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escape velocity

(Encyclopedia)escape velocity, the velocity a body must be given in order to escape the gravitational hold of some other larger body, e.g., the earth, moon, or sun. A body given less than the escape velocity will f...

mantle

(Encyclopedia)mantle, portion of the earth's interior lying beneath the crust and above the core. No direct observation of the mantle, or its upper boundary, has been made; its boundaries have been determined solel...

short waves

(Encyclopedia)short waves, radio waves whose frequencies range from about 3 to 25 megahertz (Mhz), corresponding roughly to the high-frequency band (see radio frequency). When they impinge on certain layers of the ...

apsis

(Encyclopedia)CE5 Apsis points, or apsides, in the earth's orbit: At perihelion the earth is closest to the sun and at aphelion it is farthest from the sun. apsis (pl. apsides), point in the orbit of a body whe...

Van Allen radiation belts

(Encyclopedia)CE5 Van Allen radiation belts: The solar wind, a stream of protons, electrons, and ions coming from the sun, gives the belts their asymmetrical shape. Van Allen radiation belts, belts of radiation...

Hindu music

(Encyclopedia)Hindu music. The music of India is entirely monodic. To Westerners it is the most accessible of all Asian musical cultures. Its tonal system divides the octave into 22 segments called srutis, not all ...

tropics

(Encyclopedia)tropics, also called tropical zone or torrid zone, all the land and water of the earth situated between the Tropic of Cancer at lat. 231⁄2°N and the Tropic of Capricorn at lat. 231⁄2°S. Every po...

globe

(Encyclopedia)globe, spherical map of the earth (terrestrial globe) or the sky (celestial globe). The terrestrial globe provides the only graphic representation of the areas of the earth without significant distort...

Hopkins, William

(Encyclopedia)Hopkins, William, 1793–1866, English geologist. Hopkins studied mathematics at Cambridge, and then supported himself as a private mathematics tutor. Many of England's best mathematicians and mathema...

equator

(Encyclopedia)equator, imaginary great circle around the earth, everywhere equidistant from the two geographical poles and forming the base line from which latitude is reckoned. The equator, which measures c.24,902...