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glacial periods

(Encyclopedia)glacial periods, times during which large portions of the earth's surface were covered with thick glacial ice sheets. In the Pleistocene epoch, in the Carboniferous and Permian periods of the Paleozoi...

Neptune, in astronomy

(Encyclopedia)Neptune, in astronomy, 8th planet from the sun at a mean distance of about 2.8 billion mi (4.5 billion km) with an orbit lying between those of Uranus and the dwarf planet Pluto; its period of revolut...

nitrogen

(Encyclopedia)nitrogen nīˈtrəjən [key], gaseous chemical element; symbol N; at. no. 7; interval in which at. wt. ranges 14.00643–14.00728; m.p. −209.86℃; b.p. −195.8℃; density 1.25 grams per liter at ...

corona, in astronomy

(Encyclopedia)corona, luminous envelope surrounding the sun, outside the chromosphere. Its density is less than one billionth that of the earth's atmosphere. The corona is visible only at the time of totality durin...

Becquerel

(Encyclopedia)Becquerel bĕkərĕlˈ [key], family of French physicists. Antoine César Becquerel, 1788–1878, was a pioneer in electrochemical science. He was professor of physics at the Muséum d'Histoire nature...

Cambridge, city, England

(Encyclopedia)Cambridge, city and district, Cambridgeshire, E central England, on the River Cam. The city, set in flat country, is most famous as the site of the Univ...

air lock

(Encyclopedia)air lock, compartment connecting two different environments, usually at different pressures, that enables personnel to transfer from one environment to the other. Space capsules have air locks to enab...

Ouro Prêto

(Encyclopedia)Ouro Prêto ōˈro͝o prāˈto͝o [key] [Port.,=black gold], city (1996 pop. 61,606), Minas Gerais state, E Brazil. Founded as Vila Rica in the gold rush near the end of the 17th cent., it became a pr...

Orbiting Geophysical Observatory

(Encyclopedia)Orbiting Geophysical Observatory (OGO), series of six orbiting observatories (see observatory, orbiting) launched between 1964 and 1969 by the National Aeronautics and Space Administration (NASA) to s...

global warming

(Encyclopedia)global warming, the gradual increase of the temperature of the earth's lower atmosphere as a result of the increase in greenhouse gases since the Industrial Revolution. Global warming and its effects,...