During the early stages of the Hot Big Bang, the universe was extremely hot, dense, and rapidly expanding. Gravity, being one of the fundamental forces of nature, did play a crucial role in the evolution of the universe. However, the behavior of gravity in the context of the expanding universe is different from its behavior in a smaller-scale system like our solar system or a black hole.
To understand why gravity did not cause all matter to collapse into one mega black hole, we need to consider the concept of the critical density of the universe and the initial conditions set by the Big Bang.
Critical Density: The critical density is a value that determines the overall geometry and fate of the universe. If the actual density of matter and energy in the universe exceeds the critical density, gravity will eventually cause the universe to collapse. If the density is less than the critical density, the universe will expand forever.
Initial Conditions: The universe started from an extremely hot and dense state known as the singularity. As the universe expanded, it cooled down, allowing particles to form and interact. At early times, the universe was filled with a hot and energetic soup of particles and radiation. However, it wasn't uniformly distributed.
In this context, the following factors contributed to the universe not collapsing into a mega black hole:
Expansion: The rapid expansion of the universe during the Hot Big Bang caused the matter and energy to spread out over vast distances. As the universe expanded, the density of matter decreased. This expansion counteracted the pull of gravity, preventing immediate gravitational collapse.
Homogeneity and Isotropy: The universe appears to be homogeneous and isotropic on large scales, meaning it is relatively uniform in all directions. This suggests that the matter and energy were distributed fairly evenly across the universe. The overall distribution of matter was not highly concentrated in one region, reducing the chances of a mega black hole formation.
Cosmic Inflation: There is evidence to suggest that the universe underwent a brief period of exponential expansion known as cosmic inflation. This inflationary phase smoothed out the distribution of matter and diluted any initial non-uniformities, resulting in a more homogeneous universe on large scales.
Dark Energy: Recent observations have shown that the expansion of the universe is accelerating. This acceleration is attributed to a mysterious form of energy called dark energy. The presence of dark energy counteracts the gravitational pull of matter, preventing the universe from collapsing.
In summary, the combination of the expansion of the universe, the initial conditions set by the Big Bang, cosmic inflation, and the influence of dark energy prevented the matter from collapsing into a mega black hole during the Hot Big Bang.