Quantum gravity tests may mistake ordinary spacetime for superposition

Everything around us, from atoms and molecules to planets and galaxies, is governed by two extraordinarily successful theories of physics: quantum mechanics and gravity.

Quantum mechanics explains the behavior of the microscopic world, while Einstein's theory of gravity describes the motion of stars, black holes and the expansion of the universe.

Yet despite their successes, physicists are still searching for a theory of "quantum gravity" that would unite them into a single description of nature. ...