Pocket Universe

A pocket universe is a concept in inflationary theory, proposed by theoretical physicist Alan Guth. It defines a realm like the one that contains the observable universe as only one of many inflationary zones. Astrophysicist Jean-Luc Lehners, of the Princeton Center for Theoretical Science, has argued that an inflationary universe produces pockets.

As he wrote in 2012, ‘Eternal inflation produces pocket universes with all physically allowed vacua and histories. Some of these pocket universes might contain a phase of slow-roll inflation, some might undergo cycles of cosmological evolution, and some might look like the Galilean genesis or other ’emergent’ universe scenarios. Which one of these types of universe we are most likely to inhabit depends on the measure we choose in order to regulate the infinities inherent in eternal inflation.’

But, Lehners continues, ‘the current leading measure proposals—namely, the global light-cone cutoff and its local counterpart, the causal diamond measure—as well as closely related proposals, all predict that we should live in a pocket universe that starts out with a small Hubble rate, thus favoring emergent and cyclic models.’ Lehners adds, deadpan, ‘Pocket universes which undergo cycles are further preferred, because they produce habitable conditions repeatedly inside each pocket.’ In narrative, pocket universes are fictional artificially-created universes that exist within the bounds of another universe. The term pocket universe is derived from its illustration in the actual universe where it is usually portrayed as an orb which would fit in a pocket.

Science fiction scholar John Clute has written at length about fictional universes; he wrote cogently in an article for ‘The Encyclopedia of Science Fiction,’ ‘It might be said that the inhabitant of any constricted environment lives in a pocket universe, whether as a child, a prisoner, a victim of dementia, a chained watcher in Plato’s cave, a resident of Hell or an inhabitant of the world inside Pantagruel’s mouth… The term should perhaps, therefore, be confined to two usages, one broad, the other narrower. It can be used broadly to describe an actual miniature universe pocketed within a larger explanatory frame or device – like the various godling-crafted worlds nesting within one another in Philip José Farmer’s World of Tiers sequence; or like the set-ups in almost any of Jack L. Chalker’s series (e.g., the ‘Well World’ sequence and the ‘Four Lords of the Diamond’ tetralogy) which feature universes constructed by godlike beings as gamelike contrivances and inhabited by victim-players who must solve their universe to escape from it; or like similar 1950s set-ups (see ‘Paranoia’) such as in Frederik Pohl’s ‘The Tunnel under the World’ (1955) or Philip K. Dick’s ‘Time Out of Joint’ (1958), whose protagonists are victims of artificial worlds shaped to delude and manipulate them; or (again trivially) like any fantasy game which involves role-playing within a virtual-reality world; or in fact like any world (such as that on which John Crowley’s ‘The Deep’ (1975) is set, or Terry Pratchett’s ‘Discworld’) whose origins and extent reflect a sense of restraining artifice.’

That is Clute’s ‘broad’ definition. In a narrower sense, Clute goes on to say, ‘the world initially perceived seems to be the entire world… The classic generation-starship tale is one in which the descendants of the original crew members have forgotten the true nature of things and have instituted a repressive, taboo-governed society which suppresses any attempt to discover the truth…’ This sort of story, Clute argues, embodies ‘the purest form of the concept of the pocket universe.’ He cites such examples as Robert A. Heinlein’s ‘Universe’ (1941), Brian Aldiss’s novel ‘Non-Stop’ (1958), and Harry Harrison’s ‘Captive Universe’ (1969). Another example would be ‘For the World Is Hollow and I Have Touched the Sky’ (1968), a third-season episode of ‘Star Trek.’ Clute adds, ‘All post-Holocaust tales in which the descendants of survivors live in underground habitats which they think to be the whole of reality are pocket-universe stories. The best of them is perhaps Daniel F. Galouye’s ‘Dark Universe’ (1961), though Margaret St. Clair’s ‘Sign of the Labrys’ (1963) and ‘The Shadow People’ (1969) play fruitfully with the concept, as do Richard Cowper’s ‘Kuldesak’ (1972), Roger Eldridge’s ‘The Shadow of the Gloom-World’ (1977) and many others.’

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