light barriern.
/ˈlʌɪt ˌbarɪə/, U.S. /ˈlaɪt ˌbɛriər/ 1. One or more beams of ultraviolet light designed to act as a barrier to infection by reducing the number of airborne microorganisms and viruses. Now rare.
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1938 Amer. Jrnl. Public Health 28 349/2 In an isolation hospital, where a light barrier is thrown across a corridor to separate two contagious diseases, the efficiency or bactericidal power of this barrier may be determined directly under the actual ventilating conditions in the corridor.
1943 I. A. Abt 1942 Year Bk. Pediatrics 233/2 Whether light barriers or mechanical barriers are equally efficient without air conditioning is now under investigation.
1993 Indoor Environment 2 307/2 This aerial disinfection technique has been advocated in Europe and in the USA and has been used in several settings in four different ways: ‘indirect’ irradiation; ‘direct’ irradiation; light barriers, and irradiation of air in supply-air ducts.
2. The speed of light as the theoretical maximum speed attainable. Cf. sound barrier n. at sound n.3 Compounds 2a.Sometimes in the context of exceeding this speed, esp. in Science Fiction.
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the world > matter > physics > electromagnetic radiation > light > emission of light, radiation > [noun] > speed of light > as limit
light barrier1950
1950 Amazing Stories July 103/2 That was only a quick run and the light barrier would be crossed for only a few seconds during the trip.
1968 A. Diment Great Spy Race x. 180 The faster than light spaceships will bring the stars down into our backyard, for once one has broken the so-called ‘light-barrier’ there is no limit to speed.
2011 Sunday Tel. (Nexis) 25 Sept. 37 Scientists at the Cern nuclear research facilities near Geneva were stunned when they appeared unwittingly to have broken the light barrier.
This entry has been updated (OED Third Edition, December 2021).
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n.1938