Flamsteed House in 1824
Royal Observatory, Greenwich c.
1902 as depicted on a postcard
The Royal Observatory, Greenwich
Royal Greenwich Observatory
) was commissioned in 1675 by King Charles II
, with the foundation stone
being laid on 10 August.
At this time the king also created the position of Astronomer Royal
(initially filled by
), to serve as the
director of the observatory and to "apply himself with the most
exact care and diligence to the rectifying of the tables of the
motions of the heavens, and the places of the fixed stars, so as to
find out the so much desired longitude
places for the perfecting of the art of navigation." It is situated on a
hill in Greenwich
Park in Greenwich, London, overlooking
the River Thames.
There had been significant buildings on this land since the reign
of Edward I. Greenwich Palace, next to the site of the present-day Observatory
was the birthplace of Henry VIII and the Tudors used Greenwich Castle, which was built on the
land that the Observatory now stands on.
was apparently a favourite place for Henry VIII to house his
mistresses, so that he could easily travel from the Palace to see
The establishment of a Royal Observatory was proposed in 1674 by
Sir Jonas Moore
who, in his role as
Surveyor General at the Ordnance Office, persuaded King Charles II
that the Observatory might be built with Flamsteed employed in it.
The Ordnance Office was given responsibility for building the
Observatory, with Moore providing the key instruments and equipment
for the observatory at his own personal cost. Flamsteed House, the
original part of the Observatory, was designed by Sir Christopher Wren
probably with the
assistance of Robert Hooke
and was the
first purpose-built scientific research facility in Britain. It was
built for a cost of £520 (£20 over budget) out of largely recycled
materials on the foundations of Duke Humphrey's Tower, which
resulted in the alignment being 13 degrees away from true North,
somewhat to Flamsteed's chagrin.
It not only housed the scientific instruments to be used by
Flamsteed in his work on stellar tables, but over time also
incorporated a number of additional responsibilities such as the
keeping of time
and later Her Majesty's Nautical
Moore donated two clocks, built by Thomas
, 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 (3.96 metres) in length
mounted above the clock face, giving a period of four seconds and
an accuracy, then unparalleled, of seven seconds per day.
British astronomers have long used the Royal Observatory as a basis
for measurement: four separate meridians have been drawn through
the building. The basis of longitude
, established in 1851
and adopted at an international conference in 1884, passes through
the Airy transit circle
of the observatory. It was
long marked by a brass strip in the courtyard, now upgraded to
stainless steel, and, since 16 December 1999, has been marked by a
powerful green laser
shining north across the
London night sky.
This old astronomical prime meridian has been replaced by a more
modern prime meridian. When Greenwich was an active observatory,
geographical coordinates were referred to a local oblate spheroid
called a datum
, whose surface closely matched local
mean sea level
, called the geoid
. Several datums were in use around the world,
all using different spheroids, because mean sea level undulates by
as much as 100 metres worldwide. Modern geodetic reference systems,
such as the World Geodetic
and the International
Terrestrial Reference Frame
, use a single Earth-centered oblate
spheroid. The shift from several spheroids to one worldwide
spheroid caused all geographical coordinates to shift by many
metres, sometimes as much as several hundred metres. The Prime
Meridian of these modern reference systems is 102.5 metres east of
the Greenwich astronomical meridian represented by the stainless
steel strip. Thus the strip is now 5.31 arcseconds
Greenwich Mean Time
(GMT) was at
one time based on the time observations made at Greenwich (until
1954). Thereafter, GMT was calculated from observations made at
other observatories which were still active. GMT is now often
called Universal Time
, which is now
calculated from observations of extra-galactic radio sources, and
then converted into several forms, including UT0 (UT at the remote
observatory), UT1 (UT corrected for polar
), and UTC
in discrete SI seconds within 0.9 s of UT1). To help others
synchronize their clocks to GMT, a time
was installed by Astronomer Royal John Pond
in 1833. It still drops daily to mark
the exact moment of 1 p.m. (13:00) year round (GMT during winter
Bomb attack of 1894
The Observatory underwent an attempted bombing in 1894. This was
possibly the first 'international terrorist' incident in Britain.
The bomb was detonated by a 26-year-old French anarchist
named Martial Bourdin. It is not known
why he chose the observatory, or whether the detonation was
intended to occur elsewhere. The incident was used as inspiration
by Joseph Conrad
in his novel
The Secret Agent
buildings include a museum of astronomical and navigational tools,
which is part of the National Maritime Museum, notably including John
Harrison's prize-winning longitude marine chronometer, H4, and its three
Several additional horological artifacts are
also displayed, documenting the history of precision timekeeping
for navigational and astronomical purposes, including the mid 20th
century Russian-made F.M. Fedchenko clock (the most accurate
pendulum clock ever built in multiple copies). It is also home to
the 28-inch Grubb refracting telescope
of 1893, the
largest of its kind in the UK. The Shepherd Clock
outside the observatory
gate is an early example of an electric slave clock. In February
2005 construction work began on a £15 million redevelopment project
to provide a new planetarium
additional display galleries and educational facilities.
Harrison Planetarium officially opened on 25 May 2007.
Royal Observatory, Greenwich vs. Royal Greenwich
During much of the twentieth century, the Royal Greenwich
Observatory was not at Greenwich. The last time that all departments were
there was 1924: in that year electrification of the railways
affected the readings of the Magnetic and
Meteorological Department and forced its
move to Abinger.
Indeed prior to this, the observatory had to insist that all the
electric trams in the vicinity could not use an earth return for
the traction current. In 1939, during World
War II, many departments were evacuated, along with the rest of
London, to the countryside (Abinger, Bradford, and
activities in Greenwich were reduced to the bare
War, in 1947, the decision was made to move to Herstmonceux
Castle and 320 adjacent acres (1.3 km²), 70 km
south-southeast of Greenwich near Hailsham in East
Sussex, due to light
pollution in London.
Although the Astronomer Royal
Harold Spencer Jones moved to the castle in 1948, the scientific
staff could not move until the completion of new observatory
buildings in 1957. Shortly thereafter, other far flung departments
were reintegrated at Herstmonceux.
Isaac Newton Telescope was
built at Herstmonceux in 1967, but was moved to Roque de los
Muchachos Observatory in Spain's Canary Islands in 1979. In 1990 the RGO moved again, to Cambridge.
Following a decision of the Particle Physics
and Astronomy Research Council
, it closed in 1998. Her Majesty's Nautical
Almanac Office was transferred to the Rutherford
Appleton Laboratory after the closure. Other work went to
the UK Astronomy Technology
Centre in Edinburgh. The castle grounds are now the home of the
International Study Centre of Queen's
University, Kingston, Canada and the Observatory Science
Royal Observatory, Greenwich
One of the hyper-accurate chronometers
at the observatory
- 1675 Royal Observatory, Greenwich founded.
- 1714 Board of Longitude,
- 1924 Hourly time signals (Greenwich Time Signal) from the Royal
Observatory, Greenwich were first broadcast on February 5.
- 1948 Astronomer Royal moves to Herstmonceux.
- 1957 Royal Observatory completes its move to Herstmonceux,
becoming the Royal Greenwich Observatory (RGO). The Greenwich site
becomes the Old Royal Observatory.
- 1990 RGO moves to Cambridge.
- 1998 RGO closes. Greenwich site becomes the Royal
Observatory, Greenwich again, and is part of the National
- Greenwich Observatory: ... the Royal Observatory at
Greenwich and Herstmonceux, 1675-1975. London: Taylor &
Francis, 1975 3v. (Vol. 1. Origins and early history
(1675-1835), by Eric G. Forbes. ISBN 0-85066-093-9; Vol. 2.
Recent history (1836-1975), by A.J. Meadows. ISBN
0-85066-094-7; Vol. 3. The buildings and instruments by
Derek Howse. ISBN 0-85066-095-5).
- Greenwich Time and the Longitude. London: Philip
Wilson, 1997, by Derek Howse. ISBN 0-85667-468-0.