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actinium

(Encyclopedia)actinium ăktĭnˈēəm [key] [Gr.,=like a ray], radioactive chemical element; symbol Ac; at. no. 89; mass number of most stable isotope 227; m.p. about 1,050℃; b.p. 3,200℃±300℃; sp. gr. 10.07;...

Perot, H. Ross

(Encyclopedia)Perot, H. Ross (Henry Ross Perot), 1930–2019, American business executive and political leader, b. Texarkana, Tex., as Henry Ray Perot, grad. Annapolis, 1953. In 1957 he resigned his naval commissio...

periodic law

(Encyclopedia)periodic law, statement of a periodic recurrence of chemical and physical properties of the elements when the elements are arranged in order of increasing atomic number. Such an arrangement in the for...

dark energy

(Encyclopedia)dark energy, repulsive force that opposes the self-attraction of matter (see gravitation) and causes the expansion of the universe to accelerate. The search for dark energy was triggered by the discov...

Geiger counter

(Encyclopedia)Geiger counter or Geiger-Müller (G-M) counter gīˈgər-mŭlˈər, –myo͞oˈlər [key], instrument for the detection and quantitative determination of ionizing radiation such as the alpha and beta ...

Jones, Quincy

(Encyclopedia)Jones, Quincy (Quincy Delight Jones, Jr.), 1933–, African-American musician, composer, bandleader, and music executive, b. Chicago. Jones played trumpet and sang gospel growing up, and studied brief...

West, Kanye Omari

(Encyclopedia) West, Kanye Omari, 1977- , African American rapper, b. Atlanta (some sources give Douglasville), Al. West’s father, Ray, was a Black Panther who ...

Teller, Edward

(Encyclopedia)Teller, Edward, 1908–2003, American physicist, b. Budapest, Hungary, Ph.D. Univ. of Leipzig, 1930, where he studied under Werner Heisenberg. Fleeing the Nazis, he came to the United States in 1935 a...

black hole

(Encyclopedia)black hole, in astronomy, celestial object of such extremely intense gravity that it attracts everything near it and in some instances prevents everything, including light, from escaping. The term was...

International Geophysical Year

(Encyclopedia)International Geophysical Year (IGY), 18-month period from July, 1957, through Dec., 1958, during a period of maximum sunspot activity, designated for cooperative study of the solar-terrestrial enviro...