A Casimir Effect Caused by Gravity

Two mirrors placed a few nanometers apart in a vacuum experience an attractive force. This so-called Casimir effect is a consequence of how the mirrors perturb fluctuations of the vacuum—a state that, because of quantum mechanics, is far from being empty and instead teems with fleeting electromagnetic waves. The electromagnetic Casimir interaction has been widely documented in experiments, but the phenomenon could, in principle, occur for any quantized field. If gravity truly has a quantum nature, then gravitational waves should also generate Casimir-like forces as they pop in and out of the vacuum. New calculations by James Quach at the University of Tokyo, Japan, suggest that a gravitational Casimir attraction might be observable, provided the two mirrors have the unusual property of being able to reflect gravitational waves.