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Theodosius II

(Encyclopedia)Theodosius II, 401–50, Roman emperor of the East (408–50), son and successor of Arcadius. He preferred the study of theology and astronomy to public affairs, which he left to the guidance of his s...

solstice

(Encyclopedia)solstice sŏlˈstĭs [key] [Lat.,=sun stands still], in astronomy, either of the two points on the ecliptic that lie midway between the equinoxes (separated from them by an angular distance of 90°). ...

aerial and satellite photography

(Encyclopedia)aerial and satellite photography, technology and science of taking still or moving-picture photographs from a camera mounted on a balloon, airplane, satellite, rocket, or spacecraft. In the 19th cent....

gamma radiation

(Encyclopedia)gamma radiation, high-energy photons emitted as one of the three types of radiation resulting from natural radioactivity. It is the most energetic form of electromagnetic radiation, with a very short ...

Barnard, Frederick Augustus Porter

(Encyclopedia)Barnard, Frederick Augustus Porter, 1809–89, American educator and mathematician, b. Sheffield, Mass., grad. Yale, 1828. After tutoring at Yale and teaching in institutions for the deaf and mute, he...

revolution

(Encyclopedia)revolution, in a political sense, fundamental and violent change in the values, political institutions, social structure, leadership, and policies of a society. The totality of change implicit in this...

Wisconsin, University of

(Encyclopedia)Wisconsin, University of, main campus at Madison; land-grant and state supported; coeducational; chartered 1848, opened 1849. Its history was disturbed by storms over the policies of Glenn Frank and o...

Struve

(Encyclopedia)Struve shtro͞oˈvə [key], family of astronomers. Friedrich Georg Wilhelm von Struve, 1793–1864, was born in Germany but later lived in Russia. While director (1817–39) of Dorpat Observatory he w...

zero

(Encyclopedia)zero, that number which, when added to any number, leaves the latter unchanged; its symbol is 0. The introduction of zero into the decimal system was the most significant achievement in the developmen...

Leiden

(Encyclopedia)Leiden or Leyden both: līˈdən [key], city (1994 pop. 114,892), South Holland prov., W Netherlands, on the Old Rhine (Oude Rijn) River. Manufactures include medical equipment, machinery, graphic art...