Why are all the planets on the same plane

[wacki]

Except for pluto they are very well aligned, why is this?

 

[EightySix Four]

I have recently been very curious on the matter also. Anyone care to enlighten us?

 

[CycloWizard]

I'd imagine that by being arranged in a plane, the potential energy is minimized. If you think about it, as soon as a body passes out of this plane, the gravity of all the bodies in the plane are exerting gravitational force on that body trying to pull it back into the plane.

The idea I'm going for is the same one discussed in the archived thread on what would happen if you fell into a hole that went all the way through the earth. When you passed the center, the direction of gravity would switch and you would again be drawn to the center. Eventually, you would come to rest there after oscillating back and forth. Extend this to higher dimensions and you will arrive at the conclusion that the equilibrium configuration is a plane.

 

[pm]

I've wondered about this too - it's a good question.

My thoughts on the subject - from musing about it - is that one of the most common shapes of rotating masses in the universe appears to be disks - think of most (all?) galaxies that you have seen pictures of. Given that general shape, it seems that if you have a bunch of stuff that eventually coalesces together, it will be in a disk shape and eventually conglomerate together to form planets that would be in the same eliptic plane. But I don't know the answer and it is certainly one of the ones that I have wondered about. It's interesting that most (all?) moons in our solar system are aligned in the same plane as well.

 

[silverpig]

If you take a random orientation of objects with some velocity, it will have a center of mass and an average angular momentum. The objects will collide and gravitate until they orbit about the center of mass of the system (sun) and are compressed into a disk. It's really just a matter of how it forms. There is a definite angular momentum vector of the system as a whole, and through friction and tidal forces everything tends to reflect this average. It really just "goes with the flow" to put it bluntly

 

[PowerEngineer]

Here's one proposed answer:

Why do most of the planets orbit the sun fairly on the same plane?

Asked by: Ilay Levie

Answer

The solar system originally formed from a huge cloud of gas and dust. This cloud hung in space with each molecule attracted to every other molecule by gravity. Also the cloud started with some net angular momentum, or spin. That is as the molecules moved about, there were a few more which orbited around the center of the mass of the cloud in one direction than in the opposite direction.

Over time, the gravitational attraction between the particles caused the cloud to condense to a smaller volume. Keep in mind that as the radius of the cloud decreased, the angular momentum didn't decrease, and so the speed of the spin increased. This is the same effect you see when an ice skater starts spinning slowly with arms outstrtched, and then picks up speed the tighter she pulls in her arms.

The cloud continued to spin and contract. However not all parts of the cloud pulled in to the center equally. Those particles around the plane perpendicular to the axis of rotation felt centrifugal "force" - actuall just their linear momentum - keeping them from moving towards the center and fighting against gravity. Particles closer to the axis of rotation felt this less, and were pulled in more. Thus the cloud became a disk, just as a blob of pizza dough thrown in the air with a spin flattens out into a pie shape.

The dust particles is areas of slightly higher density within this disk coalesced to form the sun, planets, asteroids, etc. and this is why most of these object are located in the same plane today.

Answered by: Rob Landolfi, None, Science Teacher, Washington, DC

 

[Remy XO]

If this is true then do molecules in atoms cirle the center on the same plane?

 

[TekViper]

why do all the planets spin in the same direction around thier axis and around the sun?

 

[Jeff7]

Originally posted by: Remy XO
If this is true then do molecules in atoms cirle the center on the same plane?

1) Molecules are made of atoms.
2) Once you start to get onto really tiny scales like that, rules of conventional physics don't always apply.

 

[cker]

why do all the planets spin in the same direction around thier axis and around the sun?

They don't. Uranus' axis of rotation is perpendicular to the solar plane. It keeps a pole pointed at the sun, though there is some question over which pole. This page at <a target=_blank class=ftalternatingbarlinklarge href="http://www.mira.org/fts0/planets/101/text/txt001x.htm">http://www.mira.org/fts0/planets/101/text/txt001x.htm</a> describes the rotation; Uranus keeps a pole pointed at the sun.

Venus rotates backwards, but in the 'right' orientation. Reference - <a target=_blank class=ftalternatingbarlinklarge href="http://www.solarviews.com/eng/venus.htm">http://www.solarviews.com/eng/venus.htm</a>

Depending on how you classify 'planet', Pluto has the most inclined orbit relative to the solar plane, about 17 degrees. That would not be unusual if it's a captured asteroid. Ref - <a target=_blank class=ftalternatingbarlinklarge href="http://www.space.com/scienceastronomy/solarsystem/pluto-ez.html">http://www.space.com/scienceastronomy/solarsystem/pluto-ez.html</a>

In general, though, the same physics will apply to any planetary formation. Think about stirring water in a sink in circles -- you'll get eddies from that rotation. Those little mini-whirlpools will all spin in the same direction. I think it's something like that but I'm no physicist.

If this is true then do molecules in atoms cirle the center on the same plane?

Different rules apply at this level. Distant large-body interactions are governed by gravity, which works at laaaaaarge scales. Gravity is pretty much irrelevant at molecular scales since it's so much weaker than electromagnetism at short distances. Molecular and atomic interactions are governed by electromagnetism, so to determine their behavior you have to look at the electrical charges electron shells.

Similarly, the important forces at the subatomic level are different, and gravity and EM are less relevant at that scale.

A really, really good book that touches on some of this stuff is Just Six Numbers by Martin Rees. Amazon Link
Again, I'm no physicist but I found it easy to get into.

 

[herm0016]

"If this is true then do molecules in atoms cirle the center on the same plane?"

electrons do not orbit the center of an atom, depending on the number of electrons the atom has there are i belive 5 or so different probibility clouds that the electrons are found in. none of them are oribiting the center. this is something that quantum mechanics deals with.

 

[Remy XO]

interesting article

http://www.newscientist.com/article.ns?id=mg18524911.600

5 Dark matter
TAKE our best understanding of gravity, apply it to the way galaxies spin, and you'll quickly see the problem: the galaxies should be falling apart. Galactic matter orbits around a central point because its mutual gravitational attraction creates centripetal forces. But there is not enough mass in the galaxies to produce the observed spin.

Vera Rubin, an astronomer working at the Carnegie Institution's department of terrestrial magnetism in Washington DC, spotted this anomaly in the late 1970s. The best response from physicists was to suggest there is more stuff out there than we can see. The trouble was, nobody could explain what this "dark matter" was.

And they still can't. Although researchers have made many suggestions about what kind of particles might make up dark matter, there is no consensus. It's an embarrassing hole in our understanding. Astronomical observations suggest that dark matter must make up about 90 per cent of the mass in the universe, yet we are astonishingly ignorant what that 90 per cent is.

Maybe we can't work out what dark matter is because it doesn't actually exist. That's certainly the way Rubin would like it to turn out. "If I could have my pick, I would like to learn that Newton's laws must be modified in order to correctly describe gravitational interactions at large distances," she says. "That's more appealing than a universe filled with a new kind of sub-nuclear particle."

 

[Mike Altieri]

Originally posted by: wacki
Except for pluto they are very well aligned, why is this?

Thats because Pluto isn't a planet, in my opinon.

 

[pm]

Originally posted by: Mike Altieri

Originally posted by: wacki
Except for pluto they are very well aligned, why is this?

Thats because Pluto isn't a planet, in my opinon.

On that note, I found this link interesting.
http://www.gps.caltech.edu/~mbrown/sedna/#planets

It's a discussion of what is a planet, and possible scientific defintions (as opposed to historical definitions) for the word "planet".

 

[Fullmetal Chocobo]

Well, given that it is the suns gravity that holds all the planets in orbit, couldn't you kind of think the entire solar system as one entity, for conversations sake. Now have you ever took a bicycle wheel on handles, spun it, and then tried to change its plane? It's a pain in the ass, as it is difficult to change. In gyros, they call it something like rigidity of plane, or rigidity of motion... Object spinning tend to keep their plane, and resist changed to the current plane on which they are spinning.

Don't all of the planets spin in the same direction around the sun. This would increase the possibility of the theory even more I would think.

Just a thought.

 

[Remy XO]

How fast are we moving away from the sun?

 

[alcoholbob]

1mm/s.

 

[Remy XO]

Originally posted by: Astrallite
1mm/s.

1 milimeter a second? seems pretty fast

 

[alcoholbob]

Yeah, it would take 12,000+ years for the Earth to drift the distance between the Earth and the Moon.

Or 4.8 Billion years to drift twice the distance from the Sun as we are now...that fast.

 

[navecko]

60*60*24*365.25=31557600 seconds in a year or 31557600 mm away per year
31557600/10=3155760 cm
3155760/2.54=1242425 inches
1242425/12=103535 feet
103535/5280=19.6 miles per year
If we are 93 million miles away from the sun than it would only take 4.7 million years to drift to a radius of 186 million miles away. Hmm 4.7 is close to 4.8. Maybe I screwed up a decimal point. Can someone see if I'm wrong. I did the math becasue 1 mm a second did seem kinda fast.

 

[archiloco]

maybe we did not start out at the sun maybe earth started drifting at different radius farther away

 

[imported_shader]

the most widely accepted theory is that we did not start off near the sun and move to where we are, the earth and all the other planets created their own mini accretion disks and formed like our sun did

some basic info/background here

 

[archiloco]

Originally posted by: shader
the most widely accepted theory is that we did not start off near the sun and move to where we are, the earth and all the other planets created their own mini accretion disks and formed like our sun did

some basic info/background here

yay..hehe seemed logical this was more the way they think it happened. and that just did not make any sense

 

[Nathelion]

1 mm/second would make 1*3600*365.25=1394.9m/yr. That would make approx. 1.11E8 yrs to double the distance between the earth and the sun. I'm sorry, but there's no way, that's only a hundred million years.

I've never heard of the earth moving at all away from the sun before, but it's not inconceivable - tidal effects, similar to those transferring rotational energy of the earth to kinetic energy of the moon could very well be at work, but I think the effects would probably be negligible.

 

[CycloWizard]

Originally posted by: Nathelion
1 mm/second would make 1*3600*365.25=1394.9m/yr. That would make approx. 1.11E8 yrs to double the distance between the earth and the sun. I'm sorry, but there's no way, that's only a hundred million years.

I've never heard of the earth moving at all away from the sun before, but it's not inconceivable - tidal effects, similar to those transferring rotational energy of the earth to kinetic energy of the moon could very well be at work, but I think the effects would probably be negligible.

Your math is a little fuzzy...
1 mm/sec * 3600 sec/hour * 24 hour/day * 365.25 days/year = 31557600 mm/year, or 31558 m/year.