Weak cosmic censorship conjecture

Let asymptotically flat initial data for Einstein's field equations be given, and let its maximal development be the corresponding spacetime. A future null infinity $\mathcal{I}^+$ is complete if it is complete as a null hypersurface; a singularity is hidden from $\mathcal{I}^+$ when it lies in a black-hole region causally disconnected from $\mathcal{I}^+$. Weak cosmic censorship conjecture. For generic asymptotically flat initial data, the maximal development of Einstein's field equations possesses a complete future null infinity $\mathcal{I}^+$ and hides the possibly formed singularities in a black-hole region causally disconnected from $\mathcal{I}^+$. This is one of the greatest open problems in classical general relativity and concerns whether singularities arising from generic gravitational data can be observed from infinity.