Columbia Encyclopedia

Search results

500 results found

avalanche

(Encyclopedia)avalanche, rapidly descending large mass of snow, ice, soil, rock, or mixtures of these materials, sliding or falling in response to the force of gravity. Avalanches, which are natural forms of erosio...

Natta, Giulio

(Encyclopedia)Natta, Giulio, 1903–79, Italian chemist, Ph.D. the Polytechnic of Milan, 1924. Natta held brief appointments at several academic institutions, including the Univ. of Pavia (1933–35), the Univ. of ...

Carothers, Wallace Hume

(Encyclopedia)Carothers, Wallace Hume kərŭᵺˈərz [key], 1896–1937, American chemist, b. Burlington, Iowa. He received his doctorate at the Univ. of Illinois in 1924, then taught organic chemistry there and a...

tarpon

(Encyclopedia)tarpon tärˈpŏn [key], common name for members of the family Megalopidae, or Elopidae, large game fish of the warm seas of the Western Hemisphere, ranging occasionally from Long Island to Brazil and...

capybara

(Encyclopedia)capybara kăpĭbârˈə [key], mammal of Central and much of South America. It is the largest living member of the order Rodentia (the rodents) reaching a length of 4 ft (120 cm) and a weight of 75 to...

chain reaction

(Encyclopedia)CE5 Chain reaction: A neutron (n) strikes the uranium nucleus (U-235), causing it to split into fission products A and B and release two neutrons. These neutrons can in turn cause further fissions....

nuclear weapons

(Encyclopedia)nuclear weapons, weapons of mass destruction powered by atomic, rather than chemical, processes. Nuclear weapons produce large explosions and hazardous radioactive byproducts by means of either nuclea...

electron-volt

(Encyclopedia)electron-volt, abbr. eV, unit of energy used in atomic and nuclear physics; 1 electron-volt is the energy transferred in moving a unit charge, positive or negative and equal to that charge on the elec...

alkali metals

(Encyclopedia)alkali metals, metals found in Group 1 of the periodic table. Compared to other metals they are soft and have low melting points and densities. Alkali metals are powerful reducing agents and form univ...

alkaline-earth metals

(Encyclopedia)alkaline-earth metals, metals constituting Group 2 of the periodic table. Generally, they are softer than most other metals, react readily with water (especially when heated), and are powerful reducin...