move 8000mls out into space (the same distance as the earth's surface to the core), doubling the distance from the centre, and you don't feel .5g but .25g double the distance, quarter the force. gravity only diminishes with distance, not disappears. if it did, the universe wouldn't hold together. if the only things in the universe were you, and a hydrogen atom at the other end of the universe, after a (very very very!) long time you'd both be stuck together, through gravitational attraction. scientists have developed instruments so precise, they can detect the moon's gravitational pull on a glass of water. and while the moon may be massive, you have to remember that the glass of water is also pulling on the moon. negligable though it may be, it IS there, so a 60km lump of rock floating around neptune may seem like nothing, it IS having some kind of influence, albeit a miniscule one.
Edited by shrooma, 06 May 2013 - 11:13 PM.