Tiny "Little Big Bangs" Successfully Recreate Primordial Universe Plasma in Smaller Collisions
In the earliest instants of the universe, matter did not exist in the form we recognize today. Roughly one millionth of a second after the Big Bang, the entire cosmos was a super-dense, scorching-hot mixture researchers have named quark-gluon plasma (QGP).
For decades, particle colliders—facilities that smash atomic particles together at nearly the speed of light—have been able to recreate this exotic primordial state. Until recently, though, most successful experiments relied on heavy elements like lead to generate detectable QGP. Now, a groundbreaking new experiment from the European Organization for Nuclear Research (better known by its French acronym CERN) has confirmed this early-universe plasma can be produced from much smaller, lower-mass particle collisions. With no naturally accessible sources of this primordial "cosmic sludge" left in the modern universe, these tiny simulated big bangs give scientists a rare new window to unpack exactly what unfolded in the first critical minutes of cosmic history.
To put the discovery in context: Quarks are the fundamental particles that form protons and neutrons, which in turn make up atomic nuclei and every type of visible matter we interact with. Gluons, true to their name, are the force-carrying particles that bind quarks together inside larger particles. In the first microseconds after the Big Bang, however, quarks and gluons were not yet locked up inside protons and neutrons. Instead, they mixed freely to form the ultra-hot QGP soup. As the universe expanded and cooled over time, quarks eventually condensed into the stable larger particles that make up all matter today.
After decades of studying QGP produced by collisions between large, heavy atomic nuclei, physicists have now turned their attention to mapping the physical limits of this strange state of matter. Specifically, they want to answer how small a collision can be while still producing a collection of particles that behaves like the fluid QGP drop observed in larger experiments.
According to a new paper published in Physical Review Letters, CERN and an international team of collaborators successfully generated QGP using collisions of oxygen-16 and neon-20 nuclei. Both of these atomic nuclei weigh less than one-tenth of a lead atom, which was previously considered one of the lightest starting materials capable of producing detectable QGP.
"We have pushed the boundary for how small the atomic nuclei can be while still recreating this primordial matter—what you could call a ‘little big bang,’" You Zhou, a researcher at the Niels Bohr Institute in the Netherlands and co-author of the study, explained in a press release. "We now know more about the fundamental conditions required for matter to transition into this extreme state."
The team found that despite the far smaller size of oxygen and neon nuclei, their collisions produced all the characteristic signals matching the expected behavior of QGP. For a fleeting instant after impact, the resulting matter expanded collectively like a fluid, before cooling down and reverting to ordinary bound particles.
"Hopefully, this will help us better understand how the plasma behaved during the first moments of the universe—and how it later evolved into the forms of matter that everything around us is made of," Zhou added.
This report originally appeared on WIRED en Español and has been adapted from the original Spanish text.
