A new experiment involving a network of entangled atomic clocks could finally help us test how quantum mechanics fits with general relativity.

Quantum mechanics is our best understanding of the universe at atomic and subatomic scales. With it, we have revolutionized our understanding of physics on teeny tiny scales. General relativity – first outlined by Albert Einstein in 1915 – meanwhile, is our best understanding of gravity. According to the theory, which has so far passed every test we have thrown at it, gravity is not a force but the result of the curvature of spacetime around matter.