Nature abhors a vacuum, so the saying goes, but nobody told the universe. Space is filled with cosmic voids—vast regions mostly free of matter that have opened between dense threads of material that make up a cosmic web.

Far from being vacant backwaters with little to study, these voids may hold solutions to some of the most persistent cosmic mysteries, such as the behavior of gravity, the nature of dark energy, and the so-called Hubble tension, an observational mismatch in the expansion rate of the universe that has caused astronomers’ headaches for years.

‘With voids, we have the power to tackle most of the interesting cosmological riddles,’ says Alice Pisani, a research professor in cosmology working at the Centre for Particle Physics in Marseille (CPPM) of the French National Centre for Scientific Research. She adds that because there’s less interference from matter, there’s a ‘high signal-to-noise’ ratio in terms of what researchers can observe.

For places defined by sparseness, voids are becoming cosmological heavyweights, where the laws of physics can be observed with unusual clarity. From a cosmology perspective, it is a very exciting time,’ Pisani says. Following the Big Bang, the universe was a uniform soup of subatomic particles. But over millions of years, as matter cooled and stabilized into atoms, the faint outlines of the cosmic web began to emerge.

The advent of new telescopes and advanced simulations has supercharged this field, inspiring a growing community of scientists worldwide to specialize in voids as unique cosmological laboratories. Some experts argue we may even live inside a colossal void, a position that may alter our view of the universe in consequential ways.