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出典:『Wikipedia』 (2011/04/22 20:39 UTC 版)

英語による解説

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Quantum foam, also referred to as spacetime foam, is a concept in quantum mechanics, devised by John Wheeler in 1955. The foam is supposedly the foundations of the fabric of the universe, but it can also be used as a qualitative description of subatomic spacetime turbulence at extremely small distances of the order of the Planck length. At such small scales of time and space the uncertainty principle allows particles and energy to briefly come into existence, and then annihilate, without violating conservation laws. As the scale of time and space being discussed shrinks, the energy of the virtual particles increases. Since energy curves spacetime according to Einstein's theory of general relativity, this suggests that at sufficiently small scales the energy of the fluctuations would be large enough to cause significant departures from the smooth spacetime seen at larger scales, giving spacetime a "foamy" character. However, without a theory of quantum gravity it is impossible to be certain what spacetime would look like at these scales, since it is thought that existing theories do not give accurate predictions in this domain. However, observations of radiation from nearby quasars by Floyd Stecker of NASA's Goddard Space Flight Center in Greenbelt, Md., have placed strong limits on the possible violations of Einstein's special theory of relativity implied by the existence of quantum foam.