Give me these forces and the current state of a system—physicists’ shorthand for specifying the precise location and speed of all components of the system—and I can tell you the state of that system at any future point in time. This is the essence of determinism. The mass, location, and velocities of the planets as they travel in their orbits around the Sun fully determines where they will be in a thousand, a million, or a billion years from today, provided only that all the forces acting on them are properly accounted for.
