Thanks, Will, for a good read. The fun part as I see it is gravity inside the planet.

In the center of our planet, we do not have any gravity. Right in the middle, all gravitational forces established an equilibrium and so there is net-zero gravity.

Moving one mile into the planet, most of the planet will still be tugging on you, but a little bit will tug in the opposite direction. The closer to the center, the more the tug will become a fully balanced tug.

It also shows that gravity is a collective force and not a specific force.

In the exact center of the planet we find matter, and that matter will still have the other forces associated with it. But not gravity; it is fully in balance; it's net-zero.

Part of the Big Whisper model.