Thread:Comments:Scientists say the moon is slowly shrinking/Comments from feedback form - "So it may be shrinking. Its ma..."/reply (4)

It's a well established fact that gravity increases with density. In other words, if the earth was smaller in diameter, given the same mass (i.e., higher density) its gravitational field would be higher (assuming the field is measured at a fixed distance from its center). If you take this to the extreme, by compressing the earth to 1 mm in diameter, it's gravitational field would be phenomenally high. The earth's mass may even be a black hole at that size.

Mass always has density, even if it's just a bunch of hydrogen atoms loosely dispersed in space. When those hydrogen atoms condense into a star, that mass is now at a much higher density and consequently produces a much stronger gravitational field. If the star eventually collapses into a black hole, you wouldn't want to be anywhere in that vicinity of space. Time to dust off the physics and astronomy textbooks. The strength of a gravitation field is directly proportional to the increase in density of a given mass as measured from a fixed point to the center of that mass (and, outside that mass - not measured from somewhere inside the mass).