I’ve been hunting for a good short film about the big bang but have yet to find one. I was hoping this film might be the one, but it doesn’t quite do the job as it doesn’t go into enough detail for me. However, it does (very briefly) explain some of the more interesting ideas Physicists have about the universe. It’s a good one to use for discussing the “true” nature of the universe…and the fact that nobody really knows.
In case you’re interested, the scientist in the film is Janna Levin, Professor of Astronomy and Physics at Columbia University, and author of How the Universe Got Its Spots, a book which combines a personal narrative / biography with science in a way that might appeal to your sixth formers.
You can download a version of this from vimeo
It's a unreal story unless someone can explain why this idea came about. Otherwise it's pixies at the bottom of the garden. But good try.