Columbia Encyclopedia

Search results

500 results found

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...

Eratosthenes

(Encyclopedia)Eratosthenes ĕrətŏsˈthənēz [key], c.275–c.195 b.c., Greek scholar, b. Cyrene. A pupil of Callimachus in Athens, he became (c.240 b.c.) head of the library at Alexandria. Known for his versatil...

Kitt Peak National Observatory

(Encyclopedia)Kitt Peak National Observatory, astronomical observatory located southwest of Tucson, Ariz.; it was founded in 1958 under contract with the National Science Foundation and is administered by the Assoc...

spectroheliograph

(Encyclopedia)spectroheliograph, device for photographing the surface of the sun in a single wavelength of light, usually one corresponding to a chief element contained in the sun, e.g., hydrogen or calcium; the re...

halo, in meteorology

(Encyclopedia)halo, in meteorology, short-lived circles or arcs, and less commonly spikes and crosses, of colored or whitish light surrounding the moon or sun or in clouds as seen from above. A halo occurs when the...

twilight

(Encyclopedia)twilight, period between sunset and total darkness or between total darkness and sunrise. Total darkness does not occur immediately when the sun sinks below the horizon because light from the sun that...

Lockyer, Sir Joseph Norman

(Encyclopedia)Lockyer, Sir Joseph Norman lŏkˈyər [key], 1836–1920, English astronomer, educated on the Continent. One of the first to make a spectroscopic examination of the sun and stars, he devised (1868), i...

orbit

(Encyclopedia)CE5 Important points in a planet's orbit as seen from the earth orbit, in astronomy, path in space described by a body revolving about a second body where the motion of the orbiting bodies is domi...

Beach, Moses Yale

(Encyclopedia)Beach, Moses Yale, 1800–1868, American journalist, b. Wallingford, Conn. As a young man he invented a rag-cutting machine and a gunpowder engine. In 1838 he bought the New York Sun from his brother-...

Webb Space Telescope

(Encyclopedia)Webb Space Telescope or James Webb Space Telescope (JWST), is an infrared space telescope, the largest in space at its launc...