“There was a long history of speculation that in quantum gravity, unlike Einstein’s classical theory, it might be possible for the topology of spacetime to change.” -Edward Witten

Quantum gravity is one of the holy grails of physics, and showing that gravitation is an inherently quantum force would be a tremendous step towards validating our present approaches to theoretical physics.

While directly detecting gravitons might still be very far off, there are a number of weak-field tests involving the CMB and macroscopic quantum systems that have this potential, as well as potential strong-field tests that could all bear fruit in the near future. While we still won’t know which approach to quantum gravity is correct, the first experiments designed to show that Einstein’s General Relativity isn’t enough are already underway.