The Big Bang is the prevailing scientific theory about the origins of the universe. According to this theory, the universe began as an extremely hot and dense point, often referred to as a singularity, approximately 13.8 billion years ago. This singularity expanded rapidly, leading to the formation of all matter and energy in the universe.
Now, regarding your question about going back in time after the Big Bang, current scientific understanding suggests that time itself began with the Big Bang. The concept of "going back" assumes a linear flow of time, which may not be applicable beyond the event horizon of the Big Bang.
The reason we cannot go back in time before the Big Bang, or even directly observe the moment of the Big Bang itself, is primarily due to two factors: the expansion of the universe and the nature of time. The universe has been expanding since the Big Bang, causing space to stretch and galaxies to move away from each other. This expansion results in an observable boundary called the cosmic microwave background radiation, which essentially acts as a barrier preventing us from seeing beyond a certain point in time.
Additionally, the nature of time itself presents a limitation. Time is a fundamental dimension of our universe, and it appears to have originated with the Big Bang. Therefore, it becomes problematic to conceive of a "before" the Big Bang because time, as we understand it, may not have existed in the same way prior to that event.
If we were somehow able to reach back in time before the Big Bang, it is unclear what would happen because our current understanding of the laws of physics breaks down at the singularity. The singularity represents an extreme state where conventional physics no longer applies, and our understanding of the universe's behavior becomes incomplete. Speculating on the consequences of such a scenario would require a theory of quantum gravity, which is still an area of active research in physics.
It's important to note that concepts like time travel and understanding the conditions before the Big Bang are highly speculative and are currently beyond the scope of scientific investigation. The Big Bang theory provides our best explanation of the early universe based on the available evidence, but there are still many unanswered questions about the nature of the singularity and what may have occurred before it.