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retrograde motion

(Encyclopedia)retrograde motion, in astronomy, real or apparent movement of a planet, dwarf planet, moon, asteroid, or comet from east to west relative to the fixed stars. The most common direction of motion in the...

red shift

(Encyclopedia)red shift or redshift, in astronomy, the systematic displacement of individual lines in the spectrum of a celestial object toward the red, or longer wavelength, end of the visible spectrum. The effect...

Peirce, Charles Sanders

(Encyclopedia)Peirce, Charles Sanders pûrs [key], 1839–1914, American philosopher and polymath, b. Cambridge, Mass., grad. Harvard, 1859; son of Benjamin Peirce. Except for occasional lectures he renounced the r...

transit

(Encyclopedia)transit, in astronomy, passage of a body across a meridian or passage of a small body across the visible disk of a larger one. (The passage of a large body across a smaller one is called an eclipse or...

Thomas, Dylan

(Encyclopedia)Thomas, Dylan dĭlˈən [key], 1914–53, Welsh poet, b. Swansea. An extraordinarily individualistic writer, Thomas is ranked among the great 20th-century poets. He grew up in Swansea, the son of a te...

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...

zodiac

(Encyclopedia)CE5 Signs of the zodiac CEE zodiac zōˈdēăk [key] [Gr. zoion=animal], in astronomy, zone of the sky that includes about 8° on either side of the ecliptic. The apparent paths of the sun, the...

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...

Pythagoras

(Encyclopedia)Pythagoras pĭthăgˈərəs [key], c.582–c.507 b.c., pre-Socratic Greek philosopher, founder of the Pythagorean school. He migrated from his native Samos to Crotona and established a secret religiou...

nebula

(Encyclopedia)nebula nĕbˈyo͝olə [key] [Lat.,=mist], in astronomy, observed manifestation of a collection of highly rarefied gas and dust in interstellar space. Prior to the 1960s this term was also applied to b...