The Encyclopedia of Physics

Welcome to physics, the science of relativity and gravitation, matter and energy, quarks and quanta, lasers and masers, and many other intriguing scientific areas.
Since the appearance of the second edition many new developments have become impor- tant, and this edition has been expanded to include as many as possible of these new ideas without neglecting older, but still valid, concepts.
In a major effort to strengthen coverage of the rapidly moving and vitally significant field of particle physics, four new articles were added: Gauge Theories, Quantum Chromo- dynamics, Electroweak Theory, and Grand Unified Theories. In addition, many revisions were made in second edition articles in this field, including Elementary Particles, Weak Interactions, Strong Interactions, Parity, Current Algebra, and Quantum Theory.
Similarly, to increase emphasis on the important role of physics in medicine and biol- ogy, articles were added on Molecular Biology and Biomedical Instrumentation, and second edition entries on Biophysics, Medical Physics, Health Physics, and Bionics were brought up-to-date. Many other fields of physics, such as optics and energy storage, have received additional emphasis.