TOK post: David Christian: History of our world in 18 minutes

In TOK class we watched a TED talk video by a man named David Christian. Christian is a well known historian responsible for a teaching method called Big History. Big history is a teaching method where we learn history on a large scale, like his TED talk, he covers the entire history of our universe and planet in a quick 18 minute video. While i thought his talk on the subject matter was very interesting and easy to understand, i cant help but think that his approach may be a bid vague. There is so much more history within the gaps of his explanation. So therefore it raises a lot of questions. TOK wise, it brings us into the matter of how do we know that his explanation is the correct one, as apposed to a religious explanation like the universe was created within 7 days. The problem with the theory of the big bang idea is that its only a theory, whereas the religious idea is also just written in a book that was written in more recent history to the big bang. Theres no cold hard factual evidence that something like this even occurred. So the problem it raises is essentially whether it is a true fact instead of theory. Is it okay to be teaching high school students something that cannot really be proven 100%? From my atheistic point of view, David Christians explanation makes more sense and i feel more comfortable believing it, but i would be interested in hearing what other people have to say. Maybe we could discuss this in TOK class one day?