Physicists at CERN’s Large Hadron Collider have captured the clearest evidence yet that quark-gluon plasma, the scorching-hot matter that filled the newborn universe, behaves like a true liquid. By tracking individual quarks as they blasted through the plasma, researchers saw them leave behind ripples, splashes, and swirling wakes much like a duck moving through water. The finding suggests this primordial “soup” is so dense that it can slow speeding quarks and respond collectively as a fluid.