More than 20 years ago, Roger Penrose and Stephen Hawking proved that every black hole must contain a singularity, a point of infinite density. Although the laws of physics break down at a singularity, this embarrassing possibility does not trouble physicists unduly because a black hole's singularity is 'cloaked' from the external Universe. It is surrounded by a barrier called an 'event horizon', across which nothing, not even light, can pass in the outward direction.
But what if the Universe contains 'naked' singularities - ones which are not concealed by the cloak of an event horizon? The possibility was so worrying that Penrose proposed a 'cosmic censorship hypothesis', which says that every singularity forms with an event horizon safely surrounding it. Unfortunately, there is no evidence that the hypothesis applies in the real Universe, and naked singularities remain an unpleasant possibility.
The latest investigation of naked singularities has been carried ...
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content.