Isaac Newton’s Theory of Gravitation proved that gravity behaves as a rational function, which can be modeled as:
g = μ/r^2
Where g is the strength of gravity in m/s^2, μ is the “standard gravitational parameter,” which is
3.986*10^14 for Earth, and r is the radial distance from the center of the planet measured in
meters. Earth has a radius of 6378 km.