Einstein’s ‘robust prediction’

As a theoretical possibility, black holes were predicted in 1916 by Karl Schwarzschild, who found them to be an inevitable consequence of Einstein's theory of general relativity. In other words, if Einstein's theory is correct – and all evidence suggests it is – then black holes must exist. They were put on even firmer ground by Roger Penrose and Stephen Hawking, who showed that any object collapsing down to a black hole will form a singularity where the traditional laws of physics break down. This has become so widely accepted that Penrose was awarded a share in the 2020 Nobel Prize in Physics “for the discovery that black hole formation is a robust prediction of the general theory of relativity.”