Entry updated 27 June 2020. Tagged: Theme.

A glass-like substance based on Imaginary Science, which in effect has a refractive index so huge that light takes significant time – from seconds to many years – to pass through a sheet or block of the material. It thus functions as a limited Time Viewer. Bob Shaw coined the term in his fine story "Light of Other Days" (August 1966 Analog), where slow-glass scenic windows or "scenedows" allow urban apartments to look out on beautiful stored country landscapes. This and other Slow Glass stories are incorporated into Shaw's Other Days, Other Eyes (fixup 1972). Glass with similar properties also features in earlier fiction: "The Mirror That Remembered" (in The Strange Papers of Dr Blayre, coll 1932) by Christopher Blayre; Le mâitre de la lumière ["Master of Light"] (8 March-2 May 1933 L'Intransigeant; 1947) by Maurice Renard; one of many Inventions in "The Exhalted" (November 1940 Astounding) by L Sprague de Camp; and "One-Way Trip" (August 1943 Astounding) by Anthony Boucher. De Camp's enhanced glass and Boucher's light-trapping "Lovestonite" anticipate a secondary point also made by Shaw: the dangerous possibilities of releasing hours of stored sunlight in a single destructive Ray, used in both these stories as a Weapon. In reality, light can in fact be enormously slowed in the laboratory: to a walking pace when passed through vapour supercooled into a "Bose-Einstein condensate", as achieved in 1995, or to an effective halt (laser light only) in a specially prepared crystal. [DRL]

see also: Perception; Physics; Unknown Worlds of Science Fiction.

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