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Janssen, Pierre Jules César

(Encyclopedia)Janssen, Pierre Jules César pyĕr zhül sāzärˈ zhäNsĕnˈ [key], 1824–1907, French astronomer. In 1857–58, in Peru, he worked on the determination of the magnetic equator; in the Azores (1867...

day

(Encyclopedia)day, period of time for the earth to rotate once on its axis. The ordinary day, or solar day, is measured relative to the sun, being the time between successive passages of the sun over a stationary o...

Langley, Samuel Pierpont

(Encyclopedia)Langley, Samuel Pierpont, 1834–1906, American scientist, b. Roxbury, Mass., received only a high school education but continued his studies in science in Boston libraries. He became, in 1866, profes...

year

(Encyclopedia)year, time required for the earth to complete one orbit about the sun. The solar or tropical year is measured relative to the sun and is equal to 365 days, 5 hr, 48 min, 46 sec of mean solar time (see...

Ångström, Anders Jöns

(Encyclopedia)Ångström, Anders Jöns änˈdərs yöns ōngˈström [key], 1814–74, Swedish physicist. He was educated at the Univ. of Uppsala and in 1839 became a member of its faculty. He is particularly noted...

earth, in geology and astronomy

(Encyclopedia) CE5 A. Cross section of the earth, showing its shells B. Detailed cross section of the crust and upper mantle: The lithosphere consists of the hard rock in the crust and upper mantle, lying above t...

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...

eclipse

(Encyclopedia) CE5 A. Lunar eclipse B. Solar eclipse eclipse ēklĭpsˈ, ĭ– [key] [Gr.,=failing], in astronomy, partial or total obscuring of one celestial body by the shadow of another. Best known are the lu...

activation energy

(Encyclopedia) CE5 Energy profile of an exothermic reaction: Although the total energy of the products is less than that of the reactants, the activation energy must be added to weaken or break existing bonds bef...
 

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