Solar flares, coronal mass ejections and gamma-ray bursts are among the universe’s many explosive events involving ionized gas, called plasma, that are associated with magnetic reconnection. Reconnection breaks magnetic field lines and turns magnetic potential energy into kinetic energy of charged particles in the plasma. This energy conversion also causes what physicists call “sawtooth crashes” in tokamaks that are potentially damaging to electricity-producing fusion devices. Scientists may have found the trigger for these explosive events and, using supercomputer simulations, can predict when and under what conditions the events will occur.