| − | '''Conservation law''' is a [[physical law]] that says that some physical quantity is conserved, which means ''never changes''. Examples of ''conserved quantities'' in physics are energy and momentum along 3 axies. So we have at least 4 independent conservation laws of momentum around axis 1, momentum along axis 2, momentum along axis 3, and energy, that is considered axis 4 by some autors or axis 0 by others. Usually mathematicians use diferent convention for numbering axes than physicists, who number axes starting from 0 for ''energy'', and so on for other axes (e.g. t, x, y, z where t denotes ''time'', and the rest relate to ''space''). | + | '''Conservation law''' is a [[physical law]] that says that some physical quantity is conserved, which means ''never changes''. Examples of ''conserved quantities'' in physics are: |