Columbia Encyclopedia

(Encyclopedia) radiochemistry, chemistry of radioactive substances (see radioactivity). Radioactive isotopes are very useful as tracers to study the mechanisms of complex organic reactions, since even minute amounts...

(Encyclopedia) Mars, in astronomy, 4th planet from the sun, with an orbit next in order beyond that of the earth. Mars has two natural satellites, discovered by Asaph Hall in 1877. The innermost of these, Phobos...

(Encyclopedia) carbon monoxide, chemical compound, CO, a colorless, odorless, tasteless, extremely poisonous gas that is less dense than air under ordinary conditions. It is very slightly soluble in water and burns ...

(Encyclopedia) Venus, in astronomy, 2d planet from the sun; it is often called the evening star or morning star and is brighter than any object in the sky except the sun and the moon. Because its orbit lies between ...

(Encyclopedia) sea level, the level of the sea, which serves as the datum used for measurement of land elevations and ocean depths. Theoretically, one would expect sea level to be a fixed and permanent horizontal su...

(Encyclopedia)  CE5 The three solid forms of pure carbon: In the diamond crystal each carbon atom is surrounded symmetrically by four other carbons (at each of the four corners of a tetrahedron). In the graphite c...

(Encyclopedia) Iwo Jima tō [key], volcanic island, c.8 sq mi (21 sq km), W Pacific, largest and most important of the Volcano Islands. Mt. Suribachi, 546 ft (166 m) high, on the south side of the island, is an exti...

(Encyclopedia) Agrigento ägrējānˈtō [key], Lat. Agrigentum, city, capital of Agrigento prov., S Sicily, Italy, on a hill above the Mediterranean Sea. It is an agricultural market an...

(Encyclopedia) keratin kĕrˈətĭn [key], any one of a class of fibrous protein molecules that serve as structural units for various living tissues. The keratins are the major protein components of hair, wool, nail...

(Encyclopedia) Archaebacteria ärˌkēbăktĭrˈēə [key], diverse group of bacteria (prokaryotes), sometimes called the archaea and considered a major group unto themselves. Archaebacteria are contrasted with the ...