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Black Rock Desert

(Encyclopedia)Black Rock Desert, arid region of lava beds and alkali flats, NW Nev., in Toiyabe National Forest, stretching c.70 mi (110 km) NE from Gerlach. The Jackson Mts. rise to the east; the Black Rock Range ...

Mercury, in astronomy

(Encyclopedia)Mercury, in astronomy, nearest planet to the sun, at a mean distance of 36 million mi (58 million km); its period of revolution is 88 days. Mercury passes through phases similar to those of the moon a...

radial velocity

(Encyclopedia)radial velocity, in astronomy, the speed with which a star moves toward or away from the sun. It is determined from the red or blue shift in the star's spectrum. ...

Guelph

(Encyclopedia)Guelph gwĕlf [key], city, S Ont., Canada, on the Speed River. It is an industrial and agricu...

optical activity

(Encyclopedia)optical activity, the ability of asymmetric compounds to rotate the orientation of planar polarized light. Such compounds and their mirror images are know as enantiomers, or optical isomers. Although ...

Fresnel, Augustin Jean

(Encyclopedia)Fresnel, Augustin Jean ōgüstăNˈ zhäN frānĕlˈ [key] 1788–1827, French physicist and engineer. He is known for his research on light, especially on conditions governing interference phenomena ...

photoelectric cell

(Encyclopedia)CE5 Photoelectric cell: Light causes a photosensitive surface to emit electrons, which flow as current to the positive terminal. A galvanometer measures the current and thus indicates light intensi...

battleship

(Encyclopedia)battleship, large, armored warship equipped with the heaviest naval guns. The evolution of the battleship, from the ironclad warship of the mid-19th cent., received great impetus from the Civil War. B...

trill

(Encyclopedia)trill, in music, ornament consisting of the more or less rapid alternation of two adjacent notes. Indicated by any of several conventional symbols, it varies in speed and duration and in the manner of...

diffraction

(Encyclopedia)diffraction, bending of waves around the edge of an obstacle. When light strikes an opaque body, for instance, a shadow forms on the side of the body that is shielded from the light source. Ordinarily...