So it says that, instead of there being a big bang, the universe has always existed, yet they don't explain how anything could have always existed. They claim this because they say that since the laws of physics break down at the singularity required in the Big Bang Theory. So, to circumvent that problem, they claim that the universe has always existed. It appears, at least to me, to be solely based on convenience. They then do their computations and modeling based on the assumption that the universe has always existed. That is ass-backwards for science: start with your conclusion, then seek proof for it.
I have always had a problem buying into quantum mechanics and physics. To me, they have become the religion of the last decade; there are true believers and skeptics. Count me among the latter.