Focused on pure physics, including entries on concepts, terms, effects, laws, principles, theories, experiments, observations, people, institutions, organizations, issues, laboratories, and other subjects. discuss interdisciplinary subjects, such as applied physics, astrophysics, biophysics, chemical physics, geophysics, and medical physics. Biographical entries present personal profiles of important physicists, past and present, and list their accomplishments. Details about their achievements are presented in separate, cross-referenced entries. While the emphasis is on the present state of physics, the science's historical background and development are explained, as appropriate, to give perspective on current issues in physics.