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Quantum foam (also referred to as space-time foam) is a concept in quantum mechanics devised by John Wheeler in 1955. The ''foam'' is supposed to be conceptualized as the foundation of the fabric of the universe.〔(【引用サイトリンク】title=Quantum foam ) *Prof. Derek Leinweber has created (calculations ) of quantum chromodynamics vacuum structure which Nobel laureate Frank Wilczek displayed during his 2004 Nobel lecture, and reviewed at the (2010 Robert Oppenheimer lecture, UC Berkeley Physics department (see the video starting at minute 32:30, up to minute 34:59) )〕 Additionally, quantum foam can be used as a qualitative description of subatomic space-time turbulence at extremely small distances (on the order of the Planck length). At such small scales of time and space, the Heisenberg uncertainty principle allows energy to briefly decay into particles and antiparticles and then annihilate without violating physical conservation laws. As the scale of time and space being discussed shrinks, the energy of the virtual particles increases. According to Einstein's theory of general relativity, energy curves space-time. This suggests that—at sufficiently small scales—the energy of these fluctuations would be large enough to cause significant departures from the smooth space-time seen at larger scales, giving space-time a "foamy" character. With an incomplete theory of quantum gravity, it is impossible to be certain what space-time would look like at these small scales, because existing theories of gravity do not give accurate predictions in that realm. Therefore, any of the developing theories of quantum gravity may improve our understanding of quantum foam as they are tested. However, observations of radiation from nearby quasars by Floyd Stecker of NASA's Goddard Space Flight Center have placed strong experimental limits on the possible violations of Einstein's special theory of relativity implied by the existence of quantum foam.〔(【引用サイトリンク】title=Einstein makes extra dimensions toe the line )〕 Thus experimental evidence so far has given a range of values in which scientists can test for quantum foam. == Experimental evidence (and counter-evidence) == The MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov) telescopes have detected that among gamma-ray photons arriving from the blazar Markarian 501, some photons at different energy levels arrived at different times, suggesting that some of the photons had moved more slowly and thus contradicting the theory of general relativity's notion of the speed of light being constant, a discrepancy which could be explained by the irregularity of quantum foam. More recent experiments were however unable to confirm the supposed variation on the speed of light due to graininess of space. Other experiments involving the polarization of light from distant gamma ray bursts have also produced contradictory results.〔(Integral challenges physics beyond Einstein / Space Science / Our Activities / ESA )〕 More Earth-based experiments are ongoing or proposed. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Quantum foam」の詳細全文を読む スポンサード リンク
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