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ether, in physics and astronomy

(Encyclopedia)ether or aether, in physics and astronomy, a hypothetical medium for transmitting light and heat (radiation), filling all unoccupied space; it is also called luminiferous ether. In Newtonian physics a...

recoilless rifle

(Encyclopedia)recoilless rifle, light artillery piece, without recoil, usually operated by two men. An American invention, it was used as an infantry weapon for attacking fortifications such as pillboxes and bunker...

Helmont, Jan Baptista van

(Encyclopedia)Helmont, Jan Baptista van yän bäptĭsˈtä vän hĕlˈmônt [key], 1577–1644, Flemish physician, chemist, and physicist. He attributed physiological changes to chemical causes, but his conclusions...

sun, in astronomy

(Encyclopedia)CE5 Structure of the sun sun, intensely hot, self-luminous body of gases at the center of the solar system. Its gravitational attraction maintains the planets, comets, and other bodies of the sola...

Gerhardt, Charles Frédéric

(Encyclopedia)Gerhardt, Charles Frédéric shärl frādārēkˈ zhārärˈ [key], 1816–56, French chemist, b. Strasbourg. He revived the theory of acid radicals, which he called the theory of residues, and did va...

Lucas, Robert Emerson, Jr.

(Encyclopedia)Lucas, Robert Emerson, Jr., 1937–2023, American economist, b. Yakima, Wash., Ph.D. Univ. of Chicago, 1964. Lucas taught at Carnegie Mellon Univ. (1963...

Weaver, Warren

(Encyclopedia)Weaver, Warren, 1894–1978, American scientist, b. Reedsburg, Wis., grad. Univ. of Wisconsin. He taught mathematics at Wisconsin (1920–32), was director of the division of natural sciences at the R...

Jevons, William Stanley

(Encyclopedia)Jevons, William Stanley jĕvˈənz [key], 1835–82, English economist and logician. After working in Australia as assayer to the mint, he taught at Owens College, Manchester, and University College, ...

photoelectric effect

(Encyclopedia)photoelectric effect, emission of electrons by substances, especially metals, when light falls on their surfaces. The effect was discovered by H. R. Hertz in 1887. The failure of the classical theory ...

Damavand

(Encyclopedia)Damavand or Demavend both: dĕmˈəvĕnd [key], volcanic cone, 18,606 ft (5,671 m) high, in the Elburz range, N Iran. A permanently snow-covered volcano of recent geologic origin, it emits gases and s...