A Term used in this encyclopedia for the special case of Parallel World universes where the laws of Physics are and always have been importantly different; some sf stories posit this kind of radical change (or the threat of such change) to our own universe. George Gamow uses the device of dreams in Mr Tompkins in Wonderland (stories 1938-1939 Discovery; 1939 chap) to present alternate cosmoi in which the speed of light and Planck's constant have very different values, making their effects instructively perceptible in everyday life (see Relativity; Thought Experiment). A fundamental change in the nature of the universe effectively causes the progressive loss of the electromagnetic spectrum, including light, and so brings Disaster in "The Xi Effect" (January 1950 Astounding) by Philip Latham. The alternate-cosmos setting of Bob Shaw's The Ragged Astronauts (1986) is flagged by the casual revelation that pi (3.14159 ...) is here exactly 3: the rules are different and the specific scenario of two planets sharing a common, breathable atmosphere is not impossible as it would seem to be in our universe. Stephen Baxter's Raft (September/October 1989 Interzone; much exp 1991) shows human colonists stranded in an alternate cosmos where the gravitational constant is enormously larger, causing Stars to be small (a mile or so across) and short-lived. The same author's The Time Ships (1995) features Time Travel back to the early moments of the universe in order to adjust this primal Jonbar Point and initiate a different, more desirable alternate cosmos; in the same author's Time: Manifold 1 (1999; vt Manifold: Time 1999), the universe is even more dramatically destroyed to make way for – it is implied – an alternate cosmos less susceptible to the long-term ravages of Entropy. The "Assassins" of Frederik Pohl's Heechee sequence are likewise tampering with the fundamentals of physics to produce a made-over universe better suited to their needs: it emerges that the resulting alternate cosmos will by design be more hospitable to Uploaded intelligence, and it is thus welcomed by a human race in process of transition to Computer-sustained form. Such universe-"Terraforming" also forms part of the background of Stephen Baxter's Xeelee sequence, with the cosmos ultimately made unsuitable for life composed of normal or baryonic matter. Richard Garfinkle presents a Ptolemaic alternate cosmos – with heavenly bodies embedded in concentric crystal spheres whose common centre is Earth – in Celestial Matters (1996). In Jay Lake's Geared Earth sequence, opening with Mainspring (2007), the solar system operates by literal clockwork: the 100-mile high Wall around Earth's equator has cogs along its top so the celestial gearing can turn the world. Greg Egan's Orthogonal sequence, opening with Orthogonal: Book One: The Clockwork Rocket (2011), is set in a rigorously developed alternate cosmos whose Physics (including Relativity) differs hugely from ours. The alternate cosmos of Catherynne M Valente's Radiance (2015) features a differently scaled Solar System in which even the Outer Planets have been accessible to humanity since the Victorian era.
We do not generally use the term "alternate cosmos" for universes governed by Magic rather than science, as found in Fantasy and Science and Sorcery scenarios. Randall Garrett's Lord Darcy series (January 1964-April 1979 var mags, chiefly Analog) is an arguable exception here, owing to the Frazerian rigour with which its "scientific" laws of magic are formulated. Christopher Priest's Inverted World (1974) is another special case: a seeming alternate cosmos in which both Earth and Sun are hyperboloids extending to infinity, all this in fact being an imposed distortion of Perception. [DRL]
see also: Pocket Universe.
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