@Shostakovich phil,
I accept the Big Bang theory as remaining inconclusive but having evidence in Hubble's findings about the expanding universe and the discovery of the three degree microwave background radiation. The theory is consistent with an evolutionary view of the universe, and since we find evolution in the history of our planet and the solar system, I expect to find it in the history of the universe too.
I think it highly probable that the universe had a beginning, and that space and time had their beginning with the universe and did not exist prior to it. But did the universe come from nothingness, from non-existence? No it can't. If the universe came from nothingness, then that nothingness must be said to have had the potentiality for the universe, and if it had the potentiality for the universe, then it was not really nothingness, was it?
The apparent nothingness from which the universe burst forth exists independent of space and time. Whatever kind of existence it may be, it incorporates the vast potential required to bring forth our universe, but it has no properties, attributes, or qualities belonging to space or time.
It has no shape or size. It is formless.
It has no inside or outside. It is boundless.
It has no location or process. It is non-dimensional.
It has neither number nor division. It is undifferentiated.
It has no objects and no events. It is indiscrete.
It has neither a beginning nor an end. It is eternal.
It has neither consciousness nor experience. It is ineffable.
It knows neither thought, nor emotion, nor desire. It is incognitive.
It knows neither becomings nor cessations. It is intransiable.
It knows neither choice, nor action, nor change. It is immutable.
Thus, whatever exists "outside" of space and time is one without other and has so many of the characteristics the mystics have attributed to the Brahman, the Tao, to Nirvana, and the Nagual. It is the ground-state of all being, the source of all universes there may be, each with their own native space and time. I call it spirit because it is transcendent and yet immanent, and because it can be what we call God but needs not be so.
If an existence has no beginning or end, then it must simply be and can never not be. This is what philosophers have called "a necessary being," a being the explanation of which is contained within itself.
Samm