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Silk Road

(Encyclopedia)Silk Road, ancient overland trade route linking Asia and Europe, consisting of a network of caravan routes running from China across central Asia to the shores of the Mediterranean. Its starting point...

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...

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...

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...

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...