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space-time

(Encyclopedia)space-time, central concept in the theory of relativity that replaces the earlier concepts of space and time as separate absolute entities. In relativity one cannot uniquely distinguish space and time...

time-division

(Encyclopedia)time-division: see multiplexing. ...

time zone

(Encyclopedia)time zone: see standard time.

sidereal time

(Encyclopedia)sidereal time (ST), time measured relative to the fixed stars; thus, the sidereal day is the period during which the earth completes one rotation on its axis so that some chosen star appears twice on ...

Royal Greenwich Observatory

(Encyclopedia)Royal Greenwich Observatory, astronomical observatory established in 1675 by Charles II of England at Greenwich and known as the Royal Observatory. It moved during 1948–57 to Herstmonceux Castle, Su...

time , sequential arrangement of all events

(Encyclopedia)time, sequential arrangement of all events, or the interval between two events in such a sequence. The concept of time may be discussed on several different levels: physical, psychological, philosophi...

prime meridian

(Encyclopedia)prime meridian, meridian that is designated zero degree (0°) longitude, from which all other longitudes are measured. By international convention, it passes through the site of the Royal Observatory ...

Greenwich, borough, Greater London, England

(Encyclopedia)Greenwich grĭnˈīj, grĕnˈ– [key], inner borough of Greater London, SE England, on the Thames River. ...

daylight saving time

(Encyclopedia)daylight saving time (DST), time observed when clocks and other timepieces are set ahead so that the sun will rise and set later in the day as measured by civil time. The amount of daylight on a given...

equal-time rule

(Encyclopedia)equal-time rule, a Federal Communications Commission rule that requires equal air time for all major candidates competing for political office. It was preceded by the fairness doctrine, abolished in 1...