10 Things About Doctor Who That Seem To Confuse Non-Fans

3. Fixed Points

Once non-fans have got their heads around the various timey-wimey aspects of the show, they then have to accept that some points in time can't be changed at all. These are what the Doctor refers to as "fixed points" which are generally moments that are particularly important or that have a lasting effect on history. Pompeii is one, for example, as Donna Noble discovered in Series 4, and it's worth looking at the character of Adelaide Brooke if you want to get a clearer understanding of what it's all about.

To put a long story short, her character had to die during the events of The Waters of Mars because her heroic demise would go on to inspire events that would literally change the future of the human race. When she lived to tell the tale, therefore, it caused all sorts of damage and she eventually killed herself in order to put the timeline back on track. It was one of the show's more extreme examples of what can happen when things go wrong but it's an important one to bear in mind nonetheless.

As such, there are some moments in time that the Doctor unequivocally cannot change, though he generally keeps what moments these are close to his chest because, admittedly, it's only ever used when it serves some sort of narrative purpose. Everything else is pretty much a free for all, really, which is useful because the Doctor would be out of a job otherwise.