Editing Sophus Lie (section)

== Life and career ==
Marius Sophus Lie was born on 17 December 1842 in the small town of [[Nordfjordeid]]. He was the youngest of six children born to Lutheran pastor Johann Herman Lie and his wife, who came from a well-known [[Trondheim]] family.<ref> {{cite book |last=James |first=Ioan |author-link= |date=2002 |title=Remarkable Mathematicians |url= |location= |publisher=Cambridge University Press |page= 201 |isbn=978-0-521-52094-2}}</ref>

He had his primary education in the south-eastern coast of Moss, before attending high school in [[Oslo]] (known then as Christiania). After graduating from high school, his ambition towards a military career was dashed when the army rejected him due to poor eyesight. He then enrolled at the [[University of Christiania]].

Sophus Lie's first mathematical work, ''Repräsentation der Imaginären der Plangeometrie'', was published in 1869 by the Academy of Sciences in [[Oslo|Christiania]] and also by ''[[Crelle's Journal]]''. That same year he received a scholarship and travelled to [[Berlin]], where he stayed from September to February 1870. There, he met [[Felix Klein]] and they became close friends. When he left Berlin, Lie travelled to [[Paris]], where he was joined by Klein two months later. There, they met [[Camille Jordan]] and [[Jean Gaston Darboux|Gaston Darboux]]. But on 19 July 1870 the [[Franco-Prussian War]] began and Klein (who was [[Kingdom of Prussia|Prussian]]) had to leave France very quickly. Lie left for [[Fontainebleau]] where he was arrested, suspected of being a German spy, garnering him fame in Norway. He was released from prison after a month, thanks to the intervention of Darboux.<ref>{{cite journal|author=Darboux, Gaston|author-link=Gaston Darboux|title=Sophus Lie|journal=Bull. Amer. Math. Soc.|year=1899|volume=5|issue=7|pages=367–370|doi=10.1090/s0002-9904-1899-00628-1|doi-access=free}}</ref>

Lie obtained his PhD at the University of Christiania (in present-day [[Oslo]]) in 1871 with a thesis entitled ''Over en Classe geometriske Transformationer'' (On a Class of Geometric Transformations).<ref name=thesis>{{cite thesis|type=PhD|last=Lie|first=Sophus|title=Over en classe geometriske Transformationer|url=http://urn.nb.no/URN:NBN:no-nb_digibok_2010012912009 |date=1871|publisher=University of Christiania}}</ref> It would be described by Darboux as "one of the most handsome discoveries of modern Geometry". The next year, the Norwegian Parliament established an extraordinary professorship for him. That same year, Lie visited Klein, who was then at [[University of Erlangen-Nuremberg|Erlangen]] and working on the [[Erlangen program]].

In 1872, Lie spent eight months together with [[Peter Ludwig Mejdell Sylow]], editing and publishing the mathematical works of their countryman, [[Niels Henrik Abel]].

At the end of 1872, Sophus Lie proposed to Anna Birch, then eighteen years old, and they were married in 1874. The couple had three children: Marie (b. 1877), Dagny (b. 1880) and Herman (b. 1884).

From 1876, he co-edited the journal ''[[Archiv for Mathematik og Naturvidenskab]]'', together with the physician Jacob Worm-Müller, and the biologist [[Georg Ossian Sars]].

In 1884, [[Friedrich Engel (mathematician)|Friedrich Engel]] arrived at Christiania to help him, with the support of [[Felix Klein|Klein]] and [[Christian Gustav Adolph Mayer|Adolph Mayer]] (who were both professors at [[University of Leipzig|Leipzig]] by then). Engel would help Lie to write his most important treatise, ''Theorie der Transformationsgruppen'', published in Leipzig in three volumes from 1888 to 1893. Decades later, Engel would also be one of the two editors of Lie's collected works.

In 1886, Lie became a professor at Leipzig, replacing Klein, who had moved to [[University of Göttingen|Göttingen]]. In November 1889, Lie suffered a mental breakdown and had to be hospitalized until June 1890. Subsequently he returned to his post, but over the years his anaemia progressed to the point where he returned to his homeland. In 1898 he tendered his resignation in May, and left for home in September the same year. He died the following year in 1899 at the age of 56, due to [[pernicious anemia]], a disease caused by impaired absorption of [[vitamin B12|vitamin B<sub>12</sub>]].

He was made Honorary Member of the [[London Mathematical Society]] in 1878, Corresponding Member of the [[French Academy of Sciences]] in 1892, Foreign Member of the [[Royal Society of London]] in 1895 and foreign associate of the [[United States National Academy of Sciences|National Academy of Sciences of the United States of America]] in 1895.<gallery>
File:Lie-1.jpg|1888 copy of "Theorie der Transformationsgruppen," volume I
File:Lie-2.jpg|Title page to "Theorie der Transformationsgruppen"
File:Lie-3.jpg|Preface to "Theorie der Transformationsgruppen"
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