The question of why everything in the universe is not entangled with everything else from the Big Bang is an interesting one. It relates to the concept of quantum entanglement and the dynamics of entanglement formation and preservation in the early universe.
Quantum entanglement arises when two or more particles interact in a way that their states become correlated. This correlation can persist even when the particles are separated by large distances. However, not all interactions lead to entanglement, and not all particles in the universe have necessarily been entangled with each other since the beginning.
The reason for this lies in the nature of quantum interactions and the expansion of the universe. The entanglement between particles typically occurs during interactions that are strong enough to generate entanglement. However, as the universe expanded after the Big Bang, the density of matter and the energy of interactions decreased.
As a result, the likelihood of new entanglement being formed decreased over time. Additionally, the expansion of the universe causes particles to move apart, making it less likely for them to interact and become entangled.
Moreover, the initial conditions of the universe, such as the distribution of matter and energy, play a crucial role in determining which particles become entangled. Entanglement depends on the specific interactions and correlations between particles, which can vary depending on initial conditions.
While some entanglement may have arisen during the early stages of the universe, such as during the inflationary epoch or the subsequent thermalization processes, it does not imply that everything in the universe is entangled with everything else. The entanglement is highly dependent on the specific circumstances and interactions involved.
It is important to note that our understanding of the early universe and quantum gravity is still evolving, and further research and theoretical developments may provide deeper insights into the dynamics of entanglement and its role in the early cosmos.