08 April 2009

Physics: Naked singularities

The February edition of Scientific American contains an article by Professor Pankaj S. Ghoshi of the Tata Institute of Fundamental Research, Mumbai, which addresses the issue of whether so-called “naked singularities” could be formed when a large star collapses.

The two possible outcomes of the collapse of a dying massive star are the formation of black holes and the formation of naked singularities. In either case we see the formation of a singularity – a wad of matter so dense that the laws of physics break down and we need new laws to describe it. Anything that hits the singularity is destroyed.

In the case of a black hole, the singularity is “clothed”, that is, surrounded by a boundary that hides it. This boundary is called the event horizon. Nothing that falls through this surface can ever get back out, and no information can get out.

A naked singularity has no such boundary. It is visible to outside observers, and objects that fall toward the singularity can in principle reverse course right up to the moment of impact.

Conventional wisdom has it that a large star eventually collapses to a black hole, but some theoretical models suggest that it might instead become a naked singularity. Sorting out what happens is one of the most important unresolved problems in astrophysics.

The Editors of Scientific American observe that discovery of naked singularities would transform the search for a unified theory of physics, not least by providing direct observational tests of such a theory.

This material is not light reading but it is written to be accessible to the lay reader and goes to the heart of what makes the universe tick, so is worth the effort. It may be accessed here on the Scientific American website.

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