Conservation laws are physical laws that postulate that during the temporal evolution of an isolated system, certain magnitudes have a constant value. Since the entire universe constitutes an isolated system, various conservation laws can be applied to it.

The most important conservation laws in classical physics are:

In classical mechanics, the conservation of a physical magnitude requires, by virtue of Noether's theorem, that a Lagrangian symmetry exists, or equivalently that the Poisson bracket of said magnitude cancels out (as long as the Hamiltonian "Hamiltonian (classical mechanics)") does not depend on time).

In quantum mechanics and nuclear physics, these others are added to the above:

In conservative systems it can be proven that a magnitude  is conserved if and only if it commutes with the Hamiltonian H:.

In addition to the above, in both classical mechanics (CM) and quantum mechanics (QM), approximate conservation laws are used in certain contexts, that is, they are not universal for all processes, although a good part of the known physical processes are:

In physical theories that admit a Lagrangian formalism, it can be proven that conservation laws are linked to symmetries of the physical system. More specifically, Noether's theorem for classical theories establishes that if there is an abstract Lagrangian symmetry associated with a uniparametric group, there is a magnitude that remains constant throughout the evolution of the system, that is, there is a conservation law associated with that symmetry.

Furthermore, the functionally observed magnitude can be constructed from the conjugate moments of the Lagrangian and the element of the Lie algebra of the uniparametric symmetry group.