Tidal force

Tidal force is a secondary effect of the force of gravity. When a large body is acted on by the gravity of another body, the difference in the gravitational force can vary considerably between the near side and the far side. This tends to distort the large body; supposing it were initially a circle, the tidal force will tend to distort it into an ellipsoid, with two bulges, pointing towards and away from the other body.

Tidal force follows an inverse cube law.

Tidal forces are responsible for the oceanic tides, where the large body is the water in Earth's oceans, and the attracting bodies are the Moon and the Sun.