Columbia Encyclopedia

Search results

274 results found

Weiss, Rainer

(Encyclopedia)Weiss, Rainer, 1932–, American physicist, b. Berlin, Germany, Ph.D. Massachusetts Institute of Technology, 1962. Weiss has been on the faculty of the Massachusetts Institute of Technology since 1964...

second

(Encyclopedia)second, abbr. sec or s, fundamental unit of time in all systems of measurement. In practical terms, the second is 1/60 of a minute, 1/3,600 of an hour, or 1/86,400 of a day. Since the length of the da...

physical fitness

(Encyclopedia)physical fitness, combined good health and physical development. The object of any program of physical fitness is to maximize an individual's health, strength, endurance, and skill relative to age, se...

psoriasis

(Encyclopedia)psoriasis sôrīˈəsĭs [key], occasionally acute but usually chronic and recurrent inflammation of the skin. The exact cause is unknown, but the disease appears to be an inherited, possibly autoimmu...

radioactive waste

(Encyclopedia)radioactive waste, material containing the unusable radioactive byproducts of the scientific, military, and industrial applications of nuclear energy. Since its radioactivity presents a serious health...

polycythemia

(Encyclopedia)polycythemia pŏlˌēsīthēˈmēə [key], condition characterized by an increase in the production of red blood cells, or erythrocytes, in the blood. Primary polycythemia, also called erythremia, or ...

glacial periods

(Encyclopedia)glacial periods, times during which large portions of the earth's surface were covered with thick glacial ice sheets. In the Pleistocene epoch, in the Carboniferous and Permian periods of the Paleozoi...

laser

(Encyclopedia)CE5 Ordinary light sources produce incoherent light, while a laser produces a beam of coherent light. laser [acronym for light amplification by stimulated emission of radiation], device for the cr...

breast cancer

(Encyclopedia)breast cancer, cancer that originates in the breast. Breast cancer is the second leading cause of cancer death in women (following lung cancer). Although the vast majority of the cases occur in women,...

fallout

(Encyclopedia)fallout, minute particles of radioactive material produced by nuclear explosions (see atomic bomb; hydrogen bomb; Chernobyl) or by discharge from nuclear-power or atomic installations and scattered th...