Columbia Encyclopedia

(Encyclopedia) mass-luminosity relation, in astronomy, law stating that the luminosity of a star is proportional to some power of the mass of the star. More massive stars are in general more luminous. For stars on t...

(Encyclopedia) toxoplasmosis, infection caused by Toxoplasma gondii, a single-celled parasitic microorganism that can infect most warm-blooded animals but reproduces only in animals of the cat family, who shed the p...

(Encyclopedia) Banneker, Benjamin, 1731–1806, African-American inventor, astronomer, and mathematician, b. Baltimore co., Md., at what is now Ellicott's Mills. A free black, Banneker was essentially self-taught. H...

(Encyclopedia) Poisson, Siméon Denis sēmāôNˈ dənēˈ pwäsôNˈ [key], 1781–1840, French mathematician and physicist. From 1802 he taught at the École polytechnique, Paris, and was also on the faculty of sc...

(Encyclopedia) emphysema ĕmfĭsēˈmə [key], pathological or physiological enlargement or overdistention of the air sacs of the lungs. A major cause of pulmonary insufficiency in chronic cigarette smokers, emphyse...

(Encyclopedia) stroboscope strŏbˈəskōp [key], optical instrument for making a moving object appear to be slowed down or stationary. This effect is created by interrupting the observer's view so that the object i...

(Encyclopedia) gas, fuel, gaseous substance that burns in air and releases enough heat to be useful as a fuel, while also remaining sufficiently stable at ordinary temperatures to permit long-term storage without de...

(Encyclopedia) blue shift or blueshift, in astronomy, the systematic displacement of individual lines in the spectrum of a celestial object toward the blue, or shorter wavelength, end of the visible spectrum. The am...

(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...

(Encyclopedia) Heliopolis hēlēŏpˈəlĭs [key] [Gr.,=city of the sun], ancient city, N Egypt, in the Nile delta, 6 mi (10 km) below modern Cairo. It was noted as the center of sun worship, and its god Ra or Re wa...