Why are planetary orbits so circular?

[D H]

Not sure I am. The centre of mass of the universe is a point that is equally the age of the universe away from all points in our 3D space, is it not?

By that definition, every point in the universe is the center of the universe. Another way to say it: The universe has no center.

All of the discussion started by post #20 is incredibly off-topic. Start a new thread, or better yet, find an existing thread that is already devoted to this topic.

 

[DaveC426913]

What two planets are you talking about? Only one of the eight planets, Mercury, has anything close to an eccentric orbit. Moreover, a big part of Mercury's eccentricity results from Jupiter.

Pluto's is eccentric enough to pass within Uranus'. And it's tilted.

 

[DaveC426913]

Not sure I am. The centre of mass of the universe is a point that is equally the age of the universe away from all points in our 3D space, is it not?

As D_H points out, so was my point: all points in the universe meet that criteria.

 

[D H]

Pluto's is eccentric enough to pass within Uranus'. And it's tilted.

I was being nitpicky. Pluto is no longer considered to be a planet.

 

[DaveC426913]

I was being nitpicky. Pluto is no longer considered to be a planet.

Is too. Dwarf planets are a subset of planets.