CERN Experiments Confirm Early Universe Behaved Like a Near-Perfect Fluid

The young universe was born from a ‘soup' of a trillion degrees, consisting of both quarks and gluons. Physicists have long believed that this ‘soup' was a near-perfect fluid, with little friction. But new experiments at CERN's Large Hadron Collider have now confirmed this in dramatic fashion: the quarks are seen to create ‘wake' disturbances in the fluid, marking the first direct observation of the fluid-like behaviour of the early universe.

Quark Wakes Reveal Fluid-like Behaviour

According to the reports, at CERN's LHC, heavy-ion collisions recreate the early-universe quark-gluon plasma. Researchers identified events producing a single energetic quark recoiling opposite a neutral Z boson (which barely interacts with the plasma). In about 2,000 events, they mapped the energy deposits in the plasma and consistently saw a bow-wave pattern of ripples trailing the quark. According to theory, the plasma is so dense it “slows down a quark and produces splashes and swirls like a liquid”. These wakes provide the first clear evidence that the primordial quark soup flows collectively as a liquid.

Collective Flows Confirm Fluid Nature

Collider experiments had previously suggested the existence of a liquid-like state of the QGP. At Brookhaven's RHIC and CERN's LHC, particles emitted from heavy ion collisions exhibited collective “elliptic” and “radial” flows due to pressure, as would be observed in a liquid. Theoretical models suggested that the wake effect would occur behind high-speed quarks in the plasma. Experimental evidence verifies that the QGP is a nearly perfect, frictionless liquid. The above-mentioned phenomena are used to measure the plasma's viscosity and the process by which the “primordial soup” cooled to create today's protons and neutrons.