This artist’s illustration depicts how the foamy structure of space-time may appear, showing tiny bubbles quadrillions of times smaller than the nucleus of an atom that are constantly fluctuating and last for only infinitesimal fractions of a second. Rather than being smooth, continuous, and uniform, at the quantum scale, spacetime has fluctuations inherent to it. Although we strongly suspect that gravity is quantum in nature, we can only be sure via experiment. (Credit: NASA/CXC/M. Weiss)

Has a new experiment just proven the quantum nature of gravity?

At a fundamental level, nobody knows if gravity is truly quantum in nature. A novel experiment strongly hints that it is.

If you were to break down the matter in our Universe to its smallest, most fundamental subatomic constituents, you’d find that everything was made up of individual quanta, each of which possesses both wave and particle properties simultaneously. If you pass one of these quantum particles through a double-slit and don’t observe which slit it passes through, the quantum will behave as a wave, interfering with itself on its journey, leaving us with only a probabilistic set of outcomes to describe its ultimate trajectory. Only by observing it can we determine precisely where it is at any moment in time.

This bizarre, indeterminate behavior has been thoroughly observed, studied, and characterized for three of our fundamental forces: the electromagnetic force as well as both the strong and weak nuclear forces. However, it’s never been tested for gravitation, which remains the one remaining force that only has a classical description in the form of Einstein’s General Relativity. Although many clever experiments have been designed to attempt to reveal whether a quantum description of gravity is required to account for…