General relativity

Spurred on by quantum experiments that scramble the ordering of causes and their effects, some physicists are figuring out how to abandon causality altogether.

A new study shows that extreme black holes could break the famous “no-hair” theorem, and in a way that we could detect.

Roger Penrose, Reinhard Genzel and Andrea Ghez were awarded the Nobel Prize in Physics for their studies of black holes.

Claudia de Rham showed how theories of “massive gravity” could potentially get rid of the need for dark energy.

We asked four physicists why gravity stands out among the forces of nature. We got four different answers.

By chewing on the problems posed by “extremal” black holes, physicists have exposed a surprising and universal connection between energy and entropy.

Einstein’s equations describe three canonical configurations of space-time. Now one of these three — important in the study of quantum gravity — has been shown to be inherently unstable.

The laws of physics imply that the passage of time is an illusion. To avoid this conclusion, we might have to rethink the reality of infinitely precise numbers.

Explore our surprisingly simple, absurdly ambitious and necessarily incomplete guide to the boundless mathematical universe.