Columbia Encyclopedia

Search results

500 results found

elongation

(Encyclopedia)elongation, in astronomy, the angular distance between two points in the sky as measured from a third point. The elongation of a planet is usually measured as the angular distance from the sun to the ...

Dawson, Sir John William

(Encyclopedia)Dawson, Sir John William, 1820–99, Canadian geologist and educator, b. Pictou, N.S., studied at the Univ. of Edinburgh. After serving (1850–55) as superintendent of education in Nova Scotia, he wa...

gamma-ray astronomy

(Encyclopedia)gamma-ray astronomy, study of astronomical objects by analysis of the most energetic electromagnetic radiation they emit. Gamma rays are shorter in wavelength and hence more energetic than X rays (see...

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 ...

Branner, John Casper

(Encyclopedia)Branner, John Casper, 1850–1922, American geologist, b. New Market, Tenn. He made geological investigations in Brazil (1874–84); the results of these studies and of others made in later years were...

Dana, James Dwight

(Encyclopedia)Dana, James Dwight, 1813–95, American geologist, mineralogist, and naturalist, b. Utica, N.Y., grad. Yale, 1833. His studies of the S Pacific, NW United States, Europe, and elsewhere led to changes ...

Braille

(Encyclopedia)Braille brāl [key], in astronomy, a small asteroid notable because it has the same atypical geologic composition as the larger asteroid Vesta. In 1999 the space probe Deep Space 1 passed within 16 mi...

Ewing, William Maurice

(Encyclopedia)Ewing, William Maurice, 1906–74, American oceanographer and geologist, b. Lackney, Tex., grad. Rice Institute, now Rice Univ. (B.S., 1926; M.A., 1927; Ph.D., 1931). He taught physics and geology at ...

Ptolemy

(Encyclopedia)Ptolemy (Claudius Ptolemaeus), fl. 2d cent. a.d., celebrated Greco-Egyptian mathematician, astronomer, and geographer. He made his observations in Alexandria and was the last great astronomer of ancie...

cycle

(Encyclopedia)cycle, in astronomy, period of time required for the recurrence of some celestial event. The length of a cycle may be measured relative to the sun or to the fixed stars (see sidereal time). A frequent...