Columbia Encyclopedia

(Encyclopedia) Toltec tŏlˈtĕk [key], ancient civilization of Mexico. The name in Nahuatl means “master builders.” The Toltec formed a warrior aristocracy that gained ascendancy in the Valley of Mexico c.a.d. ...

(Encyclopedia) universe, totality of matter and energy in existence. The study of the origin of the universe, or cosmos, is known as cosmogony, and that of its structure and evolution, cosmology. The age of the univ...

(Encyclopedia) Egyptian architecture, the architecture of the ancient Egyptians, formulated prior to 3000 b.c. and lasting through the Ptolemaic period (323–30 b.c.). Egyptian architectural development parallel...

(Encyclopedia) Galileo (Galileo Galilei) gălˌĭlēˈō; gälēlĕˈō gälēlĕˈē [key], 1564–1642, great Italian astronomer, mathematician, and physicist. By his persistent investigation of natural laws he la...

(Encyclopedia) migration of animals, movements of animals in large numbers from one place to another. In modern usage the term is usually restricted to regular, periodic movements of populations away from and back t...

(Encyclopedia) Pawnee pônēˈ [key], Native North Americans whose language belongs to the Caddoan branch of the Hokan-Siouan linguistic stock (see Native American languages). At one time the Pawnee lived in what is...

(Encyclopedia) neutrino astronomy, study of stars by means of their emission of neutrinos, fundamental particles that result from nuclear reactions and are emitted by stars along with light. Approximately 100 billio...

(Encyclopedia) Pachacamac päˌchäkämäkˈ [key], ruins of a walled Native American settlement, Peru, about 25 mi (40 km) SE of Lima in the Lurin Valley. This site, which contains a number of pyramids, was conside...

(Encyclopedia) pigeon, common name for members of the large family Columbidae, land birds, cosmopolitan in temperate and tropical regions, characterized by stout bodies, short necks, small heads, and thick, heavy pl...

(Encyclopedia)  CE5 Centripetal and centrifugal forces: When a ball is swung in a circle at the end of a string, centripetal and centrifugal forces act as shown above. centripetal force and centrifugal force, act...