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Greenwich mean time

(Encyclopedia)Greenwich mean time or Greenwich meridian time (GMT), the former name for mean solar time at the site of the Royal Observatory in Greenwich, England, which is located on the prime meridian. In 1925 th...

longitude

(Encyclopedia)longitude lŏnˈjĭto͞odˌ [key], angular distance on the earth's surface measured along any latitude line such as the equator east or west of the prime meridian. A meridian of longitude is an imagin...

universal time

(Encyclopedia)universal time (UT), the international time standard common to every place in the world, it nominally reflects the mean solar time along the earth's prime meridian (renumbered to equate to civil time)...

transit instrument

(Encyclopedia)transit instrument or transit, telescope devised to observe stars as they cross the meridian and used for determining time. Its viewing tube swings on a rigid horizontal axis restricting its movements...

standard time

(Encyclopedia)standard time, civil time used within a given time zone. The earth is divided into 24 time zones, each of which is about 15° of longitude wide and corresponds to one hour of time. Within a zone all c...

compass

(Encyclopedia)compass. 1 In mathematics, an instrument for making circles and measuring distances. Frequently called a pair of compasses, it consists of two metal legs with one end of each attached to a pivot to fo...

culminate

(Encyclopedia)culminate, in astronomy, the maximum height in the sky reached by a celestial body on a given day. At the culminate the body is crossing the observer's celestial meridian and is said to be in upper tr...

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