An alternate world - some writers and commentators prefer the designation alternative world on grammatical grounds - is an account of Earth as it might have become in consequence of some hypothetical alteration in history. Many sf stories use PARALLEL WORLDS as a frame in which many alternate worlds can be simultaneously held, sometimes interacting with one another. Hypothetical exercises of this kind have long been popular with historians (HISTORY IN SF) and their virtue was proclaimed by Isaac d'Israeli in The Curiosities of Literature (coll 1791-1823). A classic collection of such essays, ed J.C.Squire, If It had Happened Otherwise (anth 1931; vt If, or History Rewritten; exp 1972) took its inspiration from G.M.Trevelyan's essay If Napoleon had Won the Battle of Waterloo (1907); its contributors included G.K.CHESTERTON, Andre MAUROIS, Hilaire BELLOC, A.J.P.Taylor and Winston Churchill. The most common preoccupations of modern speculative historians were exhibited in two essays written for Look: If the South had Won the Civil War (1960; 1961) by MacKinlay KANTOR and If Hitler had Won World War II (1961), by William L.Shirer. The tradition has been continued in the MAINSTREAM by the film IT HAPPENED HERE (1963), Frederic MULLALLY's Hitler Has Won (1975) and Len DEIGHTON's SS-GB (1978). Another event seen today as historically pivotal, the invention of the atom bomb, is the basis of two novels by Ronald W.CLARK: Queen Victoria's Bomb (1967), in which the atom bomb is developed much earlier in history, and The Bomb that Failed (1969; vt The Last Year of the Old World UK), in which its appearance on the historical scene is delayed. Alternative histories are used satirically by non-genre writers in R.Egerton Swartout's It Might Have Happened (1934) and Marghanita LASKI's Tory Heaven (1948), and the notion is given a more philosophical twist in Guy DENT's Emperor of the If (1926). The continuing popularity of alternative histories with mainstream writers is further illustrated by John HERSEY's White Lotus (1965), Vladimir NABOKOV's Ada (1969), Martin Cruz SMITH's The Indians Won (1970), Guido Morselli's Past Conditional (1975; trans 1981) and Douglas Jones's The Court Martial of George Armstrong Custer (1976). Murray LEINSTER introduced the idea of alternate worlds to GENRE SF in Sidewise in Time (1934), and Stanley G.WEINBAUM used it in a light comedy, The Worlds of If (1935); but the first serious attempt to construct an alternative history in sf was L.Sprague DE CAMP's LEST DARKNESS FALL (1939; 1941), in which a man slips back through time and sets out to remould history by preventing or ameliorating the Dark Ages. This story is set entirely in the distant past, but in The Wheels of If (1940) de Camp displayed a contemporary USA which might have resulted from 10th-century colonization by Norsemen. Most subsequent sf stories in this vein have tended to skip lightly over the detailed process of historical development to examine alternative presents, but sf writers with a keen interest in history often devote loving care to the development of imaginary pasts; a recent enterprise very much in the tradition of LEST DARKNESS FALL is Harry TURTLEDOVE's Agent of Byzantium (coll of linked stories 1986). The extraordinary melodramatic potential inherent in the idea of alternate worlds was further revealed by Jack WILLIAMSON's THE LEGION OF TIME (1938; 1952), which features alternative futures at war for their very existence, with crucial battles spilling into the past and present. The idea of worlds battling for survival by attempting to maintain their own histories was further developed by Fritz LEIBER in Destiny Times Three (1945; 1957) and in the Change War series, which includes THE BIG TIME (1958; 1961). Such stories gained rapidly in extravagance: The Fall of Chronopolis (1974) by Barrington J.BAYLEY features a time-spanning Empire trying to maintain its reality against the alternative versions which its adversaries are imposing upon it. Attempts by possible futures to influence the present by friendly persuasion were
presented by C.L.MOORE in Greater than Gods (1939) and by Ross ROCKLYNNE in The Diversifal (1951). The notion of competing alternative histories is further recomplicated in TIME-TRAVEL stories in which the heroes range across a vast series of parallel worlds, each featuring a different alternative history (alternate universes are often created wholesale, though usually ephemerally, in tricky time-travel stories; see also TIME
PARADOXES). The policing of time-tracks - either singly, as in Isaac ASIMOV's The End of Eternity (1955), which features the totalitarian control of history by social engineers, or in great profusion - has remained a consistently popular theme in sf. One of the earliest such police forces is featured in Sam MERWIN's House of Many Worlds (1951) and Three Faces of Time (1955); the exploits of others are depicted in H.Beam
PIPER's Paratime series, begun with Police Operation (1948), in Poul ANDERSON's Time Patrol series, whose early stories are in Guardians of Time (coll 1960), in John BRUNNER's Times without Number (fixup 1962 dos), and - less earnestly - in Simon Hawke's Time Wars series (Nicholas Yermakov), begun with The Ivanhoe Gambit (1984). Keith LAUMER's Worlds of the Imperium (1962 dos) and sequels, Avram DAVIDSON's Masters of the Maze (1965), Jack L.CHALKER's Downtiming the Night Side (1985), Frederik POHL's The Coming of the Quantum Cats (1986), Mike MCQUAY's Memories (1987) and Michael P.KUBE-MCDOWELL's Alternities (1988) are convoluted adventure stories of an essentially similar kind. John CROWLEY's Great Work of Time (1989) is a more thoughtful work about a conspiracy which attempts to use
time travel to take charge of history. Early genre-sf stories of conflict between alternate worlds tend to assume that our world is better than most of the alternatives. This assumption owes much to our conviction that the
right side won both the American Civil War and WWII. Ward MOORE's classic BRING THE JUBILEE (1953) paints a relatively grim portrait of a USA in which the South won the Civil War; and images of worlds in which the Nazis triumphed (HITLER WINS) tend to be nightmarish - notable examples include Two Dooms (1958) by C.M.KORNBLUTH, THE SOUND OF HIS HORN (1952) by SARBAN, THE MAN IN THE HIGH CASTLE (1962) by Philip K.DICK, The Proteus Operation (1985) by James P.HOGAN, and Moon of Ice (1988) by Brad LINAWEAVER. An interesting exception is Budspy (1987) by David DVORKIN, where a successful Third Reich is presented more evenhandedly. Other turning-points in which our world is held to have gone the right way include the Reformation and the Industrial Revolution - whose suppression produces technologically primitive worlds in Keith ROBERTS's excellent PAVANE (fixup 1968), Kingsley AMIS's The Alteration (1976), Martin GREEN's The Earth Again Redeemed (1978), Phyllis EISENSTEIN's Shadow of Earth (1979) and John Whitbourn's A Dangerous Energy (1992) - and the Black Death, which aborts the rise of the West in Robert SILVERBERG's The Gate of Worlds (1967) and L.Neil SMITH's The Crystal Empire (1986). The idea
that our world might have turned out far better than it has is more often displayed by ironic satires, including: Harry HARRISON's Tunnel Through the Deeps (1972; vt A Transatlantic Tunnel, Hurrah! UK), in which the
American colonies never rebelled and the British Empire remains supreme; D.R.BENSEN's And Having Writ... (1978), in which the aliens whose crashing starship is assumed to have caused the Tunguska explosion survive to interfere in the course of progress; S.P.SOMTOW's The Aquiliad (fixup 1983), in which the Roman Empire conquered the Americas; and William GIBSON's and Bruce STERLING's THE DIFFERENCE ENGINE (1990), in which Babbage's calculating machine precipitates an information-technology revolution in Victorian England. More earnest examples are fewer in number, but they include The Lucky Strike (1984) by Kim Stanley ROBINSON, in which a US pilot refuses to drop the atom bomb on Hiroshima, and Elleander Morning (1984) by Jerry YULSMAN, which imagines a world where Hitler was assassinated before starting WWII. More philosophically inclined uses of the alternate-worlds theme, involving the worldviews of individual characters rather than diverted histories, were pioneered in genre sf by Philip K.Dick in such novels as Eye in the Sky (1957), Now Wait for Last Year (1967) and Flow My Tears, the Policeman Said (1974). Intriguing homage is paid to Dick's distinctive use of the theme by Michael BISHOP's The Secret Ascension (1987; vt Philip K.Dick is Dead, Alas). Other novels which use alternate worlds to explore personal problems and questions of identity include Bob SHAW's The Two-Timers (1968), Gordon EKLUND's All Times Possible (1974), Sheila FINCH's Infinity's Web (1985), Josephine SAXTON's Queen of the States (1986), Ken Grimwood's Replay (1986) and Thomas BERGER's Changing the Past (1989). Radical alternative histories, which explore the consequences of fundamental shifts in biological evolution, include Harry Harrison's
series about the survival of the dinosaurs, begun with West of Eden (1984); Harry Turtledove's A Different Flesh (fixup 1988), in which Homo erectus survives in the Americas until 1492; and Brian M.STABLEFORD's The Empire of Fear (1988), in which 17th-century Europe and Africa are ruled by vampires. More radical still are novels which portray universes where the laws of physics are different. Some of these are described in George GAMOW's series of educative parables Mr Tompkins in Wonderland (coll 1939), and the many worlds interpretation of quantum theory has encouraged their use in more recent sf, a notable example being The Singers of Time (1990) by Frederik Pohl and Jack Williamson. Worlds of Maybe: Seven Stories of Science Fiction (anth 1970) ed Robert Silverberg contains further work on the theme by Poul Anderson, Philip Jose FARMER, Larry NIVEN and Silverberg, as well as the Murray Leinster story cited above. In addition to further stories, including the de Camp story mentioned above, Alternative Histories: Eleven Stories of the World as it Might have Been (anth 1986) ed Martin H.GREENBERG and Charles G.WAUGH includes the definitive version of Barton C.Hacker's and Gordon B.Chamberlain's invaluable bibliography of the theme, Pasts that Might Have Been, II; the first version appeared in EXTRAPOLATION in 1981. Gregory BENFORD edited
four anthologies on the theme: Hitler Victorious (anth 1985); plus What Might Have Been 1: Alternate Empires (anth 1989), 2: Alternate Heroes (anth 1989) and 3: Alternate Wars (anth 1991). Alternatives (anth 1989), ed Robert ADAMS and Pamela Crippen Adams, presented original stories told from LIBERTARIAN perspectives. Alternate Presidents (anth 1992) ed Michael RESNICK examines a particular aspect from Benjamin Franklin to Michael Dukakis; the same editor's Alternate Kennedys (anth 1992) narrows the focus yet further. See also: PARANOIA; STEAMPUNK.