According to the prevailing scientific understanding, space and time, as we know them, came into existence with the Big Bang. The Big Bang theory is the leading explanation for the origin and evolution of the universe. It suggests that the universe began as an extremely hot and dense state, and it has been expanding and cooling ever since.
The concept of space and time as we understand them breaks down at the earliest moments of the universe, specifically at the Planck time (approximately 10^-43 seconds after the Big Bang) and the Planck length scale (approximately 10^-35 meters). At this scale, the laws of physics as we currently understand them are not applicable, and our current theories, such as general relativity, do not provide a complete description of the universe's behavior.
Therefore, the question of whether space and time existed prior to the Big Bang is still an open question in cosmology and theoretical physics. Some theoretical models, such as certain interpretations of string theory and loop quantum gravity, propose ideas about pre-Big Bang or multiverse scenarios. However, these ideas are still highly speculative and have not been confirmed by empirical evidence.
In summary, while space and time as we know them originated with the Big Bang, the nature of existence before that moment is still a topic of ongoing scientific investigation and speculation.