Editing Barn (unit) (section)

==Etymology==
[[File:Helium atom QM DE.svg|thumb|Image of a [[helium-4]] nucleus; <sup>4</sup>He has a very small cross-section, less than 0.01 barn.]]
During [[Manhattan Project]] research on the [[atomic bomb]] during [[World War II]], American physicists [[Marshall Holloway]] and [[Charles P. Baker]] were working at [[Purdue University]] on a project using a particle accelerator to measure the [[cross section (physics)|cross section]]s of certain nuclear reactions. According to an account of theirs from a couple years later, they were dining in a cafeteria in December 1942 and discussing their work. They "lamented" that there was no name for the unit of cross section and challenged themselves to develop one. They initially tried [[eponym]]s, names of "some great men closely associated with the field" that they could name the unit after, but struggled to find one that was appropriate. They considered "[[J. Robert Oppenheimer|Oppenheimer]]" too long (in retrospect, they considered an "Oppy" to perhaps have been allowable), and considered "[[Hans Bethe|Bethe]]" to be too easily confused with the commonly-used Greek letter [[beta]]. They then considered naming it after [[John Henry Manley|John Manley]], another scientist associated with their work, but considered "Manley" too long and "John" too closely associated with [[toilet]]s. But this latter association, combined with the "rural background" of one of the scientists, suggested to them the term "[[barn]]", which also worked because the unit was "really as big as a barn." According to the authors, the first published use of the term was in a (secret) Los Alamos report from late June 1943, on which the two originators were co-authors.<ref>M.G. Holloway and C.P. Baker, "Note on the origin of the term 'barn'"], [https://permalink.lanl.gov/object/tr?what=info:lanl-repo/lareport/LA-00523-MS LAMS-523] (submitted 13 September 1944, issued 5 March 1947). Reprinted as {{cite journal|last1=Holloway|first1=M.G.|last2=Baker|first2=C.P.|title=How the barn was born|journal=Physics Today|volume=25|number=7|page=9|year=1972|doi=10.1063/1.3070918}} The initial published report to feature the unit was C.P. Baker, M.G. Holloway, L.D.P. King, and R.E. Schreiber, "Cross section for the reaction 20(230, 240)10," [LAMS-2](https://permalink.lanl.gov/object/tr?what=info:lanl-repo/lareport/LA-00002-MS) (June 28, 1943), which also defines the unit in its abstract.</ref>