What happened before the Big Bang?
There is a growing list of possible answers to that question ranging from "nothing" (literally) to "many repeating cycles in an endlessly cyclic Universe".
Recently Roger Penrose (one of the most distinguished mathematical physicists of our age) and a collaborator Vahe Gurzadyan claimed to have found evidence for a Pre-Big Bang Universe. They pointed to "rings" of structure embedded in the Cosmic Microwave Background which is fossil radiation left over from the Post-Big Bang Universe. It was an exciting announcement. Today it seems the wind is out of their sails.
Two groups have published a response to the cyclic Universe paper showing that Penrose's effect was nothing more than a statistical fluke. As one of the papers puts it,
Gurzadyan and Penrose have not found evidence for pre-Big Bang phenomena, but have simply rediscovered that the CMB contains structure.
I am sure the story is not over yet. Gurzadyan and Penrose are unlikely to just fold up their tents and go home. On the other hand getting beyond (or before) the Big Bang is not going to be easy. So stay tuned kids. There may be more Universe out there yet.