The concept of "how far back" we can trace the history of the universe depends on the limitations of our current scientific understanding and observational capabilities. The Big Bang theory itself describes the origin of the universe as a hot, dense, and rapidly expanding state from which our observable universe emerged.
According to the Big Bang theory, the universe began approximately 13.8 billion years ago. Our knowledge of the early universe is derived from various lines of evidence, including the cosmic microwave background radiation, the abundance of light elements, and the distribution of galaxies.
However, our ability to probe the conditions immediately before the Big Bang is limited due to the extreme physical conditions at that time. The universe was in a highly dense and energetic state, and our current understanding of physics, particularly our lack of a complete theory of quantum gravity, makes it difficult to describe what happened precisely at the moment of the singularity.
The singularity represents a point of infinite density and temperature, where the known laws of physics break down. It is currently beyond our scientific reach to investigate what occurred before or at the singularity. Our current theories cannot reliably describe the physics in that regime.
Therefore, in terms of our observational capabilities and theoretical understanding, we currently have no direct information about what happened before the Big Bang or at the singularity. It is an area of active scientific research and the subject of ongoing theoretical investigations, such as the development of theories of quantum gravity, which seek to address these fundamental questions about the origins of the universe.
In summary, the concept of "before" the Big Bang is still a topic of scientific inquiry, and our understanding is limited by the extreme conditions at that time and the lack of a complete theoretical framework to describe it.