Shell theorem is a simplification stating that a spherical body affects external objects gravitationally as though all of its mass were concentrated at a point at its center.
The direction of Earth’s gravity toward the center of the Earth made some flat-Earthers to assume that we think gravity is caused by something in the center, and that our inability to go there “disproves” gravity. They are wrong. Earth’s gravity is the result of the entire mass of Earth. Using the center of the Earth is merely a simplification.
If we were to subdivide the Earth into many smaller parts, each of the constituent elements would exert gravitational acceleration to an object. Summing all the individual accelerations together will result in a larger gravitational acceleration that has the direction toward Earth’s center. It will give us the same result no matter how we subdivide the Earth.
Earth’s gravity is the sum of each of the accelerations exerted by all the masses that comprise the Earth. Earth’s gravity is not caused by a specific thing in the center of the Earth.
- Shell theorem – Wikipedia
- Verified solutions for the gravitational attraction to an oblate spheroid: Implications for planet mass and satellite orbits – Planetary and Space Science