system
Given the following post, respond as if you're commenting on Reddit:
human
What would happen if you held a plumb bob/line directly at earth's center?
gpt
There's no net force of gravity at the center of the earth, so it would float freely, just as it would in space. More generally, for a spherically symmetric mass (which the earth is *very* nearly), the only force you'll feel at any location is the force of all the mass closer than you to the center. All of the mass farther than you from the center will cancel out, producing no net force. As you get closer to the center, the total mass closer than you decreases, so the net force decreases as well, until it reaches zero at the very center.