CERN has recreated the primordial soup that composed the universe a few billionths of a second after the Big Bang in order to understand it better—with some surprising results.
The recipe for such a soup is simple. It requires a few lead nuclei; a 16.8-mile-long Large Hadron Collider, the world’s most powerful particle accelerator; and sprinkle of 5.02 tera electron volts (TeV), the highest amount of energy ever used in such an experiment. What comes out is known as quark-gluon plasma, an extremely hot and dense material composed of the most fundamental particles, but especially (surprise) quarks and gluons.
This isn’t the first time this soup has been made by humans—that honor falls to CERN in June of 2015. But more than recreating the quark-gluon plasma, researchers have now been able to discover properties of the primordial soup that they couldn’t determine before.
“The analyses of the collisions make it possible, for the first time, to measure the precise characteristics of a quark-gluon plasma at the highest energy ever and to determine how it flows,” said You Zhou, a postdoc in the ALICE research group at the Niels Bohr Institute and a member of the international team tasked with examining the soup, in a statement.
Behaving like a liquid
In fact, the researchers have been hard at work studying the plasma’s collective properties—which has revealed that it actually behaves more like a liquid than a gas, even at its highest energy densities. Further, they were able to determine the viscosity of this fluid with high precision.
In order to discover such things, the researchers shot the spherical lead nuclei at each other so that they hit off-center, forming primordial soup in the shape of a very tiny football. Because of its non-spherical shape, the difference in pressure between the center of the “football” and the surface varies along the different axes. Further, the pressure differential pushes the “football” to expand and flow, meaning one can measure a characteristic variation in the number of particles produced in the collisions as a function of the angle.
“It is remarkable that we are able to carry out such detailed measurements on a drop of ‘early universe’, that only has a radius of about one millionth of a billionth of a meter,” said Jens Jørgen Gaardhøje, professor and head of the ALICE group at the Niels Bohr Institute at the University of Copenhagen.
“The results are fully consistent with the physical laws of hydrodynamics, i.e. the theory of flowing liquids and it shows that the quark-gluon plasma behaves like a fluid. It is however a very special liquid, as it does not consist of molecules like water, but of the fundamental particles quarks and gluons.”
These results have been submitted to Physical Review Letters, the top scientific journal for nuclear and particle physics but the researchers aren’t stopping with these results. According to Jens Jørgen Gaardhøje, the team is now aiming to map the quark-gluon plasma with even more precision—and to study it even farther back in time.
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Feature Image: Thinkstock
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