In the beginning, there was nothing. Then a big bang happened and the universe came into existence. It was not as big as it is now. It was hot and dense and it kept expanding radically and 13.8 billion years later, we know how it looks now. However, how exactly the hot and dense matter cooled down is not so obvious for scientists. Scientists have been trying for more than 20 years to understand what exactly happened in the first microsecond of the big bang leading to the universe as we know it today. Now, scientists have found answers to what the hot dense matter was like and how it transformed.
Scientists studied the data from an experiment conducted by the Large Hadron Collider at the European Organization for Nuclear Research(CERN). In the experiment, they had created the hot and dense matter that existed in the initial phase of the universe. Scientists at the University of Copenhagen found that the data from the experiment was precise enough to deduce that the initial matter was a fluent liquid form. It could be distinguished because it constantly changed its shape over time. The hot and dense matter, the only matter that existed in the initial phase of the universe, was made up of quarks and gluons and is also known as Quark-Gluon plasma(QGP). Quarks are the fundamental particles that together make up protons and neutrons. Gluons are like binding material, such as glue, that keeps quarks together.
"First the plasma that consisted of quarks and gluons was separated by the hot expansion of the universe. Then the pieces of quark reformed into so-called hadrons. A hadron with three quarks makes a proton, which is part of atomic cores. These cores are the building blocks that constitute earth, ourselves and the universe that surrounds us," explained You Zhou, one of the authors of the study and an associate professor at the Niels Bohr Institute, University of Copenhagen, in a news release by the University. The study was published in the July issue of Physics Letters B.