Editing Niels Bohr (section)

== Early life ==
Niels Henrik David Bohr was born in [[Copenhagen]], Denmark, on 7 October 1885, the second of three children of [[Christian Bohr]],<ref name=cphpolice3308989>{{cite book |author= <!--Staff writer(s); no by-line.--> |title= Politiets Registerblade |trans-title= Register cards of the Police |location= Copenhagen |publisher= Københavns Stadsarkiv |url= http://www.politietsregisterblade.dk/en/component/sfup/?controller=politregisterblade&task=viewRegisterblad&id=3308989 |at= Station Dødeblade (indeholder afdøde i perioden). Filmrulle 0002. Registerblad 3341 |date= 7 June 1892 |id= ID 3308989 |language= da |archive-url= https://web.archive.org/web/20141129033630/http://www.politietsregisterblade.dk/en/component/sfup/?controller=politregisterblade&task=viewRegisterblad&id=3308989 |archive-date= 29 November 2014}}</ref>{{sfn|Pais|1991|pp=44–45, 538–539}} a professor of [[physiology]] at the University of Copenhagen, and his wife Ellen {{nee}} Adler, who came from a wealthy [[Jewish]] banking family.{{sfn|Pais|1991|pp=35–39}} He had an elder sister, Jenny, and a younger brother [[Harald Bohr|Harald]].<ref name=cphpolice3308989 /> Jenny became a teacher,{{sfn|Pais|1991|pp=44–45, 538–539}} while Harald became a [[mathematician]] and [[association football|footballer]] who played for the [[Denmark national football team|Danish national team]] at the [[1908 Summer Olympics]] in London. Niels was a passionate footballer as well, and the two brothers played several matches for the Copenhagen-based [[Akademisk Boldklub]] (Academic Football Club), with Niels as [[Goalkeeper (association football)|goalkeeper]].<ref>There is no truth in the oft-repeated claim that Bohr emulated his brother, Harald, by playing for the Danish national team. {{cite news |last=Dart |first=James |date=27 July 2005 |url=https://www.theguardian.com/football/2005/jul/27/theknowledge.panathinaikos |title=Bohr's footballing career |work=The Guardian |location=London |access-date=26 June 2011 |archive-date=27 May 2023 |archive-url=https://web.archive.org/web/20230527043508/https://www.theguardian.com/football/2005/jul/27/theknowledge.panathinaikos |url-status=live }}</ref>

Bohr was educated at Gammelholm Latin School, starting when he was seven.<ref>{{cite web |url=http://www.nbi.ku.dk/english/www/niels/bohr/skole/ |title=Niels Bohr's school years |publisher=Niels Bohr Institute |access-date=14 February 2013 |date=18 May 2012 |archive-date=4 October 2013 |archive-url=https://web.archive.org/web/20131004220548/http://www.nbi.ku.dk/english/www/niels/bohr/skole/ |url-status=live }}</ref> In 1903, Bohr enrolled as an undergraduate at [[Copenhagen University]]. His major was physics, which he studied under Professor [[Christian Christiansen (physicist)|Christian Christiansen]], the university's only professor of physics at that time. He also studied astronomy and mathematics under Professor [[Thorvald Thiele]], and philosophy under Professor [[Harald Høffding]], a friend of his father.{{sfn|Pais|1991|pp=98–99}}<ref name="university">{{cite web |url=http://www.nbi.ku.dk/english/www/niels/bohr/universitetet/ |title=Life as a Student |publisher=Niels Bohr Institute |access-date=14 February 2013 |date=16 July 2012 |archive-date=4 October 2013 |archive-url=https://web.archive.org/web/20131004220131/http://www.nbi.ku.dk/english/www/niels/bohr/universitetet/ |url-status=live }}</ref>

[[File:Niels Bohr - LOC - ggbain - 35303.jpg|thumb|left|upright|Bohr as a young man|alt=Head and shoulders of young man in a suit and tie]]
In 1905 a gold medal competition was sponsored by the [[Royal Danish Academy of Sciences and Letters]] to investigate a method for measuring the [[surface tension]] of liquids that had been proposed by [[Lord Rayleigh]] in 1879. This involved measuring the frequency of oscillation of the radius of a water jet. Bohr conducted a series of experiments using his father's laboratory in the university; the university itself had no physics laboratory. To complete his experiments, he had to [[glass blowing|make his own glassware]], creating test tubes with the required [[ellipse|elliptical]] cross-sections. He went beyond the original task, incorporating improvements into both Rayleigh's theory and his method, by taking into account the [[viscosity]] of the water, and by working with finite amplitudes instead of just infinitesimal ones. His essay, which he submitted at the last minute, won the prize. He later submitted an improved version of the paper to the [[Royal Society]] in London for publication in the ''[[Philosophical Transactions of the Royal Society]]''.{{sfn|Rhodes|1986|pp=62–63}}{{sfn|Pais|1991|pp=101–102}}<ref name="university" />{{sfn|Aaserud|Heilbron|2013|p=155}}

Harald became the first of the two Bohr brothers to earn a [[master's degree]], which he earned for mathematics in April 1909. Niels took another nine months to earn his on the electron theory of metals, a topic assigned by his supervisor, Christiansen. Bohr subsequently elaborated his master's thesis into his much-larger [[Doctor of Philosophy]] thesis. He surveyed the literature on the subject, settling on a model postulated by [[Paul Drude]] and elaborated by [[Hendrik Lorentz]], in which the electrons in a metal are considered to behave like a gas. Bohr extended Lorentz's model, but was still unable to account for phenomena like the [[Hall effect]], and concluded that electron theory could not fully explain the magnetic properties of metals. The thesis was accepted in April 1911,<ref>{{Cite encyclopedia|url=https://www.britannica.com/biography/Niels-Bohr|title=Niels Bohr {{!}} Danish physicist|encyclopedia=Encyclopedia Britannica|access-date=25 August 2017|archive-date=8 August 2023|archive-url=https://web.archive.org/web/20230808044009/https://www.britannica.com/biography/Niels-Bohr|url-status=live}}</ref> and Bohr conducted his formal defence on 13 May. Harald had received his doctorate the previous year.{{sfn|Pais|1991|pp=107–109}} Bohr's thesis was groundbreaking, but attracted little interest outside Scandinavia because it was written in Danish, a Copenhagen University requirement at the time. In 1921, the Dutch physicist [[Hendrika Johanna van Leeuwen]] would independently derive a theorem in Bohr's thesis that is today known as the [[Bohr–Van Leeuwen theorem]].{{sfn|Kragh|2012|pp=43–45}}

[[File:Niels Bohr and Margrethe engaged 1910.jpg|thumb|right|upright|Bohr and [[Margrethe Nørlund]] on their engagement in 1910|alt=A young man in a suit and tie and a young woman in a light coloured dress sit on a stoop, holding hands]]
In 1910, Bohr met [[Margrethe Nørlund]], the sister of the mathematician [[Niels Erik Nørlund]].{{sfn|Pais|1991|p=112}} Bohr resigned his membership in the [[Church of Denmark]] on 16 April 1912, and he and Margrethe were married in a civil ceremony at the town hall in [[Slagelse]] on 1 August. Years later, his brother Harald similarly left the church before getting married.{{sfn|Pais|1991|pp=133–134}} Bohr and Margrethe had six sons.{{sfn|Pais|1991|pp=226, 249}} The oldest, Christian, died in a boating accident in 1934,{{sfn|Stuewer|1985|p=204}} and another, Harald, was severely mentally disabled. He was placed in an institution away from his family's home at the age of four and died from childhood meningitis six years later.<ref>{{Cite web |date=11 April 2022 |title=Udstilling om Brejnings historie hitter i Vejle |url=https://ugeavisen.dk/ugeavisenvejle/artikel/udstilling-om-brejnings-historie-hitter-i-vejle |access-date=17 July 2022 |website=ugeavisen.dk |language=da |archive-date=14 July 2022 |archive-url=https://web.archive.org/web/20220714232348/https://ugeavisen.dk/ugeavisenvejle/artikel/udstilling-om-brejnings-historie-hitter-i-vejle |url-status=live }}</ref>{{sfn|Pais|1991|pp=226, 249}} [[Aage Bohr]] became a successful physicist, and in 1975 was awarded the Nobel Prize in physics, like his father. A son of Aage, Vilhelm A. Bohr, is a scientist affiliated with the University of Copenhagen<ref>{{Cite web |last=Schou |first=Mette Kjær |date=22 August 2019 |title=Bohr Group |url=https://icmm.ku.dk/english/research-groups/bohr-group/ |access-date=19 October 2022 |website=icmm.ku.dk |language=en |archive-date=19 October 2022 |archive-url=https://web.archive.org/web/20221019200544/https://icmm.ku.dk/english/research-groups/bohr-group/ |url-status=live }}</ref> and the [[National Institute on Aging]] in the U.S.<ref>{{Cite web |title=Neuroscience@NIH > Faculty > Profile |url=https://dir.ninds.nih.gov/Faculty/Profile/vilhelm-bohr.html |access-date=19 October 2022 |website=dir.ninds.nih.gov |archive-date=19 October 2022 |archive-url=https://web.archive.org/web/20221019200544/https://dir.ninds.nih.gov/Faculty/Profile/vilhelm-bohr.html |url-status=live }}</ref> {{Interlanguage link|Hans Bohr|da|lt=Hans}} became a physician; {{Interlanguage link|Erik Bohr|da|lt=Erik}}, a chemical engineer; and [[Ernest Bohr|Ernest]], a lawyer.<ref name="nobelprize.org">{{cite web|title=Niels Bohr&nbsp;– Biography|url=https://www.nobelprize.org/nobel_prizes/physics/laureates/1922/bohr-bio.html|publisher=[[Nobelprize.org]]|access-date=10 November 2011|archive-date=11 November 2011|archive-url=https://web.archive.org/web/20111111014801/http://www.nobelprize.org/nobel_prizes/physics/laureates/1922/bohr-bio.html|url-status=live}}</ref> Like his uncle Harald, Ernest Bohr became an Olympic athlete, playing [[field hockey]] for Denmark at the [[1948 Summer Olympics]] in London.<ref name="hockey">{{cite web |url=https://www.sports-reference.com/olympics/athletes/bo/ernest-bohr-1.html |archive-url=https://web.archive.org/web/20200418093355/https://www.sports-reference.com/olympics/athletes/bo/ernest-bohr-1.html  |archive-date=18 April 2020 |title=Ernest Bohr Biography and Olympic Results – Olympics |publisher=Sports-Reference.com |access-date=12 February 2013}}</ref>