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rock

(Encyclopedia)rock, aggregation of solid matter composed of one or more of the minerals forming the earth's crust. The scientific study of rocks is called petrology. Rocks are commonly divided, according to their o...

gravitation

(Encyclopedia)gravitation, the attractive force existing between any two particles of matter. The term gravitygravity is commonly used synonymously with gravitation, but in correct usage a definite distinction is...

endocytosis

(Encyclopedia)endocytosis ĕnˌdōsītōˈsəs [key], in biology, process by which substances are taken into the cell. When the cell membrane comes into contact with a suitable food, a portion of the cell cytoplasm...

induction, in electricity and magnetism

(Encyclopedia)induction, in electricity and magnetism, common name for three distinct phenomena. Electromagnetic induction is the production of an electromotive force (emf) in a conductor as a result of a changing ...

cosmology

(Encyclopedia)cosmology, area of science that aims at a comprehensive theory of the structure and evolution of the entire physical universe. The earliest pre-Ptolemaic theories assumed that the earth was the cent...

magnetic resonance

(Encyclopedia)magnetic resonance, in physics and chemistry, phenomenon produced by simultaneously applying a steady magnetic field and electromagnetic radiation (usually radio waves) to a sample of atoms and then a...

sand

(Encyclopedia)sand, rock material occurring in the form of loose, rounded or angular grains, varying in size from .06 mm to 2 mm in diameter, the particles being smaller than those of gravel and larger than those o...

teeth

(Encyclopedia)CE5 A. Upper and lower teeth of an adult B. Cross section of a molar teeth, hard, calcified structures embedded in the bone of the jaws of vertebrates that perform the primary function of masticat...

tunicate

(Encyclopedia)tunicate to͞oˈnəkĭt [key], marine animal of the phylum Chordata, which also includes the vertebrates. The adult form of most tunicates (also called urochordates) shows no resemblance to vertebrate...

ozone layer

(Encyclopedia)ozone layer or ozonosphere, region of the stratosphere containing relatively high concentrations of ozone, located at altitudes of 12–30 mi (19–48 km) above the earth's surface. Ozone in the ozone...