In the first moments of the Big Bang, the universe was in an extremely hot and dense state, often referred to as the primordial plasma. During this early phase, the fundamental forces of nature, such as gravity, electromagnetism, and the strong and weak nuclear forces, were not yet distinct as we understand them today. Instead, they were unified into a single force.
At such high energies, according to our current understanding of physics, the universe was filled with a form of energy called "pure energy." This term is used to describe the energy that existed in a state where it was not yet associated with any specific particles. In this state, the energy was not confined to the presence of particles but was rather a pervasive aspect of the entire universe.
The concept of "pure energy" arises from the framework of quantum field theory, which describes the fundamental particles and forces in the universe as excitations of quantum fields. These fields permeate all of space, and their fluctuations give rise to particles and their associated energy. However, in the extreme conditions of the early universe, the energies were so high that the particles we are familiar with today had not yet formed, and instead, the energy existed in a more fundamental, undifferentiated state.
It's important to note that the term "pure energy" is a simplified way of describing the conditions in the early universe. In reality, the nature of energy and its behavior at such high energies is described by more complex theories, such as quantum field theory and the Standard Model of particle physics. These theories provide a mathematical framework for understanding the behavior of energy and particles at different energy scales and have been successful in describing the early universe, as well as the particles and forces we observe today.