How did time begin and how will it end?

Time, a fundamental concept of our existence, has both a beginning and an end, but their nature remains a mystery. While the Big Bang theory is widely accepted as the origin of the universe and time itself, the exact conditions during this event and the moments immediately after remain uncertain. Some physicists question the concept of time before the universe existed, proposing a super-universe context where our Big Bang is just one event among many.

Since the Big Bang, time has consistently moved forward, creating a distinct arrow of time. This unidirectional flow is often explained by the increasing entropy or disorder in the universe. However, this explanation presents challenges, as the early universe seems to have already been in a state of high entropy. Some theorists suggest that our universe is simply one among many, each with different initial states, and conscious beings can only exist in universes with increasing entropy.

The end of time, much like its beginning, is also uncertain. The heat death of the universe, a scenario where all energy is evenly distributed and entropy is maximized, is a leading hypothesis. This state would make time meaningless, as there would be no further change or directionality. However, the underlying structure of time, often described as a linear progression, may persist even in the absence of observable events or conscious beings. The end of time, therefore, might be more of a conceptual shift than a definitive conclusion.

Source: BBC - How did time begin, and how will it end?