Physics Van 3-site Navigational Menu

Physics Van Navigational Menu

Q & A: why do planets orbit almost in a plane?

Learn more physics!

Most recent answer: 12/21/2013
why is it that the planets orbit "around" the sun and no over it? do magnetic poles have anything to do with a planet or stars bending of space
- chad (age 27)

With any one planet you could say that it orbited around the sun in a plane regardless of how the orbit was oriented. I think what you're asking is why all the planets have orbits that are nearly in the same plane. The sun itself also spins around an axis that is nearly at right angles to the same plane. As I understand it, as the solar system started to condense, it had some net angular momentum, just by the usual accidents of motion in a lumpy environment. That angular momentum was conserved as the material started to lump together.  The planets were left behind orbiting around that angular momentum axis, as nature's way of conserving angular momentum.

Some similar process is quite typical in star formation. Many stars have orbiting planets. Some stars form pairs, orbiting each other.

As for your other question, the "bending of space" is gravity, caused by any form of energy or momentum. Magnetism plays a negligible role in it since it accounts for a negligible fraction of the total energy of the solar system. It's interesting that very many of the people who write us want to know about the connection between magnetism and gravity, although there's almost none.

Mike W.

(published on 03/27/2011)

Follow-Up #1: Planets rotate same way in almost same plane

Why do all of the planets in our solar system move the same direction around the sun? Why are the planets more or less all on a grid compared to one another and eventually all line up with each other? Surely this isn't a coincidence.
- Nick (age 14)

It all comes from the initial accidental angular momentum, as described in the thread where I've placed your question. Since the angular momentum of all the planets comes from that same starting accident, they all have about the same rotation axis. That makes them all be in orbits close to the plane through the Sun at right angles to that axis.

Mike W.

(published on 12/08/2013)

Follow-Up #2: Rotational invariance of the universe

I hope some body to help me in this logical question.As we know that every body in this universe move around another body in anticlock wise motion like the motion of electron around the nucleus,motion of planets around the sun and the most common is the revolution of earth around the sun,why they did'nt revolve in clock wise motion.?
- Muhammad uzair ahmad (age 15)

Hello Muhammad,

Your premise is not true, both in atomic and cosmic senses. One can always find local fluctuations in symmetries of the universe: mass distributions, momentum directions, angular rotations, etc. Studies have been made of clockwise and anti-clockwise rotations of spiral galaxies  and as far as we can tell they average out.   Likewise there are fluctuations in all the other variables but they 'invariably' average out. 




(published on 12/21/2013)

Follow-up on this answer.