Is Supersymmet Layer of Structur by MICHAEL DINE S

16 WINTER 1999 YMMETRY IS A FAMILIAR CONCEPT in art and design. In daily conversation, it usually refers to transformations in space, such as rotations of an object about an axis. In science, the word has a more general meaning and a profound significance, because its role in understanding the laws of Nature has been one of the dominant themes in physics. It figured heavily, for example, in much of Albert Einstein’s work. He realized that the laws of electricity and magnetism, the great triumph of nineteenth century physics, had a puzzling symmetry. Postulating that it was common to all of the laws of Nature led him to special relativity, in which space and time are not absolute and fixed. Reconciling Newton’s laws of gravity with this symmetry principle led him to develop the theory of general relativity. Symmetries were also crucial to the post-war development of particle physics. By the mid-1960s, huge numbers of particles had been discovered with accelerators. Murray GellMann and Yuval Ne’eman brought order to this chaos by searching for symmetries and discovering that they provided a periodic table for the elementary particles which then led to the idea of quarks. Symmetries also can determine the basic laws themselves. Electricity and magnetism can be understood as a consequence of a symmetry called gauge invariance. In 1954, Chen Ning Yang and Robert Mills generalized the symmetry of electromagnetism to larger symmetries. While their discovery was originally purely theoretical, within 25 years such symmetries were experimentally established as the basis for the Standard Model, the reigning theory of subatomic particles and their interactions. In the early 1970s a new type of hypothetical symmetry, “supersymmetry,” was discovered. To understand it, one needs to recall a rule learned in chemistry. In building the Periodic Table, no two electrons can occupy the same state. Is Supersymmet Layer of Structur