Multiple star systems aren't stable unless they're in a hierarchy.
Imagine the earth and the moon as stars.. that's what it's like.

Both the earth and the moon are orbiting a common center of gravity,
like a spinning dumbbell ( emitting gravitational waves ).
The moon itself might have a smaller moon, and so on.

What makes you think I think the earth-moon system isn't stable ?

When calculating orbits around the sun,
the center of gravity of the earth-moon system
might be simplified to a single point.

Simplifications like that are possible because
the earth-moon system is such a “ stable hierarchy ”.

Multiple star systems aren't stable unless they're in a hierarchy.

Imagine the earth and the moon as stars.. that's what it's like.

Both the earth and the moon are orbiting a common center of gravity,
like a spinning dumbbell ( emitting gravitational waves ).
The moon itself might have a smaller moon, and so on.

Multiple star systems aren't stable unless they're in a hierarchy.
Imagine the earth and the moon as stars.. that's what it's like.

Both the earth and the moon are orbiting a common center of gravity,
like a spinning dumbbell ( emitting gravitational waves ).
The moon itself might have a smaller moon, and so on.

. . .
Re: http://paine_ellsworth.home.att.net/Selene_pics.html

I didn't quite grasp what this was trying to illustrate.

You told me:
â?o The Moon never fully goes all the way "around" the Earth
due to the way the Earth-Moon system orbits the Sun. â?�.

I don't understand, WikiPedia says:
â?o The Moon makes a complete orbit around the Earth
with respect to the fixed stars ( its sidereal period )
about once every 27.3 days. â?�.
-- http://WikiPedia.ORG/wiki/Moon#Orbit_and_relationship_to_Earth

P.S. My handle is â?o Jeffâ-²Relf â?�, not â?o Jeff?Relf â?�,
please turn-on your 8-bit characters and Unicode.

Thanks to your help,
I now picture the earth and moon as two fast moving cars
taking turns passing each other, thus orbiting each other.

Relative to the cars' center of mass, it's a different orbit, i.e.:
â?o Motion must always be specified with respect to another object. â?�.
-- http://WikiPedia.ORG/wiki/Milky_Way#Velocity

Our Milky Way is moving at 1.2 mega miles per hour ( 552 km/s )
relative to the Cosmic Microwave Background ( from the Big Bang ).

And the maser inside a GPS bird is moving at c
( relative to its inertial frame ) despite the fact that
the bird's angular velocity is 8.7 kilo miles per hour,
relative to the center of the earth.
-- www.Astronomy.Ohio-State.EDU/~pogge/Ast162/Unit5/gps.html

Yes lots of question marks. Reality is,even if there were just three
heavenly bodies the equations become so complicated that no one has
solved a three body system. So we by pass this by just using the great
mass of the sun,and its proximity to the earth. We get a good estimate
by considering only the sun's gravitational influence. Still maybe with
computers we can bring in the next most relevant bodies (moon+ close
planets) to sharpen up this situation. Still I worry about this when
I think of Tri-stars Go figure Bert

Jeff Please do not change the posts headings I think that is not good.
Post your shit6 under the titled post. Don't act like A DUMBBELL

I didn't mean to imply that the Moon actually had
a " smaller satellite ", I was asking Bert to imagine it.

Also, Bert thought I was calling him a Dumbbell, it seems.
I think he's only reading the titles of my posts, if that.

Re: http://paine_ellsworth.home.att.net/Selene_pics.html

I didn't quite grasp what this was trying to illustrate.

You told me:
" The Moon never fully goes all the way "around" the Earth
due to the way the Earth-Moon system orbits the Sun. ".

I don't understand, WikiPedia says:
" The Moon makes a complete orbit around the Earth
with respect to the fixed stars ( its sidereal period )
about once every 27.3 days. ".
-- http://WikiPedia.ORG/wiki/Moon#Orbit_and_relationship_to_Earth

P.S. My handle is " Jeff?Relf ", not " Jeff?Relf ",
please turn-on your 8-bit characters and Unicode.