Johann Georg Liebknecht (23 April 1679 in

Wasungen Wasungen () is a town in the Schmalkalden-Meiningen district, in Thuringia, Germany. It is situated on the river Werra, 11 km north of Meiningen Meiningen () is a town in the southern part of the state of Thuringia, Germany. It is locate ...

Thuringia Thuringia (; officially the Free State of Thuringia, ) is one of Germany, Germany's 16 States of Germany, states. With 2.1 million people, it is 12th-largest by population, and with 16,171 square kilometers, it is 11th-largest in area. Er ...

– 17 September 1749 in

Giessen Giessen, spelled in German (), is a town in the Germany, German States of Germany, state () of Hesse, capital of both the Giessen (district), district of Giessen and the Giessen (region), administrative region of Giessen. The population is appro ...

) was a German theologian and scientist. He was professor of mathematics and theology at the Ludoviciana (University) in Giessen, Germany.

Biography

He was born the son of Michael Liebknecht, schoolmaster, of Wasungen, and his wife, Margarethe Turckin and was educated in the Gymnasium at

Schleusingen Schleusingen is a town in the Hildburghausen (district), district of Hildburghausen, in Thuringia, Germany. It is situated 10 km north of Hildburghausen, and 12 km southeast of Suhl. Geography The town of Schleusingen in the Henneber ...

and at

Jena Jena (; ) is a List of cities and towns in Germany, city in Germany and the second largest city in Thuringia. Together with the nearby cities of Erfurt and Weimar, it forms the central metropolitan area of Thuringia with approximately 500,000 in ...

. He was awarded MA (1702), BD (1717) and DD (1719) Liebknecht was offered a position, on the recommendation of

Gottfried Wilhelm Leibniz Gottfried Wilhelm Leibniz (or Leibnitz; – 14 November 1716) was a German polymath active as a mathematician, philosopher, scientist and diplomat who is credited, alongside Sir Isaac Newton, with the creation of calculus in addition to ...

, at the small state university in Giessen; he was versatile and could teach several subjects competently. He was both a respected evangelical theologian and a leading mathematician. Other focal points of his work lay in the application of mathematics in the military (artillery, fortresses), geology (mineral deposits), archeology (excavations of grave mounds near Giessen), fossils and astronomy. Like other

Protestant Protestantism is a branch of Christianity that emphasizes Justification (theology), justification of sinners Sola fide, through faith alone, the teaching that Salvation in Christianity, salvation comes by unmerited Grace in Christianity, divin ...

theologians he avoided, even 200 years after

Copernicus Nicolaus Copernicus (19 February 1473 – 24 May 1543) was a Renaissance polymath who formulated a mathematical model, model of Celestial spheres#Renaissance, the universe that placed heliocentrism, the Sun rather than Earth at its cen ...

, supporting the

heliocentric Heliocentrism (also known as the heliocentric model) is a Superseded theories in science#Astronomy and cosmology, superseded astronomical model in which the Earth and Solar System, planets orbit around the Sun at the center of the universe. His ...

world view. He was in contact with famous scientists such as Leibniz. From 1707 to 1737 he was Professor of Mathematics at Giessen and from 1721 until his death also Professor of Theology. From 1715 he was a member of the Leopoldina (''Deutsche Akademie der Naturforscher Leopoldina'') and from 1716 a member of the Royal Prussian Society of Sciences. In 1728 he was elected a

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 ...

''Sidus Ludoviciana''

Liebknecht was a keen astronomer. He made some of the rare

aurora An aurora ( aurorae or auroras), also commonly known as the northern lights (aurora borealis) or southern lights (aurora australis), is a natural light display in Earth's sky, predominantly observed in high-latitude regions (around the Arc ...

observations during the period 1711–1721. For another observation, however, he gained no credit. On 2 December 1722, he observed a faint star in the telescope and thought he observed

relative motion In geometry, a position or position vector, also known as location vector or radius vector, is a Euclidean vector that represents a point ''P'' in space. Its length represents the distance in relation to an arbitrary reference origin ''O'', and ...

(

proper motion Proper motion is the astrometric measure of changes in the apparent places of stars or other celestial objects as they move relative to the center of mass of the Solar System. It is measured relative to the distant stars or a stable referenc ...

) to the neighbouring stars of the

Big Dipper The Big Dipper (American English, US, Canadian English, Canada) or the Plough (British English, UK, Hiberno-English, Ireland) is an asterism (astronomy), asterism consisting of seven bright stars of the constellation Ursa Major; six of them ar ...

Mizar and Alcor Mizar and Alcor are two stars forming a naked eye double in the handle of the Big Dipper (or Plough) asterism in the constellation of Ursa Major. Their magnitudes are 2.2 and 3.9, and the pair can easily be seen without the aid of a telescope. M ...

. He called the supposed new planet ''Sidus Ludoviciana''. Liebknecht was unaware, however, that this star had already been observed in the same position in 1616 by

Benedetto Castelli Benedetto Castelli (1578 – 9 April 1643), born Antonio Castelli, was an Italians, Italian mathematician. Benedetto was his name in religion on entering the Benedictine Order in 1595. Life Born in Brescia, Castelli studied at the University of ...

and could not therefore be a planet.

Family

He married twice; firstly Catharine Elisabeth, daughter of Nikolaus Caspar Elwerten, physician, of

Bensheim Bensheim () is a town in the Kreis Bergstraße, Bergstraße district in southern Hessen, Germany. Bensheim lies on the Bergstraße Route, Bergstraße and at the edge of the Odenwald mountains while at the same time having an open view over the Rhi ...

and secondly Regina Sophie, daughter of Johann Just Hoffmann, physician, of Isenburg. He had 21 children from his two marriages.

References

1679 births 1749 deaths People from Schmalkalden-Meiningen 18th-century German Protestant theologians 18th-century German astronomers Fellows of the Royal Society German male non-fiction writers 18th-century German male writers Members of the German National Academy of Sciences Leopoldina Members of the Prussian Academy of Sciences {{Germany-scientist-stub