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Sir David Gill (12 June 1843 – 24 January 1914) was a Scottish astronomer who is known for measuring astronomical distances, for astrophotography, and for geodesy. He spent much of his career in South Africa.


Life and work

David Gill was born at 48 Skene Terrace in
Aberdeen Aberdeen (; sco, Aiberdeen ; gd, Obar Dheathain ; la, Aberdonia) is a city in North East Scotland, and is the third most populous city in the country. Aberdeen is one of Scotland's 32 local government council areas (as Aberdeen City), and ...
the son of David Gill, watchmaker and his wife Margaret Mitchell. He was educated first at Bellevue Academy in Aberdeen then at
Dollar Academy Dollar Academy, founded in 1818 by John McNabb, is an independent co-educational day and boarding school in Scotland. The open campus occupies a site in the centre of Dollar, Clackmannanshire, at the foot of the Ochil Hills. Overview As of 2 ...
. He spent two years at
Aberdeen University , mottoeng = The fear of the Lord is the beginning of wisdom , established = , type = Public research university Ancient university , endowment = £58.4 million (2021) , budget ...
, where he was taught by
James Clerk Maxwell James Clerk Maxwell (13 June 1831 – 5 November 1879) was a Scottish mathematician and scientist responsible for the classical theory of electromagnetic radiation, which was the first theory to describe electricity, magnetism and light ...
, and then joined his father's clock-making business. His most important influence at university was probably from Prof David Thomson. In 1863 they jointly repaired the university clock and both set up a new mechanical telescope at the Cromwell Tower Observatory. This was his introduction to astronomy. It would seem that Gill's interests lay elsewhere since after a few years he sold the business, and then spent time equipping Lord Lindsay's private observatory at Dun Echt,
Aberdeenshire Aberdeenshire ( sco, Aiberdeenshire; gd, Siorrachd Obar Dheathain) is one of the 32 council areas of Scotland. It takes its name from the County of Aberdeen which has substantially different boundaries. The Aberdeenshire Council area includ ...
. In 1874, Gill joined the expedition to
Mauritius Mauritius ( ; french: Maurice, link=no ; mfe, label=Mauritian Creole, Moris ), officially the Republic of Mauritius, is an island nation in the Indian Ocean about off the southeast coast of the African continent, east of Madagascar. It inc ...
to observe the
transit of Venus frameless, upright=0.5 A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and a superior planet, becoming visible against (and hence obscuring a small portion of) the solar disk. During a trans ...
. Three years later he went to
Ascension Island Ascension Island is an isolated volcanic island, 7°56′ south of the Equator in the South Atlantic Ocean. It is about from the coast of Africa and from the coast of South America. It is governed as part of the British Overseas Territory ...
to observe a near approach of
Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin atm ...
and to calculate its distance. While carrying out these laborious calculations, he was notified of his appointment to the
Cape Observatory South African Astronomical Observatory (SAAO) is the national centre for optical and infrared astronomy in South Africa. It was established in 1972. The observatory is run by the National Research Foundation of South Africa. The facility's funct ...
, which, over the following 27 years he was to refurbish completely, turning it into a first-rate institution. Gill was a meticulous observer and had a flair for getting the best out of his instruments. His
solar parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby objects ...
observations with a
heliometer A heliometer (from Greek ἥλιος ''hḗlios'' "sun" and ''measure'') is an instrument originally designed for measuring the variation of the sun's diameter at different seasons of the year, but applied now to the modern form of the instrumen ...
and his calculations of distances to the nearer stars, are testimony to his outstanding work. He recruited Robert Innes to the
Cape Observatory South African Astronomical Observatory (SAAO) is the national centre for optical and infrared astronomy in South Africa. It was established in 1972. The observatory is run by the National Research Foundation of South Africa. The facility's funct ...
. Gill used the
parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby objects ...
of Mars to determine the distance to the
Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
, and also measured distances to the
star A star is an astronomical object comprising a luminous spheroid of plasma held together by its gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night, but their immense distances from Earth ma ...
s. He perfected the use of the heliometer. He was Her Majesty's Astronomer at the Royal Observatory at
Cape of Good Hope The Cape of Good Hope ( af, Kaap die Goeie Hoop ) ;''Kaap'' in isolation: pt, Cabo da Boa Esperança is a rocky headland on the Atlantic coast of the Cape Peninsula in South Africa. A common misconception is that the Cape of Good Hope is t ...
from 1879 to 1906. He was a pioneer in the use of
astrophotography Astrophotography, also known as astronomical imaging, is the photography or imaging of astronomical objects, celestial events, or areas of the night sky. The first photograph of an astronomical object (the Moon) was taken in 1840, but it was no ...
, making the first photograph of the
Great Comet of 1882 The Great Comet of 1882 formally designated C/1882 R1, 1882 II, and 1882b, was a comet which became very bright in September 1882. It was a member of the Kreutz Sungrazers, a family of comets which pass within of the Sun's photosphere at per ...
, and one of the early proponents of the ''
Carte du Ciel The Carte du Ciel (literally, 'Map of the Sky') and the Astrographic Catalogue (or Astrographic Chart) were two distinct but connected components of a massive international astronomical project, initiated in the late 19th century, to catalogue an ...
'' project. The invention of dry plate photography by
Richard Leach Maddox Richard Leach Maddox (4 August 1816 – 11 May 1902) was an English photographer and physician who invented lightweight gelatin negative dry plates for photography in 1871. Early life Richard Leach Maddox was born at Bath, England, on 4 Aug ...
made Gill realise that the process could be used to create images of the stars and to more easily determine their relative positions and brightness. This led to a massive project in collaboration with the Dutch astronomer J.C. Kapteyn, and the compiling of an index of brightness and position for some half a million southern stars. The work was published as '' Cape Photographic Durchmusterung'' in 3 volumes between 1896 and 1900. Gill also played a leading role in the organising of the ''Carte du Ciel'', an ambitious international venture aimed at mapping the entire sky. He initiated the idea of a geodetic survey along the
30th meridian east The meridian 30° east of Greenwich is a line of longitude that extends from the North Pole across the Arctic Ocean, Europe, Turkey, Africa, the Indian Ocean, the Southern Ocean, and Antarctica to the South Pole. The 30th meridian east forms a ...
stretching from South Africa to
Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and th ...
, resulting in the longest meridian yet measured on Earth. His concern with measurement led to him becoming a member of the International Committee for Weights and Measures (CIPM) from 1907 - 1914. As president of the British Association for the Advancement of Science, he gave a presidential address in 1907 in which he advocated definitions based on fundamental physical properties, rather than on arbitrary standards such as a rod of metal with lines ruled upon it to mark the yard or metre. Gill married Isobel Black in 1870, and she accompanied him to Ascension Island for his Mars observations. On Gill's retirement in 1906, the couple moved to London, where Gill served for two years (1909–1911) as president of the
Royal Astronomical Society (Whatever shines should be observed) , predecessor = , successor = , formation = , founder = , extinction = , merger = , merged = , type = NGO ...
before his death in 1914. He was buried with his wife, Isobel Sarah Gill, in the grounds of
St Machar's Cathedral St Machar's Cathedral usually called Old Machar (Scottish Gaelic: Cathair-eaglais Naomh Machar), (or, more formally, the Cathedral Church of St Machar) is a Church of Scotland church in Aberdeen, Scotland. It is located to the north of the ...
, Aberdeen. The grave lies on the east outer wall of the church.


Selected writings

His writings include: * * *"A Determination of the Solar Parallax from Observations of Mars at the Island of Ascension" (in the ''Memoirs of the
Royal Astronomical Society (Whatever shines should be observed) , predecessor = , successor = , formation = , founder = , extinction = , merger = , merged = , type = NGO ...
'', volumes xlvi and xlviii, 1881 and 1885).
New International Encyclopedia ''The New International Encyclopedia'' was an American encyclopedia first published in 1902 by Dodd, Mead and Company. It descended from the ''International Cyclopaedia'' (1884) and was updated in 1906, 1914 and 1926. History ''The New Inter ...
* *


Honours

* Elected
Fellow of the Royal Society Fellowship of the Royal Society (FRS, ForMemRS and HonFRS) is an award granted by the judges of the Royal Society of London to individuals who have made a "substantial contribution to the improvement of natural knowledge, including mathematic ...
, 7 June 1883 * Companion of the
Order of the Bath The Most Honourable Order of the Bath is a British order of chivalry founded by George I on 18 May 1725. The name derives from the elaborate medieval ceremony for appointing a knight, which involved bathing (as a symbol of purification) as one ...
, 20 May 1896 * Knight Commander of the Order of the Bath, 24 May 1900 * President,
Royal Astronomical Society (Whatever shines should be observed) , predecessor = , successor = , formation = , founder = , extinction = , merger = , merged = , type = NGO ...
, 1909–1911 * Member of the
Royal Swedish Academy of Sciences The Royal Swedish Academy of Sciences ( sv, Kungliga Vetenskapsakademien) is one of the royal academies of Sweden. Founded on 2 June 1739, it is an independent, non-governmental scientific organization that takes special responsibility for prom ...
, 1910


Lectures

In 1909 he was invited to deliver the Royal Institution Christmas Lecture on ''Astronomy, Old and New''.


Awards

* Valz Prize (1879) *
Bruce Medal The Catherine Wolfe Bruce Gold Medal is awarded every year by the Astronomical Society of the Pacific for outstanding lifetime contributions to astronomy. It is named after Catherine Wolfe Bruce, an American patroness of astronomy, and was f ...
(1900) *
Gold Medal of the Royal Astronomical Society The Gold Medal of the Royal Astronomical Society is the highest award given by the Royal Astronomical Society (RAS). The RAS Council have "complete freedom as to the grounds on which it is awarded" and it can be awarded for any reason. Past awar ...
(1882 and 1908) * James Craig Watson Medal (1899)


Named after him

* Gill (lunar crater) * Gill (Martian crater)


References


External links

*
Bruce Medal page


Obituaries



{{DEFAULTSORT:Gill, David 1843 births 1914 deaths Scottish astronomers 19th-century British astronomers South African astronomers Alumni of the University of Aberdeen Fellows of the Royal Society Royal Medal winners Members of the Royal Swedish Academy of Sciences Corresponding members of the Saint Petersburg Academy of Sciences Recipients of the Gold Medal of the Royal Astronomical Society Foreign Fellows of the Royal Astronomical Society Fellows of the Royal Astronomical Society Foreign associates of the National Academy of Sciences Recipients of the Bruce Medal Presidents of the British Science Association People educated at Dollar Academy Presidents of the Royal Astronomical Society Knights Commander of the Order of the Bath Recipients of the Pour le Mérite (civil class) 20th-century British astronomers Presidents of the Southern Africa Association for the Advancement of Science