The world’s most powerful particle accelerator, the Large Hadron Collider (LHC), famously upended physics with the discovery of the long-sought Higgs boson in 2012. But it was only operating at half power. Since then, the LHC has undergone a massive upgrade, and this spring, it will ramp back up for a second run at near full strength. For the next three years, more than 12,000 scientists will use the LHC to explore the deepest and weirdest questions in particle physics. What they will find--new particles, forces, or even dimensions--is anyone’s guess.