Laws of thermodynamics
Main article: Second law of thermodynamics
The entropy of an isolated system not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium.
Conservation laws (physics)
Principles which state that the total values of specified quantities remain constant in time for an isolated system. Conservation laws occupy enormously important positions both at the foundations of physics and in its applications.
In the [color=#cc0000]natural sciences [/color]an isolated system, as contrasted with a open system, [color=#cc0000]is a physical system that does not interact with its surroundings[/color]. It obeys a number of conservation laws: its total energy and mass stay constant. They cannot enter or exit, but can only move around inside. An example is in the study of spacetime, where it is assumed that asymptotically flat spacetimes exist.
Truly isolated physical systems do not exist in reality..