For decades now physicists have contemplated the idea of an entire shadow world of elementary particles, called supersymmetry. It would elegantly solve mysteries that the current Standard Model of particle physics leaves unexplained, such as what cosmic dark matter is. Now some are starting to wonder. The most powerful collider in history, the Large Hadron Collider (LHC), has yet to see any new phenomena that would betray an unseen level of reality. Although the search has only just begun, it has made some theorists ask what physics might be like if supersymmetry is not true after all.

Theorists introduced supersymmetry in the 1960s to connect the two basic types of particles seen in nature, called fermions and bosons. “It is the next step up toward the ultimate view of the world, where we make everything symmetric and beautiful,” says Michael Peskin, a theorist at SLAC National Accelerator Laboratory. But despite the high expectations, so far nature has not cooperated. LHC physicists have been searching for signs of particles new to science and have seen none. If super­particles exist, they must be even heavier than many physicists had hoped.