David Peat

From Object to Process 59metry. Just as, in Einstein’s relativity, invariant laws underlie relativeappearances, so too symmetry principles govern the way the elementaryparticles transform and group into families.These symmetries are like mirrors so that, for example, a negativelycharged electron is reflected by the mirror of charge into a positivelycharged positron. Likewise a proton is reflected into an anti-proton.Some mirrors reflect left-hand spinning particles into right-handspinning ones, or reflect other properties such as hypercharge.Of course these are not physical mirrors but rather metaphors forthe way the equations that described elementary particles can be transformedand reflected one into the other. By transforming one particleinto another, according to these symmetry transformations, one buildsup whole families of elementary particles. In one sense these are thesame particle but reflected in different ways. For many physicists theunderlying laws of symmetry and transformation are more fundamentalthan the particles themselves.The quantum world is in a constant process of change and transformation.On the face of it, all possible processes and transformationscould take place, but nature’s symmetry principles place limits on arbitrarytransformation. Only those processes that do not violate certainvery fundamental symmetry principles are allowed in the naturalworld.Just as the ancient Greeks believed that fundamental forms andarchetypes lay deeper than supposed atoms, so too contemporaryphysicists contrast elementary particles with more basic symmetryprinciples.Grand Unified TheoriesFor 80 years physics has pursued the “Holy Grail” of a Grand UnifiedTheory, a single set of equations that is supposed to describe all that is.Like the Grail of Arthurian legend, it is occasionally glimpsed in the fardistance. Yet as scientists approach more closely it disappears, or turnsout to be made of tin and not gold.One of the first of these dreams was that of Einstein, who showedthat the force of gravity could be explained as the curvature of space-