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Mach number
(Encyclopedia)Mach number mäk [key] [for E. Mach], ratio between the speed of an object and the speed of sound in the medium in which the object is traveling. An airplane that has the velocity of Mach 3.0 is trave...Doppler effect
(Encyclopedia)Doppler effect, change in the wavelength (or frequency) of energy in the form of waves, e.g., sound or light, as a result of motion of either the source or the receiver of the waves; the effect is nam...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...Hubble's law
(Encyclopedia)Hubble's law, in astronomy, statement that the distances between galaxies (see galaxy) or clusters of galaxies are continuously increasing and that therefore the universe is expanding. Hubble's law ...scalar
(Encyclopedia)scalar, quantity or number possessing only sign and magnitude, e.g., the real numbers (see number), in contrast to vectors and tensors; scalars obey the rules of elementary algebra. Many physical quan...Rømer, Olaus
(Encyclopedia)Rømer, Olaus or Ole ōläˈo͝os, ōˈlə römˈər [key], 1644–1710, Danish astronomer. He is noted for his discovery that light travels at a definite speed and does not move through space instant...space science
(Encyclopedia)space science, body of scientific knowledge as it relates to space exploration; it is sometimes also called astronautics. Space science draws on the conventional sciences of physics, chemistry, biolog...force
(Encyclopedia)force, commonly, a “push” or “pull,” more properly defined in physics as a quantity that changes the motion, size, or shape of a body. Force is a vector quantity, having both magnitude and dir...Norrish, Ronald George Wreyford
(Encyclopedia)Norrish, Ronald George Wreyford, 1897–1978, British chemist, Ph.D. Cambridge, 1925. He joined the faculty at Cambridge in 1925 and was a professor there until he retired in 1965. Norrish was awarded...snow line
(Encyclopedia)snow line, altitude above which or latitude beyond which snow does not melt in summer (usually called the permanent snow line), or, in winter, the line to which snow extends at a given point in time. ...Browse by Subject
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