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actinometer

(Encyclopedia)actinometer ăkˌtənŏmˈətər [key], instrument used to measure the heating power of radiation. Actinometers are used chiefly in meteorology to measure solar radiation as transmitted directly by th...

sky

(Encyclopedia)sky, apparent dome over the earth, background of the clouds, sun, moon, and stars. The blue color of the clear daytime sky results from the selective scattering of light rays by the minute particles o...

stratosphere

(Encyclopedia)stratosphere strătˈəsfēr [key], second lowest layer of the earth's atmosphere. The level from which it extends outward varies with latitude; it begins c.51⁄2 mi (9 km) above the poles, c.6 or 7 ...

Haleakala Observatories

(Encyclopedia)Haleakala Observatories häˌlāäˌkäläˈ [key], astronomical facilities located on the summit of Haleakala volcano, 10,023 ft (3,055 m), in Haleakala National Park, Maui island, Hawaii. Because of...

coronagraph

(Encyclopedia)coronagraph kərōˈnəgrăfˌ [key], device invented by the French astronomer B. Lyot (1931) for the purpose of observing the corona of the sun and solar prominences occurring in the chromosphere. Be...

Empedocles

(Encyclopedia)Empedocles ĕmpĕdˈəklēz [key], c.495–c.435 b.c., Greek philosopher, b. Acragas (present Agrigento), Sicily. Leader of the democratic faction in his native city, he was offered the crown, which h...

Utrillo, Maurice

(Encyclopedia)Utrillo, Maurice o͞otrēˈlō, Fr. mōrēsˈ ütrēlōˈ [key], 1883–1955, French painter. He was the son of the painter Suzanne Valadon and was adopted by the writer Miguel Utrillo. His mother tau...

Broecker, Wallace Smith

(Encyclopedia)Broecker, Wallace Smith brōkˈər [key], 1931–2019, American geophysicist, b. Chicago, Ph.D. Columbia, 1958. He was a member of Columbia's faculty from 1959. In the 1970s he predicted rising temper...

mirage

(Encyclopedia)mirage mĭräzhˈ [key], atmospheric optical illusion in which an observer sees in the distance a nonexistent body of water or an image, sometimes distorted, of some object or of a complete scene. Exa...

space medicine

(Encyclopedia)space medicine, study of the medical and biological effects of space travel on living organisms. The principal aim is to discover how well and for how long humans can withstand the extreme conditions ...