Computational astrophysicist Alice Pisani put on a virtual-reality headset and stared out into the void—or rather a void, one of many large, empty spaces that pepper the cosmos. “It was absolutely amazing,” Pisani recalls. At first, hovering in the air in front of her was a jumble of shining dots, each representing a galaxy. When Pisani walked into the jumble, she found herself inside a large swath of nothing with a shell of galaxies surrounding it. The image wasn't just a guess at what a cosmic void might look like; it was Pisani's own data made manifest. “I was completely surprised,” she says. “It was just so cool.”
The visualization, made in 2022, was a special project by Bonny Yue Wang, then a computer science undergraduate at the Cooper Union for the Advancement of Science and Art in New York City. Pisani teaches a course there in cosmology—the structure and evolution of the universe. Wang had been aiming to use Pisani's data on voids, which can stretch from tens to hundreds of millions of light-years across, to create an augmented-reality view of these surprising features of the cosmos.
The project would have been impossible a decade ago, when Pisani was starting out in the field. Scientists have known since the 1980s that these fields of nothing exist, but inadequate observational data and insufficient computing power kept them from being the focus of serious research. Lately, though, the field has made tremendous progress, and Pisani has been helping to bring it into the scientific mainstream. Within just a few years, she and an increasing number of scientists are convinced, the study of the universe's empty spaces could offer important clues to help solve the mysteries of dark matter, dark energy and the nature of the enigmatic subatomic particles called neutrinos. Voids have even shown that Einstein's general theory of relativity probably operates the same way at very large scales as it does locally—something that has never been confirmed. “Now is the right moment to use voids” for cosmology, says David Spergel, former chair of astrophysics at Princeton University and current president of the Simons Foundation. Benjamin Wandelt of the Lagrange Institute in Paris echoes the sentiment: “Voids have really taken off. They're becoming kind of a hot topic.”
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