How it works: Free fall near Earth’s surface (g = 9.81 m/s², ignoring air resistance): distance = ½gt² and velocity = gt. Between any two masses, Newton’s law of universal gravitation gives F = G·m₁·m₂ ÷ r² with G = 6.674×10⁻¹¹. That force is real but tiny between everyday objects — about 7×10⁻⁸ N between two people 2 m apart — which is why only planet-sized masses make it noticeable.