Solar System Mechanics

The gravitational dynamics and composition of our local planetary neighborhood.

Kepler's Laws of Planetary Motion

• First Law (Law of Ellipses): The orbit of a planet is an ellipse with the Sun at one of the two foci.
• Second Law (Law of Equal Areas): A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time. (Planets move faster at perihelion than at aphelion).
• Third Law (Law of Harmonies): The square of a planet's orbital period ($T$) is proportional to the cube of the semi-major axis of its orbit ($a$). $T^2 \propto a^3$.