noether's theorem has become a fundamental tool of modern theoretical physics, both because of the insight it gives into conservation laws, and also, as a practical calculation tool. her theorem allows researchers to determine the conserved quantities from the observed symmetries of a physical system. conversely, it facilitates the description of a physical system based on classes of hypothetical physical laws. for illustration, suppose that a new physical phenomenon is discovered. noether's theorem provides a test for theoretical models of the phenomenon:if the theory has a continuous symmetry, then noether's theorem guarantees that the theory has a conserved quantity, and for the theory to be correct, this conservation must be observable in experiments.