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

Life and work

David Gill was born at 48 Skene Terrace in

Aberdeen Aberdeen ( ; ; ) is a port city in North East Scotland, and is the List of towns and cities in Scotland by population, third most populous Cities of Scotland, Scottish city. Historically, Aberdeen was within the historic county of Aberdeensh ...

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 is a 5–18 Private schools in the United Kingdom, private co-educational day and boarding school for boys and girls in Scotland. The open campus occupies a site in the centre of Dollar, Clackmannanshire, at the foot of the Ochil ...

. He spent two years at

Aberdeen University The University of Aberdeen (abbreviated ''Aberd.'' in post-nominals; ) is a public research university in Aberdeen, Scotland. It was founded in 1495 when William Elphinstone, Bishop of Aberdeen and Chancellor of Scotland, petitioned Pope Al ...

, where he was taught by

James Clerk Maxwell James Clerk Maxwell (13 June 1831 – 5 November 1879) was a Scottish physicist and mathematician who was responsible for the classical theory of electromagnetic radiation, which was the first theory to describe electricity, magnetism an ...

, 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 (; ) is one of the 32 Subdivisions of Scotland#council areas of Scotland, council areas of Scotland. It takes its name from the Shires of Scotland, historic county of Aberdeenshire (historic), Aberdeenshire, which had substantial ...

. In 1874, Gill joined the expedition to

Mauritius Mauritius, officially the Republic of Mauritius, is an island country in the Indian Ocean, about off the southeastern coast of East Africa, east of Madagascar. It includes the main island (also called Mauritius), as well as Rodrigues, Ag ...

to observe the

transit of Venus A transit of Venus takes place when Venus passes directly between the Sun and the Earth (or any other superior planet), becoming visible against (and hence obscuring a small portion of) the solar disk. During a transit, Venus is visible as ...

. Three years later he went to

Ascension Island Ascension Island is an isolated volcanic island, 7°56′ south of the Equator in the Atlantic Ocean, 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 Overs ...

to observe a near approach of

Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...

and to calculate its distance. While carrying out these laborious calculations, he was notified of his appointment to the

Cape Observatory The 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 f ...

, 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 The most important fundamental distance measurements in astronomy come from trigonometric parallax, as applied in the '' stellar parallax method''. As the Earth orbits the Sun, the position of a nearby star will appear to shift slightly agains ...

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

. Gill used the

parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to perspective (graphica ...

of Mars to determine the distance to the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

, and also measured distances to the

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

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 ( ) is a rocky headland on the Atlantic Ocean, Atlantic coast of the Cape Peninsula in South Africa. A List of common misconceptions#Geography, common misconception is that the Cape of Good Hope is the southern tip of Afri ...

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 1839, but it was no ...

, making the first photograph of the Great Comet of 1882, 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 ...

'' project. The invention of

dry plate The gelatin silver print is the most commonly used chemical process in black-and-white photography, and is the fundamental chemical process for modern analog color photography. As such, films and printing papers available for analog photography r ...

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 astronomy, Durchmusterung or Bonner Durchmusterung (BD) is an astrometric star catalogue of the whole sky, published by the Bonn Observatory in Germany from 1859 to 1863, with an extension published in Bonn in 1886. The name comes from ('run-t ...

'' 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 countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. The remote Arctic island of Jan Mayen and the archipelago of Svalbard also form part of the Kingdom of ...

, resulting in the longest

meridian arc In geodesy and navigation, a meridian arc is the curve (geometry), curve between two points near the Earth's surface having the same longitude. The term may refer either to a arc (geometry), segment of the meridian (geography), meridian, or to its ...

yet measured on Earth (see

arc measurement Arc measurement, sometimes called degree measurement (), is the astrogeodetic technique of determining the radius of Earth and, by Circumference#Circle, extension, Earth's circumference, its circumference. More specifically, it seeks to determine ...

). 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 The Royal Astronomical Society (RAS) is a learned society and charitable organisation, charity that encourages and promotes the study of astronomy, planetary science, solar-system science, geophysics and closely related branches of science. Its ...

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 is a Church of Scotland church (building), church in Aberdeen, Scotland, located to the north of the city centre, in the former burgh of Old Aberdeen. Technically, St Machar's is no longer a cathedral but rather a Kirk ...

, 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

'', 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 & Co. It descended from the ''International Cyclopaedia'' (1884) and was updated in 1906, 1914 and 1926. History ''The New Internatio ...

* *

Honours

* Elected

Fellow of the Royal Society Fellowship of the Royal Society (FRS, ForMemRS and HonFRS) is an award granted by the Fellows of the Royal Society of London to individuals who have made a "substantial contribution to the improvement of natural science, natural knowledge, incl ...

, 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 King George I of Great Britain, George I on 18 May 1725. Recipients of the Order are usually senior British Armed Forces, military officers or senior Civil Service ...

, 20 May 1896 * Elected International Member of the United States

National Academy of Sciences The National Academy of Sciences (NAS) is a United States nonprofit, NGO, non-governmental organization. NAS is part of the National Academies of Sciences, Engineering, and Medicine, along with the National Academy of Engineering (NAE) and the ...

, 1898 * Knight Commander of the Order of the Bath, 24 May 1900 * President,

, 1909–1911 * Member of the

Royal Swedish Academy of Sciences The Royal Swedish Academy of Sciences () is one of the Swedish Royal Academies, royal academies of Sweden. Founded on 2 June 1739, it is an independent, non-governmental scientific organization that takes special responsibility for promoting nat ...

, 1910 * Elected International Member of the

American Philosophical Society The American Philosophical Society (APS) is an American scholarly organization and learned society founded in 1743 in Philadelphia that promotes knowledge in the humanities and natural sciences through research, professional meetings, publicat ...

, 1910 * Elected International Honorary Member of the

American Academy of Arts and Sciences The American Academy of Arts and Sciences (The Academy) is one of the oldest learned societies in the United States. It was founded in 1780 during the American Revolution by John Adams, John Hancock, James Bowdoin, Andrew Oliver, and other ...

Lectures

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

Awards

Valz Prize The Valz Prize ''(Prix Valz)'' was awarded by the French Academy of Sciences, from 1877 through 1970, to honor advances in astronomy. History The Valz Prize was established in June 1874 when the widow of astronomer Benjamin Valz, Marie Madeleine ...

(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 ...

(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 image:Watson_medal_NAS.gif, 400px, James Craig Watson Medal The James Craig Watson Medal was established by the bequest of James Craig Watson, an astronomer the University of Michigan between 1863 and 1879, and is awarded every 1-4 years by the U.S. ...

(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 International members of the American Philosophical Society