Science cannot explain the origins of the beginning. Yeah, we can trace your universes expansion all the way back to the initial singularity, but it stops there, because there is no naturalistic reasoning after you take away space and matter, which is exactly what you do once you go back in time. So we need a transcendent cause.
Huh? According to Big Bang cosmology, THERE WAS NO UNIVERSE BEFORE THE BIG BANG. There is no "as we know it" business going on here. Physicists recognize that that our universe began to exist, that is why they have been panicking in their attempts to come up with naturalistic explanations for WHY and HOW our universe began to exist. The universe begin to exist, suggesting that there was a time at which THERE WAS NO UNIVERSE AT ALL.
Actually there is, it is called the "Standard Model" of the big bang. In this model, literally nothing existed before the big bang. This is by far the best explanation, and it has the most evidence supporting it. All other models and proposals fall short. And you are right, it doesn't explain the origin, but it does give support to the second premise of the argument, that the universe began to exist. This is evidence from cosmology, which is independent evidence from the evidence from entropy and the second law of thermodynamics as well. And in case empirical evidence isn't enough, we have logical reasoning from philosophy that the universe had to have had a beginning. So I think we have more reasons than not to believe that the universe began to exist, and therefore require a transcendent cause. If you don't believe this, then you should have no problem tearing down all the arguments that support a finite universe and replacing them with the opposite.