Columbia Encyclopedia

Search results

102 results found

synthetic elements

(Encyclopedia)synthetic elements, in chemistry, radioactive elements that were not discovered occurring in nature but as artificially produced isotopes. They are technetium (at. no. 43), which was the first element...

helium

(Encyclopedia)helium hēˈlēəm [key], gaseous chemical element; symbol He; at. no. 2; at. wt. 4.0026; m.p. below −272℃ at 26 atmospheres pressure; b.p. −268.934℃ at 1 atmosphere pressure; density 0.1785 g...

neutrino

(Encyclopedia)neutrino no͞otrēˈnō [key] [Ital.,=little neutral (particle)], elementary particle with no electric charge and a very small mass emitted during the decay of certain other particles. The neutrino wa...

nucleosynthesis

(Encyclopedia)nucleosynthesis or nucleogenesis, in astronomy, production of all the chemical elements from the simplest element, hydrogen, by thermonuclear reactions within stars, supernovas, and in the big bang at...

stellar evolution

(Encyclopedia)CE5 The above Hertzsprung-Russell (H-R) diagram shows the track of stellar evolution for a typical star. After spending much of its life evolving toward or along the main sequence, the star becomes...

chivalry

(Encyclopedia)chivalry shĭvˈəlrē [key], system of ethical ideals that arose from feudalism and had its highest development in the 12th and 13th cent. Chivalric ethics originated chiefly in France and Spain and ...

fuel

(Encyclopedia)fuel, material that can be burned or otherwise consumed to produce heat. The common fuels used in industry, transportation, and the home are burned in air. The carbon and hydrogen in fuel rapidly comb...

Visigoths

(Encyclopedia)Visigoths (West Goths), division of the Goths, one of the most important groups of Germans. Having settled in the region W of the Black Sea in the 3d cent. a.d., the Goths soon split into two division...

Greek religion

(Encyclopedia)Greek religion, religious beliefs and practices of the ancient inhabitants of the region of Greece. The civil strife that followed the classical period (from c.500 b.c.) placed the old gods on trial...

water

(Encyclopedia)CE5 A. Water molecule (black circles represent valence-shell electrons) B. Structure of ice: Each oxygen atom (white circles) is bonded to four other oxygen atoms by hydrogen bonds, the hydrogen at...