Interview with the authors

Brian Cox & Jeff Forshaw

How do we know what we know about black holes?

The Event Horizon Telescope collaboration recently captured photos of the supermassive black hole in the centre of our Galaxy and the bigger one in M87. Before EHT, our central black hole was inferred from how it shapes the orbits of nearby stars. Small black holes of a few solar masses have also been detected in binary systems. But what interests us most is more theoretical: none of the observations can probe what happens inside a black hole. We develop our understanding by calculating how the laws of physics play out. This is not as speculative as it sounds: a lot of ideas fit logically together in a single, compelling framework. It’s led to the idea of emergent space, and to the related idea that the world is a hologram.

What’s left to be discovered?

We’re only just getting to grips with the quantum physics of black holes and the nature of the black hole interior. One exciting prospect is to try to ‘build space’ in Earth laboratories using quantum entanglement. The way space appears to be built has similarities to the way quantum engineers are trying to build quantum computers – the robustness of space seems related to an idea called quantum error correction, central to the construction of robust quantum computers. Perhaps finding the theory of quantum gravity is intimately related to one of the big technological challenges of the 21st century: building a quantum computer. We think that’s a thrilling possibility.

Jeff Forshaw and Brian Cox are particle physicists based at the University of Manchester