A black hole is a mass that is so compact that it disappears inside an invisible surface called an event horizon. The actual mass is compressed into a mathematical point, called a singularity, sitting at the center of the event horizon sphere. The term event horizon comes from the fact that no event happening inside it can be observed from the outside.

Event horizons are a direct consequence of Einstein's theory of general relativity. The reason why no events on the inside of an event horizon can be observed from the outside is that gravity is so strong there that nothing can escape from within, and that includes light and any other form of signal.

The event horizon effectively "dresses" the singularity at the center of the black hole and nature is apparently very reluctant to get rid of these "clothes". In 1969, Sir Roger Penrose proposed the cosmic censorship hypothesis, which was also stated as: "nature abhors a naked singularity".

So how can a naked singularity possibly be formed and how does nature prevent it from happening? In 1963 Roy Kerr, a native New Zealander, discovered an exact solution to Einstein's equations of general relativity, representing the space-time around a rotating (spinning) black hole.

Because most (if not all) stars rotate, it is thought that most black holes that have formed from the collapse of massive stars must be spinning. And just like a ballerina that spins faster when she pulls her arms in towards her body, a star collapsing under its own gravity will spin faster the more compact it gets.

Every ordinary object has a maximum rate of spin, where the centrifugal forces tend to overwhelm the binding force between its molecules and/or atoms. Exceed that spin rate and the object breaks up and may fly apart. The Kerr solution shows that a black hole also has a maximum spin rate, above which it may destroy itself.

Because of the immensely strong gravity of a black hole, it cannot just break up and fly apart. Should it be able to spin faster than the maximum theoretical spin rate, its "clothes" (the event horizon surface) may shrink to zero size and essentially disappear.

This means that the "clothes" become part of the central singularity of the black hole, essentially leaving it "naked". For this reason, it is called a naked singularity, the kind that nature apparently "abhors".

There is some uncertainty amongst scientists as to whether singularities, naked or not, actually do exist. It is possible that quantum mechanical effects may prevent such bizarre things to exist in nature.

In any case, if singularities do exist, the Penrose cosmic censorship may, by means of a compulsory event horizon, forever prevent their exposure to man's observing telescopes?