Quantum gravity

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

It has been thought of as many things: a pointlike object, an excitation of a field, a speck of pure math that has cut into reality. But never has physicists’ conception of a particle changed more than it is changing now.

In a landmark series of calculations, physicists have proved that black holes can shed information.

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

New calculations show how hypothetical particles called gravitons would give rise to a special kind of noise.

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

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.

By considering simple symmetries, physicists working on the “bootstrap” can rediscover the basic form of the known forces that shape the universe.

For the first time, physicists have calculated exactly what kind of singularity lies at the center of a realistic black hole.