A hypothesis concerning singularities and black holes in the general theory of relativity. It was suggested in 1969 by the British physicist Roger Penrose (1931– ). The cosmic censorship conjecture asserts that all singularities in general relativity are hidden behind an event horizon (see death of a star). The conjecture has never been proved mathematically, although there is some evidence for it in many situations. Even if cosmic censorship is not correct, singularities would not be seen experimentally if the singularities are removed by quantum gravity. It may be that in classical general relativity the cosmic censorship hypothesis is true for ‘reasonable’ physical situations but that it is possible to construct counter-examples to it for various special situations.