“Quantum Foam” Scrubs Away Gigantic Cosmic Energy

Many theoretical approaches that work toward a quantum theory of gravity suggest that all of spacetime should be filled with an energy that is as much as 10 ²⁰ times larger than observations allow. Theorists have proposed various tweaks to make this energy go away, but a new proposal hints at a different type of solution: the energy really is huge, but it has no large-scale significance for cosmic expansion because its effects cancel out on the very smallest scales.