If you watch the Science Channel enough, your early fascination with all the theories and possibilities will gradually turn to confusion and frustration. There are SO many theories, so very MANY possibilities, they can't ALL be right, and, in fact, they may NONE of them be right.
The thing is, YOUR theory of everything may have just as much chance of being correct as the theory of the brightest and most educated scientist.
What I want to know is: Why am I NOT living on the timeline where I won the lottery?
There is a school of thought that says we live inside a black hole. This same school thinks that black holes in OUR universe give rise to other universes - thus, we have a "parent" universe where a black hole formed causing OUR universe to burst into existence through a "white" hole.
Then there's "Brane Theory", where our universe is like a thin sheet, or membrane (thus BRANE Theory) that bumped into the Brane next door and the point of contact was the explosive birth of our "stuff".
One theory directly contradicts the other, yet very convincing arguments exist in support of either.
Then, of course, there's String Theory, and M Theory, which is like String Theory on crack. These theories describe a Universe of many dimensions, of which we are aware of 3. 4 if you count Time. Personally, I favor this set of theories over others - it makes more sense to me. And it presents a reasonable explanation for the existence of Dark Matter - to me. I think (my intuition says) that Dark Matter is matter which exists in another dimension - a fourth physical dimension to go along with our familiar three. Which would make Time the fifth dimension.
Of course, Time doesn't sing.