Gravitation is one of the four fundamental forces, governed by Newton's law F = $\frac{GMm}{r}$^2. The gravitational constant G = 6.674 x 10^{-11} N*$m^2$/$kg^2$ is universal, and the force is always attractive.

Gravitational field (E = $\frac{GM}{r}$^2) and potential (V = -GM/r) describe the effect of a mass on surrounding space. The field is a vector; potential is a scalar (always negative). At Earth's surface, g = 9.8 m/$s^2$.

g varies with height (inverse-square: $g_h$ = gR^$\frac{2}{R+h}$^2) and depth (linear: $g_d$ = g(1-d/R)). The approximation $g_h$ ≈ g(1-2h/R) works only for h << R.

Escape velocity ($v_e$ = sqrt(2gR) = 11.2 km/s) is independent of mass and direction. Orbital velocity ($v_o$ = sqrt(gR) near surface) relates by $v_e$ = sqrt(2)*$v_o$.

Kepler's laws govern planetary motion: elliptical orbits (1st), equal areas in equal times (2nd, angular momentum conservation), and $T^2$ proportional to $r^3$ (3rd). Satellite energetics: KE = $\frac{GMm}{2r}$, PE = -GMm/r, Total E = -$\frac{GMm}{2r}$.