Comments from feedback form - "So it may be shrinking. Its ma..."

No, it doesn't imply that the Earth is hollow. What it implies is that if you dug a tunnel straight through the entire Earth (and used... I dunno... a forcefield to keep it open), at the very centre of the Earth you would be weightless, because all of the Earth's mass would be tugging on you equally in every direction.

Gopher65talk01:25, 27 August 2010