Why, according to the laws of gravity, does the moon technically not orbit the Earth?

achernar

Because the moon actually orbits around the centre of mass of the Earth-Moon system, which is about 4,700 km from the Earth's centre (approx. 3/4ths of the way to the surface). Mar 19 05, 1:31 AM

peasypod

Very good......And the name of this place is? Mar 19 05, 8:01 AM

achernar

Barycenter...or is that too general a term? Mar 19 05, 8:35 AM

Baloo55th

And what makes things worse is that the Earth and the Sun both orbit round their centre of mass, but as the Earth is already doing this with the Moon the centre of mass for the Earth-Sun pair is sort of oscillating. And then, of course, the Sun does the same with Marcury, Venus and so on. Of course, with the Sun as a partner, the centre of mass is going to be not too far from the actual centre of mass of the Sun itself, but it does make calculations of orbits rather tricky. Much as I regard astrology as a load of drivel, it is interesting that the planets DO have influence at a distance. Not that that influence will cause you to meet a tall dark handsome stranger (unless you're driven to do some astronomical observations in Ethiopia, when you are bound to meet quite a few tall dark handsome strangers - not to mention quite a few short fat ugly ones...). Mar 19 05, 11:00 AM

peasypod

Yeah, the planets do have influence at a distance....it's called, cough, gravity. Nice one with Barycenter by the way. Golden Banana comin' at ya. All this talk of tall dark and handsomes dudes makes me compelled to read my horoscope. And waddya know? Apparently I'm gonna win the lottery, find peace within myself and find the man of my dreams. Well, 2 out of 3 ain't bad I guess. * Mar 19 05, 4:07 PM