Time and space were suddenly created in an instant. Therefore, do not ask what happened before the big bang. There was never such a period as "before the big bang".

Why is it said that the universe was created in a big bang? The direct evidence comes from three aspects of observation: first, and the most direct, the universe is still expanding; second, everywhere in the universe It is permeated with thermal radiation, which is the dimmed afterglow of the original hot fireball produced during the Big Bang; third, the chemical elements of the universe observed by astronomers can describe the trajectory of the universe from its creation to its development.

However, what happened before the Big Bang? What caused the Big Bang to happen? Where is the center of the explosion? Where is the edge of the universe? In fact, these questions completely misunderstand the meaning of the Big Bang. The Big Bang is not the violent spread of numerous galaxies from the center of a celestial body into the depths of infinite vacuum. Here, space itself was created in the Big Bang, and time itself was also created in the Big Bang.

The small point where space appears is not located on any object. It is not an object surrounded by nothingness, but the starting point of infinitely compressed space itself. The small point does not remain there for an infinite duration. It immediately appears from nothing and expands immediately. The material event itself begins at this small point. Time, space and the material universe also have a starting point. This is probably the most critical and difficult to understand aspect of the Big Bang theory.

This small starting point is technically called the singularity. As you go back in time, the universe shrinks more and more, and the curvature of space-time increases infinitely, until it becomes infinity at the singularity. Roughly speaking, it resembles the apex of a cone, a structure that tapers to an infinitely pointed point where space and time begin.

Once this concept is accepted, then the question "what happened before the big bang" is obviously meaningless. There has never been such a period as "before the big bang" because time began with the big bang.

Unfortunately, this question is often answered with such simple words: "There was nothing before the big bang." Many people interpret "nothing" as space with nothing, but as I tried above As pointed out, space did not exist before the Big Bang.

Does the "nothing" here refer to something more subtle like "pre-space" from which space emerges? Or is it some kind of abstract state?

Both No, as Stephen Hawking said, "Where is the north of the North Pole?" This question can also be answered with "nothing", not because there is a mysterious "Wuji Land" there, but because of the mentioned The region does not exist at all, not only physically but also logically.