Editing Parallel universes in fiction (section)

=== Early examples ===
One of the first science-fiction examples of a parallel universe is [[Murray Leinster]]'s short story ''[[Sidewise in Time]]'', published in 1934. Although Leinster's story was not the first example of parallel universes, it is credited with popularizing the concept.<ref>{{Cite web |title=NOVA {{!}} Parallel Worlds, Parallel Lives {{!}} Science Fiction and Fact (non-Flash) {{!}} PBS |url=https://www.pbs.org/wgbh/nova/manyworlds/time-nf.html |access-date=2025-03-26 |website=www.pbs.org}}</ref><ref name=":0">{{Cite magazine |last=Burt |first=Stephanie |date=31 October 2022 |title=Is the Multiverse Where Originality Goes to Die? |url=https://www.newyorker.com/magazine/2022/11/07/is-the-multiverse-where-originality-goes-to-die |magazine=The New Yorker |via=www.newyorker.com}}</ref><ref>{{Cite journal |last=Wolfe |first=Gary |date=2007-07-04 |title=Surfing the multiverse |url=https://www.nature.com/articles/448025a |journal=Nature |language=en |volume=448 |issue=7149 |pages=25–26 |doi=10.1038/448025a |issn=1476-4687}}</ref>

The use of parallel universes as a device in [[superhero fiction]] was popularized with the publication of the 123rd issue of ''[[The Flash (comic book)|The Flash]]'', "[[Flash of Two Worlds]]", in 1961. In the issue, the [[The Flash|Flashes]] of [[Earth-One]] and [[Earth-Two]], [[Barry Allen]] and [[Flash (Jay Garrick)|Jay Garrick]], meet, establishing the concept of the [[Multiverse (DC Comics)|DC Comics multiverse]].<ref name="esquire" />