Scientists are re-creating the early universe using the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. This is allowing researchers to probe the properties of quark-gluon plasma, the fluid-like substance believed to exist microseconds after the Big Bang. Studying this will help cosmologists better understand how the universe evolved after the blast that created it. The RHIC has created a “Little Bang”, in which two beams of gold nuclei were collided at close to the speed of light, creating quark-gluon plasma for a very brief period.
This plasma stage could have lasted anywhere from a few seconds to thousands of years. It may even exist today in the dense cores of neutron stars, so learning about its properties could help characterise the physics of the most extreme cosmic environments. Quarks and gluons are never found solo in nature, making it difficult to study them in isolation, so studying how they behave in a fluid will be key.
The early universe is otherwise impossible to study with telescopes, which only reach as far back as the cosmic microwave background, essentially the first light that emerged from the dense early universe. Everything before that is both literally and figuratively a dark era of cosmology. Theoretical simulations won’t allow researchers to actually experimentally understand a system that exists in a similar way to the Big Bang, but the RHIC could.
The possibility that quark-gluon plasma could exist in the densest areas of space means studying its properties has a broader relevance than solely understanding the early universe. Plasma might be a misnomer, given that it actually behaves more like a fluid. While it is confined to a volume, the quarks and gluons within this space are no longer fused together. Testing the quark-gluon plasma is also providing insights into how the affects of high-energy particles in the atmosphere behave.