What represents the initial event of the universe's existence?

The Big Bang represents the initial event of the universe's existence because it is the theory that describes how the universe began approximately 13.8 billion years ago. According to this theory, the universe started from an extremely hot and dense point and expanded rapidly in a process known as cosmic inflation. The aftermath of the Big Bang led to the formation of basic elements, such as hydrogen and helium, which subsequently allowed for the development of stars, galaxies, and other cosmic structures.

In contrast, the solar nebula refers specifically to the cloud of gas and dust from which our solar system formed much later. Cosmic evolution involves the changes and development of the universe over time, not the initial creation event. Stellar formation pertains to the process by which stars develop from clouds of gas and dust, which is a subsequent event that followed the creation of the universe after the Big Bang. Thus, the Big Bang is the foundational event that marks the inception of all cosmic history.