I don't know much about this and I have done very little research but my opinion is that the only full explanation is that before the Big Bang there was nothingness - no time, no energy, no life, no beings and every billion or so years there is a big bang and a new universe is made and that we are just one of many massive universes created from this land of nothingness which is god knows where - perhaps through a wormhole or perhaps its non-existent to us now. The biggest question in my opinion though is 'What was before the big bang?'.
