Physicists working at CERN’s Large Hadron Collider have captured what they describe as the clearest evidence yet that quark-gluon plasma, the extreme state of matter that filled the early universe, behaves as a true liquid. The team achieved this by tracking individual quarks as they traveled through the plasma, a method that allowed them to observe how the medium responded to the particles’ passage.
The quark-gluon plasma is created in high-energy collisions that briefly recreate conditions similar to those of the newborn universe. Until now, its collective behavior had been inferred from broad patterns, but the new measurements provide a more direct view. By following single quarks, the researchers could see how the plasma pushed back and flowed around them, matching the signature of a liquid rather than a gas or a weakly interacting gas-like state.
These results sharpen the picture of how matter behaved in the first instants after the Big Bang. They also give theorists a more precise benchmark for modeling the strong force, which governs quarks and gluons. The study adds to a growing body of evidence that the primordial soup was not an exotic exception but a fluid with properties that can now be studied in detail.