ABSTRACT
If something is conserved, it does not increase or decrease; it does not change; it does not vary. In other words, it remains invariant. So, we can give the following de nition to conservation:
Of course, this sounds almost identical to our de nition of symmetry. It is no accident. Emmy Noether, a woman mathematician, proved that symmetry principles lead directly to conservation laws. For instance, space translation symmetry leads to the conservation of momentum, and time translation symmetry leads to the conservation of energy. We will discuss both of these conservation laws in this chapter. Using these as examples, we will be able to see why conservation laws are so powerful.
