Editing Joseph Rotblat (section)

==Marriage and early physics work==
During this period, Rotblat married a literature student, Tola Gryn, whom he had met at a student summer camp in 1930.<ref name="obit">{{cite journal |last=Noble |first=Holcomb B. |title=Joseph Rotblat, 96, Dies; Resisted Nuclear Weapons |journal=The New York Times |url=https://www.nytimes.com/2005/09/02/obituaries/joseph-rotblat-96-dies-resisted-nuclear-weapons.html |date=2 September 2005 |access-date=3 June 2016 |archive-date=29 May 2015 |archive-url=https://web.archive.org/web/20150529170209/http://www.nytimes.com/2005/09/02/obituaries/joseph-rotblat-96-dies-resisted-nuclear-weapons.html |url-status=live }}</ref>{{sfn|Brown|2012|p=13}}

Before the outbreak of [[World War II]], he conducted experiments that showed that in the [[Nuclear fission|fission process]], [[neutron]]s were emitted.<ref>{{cite journal |journal=[[Nature (journal)|Nature]] |date=20 May 1939 |title=Emission of Neutrons accompanying the Fission of Uranium Nuclei |first=J. |last=Rotblat |volume=143 |issue=470 |page=852 |doi=10.1038/143852a0 |bibcode=1939Natur.143..852R |s2cid=4129149 |doi-access=free }}</ref> In early 1939, he envisaged that a large number of fissions could occur and if this happened within a sufficiently short time, then considerable amounts of energy could be released. He went on to calculate that this process could occur in less than a [[microsecond]], and as a consequence would result in an explosion.<ref name="retro">{{Cite journal
 | last1 = Holdren | first1 = J. P.
 | doi = 10.1126/science.1121081
 | title = Retrospective: Joseph Rotblat (1908–2005)
 | journal = Science
 | volume = 310
 | issue = 5748
 | pages = 633
 | year = 2005
 | pmid = 16254178
| s2cid = 26854983
 }}</ref><ref name="dida">{{cite web|url=http://www.bbc.co.uk/radio4/features/desert-island-discs/castaway/04f8ac96 |title=Joseph Rotblat BBC Radio 4 Desert Island Discs Castaway 8 November 1998 |publisher=BBC |archive-date=28 May 2011 |archive-url=https://web.archive.org/web/20110528082706/http://www.bbc.co.uk/radio4/features/desert-island-discs/castaway/04f8ac96 |url-status=dead }}</ref>

In 1939, through Wertenstein's connections, Rotblat was invited to study in Paris and at the [[University of Liverpool]] under [[James Chadwick]], winner of the 1932 Nobel Prize for discovering the neutron. Chadwick was building a particle accelerator called a "[[cyclotron]]" to study fundamental nuclear reactions, and Rotblat wanted to build a similar machine in Warsaw, so he decided to join Chadwick in Liverpool. He travelled to England alone because he could not afford to support his wife there.{{sfn|Brown|2012|pp=12–14}}

Before long, Chadwick gave Rotblat a [[Research fellow#United Kingdom|fellowship]] (the [[Oliver Lodge]] Fellowship), doubling his income, and in that summer of 1939, the young Pole returned home, intending to bring Tola back with him.{{sfn|Brown|2012|pp=23–24}} When the time came to leave Warsaw in late August, however, she was ill following an operation for appendicitis, and remained behind, expecting to follow within days; however, the outbreak of war brought calamity.{{sfn|Brown|2012|pp=25–27}} Tola was trapped, and desperate efforts in the ensuing months to bring her out through Denmark (with the help of [[Niels Bohr]]), Belgium, and finally Italy came to nothing, as each country in turn was closed off by the war.{{sfn|Brown|2012|pp=32–33}} He never saw her again; she was murdered in [[the Holocaust]] at the [[Belzec concentration camp]].{{sfn|Brown|2012|p=65}} This affected him deeply for the rest of his life, and he never remarried.<ref>{{cite web|last1=Underwood|first1=Martin|title=Liverpool University (1939–43)|year=2011|url=http://www.josephrotblat.com/nuclear-physics.html|publisher=Joseph Rotblat: The bomb, peace, and his archive|access-date=13 October 2015|archive-url=https://web.archive.org/web/20110713121201/http://www.josephrotblat.com/nuclear-physics.html|archive-date=13 July 2011}}</ref>