I used to have a more interesting morning commute. At daybreak I’d squeeze into a tiny Fiat with all the physicists it could fit. We’d drive through winding Italian roads and onto a highway that cuts across the peninsula, with a tunnel right through its grandest mountain, Gran Sasso. At the tunnel’s deepest point, with nearly a mile of bedrock resting above our heads, we’d turn off through a guarded gate and enter one of the quietest places on Earth.
In spare moments while turning a wrench or staring at a pressure gauge, I’d sometimes ask my teammates what our chances were of winning that race. “Zero,” they’d usually reply. Surprised, I began questioning colleagues beyond my several hundred collaborators, polling them at conferences and happy hours, and found that it wasn’t just us. Few experts—among the younger generation basically no one—thought any scientific effort was on the brink of discovering dark matter.
In the seven years since, these murmurs have grown only louder. For four decades now we’ve failed to identify the particles that make up dark matter—the invisible chunk of the universe that we know is there, that suffuses every galaxy we see. And more physicists than ever are conceding that this situation might never change. “Nature doesn’t always promise us the results we’d like,” says physicist and mathematician Edward Witten, whose 1985 paper proposing that weakly interacting massive particles, or WIMPs, could be observed on Earth launched the field that I focused my Ph.D. work on. “It’s unfortunate, but it’s certainly possible that nature chose a dark matter particle that we won’t be able to detect,” Witten observes.
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