The moon gravitates towards the earth, and by the force of gravity is continually drawn off from a rectilinear motion, and retained in its orbit.
It is solely the gravity of the earth that keeps the moon in orbit.
Law of universal gravitation- there is a power of gravity pertaining to all bodies, proportional to the several quantities of matter which they contain.
Henry Cavendish (1731-1810)
Hypotheses non fingo
Inside a homogeneous hollow spherical shell, a point mass experiences no net gravitational force
Next, if a point mass is placed outside the shell, it is attracted to the exact center as if all of its mass were concentrated at a point
Same for solid sphere of uniform density
Teachers' Domain: String Theory: Newton's Embarrassing Secret
Inertial vs. Gravitational mass
Inertial mass vs. weight – “The mass is known by the weight of each body, for it is proportional to the weight, as I have found by experiments on pendulums.”
Kepler’s 3rd Law
A Final Thought
“Nature and nature’s laws lay hid in night; God said ‘Let Newton be!’ and all was light.”