Mathematical modeling of evolving systems.

System evolving according to rules.

In astrophysics, dynamical friction or Chandrasekhar friction, sometimes called gravitational drag, is loss of momentum and kinetic energy of moving bodies through gravitational interactions with surrounding matter in space.

In astronomy, the distance to a visual binary star may be estimated from the masses of its two components, the angular size of their orbit, and the period of their orbit about one another.

Time scale for Earth's motion.

Electricity generated through mechanical motion.

Study of systems and change.

Theory linking heat to motion.