Conservation law

For the legal aspects of environmental conservation, see conservation movement.

In physics, a conservation law states that a particular measurable property of an isolated physical system does not change as the system evolves. Any particular conservation law is a mathematical identity to certain symmetry of a physical system. A partial listing of conservation laws that are said to be exact laws, or more precisely have never been shown to be violated:

• Conservation of energy
• Conservation of linear momentum
• Conservation of angular momentum
• Conservation of electric charge
• Conservation of color charge
• Conservation of weak isospin
• Conservation of probability

There are also approximate conservation laws. These are approximately true in particular situations, such as low speeds, short time scales, or certain interactions.

• Conservation of mass (applies for low speeds)
• Conservation of baryon number (See chiral anomaly)
• Conservation of lepton number (In the Standard Model)
• Conservation of flavor (violated by the weak interaction)
• Conservation of parity
• CP symmetry

See also

• Continuity equation
• Philosophy of physics
• Noether's theorem

References

• Stenger, Victor J., 2000. Timeless Reality: Symmetry, Simplicity, and Multiple Universes. Prometheus Books. Chpt. 12 is a gentle introduction to symmetry, invariance, and conservation laws.

External links

• Conservation Laws — an online textbookar:قوانين الانحفاظ