Editing Many-worlds interpretation (section)

== History ==
MWI originated in Everett's [[Princeton University]] [[PhD]] thesis "The Theory of the [[Universal wavefunction|Universal Wave Function]]",<ref name=dewitt73/> developed under his thesis advisor [[John Archibald Wheeler]], a shorter summary of which was published in 1957 under the title "Relative State Formulation of Quantum Mechanics" (Wheeler contributed the title "relative state";<ref name=geons-wheeler>{{cite book|first=John Archibald |last=Wheeler |author-link=John Archibald Wheeler |title=Geons, Black Holes and Quantum Foam |isbn=0-393-31991-1 |year=2000 |publisher=W. W. Norton & Company |pages=268–270 }}</ref> Everett originally called his approach the "Correlation Interpretation", where "correlation" refers to quantum entanglement). The phrase "many-worlds" is due to Bryce DeWitt,<ref name=dewitt73/> who was responsible for the wider popularization of Everett's theory, which had been largely ignored for a decade after publication in 1957.<ref name=Heresy/>

Everett's proposal was not without precedent. In 1952, [[Erwin Schrödinger]] gave a lecture in [[Dublin]] in which at one point he jocularly warned his audience that what he was about to say might "seem lunatic". He went on to assert that while the [[Schrödinger equation]] seemed to be describing several different histories, they were "not alternatives but all really happen simultaneously". According to David Deutsch, this is the earliest known reference to many-worlds; [[Jeffrey A. Barrett]] describes it as indicating the similarity of "general views" between Everett and Schrödinger.<ref>{{cite book | last1=Deutsch |first1=David | author-link=David Deutsch |chapter=Apart from Universes|title=Many Worlds? Everett, Quantum Theory and Reality |editor=S. Saunders |editor-link1=Simon Saunders |editor2=J. Barrett |editor-link2=Jeffrey A. Barrett |editor3=A. Kent |editor-link3=Adrian Kent |editor4=D. Wallace |publisher=Oxford University Press|year=2010}}</ref><ref>{{cite book |last1=Schrödinger |first1=Erwin |editor1-last=Bitbol |editor1-first=Michel |editor-link=Michel Bitbol |title=The Interpretation of Quantum Mechanics: Dublin Seminars (1949–1955) and other unpublished essays |date=1996 |publisher=OxBow Press}}</ref><ref>{{cite book |last=Barrett |first=Jeffrey A. |author-link=Jeffrey A. Barrett |title=The Quantum Mechanics of Minds and Worlds |publisher=Oxford University Press |year=1999 |isbn=9780191583254 |pages=62–63 }}</ref> Schrödinger's writings from the period also contain elements resembling the [[modal interpretation]] originated by [[Bas van Fraassen]]. Because Schrödinger subscribed to a kind of post-[[Ernst Mach|Machian]] [[neutral monism]], in which "matter" and "mind" are only different aspects or arrangements of the same common elements, treating the wave function as physical and treating it as information became interchangeable.<ref>{{cite book |last=Bitbol |first=Michel |url=https://www.worldcat.org/oclc/851376153 |title=Schrödinger's Philosophy of Quantum Mechanics |date=1996 |publisher=Springer Netherlands |isbn=978-94-009-1772-9 |location=Dordrecht |oclc=851376153 }}</ref>

[[Leon Cooper]] and Deborah Van Vechten developed a very similar approach before reading Everett's work.<ref>{{Cite journal |last1=Cooper |first1=Leon N. |last2=Van Vechten |first2=Deborah |date=1969-12-01 |title=On the Interpretation of Measurement within the Quantum Theory |url=https://pubs.aip.org/ajp/article/37/12/1212/1048185/On-the-Interpretation-of-Measurement-within-the |journal=American Journal of Physics |language=en |volume=37 |issue=12 |pages=1212–1220 |doi=10.1119/1.1975279 |issn=0002-9505}}</ref> Zeh also came to the same conclusions as Everett before reading his work, then built a new theory of [[quantum decoherence]] based on these ideas.<ref>{{Cite journal |last=Camilleri |first=Kristian |date=2009 |title=A history of entanglement: Decoherence and the interpretation problem |url=https://linkinghub.elsevier.com/retrieve/pii/S1355219809000562 |journal=Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics |language=en |volume=40 |issue=4 |pages=290–302 |doi=10.1016/j.shpsb.2009.09.003 }}</ref>

According to people who knew him, Everett believed in the literal reality of the other quantum worlds.<ref name="MAD">{{cite book |author1=Byrne |first=Peter |title=The Many Worlds of Hugh Everett III: Multiple Universes, Mutual Assured Destruction, and the Meltdown of a Nuclear Family |date=2010 |publisher=Oxford University Press |isbn=978-0-19-955227-6}}</ref> [[Mark Oliver Everett|His son]] and wife reported that he "never wavered in his belief over his many-worlds theory".<ref name="newsciMark">{{Cite news | last = Aldhous | first = Peter | title = Parallel lives can never touch | magazine = New Scientist | issue = 2631 |date=2007-11-24 | url = https://www.newscientist.com/article/mg19626311.800-interview-parallel-lives-can-never-touch.html | access-date = 2007-11-21 }}</ref> In their detailed review of Everett's work, Osnaghi, Freitas, and Freire Jr. note that Everett consistently used quotes around "real" to indicate a meaning within scientific practice.<ref name="Heresy">{{cite journal | last1 = Osnaghi | first1 = Stefano | last2 = Freitas | first2 = Fabio | last3 = Olival Freire | first3 = Jr | author-link3 = Olival Freire, Jr. | year = 2009 | title = The Origin of the Everettian Heresy | journal = Studies in History and Philosophy of Modern Physics | volume = 40 | issue = 2| pages = 97–123 | doi=10.1016/j.shpsb.2008.10.002| bibcode = 2009SHPMP..40...97O | citeseerx = 10.1.1.397.3933 }}</ref>{{rp|107}}