Doctor Who: 10 Things About NuWho That Don't Quite Add Up

7. Who Knows What The Crack Is?

At the beginning of Series 5, the Eleventh Doctor was faced with a crack in the universe which happened to lead to an alternative world from which Prisoner Zero managed to escape from prison and almost cause the destruction of the Earth (because you can't be accepted as a true Doctor Who villain without almost causing the destruction of the planet at least once, right?). But as always, the Doctor was able to save the day and "seal" the crack in the universe. However, that begs the question... If Prisoner Zero was able to enter through a crack, why didn't the Time Lords do it too. Yes, they were asking the "First Question" to determine which universe to enter back into, but, without knowing exactly how many universes there were, why couldn't they just send a Time Lord volunteer through to determine if it was the right one? If Prisoner Zero could do it, why couldn't they? Perhaps they're not so powerful after all...