Royal Observatory Greenwich with 24-hour Gate Clock, Ordnance Survey Bench Mark and Public Measures of Length
Charles Shepherd built and installed the 24-hour Galvano-Magnetic clock at Greenwich Observatory in August 1852. The clock is a slave mechanism controlled by electric pulses transmitted by a master clock inside the main building (now a quartz mechanism) and was probably the first to display GMT to the general public. It originally displayed astronomical time, with the 24 hours of each day starting at noon, but in the 20th century was changed to indicate Greenwich Mean Time, with the counting of the 24 hours of each day starting at midnight; it does not show daylight saving time. The Standard lengths on the wall are 1 yard, 2 feet, 1 foot, 6 inches and 3 inches and are exact at an ambient temperature of 60 °F.
Size: 5072px × 3311px
Location: Greenwich Park, London, England
Photo credit: © SJ Images / Alamy / Afripics
License: Licensed
Model Released: No
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