Scientists Discover Early Universe Was Like a ‘Soup’
Jakarta, CNN Indonesia – New research suggests that the universe following the Large Bang wasn’t a void, but a superhot “soup” reaching temperatures of trillions of degrees. A recent experiment has provided the first evidence that this primordial fluid churned and swirled like a liquid.
In scientific terms, this viscous fluid is known as quark-gluon plasma (QGP). It is considered the first and hottest liquid to have ever existed. Predictions indicate that QGP was a billion times hotter than the surface of the Sun, lasting for several million seconds before expanding, cooling, and forming atoms.
A team of physicists from MIT and CERN reconstructed heavy ion collisions, similar to those that created QGP, to explore its properties. They investigated whether quarks flowing through the plasma would bounce and surge like a cohesive liquid or scatter randomly like particles. The experiment took place at CERN’s Large Hadron Collider (LHC), colliding lead particles at nearly the speed of light. These collisions generated high-energy particles, including quarks, and droplets of QGP resembling the early universe’s material.
Using a novel approach to provide a clearer picture of heavy ion collisions, researchers tracked the movement of quarks through QGP and mapped the QGP energy after the collisions. “Now we notice that this plasma is so dense that it can slow down quarks and produce liquid-like splashes and vortices. So, quark-gluon plasma really is a primordial soup,” said physicist Yen-Jie Lee from MIT, as quoted in ScienceAlert.
Quarks passing through QGP transfer energy to the plasma, losing speed and creating a trail similar to a speeding boat. MIT physicist Krishna Rajagopal explained, “As an analogy, when a boat moves through a lake, the trail is the water behind the boat that is moving in the same direction as the boat. The boat has transferred momentum to a portion of the water, which ‘follows’ the boat.”
The passing quarks create a shock wave, but ripples in QGP are difficult to detect. This plasma exists for a fraction of a trillionth of a second at trillions of degrees. Scientists must analyze tens of thousands of particles from collisions to find those pushed by the quark “trail.” Another challenge is that quarks are typically created in pairs with antiquarks moving in opposite directions, creating similar traces.
To overcome this, researchers looked for rare events producing quarks and Z bosons, neutral particles that don’t interact with QGP and leave no trace. Out of 13 billion collisions analyzed, only about 2,000 produced Z bosons. Although, these rare events allowed scientists to observe the “ripple” effect of a single quark more clearly.
As predicted by Rajagopal’s model, QGP reacts like a fluid, swaying and spinning in the quark trail. Rajagopal stated this is “definitive and irrefutable evidence” of QGP’s liquid behavior. The new technique provides a framework for exploring similar processes in high-energy collisions, potentially illuminating one of the universe’s most mysterious substances. “In many other fields of science, the way you study the properties of a material is by perturbing the material in some way, and measuring how that perturbation propagates and dissipates,” Rajagopal said. (CNN Indonesia)