Columbia Encyclopedia

Search results

500 results found

ephemeris time

(Encyclopedia)ephemeris time (ET), astronomical time defined by the orbital motions of the earth, moon, and planets. The earth does not rotate with uniform speed, so the solar day is an imprecise unit of time. Ephe...

Gill, Sir David

(Encyclopedia)Gill, Sir David gĭl [key], 1843–1914, Scottish astronomer, educated at the Univ. of Aberdeen. He made observations of the transits of Venus and Mars and investigated the solar parallax. As astronom...

gegenschein

(Encyclopedia)gegenschein gāˈgənshīnˌ [key] or counterglow, a slight brightening of the night sky in the region of the zodiac directly opposite the sun, i.e., 180° from the sun. Discovered by the Danish astro...

Lacaille, Nicolas Louis de

(Encyclopedia)Lacaille, Nicolas Louis de nēkôläˈ lwē də läkäˈyə [key], 1713–62, French astronomer. As a result of his success in making meridional measurements in France under the patronage of the duke ...

terrestrial planet

(Encyclopedia)terrestrial planet, the earth or a planet that resembles the earth in its physical characteristics. The terrestrial planets in the solar system are the earth, Mercury, Venus, and Mars. These planets a...

Bode, Johann Elert

(Encyclopedia)Bode, Johann Elert yōˈhän āˈlĕrt bōˈdə [key], 1747–1826, German astronomer. From 1772 to 1825 he was astronomer of the Academy of Science, Berlin, and from 1786, director of the Berlin Obse...

Birkeland, Kristian

(Encyclopedia)Birkeland, Kristian or Olaf Christian krĭsˈtyän bērˈkəlän, ōˈläv [key], 1867–1917, Norwegian physicist. From 1898 Birkeland was a professor at the Univ. of Christiania (now Oslo). Noted fo...

Pickering, William Henry

(Encyclopedia)Pickering, William Henry, 1858–1938, American astronomer, b. Boston, grad. Massachusetts Institute of Technology (B.S., 1879). He taught at the Massachusetts Institute of Technology (1880–87) and ...

actinometer

(Encyclopedia)actinometer ăkˌtənŏmˈətər [key], instrument used to measure the heating power of radiation. Actinometers are used chiefly in meteorology to measure solar radiation as transmitted directly by th...

glycolysis

(Encyclopedia)glycolysis glīkŏlˈĭsĭs [key], term given to the metabolic pathway utilized by most microorganisms (yeast and bacteria) and by all “higher” animals (including humans) for the degradation of gl...