To reconcile quantum mechanics and gravity, a new theory flips the usual script. Space-time and gravity may emerge from quantum effects, not the other way round
We first discovered the laws of gravity, and then those of quantum mechanics. But new work suggests nature might go about it the other way around: space-time, and hence gravity, could emerge from a fundamental quantum mechanical description of the universe.
According to Einstein’s general relativity, gravity is the curvature of space-time. That this geometry might be related to the minuscule quantum world was first understood in the 1970s when Stephen Hawking and Jacob Bekenstein showed that the entropy of a black hole – which depends on the black hole’s microscopic quantum structure – is proportional to its surface area.
While at Harvard University in the late 1990s, Juan Maldacena discovered a connection between a theory of gravity that describes a volume of space and a quantum field theory that describes the volume’s surface, and doesn’t include gravity. Since then, others have used