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

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

## References

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* 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

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* Conservation Laws — an online textbook

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