Initially I thought it was a nonsense question as my preconception was that there couldn't be anything before the Big Bang because that's where everything started, including time. Turns out this theory is being challenged by many new ideas which think if the Big Bang even happened, it's either a cyclical event or something that occurred in a previous universe. It turns out it's quite a fertile time for alternative theories and the documentary gives each theory 5-10 minutes explaining the pros and cons. It's refreshing that the show allows the other cosmologists to comment on rivalling theories and it's fun to see how each one is convinced the others are seriously flawed.
After introducing the different theories, several of which overlap the show spends its remaining time looking at evidence that can back up, or more importantly disprove some of these theories. It's nice that the show spends some time to show this aspect of science as there's sometimes a tendency to present all these "out-there" theories as if they are accepted fact and this segment shows that these are all theories as of yet. In an attempt to draw a comparison to Biology, I think all these conflicting ideas mimic evolution in the sense that the strongest one will ultimately survive but i guess science as a whole has always been in service of natural selection in one way or other.
What was my favourite theory? I did like the idea of Big Bangs originating from a Black hole in another universe as it seemed to philosophically get round that whole "infinitely small/dense" problem. I also liked the cyclical arguments of either the universe condensing back in on itself until gravity becomes a repulsive force and the Big Bang is more a Big Bounce (Param Singh) or the similar argument that the end of the universe would actually mirror the environment before the Big Bang and therefore be fertile ground for another one (Roger Penrose). I wasn't so keen on the "Brane theory" (Neil Turok) largely because i couldn't wrap my head around it and it sounded too much like a fairy tale to a lay person like myself (although it makes excellent Sci-fi imagery). There was also a theory at the end that the shows makers and discover (Laura Mersini-Houghton) claimed worked perfectly with the mathematics in that it allowed there to be something from nothing as well as explained three observational findings in cosmology that are currently hard to explain using other models. Unfortunately I had to take their word on that as it wasn't explained why it worked. I imagine it was probably one of those things that couldn't be easily explained in a couple of minutes.
A great little documentary that ignited my imagination that took time to present multiple arguments and suggest ongoing experiments that may help prove which one (if any) is correct. The scientist's in the show all did a great job of getting across the point that even if they are wrong it's good to generate these theories to push the field forward. I was left with one remaining question though and that is whether hardcore mathematicians/physicists really do spend all day scribbling things down on a blackboard?