Deep underground, straddling the French-Swiss border, the Large Hadron Collider came roaring back to life in early April, following two years of upgrades. The souped-up machine has eclipsed its own records again and again for particle-smashing-prowess.

Its first run, between 2009 and 2013, reached a power of 8 teraelectronvolts, collided zillions of protons, and gathered enough data (the coveted "five-sigma," meaning that chances are one in three and a half million that the signal isn't really there) to announce the discovery of the long-awaited Higgs Boson. This particle, which imparts mass to others, was the last particle found among those predicted by the Standard Model.

Physicists have high hopes for the LHC's second run. Physicists desperately want to uncover new particles that'll lead the way to exploring undiscovered lands: supersymmetry and dark matter, for instance. In order to get more interesting—more complex and higher energy—collisions, physicists at CERN have recently begun colliding lead ions. The switch is like going from throwing tennis balls to cannonballs: A lead nucleus has 82 times the energy of a proton. In the LHC's latest incarnation, about 1 billion cannonball collisions are occurring every second. (For early results from the LHC's second run, see "Rumours of Cracks in the Standard Model".)