The contemporary notion of black holes originates in Oppenheimer and Snyder’s 1939 article “On Continued Gravitational Contraction” (Phys. Rev. 56:455, 1939). Later Roger Penrose (Phys. Rev. Lett. 14:57, 1965) showed that the O&S metric gave rise to trapped surfaces, ie. regions of space from which no light rays can escape, and proved that within such surfaces black-hole formation is inevitable. But what if their metric is faulty?
Trevor Marshall’s challenging article uses differential geometry to show that a simple modification of the O&S metric, fully consistent with General Relativity, enables all radial light rays originating in the interior escape to the exterior. There is no trapped surface and no black hole; on the contrary there is a stable end state with finite density, contained within a sphere of Schwarzschild radius, contracting ever more slowly on itself over infinite time.
Such solutions may be seen as counter-intuitive if, above a certain density, “no force can countervail against gravity”. Indeed, they require gravity to be repulsive in the extreme high regime, where its energy density is comparable to mass densities. It therefore fits intuitively with the field interpretation of gravity. On the other hand, the purely geometric interpretation based on the extreme form of the ‘Equivalence Principle’ has no light-ray connectivity, so is not consistent with causality. Is that not counter-intuitive?
Trevor Marshall’s full paper is in the December issue of Astrophys. Space Sci. (2012) 342:329–332. DOI 10.1007/s10509-012-1170-y