Editing James Chadwick (section)

== Education and early life ==
James Chadwick was born in [[Bollington]], [[Cheshire]], on 20 October 1891,{{sfn|Falconer|2004}}{{sfn|Oliphant|1974}} the first child of John Joseph Chadwick, a cotton spinner, and Anne Mary Knowles, a domestic servant. He was named James after his paternal grandfather. In 1895, his parents moved to [[Manchester]], leaving him in the care of his maternal grandparents. He went to Bollington Cross Primary School, and was offered a scholarship to [[Manchester Grammar School]], which his family had to turn down as they could not afford the small fees that still had to be paid. Instead he attended the [[Central Grammar School for Boys]] in Manchester, rejoining his parents there. He now had two younger brothers, Harry and Hubert; a sister had died in infancy. At the age of 16, he sat two examinations for university scholarships, and won both of them.{{sfn|Brown|1997|pp=3–5}}<ref name="Nobel" />

Chadwick chose to attend [[Victoria University of Manchester]], which he entered in 1908. He meant to study mathematics, but enrolled in [[physics]] by mistake. Like most students, he lived at home, walking the {{convert|4|miles}} to the university and back each day. At the end of his first year, he was awarded a Heginbottom Scholarship to study physics. The physics department was headed by [[Ernest Rutherford]], who assigned research projects to final-year students, and he instructed Chadwick to devise a means of comparing the amount of radioactive energy of two different sources. The idea was that they could be measured in terms of the activity of {{convert|1|g}} of [[radium]], a unit of measurement which would become known as the [[Curie (unit)|curie]]. Rutherford's suggested approach was unworkable—something Chadwick knew but was afraid to tell Rutherford—so Chadwick pressed on, and eventually devised the required method. The results became Chadwick's first paper, which, co-authored with Rutherford, was published in 1912.{{sfn|Rutherford|Chadwick|1912}} He graduated with [[first class honours]] in 1911.{{sfn|Brown|1997|pp=6–14}}

Having devised a means of measuring gamma radiation, Chadwick proceeded to measure the absorption of gamma rays by various gases and liquids. This time the resulting paper was published under his name alone. He was awarded his [[Master of Science]] (MSc) degree in 1912, and was appointed a Beyer Fellow. The following year he was awarded an [[1851 Exhibition Scholarship]], which allowed him to study and research at a university in continental Europe. He elected to go to the [[Physikalisch-Technische Reichsanstalt]] in Berlin in 1913, to study [[beta radiation]] under [[Hans Geiger]].{{sfn|Brown|1997|pp=16–21}} Using Geiger's recently developed [[Geiger counter]], which provided more accuracy than the earlier photographic techniques, he was able to demonstrate that beta radiation did not produce [[spectral lines|discrete lines]], as has been previously thought, but rather a [[Beta decay#Beta emission spectrum|continuous spectrum]] with peaks in certain regions.{{sfn|Chadwick|1914}}{{sfn|Chadwick|Ellis|1922}}{{sfn|Weiner|1969}}{{sfn|Jensen|2000|pp=88–90}} On a visit to Geiger's laboratory, [[Albert Einstein]] told Chadwick that: "I can explain either of these things, but I can't explain them both at the same time."{{sfn|Weiner|1969}} The continuous spectrum would remain an [[Beta decay#History|unexplained phenomenon for many years]].{{sfn|Brown|1997|pp=24–26}}

Chadwick was still in Germany at the start of the [[First World War]], and was interned in the [[Ruhleben internment camp]] near Berlin, where he was allowed to set up a laboratory in the stables and conduct scientific experiments using improvised materials such as [[radioactive quackery|radioactive toothpaste]].<ref name=APSNews>{{cite journal |year=2007 |title= This Month in Physics History: May 1932: Chadwick reports the discovery of the neutron |url=http://www.aps.org/publications/apsnews/200705/physicshistory.cfm |journal=[[APS News]] |volume=16 |issue=5 |page=2}}</ref> With the help of [[Charles Drummond Ellis]], he worked on the [[ionisation]] of [[phosphorus]], and the [[mechanistic organic photochemistry|photochemical reaction]] of [[carbon monoxide]] and [[chlorine]].<ref>{{cite news |title=Obituary: Sir James Chadwick |newspaper=[[The Times]] |date=25 July 1974 |page=20, column F}}</ref><ref>{{cite news |title=Obituary: Sir Charles Ellis |newspaper=[[The Times]] |date=15 January 1980 |page=14, column F}}</ref> He was released after the [[Armistice with Germany]] came into effect in November 1918, and returned to his parents' home in Manchester, where he wrote up his findings over the previous four years for the 1851 Exhibition commissioners.{{sfn|Brown|1997|p=39}}

Rutherford gave Chadwick a part-time teaching position at Manchester, allowing him to continue research.{{sfn|Brown|1997|p=39}} He looked at the [[nuclear charge]] of [[platinum]], [[silver]], and [[copper]], and experimentally found that this was the same as the [[atomic number]] within an error of less than 1.5 per cent.{{sfn|Brown|1997|pp=43}} In April 1919, Rutherford became director of the [[Cavendish Laboratory]] at the [[University of Cambridge]], and Chadwick joined him there a few months later. Chadwick was awarded a Clerk-Maxwell studentship in 1920, and enrolled as a [[Doctor of Philosophy]] (PhD) student at [[Gonville and Caius College, Cambridge]]. The first half of his thesis was his work with atomic numbers. In the second, he looked at the [[nuclear force|forces]] inside the [[atomic nucleus|nucleus]]. His degree was awarded in June 1921.{{sfn|Brown|1997|pp=43–50}} In November, he became a Fellow of Gonville and Caius College.{{sfn|Brown|1997|p=58}}