| Revision as of 07:30, 19 February 2004 edit211.28.5.250 (talk) Revert. Funny that nobody can justify their deletion of Time Cube article link. I guess they're pedantic cowards, afraid of anything that contradicts what they've been taught.← Previous edit | Revision as of 07:31, 19 February 2004 edit undoMorwen (talk | contribs)Administrators56,993 editsm Reverted edits by 211.28.5.250 to last version by Maximus RexNext edit → | ||
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| Hourly time signals from Greenwich Observatory were first broadcasted on ], ]. | Hourly time signals from Greenwich Observatory were first broadcasted on ], ]. | ||
| ''See also'' ], ], ], ], ], ], ] | ''See also'' ], ], ], ], ], ] | ||
Revision as of 07:31, 19 February 2004
Greenwich Mean Time (GMT) is the mean solar time at the Royal Greenwich Observatory in Greenwich near London, England, which by convention is at 0 degrees geographic longitude. Theoretically, noon Greenwich Mean Time is the moment when the Sun crosses the Greenwich meridian (and reaches its highest point in the sky in Greenwich). Because of the Earth's uneven speed in its elliptic orbit, this event may be up to 16 minutes off apparent solar time (known as the analemma); but this is averaged out over the year through the use of the mean sun.
The daily rotation of the Earth is somewhat irregular (see Delta-T) and is slowing down. Therefore, GMT is not used as official clock time anymore. Nowadays, the official clock time is measured by atomic clocks and is known as Coordinated Universal Time (UTC). By using leap seconds, UTC is kept within 0.9 seconds from GMT.
Hourly time signals from Greenwich Observatory were first broadcasted on February 5, 1924.
See also sidereal time, solar time, BPM, CHU, VNG, WWV