In recent years, black holes have morphed from highly theoretical exotic possibilities to well-observed astrophysical objects. The observational evidence has come from sources such as the first observation of ripples in spacetime caused by black hole collisions and the first image of a black hole published in 2019.
Black holes are predicted by Einstein’s theory of general relativity, which describes the universe on the largest scale. But these objects must also distort spacetime on the tiniest scale, meaning that black holes must also have interesting quantum properties. The challenge for theorists is to find ways to unite the disparate theories of relativity and quantum mechanics in a theory of ‘loop’ quantum gravity that correctly predicts observations.
And these theorists have been busy. Over the last decade, they have developed an increasingly sophisticated theoretical understanding of black holes that could explain some of the biggest mysteries of cosmology.
