Conservation law (physics)

In physics, a conservation law states that a particular measurable property of an isolated physical system does not change as the system evolves.

One particularly important physical result concerning laws of conservation is Noether's theorem, which states that there is a one-to-one correspondence between laws of conservation and differentiable symmetries of physical systems. For example, the conservation of energy follows from the time-invariance of physical systems, and the fact that physical systems behave the same regardless of how they are oriented in space gives rise to the conservation of angular momentum.

Exact laws

A partial listing of physical laws of conservation due to symmetry that are said to be exact laws, or more precisely have never been [proven to be] violated:
Conservation Law Respective Noether symmetry invariance Number of dimensions
Conservation of mass-energy Time invariance Lorentz invariance symmetry 1 translation about time axis
Conservation of linear momentum Galilean invariance 3 translation about x,y,z position
Conservation of angular momentum Rotation invariance 3 rotation about x,y,z axes
CPT symmetry (combining charge, parity and time conjugation) Lorentz invariance 1+1+1 (charge inversion q→-q) + (position inversion r→-r) + (time inversion t→-t)
Conservation of electric charge Gauge invariance 1⊗4 scalar field (1D) in 4D spacetime (x,y,z + time evolution)
Conservation of color charge SU(3) Gauge invariance 3 r,g,b
Conservation of weak isospin SU(2)L Gauge invariance 1 weak charge
Conservation of probability Probability invariance 1⊗4 total probability always=1 in whole x,y,z space, during time evolution

Approximate laws

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

See also

References

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

External links

  • Conservation Laws — an online textbook
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.