CERN’s ‘Mini Big Bang’ Helps Scientists Study the Universe’s Earliest Moments

A new paper in the journal Physical Review Letters details a fascinating study conducted at CERN that succeeded in creating a quark-gluon plasma (QGP) with lighter elements than ever.

This matters because, directly after the Big Bang, nearly all matter and energy existed as QGP. Physicists and cosmologists are very interested in its properties, and this study offers a new pathway for how it could have formed and evolved in the early universe.

Physicists have created this primordial plasma before in large particle colliders, but previous successes used heavy atoms like lead. This study used the oxygen-16 and neon-20 isotopes, which are all less than a tenth the weight of the lead isotopes used before.

You Zhou, a researcher at the Niels Bohr Institute in the Netherlands and a coauthor of the study, says that the team now knows more “about the fundamental conditions required for matter to transition into this extreme state.” That means that they can build more accurate models of the evolution of the early universe, a large portion of which would have been driven by the properties of QGP.

Their main initial finding from this experiment is that the oxygen-neon plasma behaved basically like they expect QGP to behave, rather than having properties unique to the pathway. In particular, the plasma went through the expected cycle of fluid-like expansion followed by cooling and condensation into particles.

An artist’s impression of the Big Bang.
Credit: NASA/Goddard Space Center

That cooling and particle-creation process would have been the mechanism of creation for all the matter we see in the universe today. This plasma exists at a theoretical temperature over two trillion Kelvin, and the tiny amounts created here on Earth cool in an instant; even when it was the entire universe, this state lasted only a fraction of a second.

Even with the Large Hadron Collider’s ALICE detector, the researchers still couldn’t observe this plasma directly, but they could measure the particles it turns into. They found that collisions between two oxygen nuclei produced a more rounded movement pattern, whereas collisions involving neon produced a bowling-pin-shaped movement pattern. In this way, they could identify each nucleus.

“It is a bit like shining light on an object and seeing its shadow,” explains postdoctoral researcher Emil Gorm Dahlbæk Nielsen. “You cannot see the object directly, but its shadow reveals its shape. In the same way, the movement of the particles reveals the geometric shape of the atomic nuclei that was present at the beginning of the collision.”

Now that this study has produced a proof of concept for creating and identifying the constituents of light plasmas, scientists can begin updating their models of exactly how the universe got to the state we see around us today.