Origin of the universe

Cosmogony (or cosmogeny) is any model concerning the origin of either the cosmos or universe. Developing a complete theoretical model has implications in both the philosophy of science and epistemology.

The word comes from the Koine Greek κοσμογονία (from κόσμος "cosmos, the world") and the root of γί(γ)νομαι / γέγονα ("come into a new state of being"). In astronomy, cosmogony refers to the study of the origin of particular astrophysical objects or systems, and is most commonly used in reference to the origin of the universe, the solar system, or the earth-moon system.

The Big Bang theory is the prevailing cosmological model of the early development of the universe. The most commonly held view is that the universe was once a gravitational singularity, which expanded extremely rapidly from its hot and dense state. However, while this expansion is well-modeled by the Big Bang theory, the origins of the singularity remain as one of the unsolved problems in physics.

Cosmologist and science communicator Sean M. Carroll explains two competing types of explanations for the origins of the singularity which is the main disagreement between the scientists who study cosmogony and centers on the question of whether time existed "before" the emergence of our universe or not. One cosmogonical view sees time as fundamental and even eternal: The universe could have contained the singularity because the universe evolved or changed from a prior state (the prior state was "empty space", or maybe a state that could not be called "space" at all). The other view, held by proponents like Stephen Hawking, says that there was no change through time because "time" itself emerged along with this universe (in other words, there can be no "prior" to the universe). Thus, it remains unclear what combination of "stuff", space, or time emerged with the singularity and this universe.

...
Wikipedia