Editing Conservation law (section)

==Conservation laws as fundamental laws of nature==
Conservation laws are fundamental to our understanding of the physical world, in that they describe which processes can or cannot occur in nature.  For example, the conservation law of energy states that the total quantity of energy in an isolated system does not change, though it may change form.  In general, the total quantity of the property governed by that law remains unchanged during physical processes.  With respect to classical physics, conservation laws include conservation of energy, mass (or matter), linear momentum, angular momentum, and electric charge.  With respect to particle physics, particles cannot be created or destroyed except in pairs, where one is ordinary and the other is an antiparticle.  With respect to symmetries and invariance principles, three special conservation laws have been described, associated with inversion or reversal of space, time, and charge.

Conservation laws are considered to be fundamental [[scientific law|laws]] of nature, with broad application in physics, as well as in other fields such as chemistry, biology, geology, and engineering.

Most conservation laws are exact, or absolute, in the sense that they apply to all possible processes.  Some conservation laws are partial, in that they hold for some processes but not for others.

One particularly important result concerning conservation laws is [[Noether's theorem]], which states that there is a one-to-one correspondence between each one of them and a differentiable [[symmetry (physics)|symmetry]] of the [[Universe]]. For example, the conservation of energy follows from the [[time-translation symmetry|uniformity of time]] and the [[conservation of angular momentum]] arises from the [[isotropy]] of [[space]],<ref name="Ibragimov"/><ref>Kosmann-Schwarzbach, Y. in The Philosophy and Physics of Noether’s Theorems: A Centenary Volume     4-24 (Cambridge University Press, 2022).</ref><ref>Rao, A. K., Tripathi, A., Chauhan, B. & Malik, R. P. Noether Theorem and Nilpotency Property of the (Anti-)BRST Charges in the BRST Formalism: A Brief Review. Universe 8 (2022). https://doi.org/10.3390/universe8110566</ref> i.e. because there is no preferred direction of space. Notably, there is no conservation law associated with [[Time reversibility |time-reversal]], although more complex conservation laws combining time-reversal with [[CPT invariance|other symmetries]] are known.