The big bang would have required a very low entropy state.  While most physicists just take such an initial state for granted, Penrose argues that such ‘improbable’ states don’t just magically come about. The probability of such as state is 1 part in 10 ^ 10 ^ 123.  (If you numbered ALL the atoms in the Universe, you would still not even get close to this number).

As per Penrose

The current big bang model, which is partially grounded in inflation, doesn’t supply a reason as to why a low entropy, highly ordered state existed at the birth of our universe. That is, UNLESS things were set in motion long before the big bang actually occurred. In Penrose’s theory, our universe has, and will again, return to a state of low entropy as it approaches its final days of expanding into eventual nothingness, leaving behind a cold, dark, featureless, abyss.