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moon

(Encyclopedia)CE5 The moon: Near side CE5 The moon: Far side moon, natural satellite of a planet (see satellite, natural) or dwarf planet, in particular, the single natural satellite of the earth. It is no...

astrophysics

(Encyclopedia)astrophysics, application of the theories and methods of physics to the study of stellar structure, stellar evolution, the origin of the solar system, and related problems of cosmology. The distinctio...

rare earths

(Encyclopedia)rare earths, in chemistry, oxides of the rare-earth metals. They were once thought to be elements themselves. They are widely distributed in the earth's crust and are fairly abundant, although they we...

Cannon, Annie Jump

(Encyclopedia)Cannon, Annie Jump, 1863–1941, American astronomer, b. Dover, Del. In 1897 she became an assistant in the Harvard College Observatory, where (1911–38) she was astronomer and curator of astronomica...

pothole

(Encyclopedia)pothole, in geology, cylindrical pit formed in the rocky channel of a turbulent stream. It is formed and enlarged by the abrading action of pebbles and cobbles that are carried by eddies, or circular ...

Eaton, Amos

(Encyclopedia)Eaton, Amos ēˈtən [key], 1776–1842, American naturalist, b. Chatham, N.Y., grad. Williams College, 1799. After practicing law for a time, he conducted pioneer geological surveys in Albany and Ren...

climate

(Encyclopedia)climate, average condition of the atmosphere near the earth's surface over a long period of time, taking into account temperature, precipitation (see rain), humidity, wind, barometric pressure, and ot...

tide

(Encyclopedia)tide, alternate and regular rise and fall of sea level in oceans and other large bodies of water. These changes are caused by the gravitational attraction of the moon and, to a lesser extent, of the s...

meteor

(Encyclopedia)meteor, appearance of a small particle flying through space that interacts with the earth's upper atmosphere. While still outside the atmosphere, the particle is known as a meteoroid. Countless meteor...

population I and II

(Encyclopedia)population I and II, in astronomy: see stellar populations. ...