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Boltzmann, Ludwig

(Encyclopedia)Boltzmann, Ludwig lo͝otˈvĭkh bôltsˈmän [key], 1844–1906, Austrian physicist, b. Vienna, educated at Univ. of Vienna. He began teaching (1869) at Graz Univ. In 1873 he became mathematics profes...

atomic weight

(Encyclopedia)atomic weight, mean (weighted average) of the masses of all the naturally occurring isotopes of a chemical element, as contrasted with atomic mass, which is the mass of any individual isotope. Althoug...

Landau, Lev Davidovich

(Encyclopedia)Landau, Lev Davidovich lyĕf dəvēˈdəvĭch ləndouˈ [key], 1908–68, Soviet physicist, b. Baku, Azerbaijan. A child prodigy in mathematics, he entered Baku Univ. at 14; at 21 he received a doctor...

decay of organic matter

(Encyclopedia)decay of organic matter or putrefaction, process whereby heterotrophic organisms, including some bacteria, fungi, saprophytic plants, and lower animals, utilize the remains of once-living tissue as a ...

Maxwell, James Clerk

(Encyclopedia)Maxwell, James Clerk klärk [key], 1831–79, great Scottish physicist. After a brilliant career at Edinburgh and Cambridge, where he won early recognition with mathematical papers, he was a professor...

Hertz, Heinrich Rudolf

(Encyclopedia)Hertz, Heinrich Rudolf hĕrts [key], 1857–94, German physicist. He confirmed J. C. Maxwell's electromagnetic theory and in the course of experiments (1886–89) produced and studied electromagnetic...

Marcellus of Ancyra

(Encyclopedia)Marcellus of Ancyra ănsīˈrə [key], fl. 350, Galatian churchman, the most violent opponent of Arianism in Asia Minor. He developed the theory that the Trinity was the result of emanations from God ...

viscosity

(Encyclopedia)viscosity, resistance of a fluid to flow. This resistance acts against the motion of any solid object through the fluid and also against motion of the fluid itself past stationary obstacles. Viscosity...

muffler

(Encyclopedia)muffler, in automobiles, device designed to reduce the noise from the exhaust of an internal-combustion engine. When the exhaust gases from an internal-combustion engine are released directly into the...

photosphere

(Encyclopedia)photosphere, luminous, apparently opaque layer of gases that forms the visible surface of the sun or any other star. The photosphere lies between the dense interior gases and the more attenuated gases...