented a convincing arguement. As for the Sun, its ecliptic plane is almost perpendicular to its direction of travel around the galaxy. Does the plane of orbiting planets or stars or galaxy spiral arms reveal the direction of travel of the main core or gravity source to be approximately perpendicular to the subject plane in all cases ?

rstevenson wrote:It might simply be a matter of stability. I'm not up to the math myself, but I can visualize the instability of a system where planetary orbits are crossing at all sorts of angles. Such a system would gradually fling miscreant planets and other bodies either out of the system or into more stable orbits. So it's not so much a question of why a more or less planar system, but why not a multi-planar system.

... [later] ...

I see you posted the same question within another thread, and Chris answered it better than I could. I'll post your question and his answer here for completeness...

How does a disk form from groupings of matter randomly located in three-dimensional space? Why don't different accretion disks form with various alignments in the same region of several square AUs? These accretion disks could develop substantial angular momentum that should resist being pulled into a common accretion disk that could form a solar system like ours or a typical binary star system.

A disc is the only possible solution when you have material that interacts, as normal matter does. As material comes together, it becomes fluid-like, subject to the laws of fluid dynamics. Angular momentum is transferred between particles, and is conserved. Material is either brought into the dominant plane, or is ejected from the system.

Henning Makholm wrote:

rriverstone wrote:I was just looking at an animation of Saturn; it reminded me of an old question I've had since I was a little girl, 45 yrs ago. Why are so many orbits flat discs? Why isn't Saturn within a bubble of snowballs, rather than rings? Why do planets orbit Sol in a relatively disc shaped order?

There are really two questions here: (1) why does each individual orbit fit into a plane? (2) why do all of the orbital planes in the solar system lie in roughly the same direction?
The second question is harder. I think a good explanation will need to involve the angular momentum of the interstellar gas cloud that collapsed to form the solar system, and probably also some statistical dynamics of the collapsing cloud. But I cannot right off the cuff produce an explanation that would convince myself ...
However, note that the nice shared-orbital-plane property we see in the solar system is not universal. Globular clusters have no preferred orbital plane. Neither do elliptical galaxies. Closer to home, the Oort cloud is not thought to be particularly aligned with the Ecliptic.

http://en.wikipedia.org/wiki/Rings_of_Saturn wrote:Saturn's rings may be very old, dating to the formation of Saturn itself. There are two main theories regarding the origin of Saturn's rings. One theory, originally proposed by Édouard Roche in the 19th century, is that the rings were once a moon of Saturn whose orbit decayed until it came close enough to be ripped apart by tidal forces (see Roche limit).[23] A variation of this theory is that the moon disintegrated after being struck by a large comet or asteroid.[24] The second theory is that the rings were never part of a moon, but are instead left over from the original nebular material from which Saturn formed.[citation needed]

It seems likely however that they are composed of debris from the disruption of a moon about 300 km in diameter, bigger than Mimas. The last time there were collisions large enough to be likely to disrupt a moon that large was during the Late Heavy Bombardment some four billion years ago.[25]

rriverstone wrote:I was just looking at an animation of Saturn; it reminded me of an old question I've had since I was a little girl, 45 yrs ago. Why are so many orbits flat discs? Why isn't Saturn within a bubble of snowballs, rather than rings? Why do planets orbit Sol in a relatively disc shaped order?