Cosmogony

Cosmogony (or cosmogeny) is any scientific theory concerning the coming into existence, or origin, of the cosmos or universe, or about how what sentient beings perceive as "reality" came to be. The word comes from the Greek κοσμογονία or κοσμογενία (from κόσμος - "cosmos", "the world") and the root of γί(γ)νομαι / γέγονα ("to be born, come about"). 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 solar system.^[1][2]
The Big Bang theory is the prevailing cosmological model of the early development of the universe.^[3] The most commonly held view is that the universe was once a gravitational singularity, which expanded extremely rapidly from its hot and dense state. While this expansion is well-modeled by the Big Bang theory, the origins of the singularity remains one of the unsolved problems in physics.
One problem is that there is currently no theoretical model that explains the earliest moments of the universe's existence (during the Planck time) because of a lack of a testable theory of quantum gravity. Researchers in string theory and its extensions (for example, M theory), and of loop quantum cosmology, have nevertheless proposed solutions. Another issue facing the field of particle physics is a need for more expensive and technologically advanced particle accelerators to test proposed theories (for example, that the universe was caused by colliding membranes).
Developing a complete theoretical model has implications in both the philosophy of science and epistemology. For example, it would clarify the meaningful ways in which people can ask the question "why do we exist?".