This Is How to Check Whether Spacetime Is Foamy

“After Einstein, “spacetime” was conventionally understood to be like a smooth surface. But in the 1950s, Wheeler began to suggest that—just like matter and energy—space had to be made up of “quanta,” or particles. That, Wheeler wrote, “forces on space a foam-like structure.” Today, researchers across the globe are pursuing evidence for Wheeler’s quantum foam because it may be a harbinger of a post-Einsteinian physics, helping scientists understand how gravity and quantum mechanics are linked.”

“The team was expecting to see some quantum foam-induced distortions, but didn’t find any. Instead, the x-ray and gamma-ray data showed that spacetime appears smooth even at distances shorter than the nucleus of a hydrogen atom, much less foamy than they and others had previously thought. “Spacetime foam remains theoretical,” says Perlman. “There has never been a direct detection of it thus far, much less whether its density varies over cosmic time.””