In both fantasy and science fiction, magical or seemingly magical “portals” often make for an interesting story. Readers like to imagine such a thing, and it provides a mechanism to get the characters rapidly into the thick of the action. The wardrobe in C.S. Lewis’s The Lion, the Witch and the Wardrobe (1950, ★★★★) is a classic example (the book’s star rating is from Goodreads).
James Davis Nicoll at Tor.com suggests that we can subdivide “portal” narratives according to whether the destination is Known or Unknown, and whether travel is Voluntary or Involuntary. Thus K/V, U/V, K/I, and U/I; with U/V (unknown & voluntary) applying to The Lion, the Witch and the Wardrobe.
In many stories, the “portal” is unique, or there are a limited number of “portals.” Like Lewis’s wardrobe, the mirror in Lewis Carroll’s Through the Looking-Glass (U/V, 1871, ★★★★) is an example of a unique portal. In Julian May’s The Many-Colored Land (K/VI, 1981, ★★★★), the “portal” is a time travel machine that goes only to the Pliocene epoch, and only at one specific location in France. It is annotated VI because some time-travellers choose to go through it, while others are transported as a penalty for crime.
Hub and Spoke Portals
Another approach to “portals” is for multiple alternate worlds to connect to a unique “hub” location. For example, the Wood between the Worlds in C.S. Lewis’s The Magician’s Nephew (U/VI, 1955, ★★★★) serves this purpose. Any trip between alternate worlds is possible if you can both enter and leave the Wood. Of course, if everybody did that, traffic in the Wood would be unbearable, so some kind of restriction on travel needs to be introduced in the story. In Genevieve Cogman’s The Invisible Library (K/V, 2015, ★★★☆) and its sequels, a mysterious library acts as the “hub” (although alternative mechanisms also exist), and few are able to travel through its doors.
Linear Systems of Portals
Alternatively, the “hub” may be a linear structure, with alternate worlds branching off to either side, like the Hall of Worlds in Raymond E. Feist’s A Darkness at Sethanon (KU/V, 1986, ★★★★). This topology makes navigation easier, and it becomes possible to assign (not necessarily integer) numbers to the alternate worlds. Unlike an arbitrary network, it is possible to effectively control or police at least parts of the structure.
In a science fiction context, Greg Bear’s Eon (U/V, 1985, ★★★★) contains an engineered version of the Hall. In Roger Zelazny’s fantasy novel Roadmarks (K/V, 1979, ★★★★), the structure is a highway that runs between times – hence the sign on the book cover: “Last Exit to Babylon.”
Arbitrary Networks of Portals
Generalising the linear structure, the “portals” may form an arbitrary network. In a science fiction context, this includes a network of “wormholes” between star systems, as in the “Alderson tramlines” of the classic novel The Mote in God’s Eye by Larry Niven and Jerry Pournelle (K/V, 1974, ★★★★).
In several science fiction novels by Peter F. Hamilton, including Salvation (K/VI, 2018, ★★★★), portals become so ubiquitous as to replace other forms of transportation. In N.D. Wilson’s children’s fantasy novel The Door Before (KU/VI,2017, ★★★★☆), the portals are physical wooden doorways between alternate worlds. In Ursula K. Le Guin’s short story collection Changing Planes (U/I, 2003, ★★★★), the stress of waiting in an airport causes one to cross to alternate worlds. This is possible from any airport, and the destination might be anywhere.
What is your favourite portal story, dear reader?
Scientific Gems 