The concept of time is closely tied to the framework of our everyday experience and the way we perceive change and causality. However, when we talk about the Big Bang and the beginning of the universe, we enter a realm where our intuitive understanding of time may not fully apply.
According to the prevailing cosmological model, the Big Bang theory, the universe as we know it originated from a singularity—an extremely dense and hot state—approximately 13.8 billion years ago. The singularity represents a point where our current understanding of physics breaks down, including our conventional understanding of time.
It is important to note that when scientists refer to the beginning of the universe at the Big Bang, they are referring to the point at which our current models and knowledge no longer provide an explanation. The singularity is a mathematical concept that suggests an extreme curvature of spacetime, making it challenging to describe the conditions prior to the Big Bang using our current understanding of physics.
The absence of a conventional notion of time before the Big Bang does not necessarily mean that nothing existed or that no events occurred. It simply means that our understanding of time breaks down at that point, and we lack a complete theoretical framework to describe what may have transpired.
Various theories and models have been proposed to explore the nature of the singularity and the state of the universe before the Big Bang, such as the concept of inflation or ideas from quantum cosmology. However, these theories are still subjects of active research and remain speculative at this stage.
In summary, the notion that time started at the Big Bang arises from the limitations of our current understanding of physics and the challenges in describing the universe at that extreme state. It is an area where our intuitive sense of time may not be directly applicable, and further scientific investigations are needed to unravel the mysteries of the early universe.