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sidereal period
(Encyclopedia)sidereal period, in astronomy, length of time a body takes to complete an orbit relative to the fixed stars. See sidereal time. ...Silurian period
(Encyclopedia)Silurian period sĭlo͝orˈēən, sī– [key] [from the Silures, ancient tribe of S Wales, where the period was first studied; named by the British geologist R. I. Murchison], third period of the Pal...Paleolithic period
(Encyclopedia)Paleolithic period pāˌlēəlĭthˈĭk, –lēō–, pălˌ– [key] or Old Stone Age, the earliest period of human development and the longest phase of mankind's history. It is approximately coexten...Quaternary period
(Encyclopedia)Quaternary period kwətûrˈnərē [key], younger of the two geologic periods of the Cenozoic era of geologic time (see Geologic Timescale, tablegeologic timescale, table) from 2 millon years ago to t...Neolithic period
(Encyclopedia)Neolithic period or New Stone Age. The term neolithic is used, especially in archaeology and anthropology, to designate a stage of cultural evolution or technological development characterized by the ...synodic period
(Encyclopedia)synodic period sĭnŏdˈĭk [key], in astronomy, length of time during which a body in the solar system makes one orbit of the sun relative to the earth, i.e., returns to the same elongation. Because ...Marsh, Othniel Charles
(Encyclopedia)Marsh, Othniel Charles, 1831–99, American paleontologist, b. Lockport, N.Y., grad. Yale, 1860. He studied abroad, and from 1866 served at Yale as the first professor of paleontology and as curator o...amber
(Encyclopedia)amber, fossilized tree resin. Amber can vary in color from yellow to red to green and blue. The best commercial amber is transparent, but some varieties are cloudy. To be called amber, the resin must ...reptile
(Encyclopedia)reptile, name for the dry-skinned, usually scaly, cold-blooded vertebrates (see Chordata) of the order Reptilia. Reptiles are found in a variety of habitats throughout the warm and temperate regions (...cuesta
(Encyclopedia)cuesta kwĕsˈtə [key], asymmetric ridge characterized by a short, steep escarpment on one side, and a long, gentle slope on the other. The steep side exposes the edge of erosion-resistant rock layer...Browse by Subject
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