Asked by: Larry Fitzgerald, London
Symmetry is something we usually think of as an aesthetic rather than a scientific concept – repeated patterns of tiles, for example. But in their quest to discover the basic laws of the Universe, physicists have found symmetry useful. That’s because if something possesses symmetry, it means it can be altered in certain ways, and yet remain unchanged. For example, if a square is flipped over or rotated by 90°, it looks as if nothing has changed.
Physicists believe that the laws of nature should be similarly ‘invariant’, applying equally well regardless of where in space and time they’re used. Around a century ago, the German mathematician Emmy Noether showed that there’s a deep connection between such symmetries and key concepts in physics like the laws of the conservation of energy and momentum. This has proved particularly useful to theorists trying to make sense of the subatomic world.