Conservation law

From Example Problems
Jump to navigation Jump to search

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

Exact laws

The following is a partial listing of conservation laws that have never been shown to be inexact.

Approximate conservation laws

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

Philosophy of conservation laws

Noether's theorem expresses the equivalence which exists between conservation laws and the invariance of physical laws with respect to certain transformations (typically called "symmetries") for systems which obey the Principle of least action and hence having a Lagrangian and a Hamiltonian (See Classical mechanics, Hamiltonian mechanics for details). For instance, time invariance implies that energy is conserved, translation invariance implies that momentum is conserved, and rotation invariance implies that angular momentum is conserved.

  • Things that remain unchanged, in the midst of change

The idea that some things remain unchanging throughout the evolution of the universe has been motivating philosophers and scientists alike for a long time.

In fact, quantities that are conserved, the invariants, seem to preserve what some would like to call some kind of a 'physical reality' and seem to have a more meaningful existence than many other physical quantities. These laws bring a great deal of simplicity into the structure of a physical theory. They are the ultimate basis for most solutions of the equations of physics.

See also


de:Erhaltungssatz el:Νόμος Διατήρησης fr:Loi de conservation id:Hukum kekekalan it:Leggi di conservazione hu:Megmaradási tétel nl:Behoudswet ja:保存則 pl:Prawa zachowania ru:Закон сохранения sk:Zákony zachovania sl:Ohranitveni zakon sv:Konserveringslag th:กฎการอนุรักษ์ uk:Закони збереження zh:守恒定律