The Royal Observatory Greenwich – A Brief History

The Royal Observatory is Britain’s oldest scientific institution. It was founded in Greenwich by King Charles II in 1675 for the specific and practical purpose of ‘rectifying 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 of Places for perfecting the art of Navigation’.

In the 1940s and 50s, it moved to the clearer skies of Herstmonceux in Sussex where its name was changed from the Royal Observatory, Greenwich to the Royal Greenwich Observatory, Herstmonceux. It was downsized and moved to Cambridge in 1990, and then shut down completely in 1998.

Of the surviving buildings, those at Greenwich are mainly in the care of the National Maritime Museum (Royal Museums Greenwich). Some at Herstmonceux are in use as a Science Centre, whilst others are occupied by the International Study Centre of the Queen's University (Canada). Those in Cambridge have been absorbed by the University.


The longitude problem

Back in 1675, although a sailor was able to measure his latitude – how far north or south he was – once out of sight of land, he had no means of measuring his longitude or how far east or west he was.  As trade routes opened up, it became increasingly urgent to find a solution to the so-called longitude problem. The maritime nations of Europe offered a variety of large rewards or prizes for a solution.

Each 15° of longitude is equivalent to a difference in time of one hour. In theory then, in order to find out how far east or west he was from his homeland, all a sailor had to do was determine his local time from observations of the Sun or stars and compare it with the time back home at the same moment. This though was easier said than done. The idea of taking a clock to sea had been considered, but even the best were far too inaccurate to be of use. The improvements that came with the invention of the pendulum clock in 1657 were substantial and revolutionised astronomy, but on board a moving ship, a pendulum would beat irregularly and occasionally stop beating altogether.

Every hour, the Moon moves by about its own diameter against the background of stars. As early as 1514, Johann Werner of Nuremberg had suggested using the Moon as an astronomical clock. At that time however, star charts were too inaccurate and the precise motion of the Moon and the effects of refraction by the Earth’s atmosphere too poorly understood for the method to be practicable. It was not until the invention of the telescope, the pendulum clock, the micrometer screw and logarithms in the seventeenth century that astronomers became equipped with the tools they needed in order to begin to turn Werner’s idea into a practical reality. And this is what the Royal Observatory was founded to do.


John Flamsteed – the first Astronomer Royal

John Flamsteed was put in charge and given the title ‘Astronomical Observator’. He later became known as the Astronomer Royal. Although the post of Astronomer Royal still exists, it ceased to have any direct connection with the Observatory following the retirement of Sir Richard Woolley in 1971.

Flamsteed realised that repeated measurements of the positions of the Sun, Moon stars and planets over long time periods was a prerequisite for understanding and predicting their motions. From its very foundation, the Observatory embarked upon systematic and long-continued programmes of observation. Until their interruption by the Second World War and the subsequent move of the Observatory to Herstmonceux these formed the Observatory’s most significant and most important contribution to astronomy.


Positional astronomy and the measurement of time

Initially, as with observatories elsewhere, the work at Greenwich was confined to positional astronomy. From 1689 onwards, the most important of these measurements at Greenwich were made using specially designed telescopes aligned north south along their own Meridian. These could be pointed higher or lower in the sky, but could not be moved to point from side to side.

The measurement of star positions with meridian instruments is intrinsically linked to the measurement of time. The stars all move across the sky in a similar way to the Sun. As far as anyone could tell, the Earth was spinning at a steady rate, and this meant that each individual star would cross the meridian of one of the telescopes at the same (sidereal) time each day. In effect, the telescope was rather like the hand of a clock, whilst the stars were like the numbers around the dial. Certain of the brighter stars, whose positions had been refined by repeated observation over a long period of years, were used as ‘clock stars’ to determine the errors of the Observatory’s clocks and hence the local time at Greenwich.


Instrumental and other improvements

As the years went by, there were improvements in the design and construction of the instruments and in their optical qualities; there were progressive refinements in technique and progressive improvements in accuracy, which in turn opened up new fields of investigation. The third Astronomer Royal James Bradley, who had already discovered the aberration of light before coming to Greenwich, went on to make the further discovery of nutation.  His observations made at Greenwich between 1750 and 1762 are the earliest from anywhere in the World whose accuracy and consistency is such, that are still of use to astronomers today.

The improvements in the tables of motions of the Sun, Moon and Planets enabled the great Continental mathematicians of the eighteenth century, to show that Newton’s laws of gravitation alone could account for the movements of the bodies in the solar system.


The longitude problem is solved

By the early 1760s, all the elements were finally in place for sailors to be able to find their longitude with the aid of the Moon, using the so-called lunar-distance method. Meanwhile, the Englishman John Harrison, after over 20 years of trying, had managed to build a timekeeper that he believed would keep good time at sea and win him the British longitude prize that had first been offered in 1714. Amongst those involved in its evaluation was Nevil Maskelyne, who in 1765 became the fifth Astronomer Royal. At this point, although both Harrison’s timekeeper and the lunar-distance method worked, neither was particularly practicable: the former, because one timekeeper was insufficient for a whole nation and the latter because it entailed too much work, in the form of many hours of complex calculations.

Up until Maskelyne’s appointment as Astronomer Royal, governance at the Observatory had either been non-existent or lacking in clarity. It wasn’t until 1710, for example that a Board of Visitors consisting of Fellows of the Royal Society was set up to oversee the Observatory’s work. Over the years the lack of governance had lead to various misunderstandings and disputes, particularly about ownership of the observations.  Maskelyne seized the opportunity of his appointment to draw up the Observatory’s first set of regulations as to how its business should be conducted. It was Maskelyne’s organisational and administrative skills that lead to the publication in 1766 of the first Nautical Almanac, a volume of tables that removed many of the onerous calculations required by the lunar-distance method of finding longitude.

The almanac sold in large numbers and was adopted by many countries. As a result, when the International Meridian Conference met in 1884 to settle on a Prime Meridian for the world, more sailors were measuring their longitude from Greenwich than anywhere else. The Greenwich Meridian was adopted and it is the Meridian Line for which the Observatory is most famous today.

Click here for a fuller account of the longitude story.


An expanding role for the Observatory

The death of Maskelyne in 1811 marked the end of an era at the Observatory. Since its foundation in 1675, the scope of its work and the way it was run had undergone few changes. Under Maskelyne’s successor John Pond, things turned out to be rather different.

Pond was the first of the Astronomers Royal to take over the running of the Observatory as a proper going concern, inheriting both previous observations and a properly functioning set of instruments. In 1816, he was asked by the Admiralty to start a series of observations of magnetic variation. A purpose built magnetic observatory was erected in 1817. But its foundations rapidly gave way and in 1824 the instruments were removed and observations ceased.

Meanwhile, the Admiralty took over the funding of the Observatory form the Board of Ordnance and in 1821 responsibility for the testing and rating of the Navy’s chronometers was transferred to it. Chronometer work continued to be an important part of the Observatory’s function until the 1960s.

Pond’s period in office coincided with the battles that were taking place between the old and the new scientific elites as they jockeyed for influence with government and a role in dispensing patronage for science. With the old guard eventually in decline, the membership of the Observatory’s Board of Visitors was widened in 1830 to include not only members of the Royal Society (as it always had), but members of the newly formed Royal Astronomical Society as well.

During Pond’s period in office, the number of assistants at the Observatory increased from one to six. Beset by ill health throughout his term as Astronomer Royal, Pond was the first Astronomer Royal to retire rather than to die in office.


The Victorian glory years

Pond’s successor was George Airy, and it was under Airy, that the Observatory’s global lead in positional astronomy was established. Airy was a formidable administrator, a compulsive record keeper, an engineer at heart and a man of great probity. Under him, new factory like working methods were introduced and the workplace transformed into something that seemed more akin to an accountant’s office than a traditional Observatory.

Amongst Airy’s first actions as Astronomer Royal was the re-establishment of a magnetic observatory, along with a meteorological one. It wasn’t long before he was taking on extra work in a personal capacity for the Government as a scientific advisor. Although the post did not then exist, he was in effect, the Chief Government Scientific Advisor of his day and advised on: the Correction of the Compass in iron ships, the Railway Gauge Commission, the Commission for the Restoration of the Standards of Length and Weight, the Maine Boundary, Lighthouses, the Westminster Clock, the London University, and many other issues.


The Greenwich Time Service

The Greenwich Time Service – the first national service in the World – began under John Pond in 1833, when the hour of one o'clock was announced by the descent of a large black ball, from the summit of a pole, surmounting the north-eastern turret of the Observatory. The time signal was primarily intended for mariners so that they could set their chronometers before setting sail. Its position was such that it was easily visible from the London Docks and the adjacent river Thames. Now painted red, the ball is a key attraction for visitors to the Greenwich site today.

The first steps in the distribution of time beyond the immediate vicinity of the Observatory became possible with the development of telegraphic communications. In 1852, an electric clock was installed at the Observatory from which a time signal was transmitted via the galvanic telegraph system of the South Eastern Railway.  Following the take-over of the telegraph system by the Post Office in 1870, a more comprehensive system of distribution was developed. Many further developments took place in the twentieth century, the most famous of which is the ‘six pip’ time signal which has been transmitted on the radio in the UK since 1924.


The boundaries of acceptable research

Airy was the longest serving of the Observatory’s leaders. Sometimes regarded as autocratic and arrogant, he took a clear view about the Observatory’s remit, particularly in light of its routine responsibilities and the limited funding available from the public purse. The wider issue of public funding of science in Britain came to a head in the late 1860s as the new subject of astrophysics was starting to open up. At the heart of the debate, was whether the government should sponsor a series of national astrophysical observatories or whether such work should be left to the combined efforts of Greenwich and the contributions of enthusiastic and often wealthy individuals (as it had been in the past). Against this background, in 1870 the government set up a Royal Commission on Scientific Instruction and the Advancement of Science, chaired by William Cavendish the Seventh Duke of Devonshire. Often referred to as the Devonshire Commission, its findings were published in a number of reports between 1872 and 1875. Click here to read Airy’s evidence to the commission.

While all this was going on, business was very much as usual back at Greenwich and new programmes of work were initiated that included the measurement of the heat radiating from stars (1869-70) together with spectroscopy and daily photography of the Sun under the auspices of a newly established Solar Department (1873).

But the problem of the Observatory’s reach was one that clearly vexed Airy. By 1875, the Observatory had been in existence for 200 years and Airy in office for 40. He took the opportunity to publicly review both the achievements of the past together with the work that the Observatory might be involved in the future. He believed most strongly that the Observatory should not involve itself with the ‘new physical investigations’, and added that if in the future the Observatory programme should be cut, it should be in the areas of Meteorology, Photoheliography and Spectroscopy; ‘not as unimportant in themselves, nor as ill fitting to the work of the Observatory, but as the least connected to its original aims’.

Airy retired in 1881, to be succeeded by his Chief Assistant, William Christie whose views and approach were altogether rather different.


Expansion and decline

Whilst Airy had been scrupulous in his requests for capital funding, each request for a new telescope being properly costed and preceded by a well-argued case; under Christie things were rather less transparent. During his period in office there was a massive increase in the number of large telescopes at the Observatory. These were funded in part by the taxpayer and in part from generous donations. On the whole, their purpose was ill defined and their installation chaotic, resulting in delays, extra costs, and a reduction in their overall usefulness.

A new Physical Building (the present South Building) was erected and new areas of work embarked upon. But Greenwich was a poor site for the erection of large telescopes. It was cramped and the skies polluted … and the pollution was getting worse. And it wasn’t only the astronomical observations that were being compromised; the electrification of London’s railways that had begun in the 1890s caused magnetic disturbances that affected the magnetic instruments as well.

History has been kind to Christie and he is often lauded for the expansion that took place under his command. But in truth, it was this expansion on the Greenwich site that sowed the seeds for the Observatory’s ultimate demise. A much better option, (though rather less palatable for Christie from a personal point of view as it would have impacted heavily on his lifestyle), would have been to expand on a new and remote site in the countryside. Had that happened, even though the best observing sites in the UK were always going to be inferior to those that would eventually be attained overseas, UK astronomy might well have evolved along different lines with the Observatory still having an operational role today.


The First World War and the setting up of the Abinger Magnetic Observatory

The coming of the First World War had relatively little long term impact.  Around half the Junior Assistants signed up as did most of the Computers. These were the young men employed to turn the many observations into something more useful. Their absence, along with that of the Chief Assistants created a publications backlog which took until the 1920s to clear. The only physical damage inflicted on the Observatory was caused not by enemy action, but a blast caused by a fire at a chemical factory several miles away across the river that had been adapted for the production of trinitrotoluene (TNT).

After the war, a rationalisation of Britain’s railways began. And with this came the likelihood of such a large increase in magnetic interference from their electrical systems that the magnetic observations would be rendered worthless. As a result, it was decided to move the magnetic observatory away from London to a new site at Abinger in Surrey.


The Second World War and evacuation

By the 1930s, the atmospheric pollution in London was so bad that the then Astronomer Royal, Spencer Jones, believed that a choice had to made: either to move somewhere else, or to stay put and watch as the Observatory inevitably degenerated into a second rate institution. The Admiralty opted for the former.

The Second World War however delayed any move. It also brought a premature end to much of the observing programme at Greenwich, together with the evacuation of those services essential to the war effort. The Nautical Almanac office was evacuated to Bath, the chronometer workshop initially to Bristol and then to Bradford on Avon, and the time service to Abinger. The two chief assistants, d’E Atkinson and Hume were loaned for special to work to another part of the Admiralty.


Post war relocation to Herstmonceux and a shift in priorities

Under Spencer Jones, not only did the Observatory relocate, but the staffing underwent a radical transformation. Instead of vacancies at all but the most senior level being filled (as they had been since the mid-1890s) by insiders who had entered the Observatory straight from school and risen through the ranks; they began to be filled with graduates from the universities. By the time he retired in 1955, Spencer Jones had overseen an increase in headcount from 57 members of staff to 195.

The process of moving the staff and telescopes to a new site at Herstmonceux eventually began in 1948, but was fraught with delays. It took a further decade for the large (equatorial) telescopes to become operational and by then most had been out of service for the best part of twenty years. In the meantime the World had moved on, new technologies had developed, and the outlook and expectations of astronomers had changed.

Despite the changes that Spencer Jones had overseen, the work of the Observatory was still almost exclusively confined to positional astronomy. When he retired, Spencer Jones was replaced by a former Chief Assistant, Richard Woolley. But as with Christie and Airy, the views of Spencer Jones and Woolley on the role of the Observatory were poles apart. Many of the long term observing programmes were axed or curtailed in favour of transforming the Observatory into a national centre for astrophysics centred on the as yet to be completed Isaac Newton Telescope – a large telescope that had been promised to British Astronomers in 1946, and was finally brought into operation in 1967. Between conception and final delivery, much had changed, and the siting of the Isaac Newton telescope at Herstmonceux rather than at a better site overseas was the cause of much bitter controversy.


The Science Research Council (SRC) and the beginning of the end

The formation of the Science Research Council (SRC) in 1965 brought the funding of all UK astronomy under the same umbrella for the first time in its history. The change in control from the Admiralty initially had little impact on the day-to-day running of the Observatory. The Board of Visitors ceased to exist. Responsibility for the chronometers transferred to the Hydrographic Department of the Ministry of Defence in 1964 and the geomagnetic work transferred to the Natural Environment Research Council (NERC) in 1967. By this time, though, the Magnetic Observatory had long been physically separate from the Astronomical Observatory, having moved first to Abinger in Surrey in 1924 and from there to Hartland in Devon in 1957.


The SRC flexes its muscles

It was when Woolley retired that the SRC began to flex its muscles and exert its influence. Its first move was to decouple the title of Astronomer Royal from the Directorship of the Observatory. The succession was bungled and much ill feeling created as the staff divided into two camps. This was followed by a fundamental change to the Observatory’s remit in January 1974 on the eve of its tercentenary and nearly 100 years after Airy had aired his views on what the future Observatory might look like.

Although it retained its responsibility for national and international services such as the provision of navigational almanacs and the maintenance of the national time service, the major part of the Observatory’s resources were now to be directed towards supporting university research. It was permitted to keep a much scaled down research programme of its own, but this too had to be in collaboration with university astronomers.

Later that same year, the SRC agreed to the funding of a new Northern Hemisphere Observatory consisting of three large telescopes, including the Isaac Newton which was to be modified and transferred from Herstmonceux.


The move to Cambridge

When Alec Boksenberg arrived as the new Director in 1981 his main remit was to get these new telescopes up and running in La Palma. His appointment came not long after Thatcher had become Prime Minister and coincided with the renaming of the SRC, as the Science and Engineering Research Council (SERC). Commencing in 1983, the Observatory was subjected to the first of what turned out to be a series of three reviews inspired by the Thatcher Government’s drive against waste and inefficiency. They were conducted by the SERC. In 1983/4 Boksenberg was instructed to commence a rapid reduction in staff numbers with the aim of reducing them from the 1980 level of 237 to just 128 by 1990.

On 18 June 1986, the SERC announced that the Observatory would be moved to Cambridge. Many in the astronomical community were baffled and angered by the decision. Of those staff who chose to move, some went in the autumn of 1989, with the rest transferring in April 1990. Meanwhile, the time service closed down during February 1990 with the BBC taking over the generation of the six pips. Only the Satellite Laser Ranging facility remained operational at Herstmonceux.


Further reorganisations and closure

Once it had arrived in Cambridge, the Observatory was subjected to further reorganisations and reviews. Then in 1997, PPARC – a new Quango formed when the SERC itself was reorganised in 1994 – announced that the Observatory would be shut down. Appeals fell on deaf ears. The 323-year-old Observatory closed its doors for the last time at the end of October 1998.

A few staff transferred to a new astronomy technology centre at the Royal Observatory Edinburgh. The Nautical Almanac Office (which had been run independently of the Observatory between and 1818 and 1829 and between 1831 and 1936) transferred to the Rutherford Appleton Laboratory in Oxfordshire and control of the Satellite Laser Ranging facility transferred to NERC.