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mechanics

(Encyclopedia)mechanics, branch of physics concerned with motion and the forces that tend to cause it; it includes study of the mechanical properties of matter, such as density, elasticity, and viscosity. Mechanics...

infrared astronomy

(Encyclopedia)infrared astronomy, study of celestial objects by means of the infrared radiation they emit, in the wavelength range from about 1 micrometer to about 1 millimeter. All objects, from trees and building...

planetary system

(Encyclopedia)planetary system, a star and all the celestial bodies bound to it by gravity, especially planets and their natural satellites. Until the last decade of the 20th cent., the only planetary system known ...

Dyson, Freeman John

(Encyclopedia)Dyson, Freeman John dīˈsən [key], 1923–2020, British-American theoretical physicist and mathematician, studied Trinity College, Cambridge (B.A., 1945) and Cornell. He did bomber operations resear...

symmetry, biological

(Encyclopedia)symmetry, biological, similarity or balance between parts of an organism so that when a straight cut is made through a point or along a line, equal, mirror-image halves are formed. Symmetry in body sh...

Mercator, Gerardus

(Encyclopedia)Mercator, Gerardus gārˈhärt krāˈmər [key], 1512–94, Flemish geographer, mathematician, and cartographer. He studied in Louvain, where he had a geographical establishment (1534). From 1537 to 1...

sextant

(Encyclopedia)CE5 Sextant sextant, instrument for measuring the altitude of the sun or another celestial body; such measurements can then be used to determine the observer's geographical position or for other n...

Polaris

(Encyclopedia)Polaris pōlârˈĭs [key] or North Star, star nearest the north celestial pole (see equatorial coordinate system). It is in the constellation Ursa Minor (see Ursa Major and Ursa Minor; Bayer designat...

X-ray astronomy

(Encyclopedia)X-ray astronomy, study of celestial objects by means of the X rays they emit, in the wavelength range from 0.01 to 10 nanometers. X-ray astronomy dates to 1949 with the discovery that the sun emits X ...

liposome

(Encyclopedia)liposome līˈpəsōmˌ, lĭpˈə– [key], microscopic, fluid-filled pouch whose walls are made of layers of phospholipids identical to the phospholipids that make up cell membranes. Liposomes are us...