A 'finite point in the past' indicates that it occurred in Time and Space, which, according to the theory, did not come into play until the Big Bang occurred. Therefore, the BB must have occurred in No-Space/Time.
I've seen the Big Bang referred to in two ways: (1) the sudden expansion of our universe very early after it began (inflation) or (2) the the very moment that the universe came into being. In the first case, time already existed. In the second case, the Big Bang was the very first moment of time.
There must be something to define the Universe as 'finite'. What is it?
By "finite" I mean a finite amount of time has elapsed since the Big Bang.
But a racetrack has an edge..and so does a sphere....so as analogies they fall short....please describe the shape of this finite universe?
They are, in fact, only analogies because we can't perceive four-dimensional shapes. For a more proper understanding of the racetrack analogy, we can imagine that the universe is an infinitely-thin ring and any one-dimensional being living in that ring can only move in two directions: forward and backward. Those are the only two directions that they can perceive or even understand. In a sense, they are living
in the edge of their own ring universe. The only directions they can move in will eventually bring them back to their starting point (if we ignore that others will invariably get in their way, since you can't go "around" things in such a universe).
The sphere (or balloon) analogy is the more common one seen in cosmology. The analogy is made by thinking of two-dimensional beings that live embedded in the surface of an expanding balloon, which represents their own two-dimensional space. They can move up, down, left and right and perceive these directions but they can't move "in" or "out" of the balloon's surface because their space is only two-dimensional, not three-dimensional like ours. Like with the ring analogy, they are sort of living inside the edge of their own universe.
Yes...I must admit I find it difficult to imagine how their flat universe could be eternal and infinite and yet consistent with the theoretical big bang beginning? But in any event, according to my understanding, there could not have been a beginning to the universe as logic defies a miraculous creation from nothing...and besides, there is no evidence that nothing could ever exist...
Nothing cannot exist, of course, as that would be a self-contradiction. That doesn't mean that time goes back forever, though. Nothing can come before time without also being an oxymoron, so questions like "what was there 25 seconds before the beginning of time?" are as nonsensical as "what does a piece of aluminum smaller than an aluminum atom look like"? This will be true regardless of how the universe came into being.