On this day in 1676, two very accurate clocks began working at the Royal Observatory in Greenwich, beginning the use of Greenwich Mean Time.
The observatory was commissioned in 1675 by King Charles II, with the foundation stone being laid on 10 August. The old hilltop site of Greenwich Castle was chosen by Sir Christopher Wren, a former Savilian Professor of Astronomy; as Greenwich Park was a royal estate, no new land needed to be bought. Moore donated two clocks, built by Thomas Tompion, which were installed in the 20-foot-high Octagon Room, the principal room of the building. They were of unusual design, each with a pendulum 13 feet (4.0 metres) in length mounted above the clock face, giving a period of four seconds and an accuracy, then unparalleled, of seven seconds per day. John Flamsteed was appointed the first Astronomer Royal.
When the observatory was founded in 1675, one of the best star catalogues was Tycho Brahe’s 1000-star catalogue from 1598. However, this catalogue was not accurate enough to determine longitudes. One of Flamsteed’s first orders of business was creating more accurate charts suitable for this purpose.
One of the noted charts made at Greenwich was by the Astronomer Royal James Bradley, who between 1750 and 1762 charted sixty thousand stars, so accurately his catalogues were used even in the 1940s.1British astronomers have long used the Royal Observatory as a basis for measurement. Four separate meridians have passed through the buildings, defined by successive instruments. The basis of longitude, the meridian that passes through the Airy transit circle, first used in 1851, was adopted as the world’s Prime Meridian at the International Meridian Conference at Washington, DC, on 22 October 1884.
A key instrument for determining time was the Airy Transit Circle, which was used primarily from 1851 to 1938. It was agreed that the (Prime) “meridian line marked by the cross-hairs in the Airy Transit Circle eyepiece would indicate 0° longitude and the start of the Universal Day”. Beginning in 1924, Hourly time signals (Greenwich Time Signal) from the Royal Observatory were first broadcast. To help mariners at the port and others in line of sight of the observatory to synchronize their clocks to GMT, in 1833 Astronomer Royal John Pond installed a very visible red time ball that drops precisely at 1 pm (13:00) every day atop the observatory.
Royal Observatory, 2006
Six drinks within reach, which will the kid choose?
there’s a story here…
On this day in 1968, Welsh singer Mary Hopkin was at No.1 on the UK singles chart with ‘Those Were The Days’. Hopkins had signed to The Beatles Apple label after appearing on UK TV talent show Opportunity Knocks. https://www.youtube.com/watch?v=JnxTT7XXMPA
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