Scientists have long been intrigued by the idea of understanding what happened before the Big Bang. The Big Bang theory suggests that the universe began with a tremendous explosion around 13.8 billion years ago, but it does not explain what triggered this event or what existed prior to it. However, recent scientific advancements and theories have shed light on this cosmic mystery.

One prevailing concept is that the universe may go through endless cycles of expansion and contraction, known as "cyclic cosmology." According to this theory, our universe is just one in a series of universes that are born, exist, collapse, and are then reborn again.

These universes exist within an expansive structure called the "multiverse." The multiverse is composed of multiple, parallel universes, each with its own set of physical laws.

In cyclic cosmology, each cycle of the universe begins with a big bang and ends with a big crunch, where the universe collapses back onto itself. After the big crunch, a new big bang follows, starting the cycle anew. This theory suggests that before the Big Bang, there may have been a collapsed universe that underwent a big crunch and preceded the current expanding universe.

Another proposition involves the concept of a "Big Bounce." This idea suggests that instead of a singularity, the universe had a previous phase of contraction, which led to a bounce and the subsequent expansion. According to this theory, the universe undergoes an eternal cycle of contraction and expansion, with each phase initiating a new universe.

In addition to cyclic cosmology and the Big Bounce, some scientists explore the possibility of pre-Big Bang scenarios within the framework of string theory. String theory suggests that the fundamental building blocks of the universe are tiny, vibrating strings of energy.

These strings can exist in various dimensions beyond our familiar four-dimensional space-time. The mathematically intricate nature of string theory allows for different scenarios before the Big Bang, such as the existence of a previous universe or the collision of two "branes," which are higher-dimensional objects.

While these theories and concepts provide fascinating insights into what may have come before the Big Bang, they are still speculative and require further investigation. The nature of time, space, and existence itself remains poorly understood in the pre-Big Bang era. Scientists continue to rely on innovative experiments, theoretical models, and technological advancements to explore this profound question and push the boundaries of our understanding.