# Are the orbits of the planets really all on the same (or a similar) plane? If so, why? If not, why do we depict it this way? [closed]

The planets orbiting the sun are always depicted as ovals or circles going around the sun in the center, and it throws me off at how two-dimensional it is.

Is this really how the planets go, or do some planets, say, orbit 'vertically' compared to us?

If it really does look that way, why? If not, then why do we always use the '2-D' imagery to show it?

• @TildalWave I didn't realize there was an astronomy SE to search. I did some google searching and it brought up none of those, odd. I'm fine with closing this then. – Ethan The Brave Feb 12 '16 at 20:54
• We depict it that way because paper is flat. – jamesqf Feb 14 '16 at 5:27

## 1 Answer

It's pretty close to flat. Close enough to draw it that way, anyhow.

One way of measuring the "flatness" of the Solar System is to compare the inclination of the planets' orbits to a measure known as the invariable plane.

Most of the planets' orbits are inclined by less than 2°. Venus is inclined at 2.19°. Mercury has the strongest inclination, at 6.34°.

(image from clearscience.tumblr.com)

• Is there a known, scientific reason for it being that way or is that just (as far as we can tell) "How it happened to end up"? – Ethan The Brave Feb 12 '16 at 20:53
• The current theory is that the planets and the sun formed at the same time from a cloud of matter. This cloud, as it condensed, naturally began to spin and flatten. Eventually most of the matter clumped together, and you have the solar system of today. – Joe Feb 12 '16 at 20:57
• The effects of planets' gravity on each other causes them to end up in a common plane (or as close to it as we see). Galaxies tend to be flat for the same reason. So yes, there is a scientific reason and it is not even very complicated! – Brian Lynch Feb 13 '16 at 0:40
• The angular momentum of the cloud of stuff is conserved, which keeps it all from falling to the center. However nothing about the angular momentum keeps matter from moving in the direction of the angular momentum vector, i.e. north or south. So the matter naturally tries to fall from both north and south to the plane perpendicular to the angular momentum vector that goes through the center of mass, the Sun. – Mark Adler Feb 13 '16 at 0:50