Mathematics and Society - OS X Lion Server

ASTRONOMYGLOSSARYmer-surmeridian (on the earth). A circle onthe surface of the earth that passesthrough the north and south poles ofthe earth.orbit. The path of a body that is revolvingaround another body or point.paraboZa. The curve of intersectionformed when a plane cuts a hollow coneparallel to a line in the cone.aparabola --*+1paraUax angZe. An angle formed at astar by two rays, one going toward theearth, the other going toward the sun.sunearthparallaxangleparaUax shift. The apparent angularshift of an object on the celestialsphere when viewed from two differ~ent points.paraZZeZ Zines. Lines in a plane thatdo not intersect.paraZZeZs of Zatitude. Imaginarycircles on the earth's surface thatare "parallel" to the equator. Theyare used in telling any point's angulardistance, in degrees, from theequator.parallels of latitude4- equatorparalZels of decZination. Imaginarycircles on the celestial sphere thatare parallel to the celestial equator.They are used in telling any point'sangular distance in degrees from thecelestial equator.perihelion. The place in a planet'sorbit when it is closest to the sun.perigee. The place in an earth satellite'sorbit when it is closest tothe earth.period. A time interval betweenrepetitions; the time required forone complete revolution.perpendicuZar. Two lines are perpendicularif they meet at right angles.phases of the moon. The lighted portionof the moon seen from earth; fullmoon, half moon, crescent moon, etc.prime hour circZe. The hour circle onthe celestial sphere that passesthrough the vernal equinox.range finder. An instrument which iscalibrated to give the distance todistant objects.right ascension. The angular distanceof an object measured eastward fromthe prime hour circle.sidereal day.the earth towith respectThe time required formake a complete rotationto the stars.similar triangles. Triangles that havethe same shape, but not necessarilythe same size.solar day. The time required for theearth to make a complete rotation withrespect to the sun.surveyor. A person who measures distancesand angles on the earth toestablish boundaries.123