When Albert Einstein proposed his special theory of relativity in 1905, he rejected the 19th-century idea that light arises from vibrations of a hypothetical medium, the "ether." Instead, he argued, light waves can travel in vacuo without being supported by any material--;unlike sound waves, which are vibrations of the medium in which they propagate. This feature of special relativity is untouched in the two other pillars of modern physics, general relativity and quantum mechanics. Right up to the present day, all experimental data, on scales ranging from subnuclear to galactic, are successfully explained by these three theories.

Nevertheless, physicists face a deep conceptual problem. As currently understood, general relativity and quantum mechanics are incompatible. Gravity, which general relativity attributes to the curvature of the spacetime continuum, stubbornly resists being incorporated into a quantum framework. Theorists have made only incremental progress toward understanding the highly curved structure of spacetime that quantum mechanics leads them to expect at extremely short distances. Frustrated, some have turned to an unexpected source for guidance: condensed-matter physics, the study of common substances such as crystals and fluids.

1 Comments

1. 1. Noyes 05:34 PM 10/14/08

   One of the most important conclusions of this paper is that if Unruh analogy between sound and light propagation is correct, then we could justify Hawking’s analogy provided we revise the geometry of spacetime. In other words spacetime is not like an idealized fluid but more like a fluid made out of small lumps. The inescapable conclusion is that unlike Einstein’s assumption spacetime is made of spacetime atoms. We find these black holes analogue experiment quite enlightening. That must be the reason why an engineering scientist like Mohamed El Naschie came to the idea of a resolution dependent spacetime. He must have been inspired by the theory of elasticity and I have indeed seen some of his papers on high energy physics starting from the analogy with thin elastic plates and wires. Many of these papers can be found on Elsevier’s Science Direct web site. Similar ideas about the relevance of the Unruh effect for proving the case of a fractal-like spacetime was discussed not only by El Naschie but also by Lee Smolin in a very readable book called Five Roads to Quantum Gravity.

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