Conservation law

In physics, a conservation law states that a particular physical quantity cannot change during the evolution? of an isolated physical system. The following are conservation laws that have never been shown inexact:

• conservation of energy (encompasses mass)
• conservation of momentum
• conservation of angular momentum
• conservation of electric charge
• conservation of color-charge?
• conservation of [quark number]?
• conservation of [lepton number]?

There is an important connection between conservation laws and the invariance? of physical laws with respect to certain transformations and. For instance, in can be shown that [time invariance]? implies that energy is conserved, that [translational invariance]? implies that momentum is conserved and that [rotational invariance]? implies that angular momentum is conserved.

Some [approximate conservation law]?s hold in many circumstances, but exceptions to them have been observed.