Time is one of the most mysterious dimensions of the universe. No one knows what it is or how it began.
The Big Bang marks the beginning of our universe and our understanding of time, but its exact nature remains unclear due to the limitations of our current understanding of physics, particularly at the infinitesimally small and dense conditions that prevailed at the singularity. The arrow of time, always moving forward, may be a result of increasing entropy in the Universe, although this explanation faces challenges, particularly regarding the entropy state of the early Universe and the possibility of other universes with different entropy levels. Some physicists propose a whole multiverse where our universe with its increasing entropy is just one possibility.
