Interesting as well because it shows pretty clearly how odd our planet is in respect to relative size of our moon. Luna is nearly 1/4 the size of Earth and that is pretty unusual in our solar system. We would actually be considered a binary planet system except for the fact that the center of mass for our system is found inside Earth. If it was outside of our surface, we'd be a binary system.

Wow. I'm a nerd.

Ok - I'm dense - whaaaaattt???????

hi, Mom!

what he's saying is this:

picture 2 equal sized spheres orbiting each other. the center of mass is located at the middle of the space between them....the axis which they rotate around.

now, make one larger than the other. the center point moves toward the heavier sphere, because it's gravitational pull is stronger. At some point, that point is located inside the surface area of the larger sphere. That makes the large object a planet, and the other a moon. If that point was located 3 feet outside the surface of the earth, .....luna would be a sister planet, not a moon.

capice?

:devil:

Thanks Jimbo - got it! Now the real question is how that affects an airplane on the treadmill - huh smartypantz?

:lol2: