My personal belief is that the universe had no beginning. Everything that is always has been. It is "recycled", after a fashion, over periods of billions, possibly trillions of years, in a grand cycle of contraction and explosion/expansion. The basis of my belief (and I admit that it IS only a belief) is the overwhelming proliferation of cyclical activity of the universe. Any planet orbiting a star - on a track toward consumption by that star, but until then ringing that star in millions upon billions of cycles. Entire galaxies rushing toward one another due to gravity's pull - eventually colliding and each individual member affecting others and creating new orbits, new cycles. The substance of any given large, planetary object continually shifting and moving - almost like water, but much, much slower. It's contents being sucked toward the center and spewed out to the surface again until the object is a near perfect sphere when seen from a distance. Even spinning - by it's definition a cycle - and one of the most prolific natural occurrences in ALL matter in the entire universe. The cycle of radioactive energies breaking down, but never truly being lost - awaiting a time when they are energized once more and made new in the culmination of the intergalactic, near-universal recycle.
I feel all of the interactions we have observed throughout the universe point to my belief. Even the idea of a "big bang" - matter being sent forth from a central "explosion" of sorts - the recycling event - even as other matter never quite made it there in time for the party. Which explains any bodies whose movement and trajectory doesn't necessarily conform to the "big bang" - because it wasn't the first, nor will it be the last.