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diatomaceous earth

(Encyclopedia)diatomaceous earth: see diatom.

earth pig

(Encyclopedia)earth pig: see aardvark.

black earth

(Encyclopedia)black earth: see chernozem.

earth goddess

(Encyclopedia)earth goddess: see Great Mother Goddess. ...

wave, in the earth sciences

(Encyclopedia)CE5 A. Diagram of wave: Wave travels one wavelength during one period B. Diagram of wave: Phase relationships wave, in oceanography, an oscillating movement up and down, of a body of water caused ...

radio astronomy

(Encyclopedia)radio astronomy, study of celestial bodies by means of the electromagnetic radio frequency waves they emit and absorb naturally. Radio waves also come from outside the Milky Way. These extragalact...

gamma-ray astronomy

(Encyclopedia)gamma-ray astronomy, study of astronomical objects by analysis of the most energetic electromagnetic radiation they emit. Gamma rays are shorter in wavelength and hence more energetic than X rays (see...

Playfair, John

(Encyclopedia)Playfair, John, 1748–1819, Scottish mathematician, physicist, and geologist. He was educated at St. Andrews and Edinburgh and taught first mathematics and then physics and astronomy at the latter un...

rare-earth metals

(Encyclopedia)rare-earth metals, in chemistry, group of metals including those of the lanthanide series and actinide series and usually yttrium, sometimes scandium and thorium, and rarely zirconium. Promethium, whi...

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...