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GR: Gravitation und Relativitätstheorie

GR 13: Alternative Zug
änge

GR 13.3: Vortrag

Montag, 7. März 2005, 18:15–18:30, TU BH262

Mach’s Principle and a Variable Speed of Light — •Alexander Unzicker — Pestalozzi-Gymnasium München

Dirac’s great number hypothesis (1938), the numerical coincidence G/c² = R_u/M_u (R_u and M_u denoting the mass and radius of the universe) remains one of the big mysteries of physics.

Sciama (MNRAS 113, p. 35ff, 1953) developed the more plausible hypothesis c²/G = ∑m_i/r_i, which may be seen as a quantitative proposal for Mach’s principle, according to which gravitation has its origin in the presence of all other masses in the universe.

While Sciama’s developed a gravitational potential −c², he did not discuss the obvious consequence of a spatial variation of the speed of light as the origin of gravitation. Such a variation was, by the way Einstein’s own idea in 1911 while developing general relativity and does therefore not contradict the relativity principle (Einstein Ann.Phys 38 (1912), 355-69; see also Ranada, gr-qc/0410120).

As a new proposal, the gravitational potential −c₀² log∑m_i/r_i is discussed, particulary what additional assumptions are needed to fulfill the classical tests of GR. Moreover, it is shown that such an approach yields a theoretical motivation of the equivalence principle.