"Well, the time-turner was a very difficult invention for me, because it created as many problems as it solved."
-- J.K. Rowling (BP2)
"Hasn't your experience with the Time-Turner taught you anything, Harry? The consequences of our actions are always so complicated, so diverse, that predicting the future is a very difficult business indeed.... Professor Trelawney, bless her, is living proof of that ..."
-- Albus Dumbledore (PA22)
I’m sure you’ve seen things online where writers take great pleasure in finding holes in the plot of the Harry Potter stories. There are memes floating around, blog posts, and videos on YouTube with titles like “10 Dumbest Harry Potter Plot Holes.” Now, it’s not that the Harry Potter stories don’t have plot holes — they do. But the ones you find in these online rants aren’t plot holes. Most are film mistakes, which are just that … film mistakes. You can’t blame Rowling for those. But others do seem like problems until you dig a little deeper into Potter lore and discover that they’ve pretty much all been explained.
One favorite “plot hole” is that if time travel exists in the Harry Potter world, why can’t it be used to fix every bad thing that happens? Rowling addressed this question in an interview in 2007 (BP2) and in more detail on Pottermore. In the interview she talked about time travel as a problem for her as a writer for the very reason that it makes it possible for characters to fix mistakes, and therefore removes the element of danger from their actions. This was the reason that she wrote the scene at the end of Order of the Phoenix where the Ministry’s entire stock of Time-Turners was destroyed:
Q: Why didn’t Harry use the time-turner to save his parents?
JKR: Oh, that’s a very good question, that … Well, the time-turner was a very difficult invention for me, because it created as many problems as it solved. And anyone who’s read Order of the Phoenix may have noticed that during the climactic scene in which they chase through the Ministry of Magic, they shatter all the time-turners, thereby preventing them using those in the future. (BP2)
Rowling wrote more about this on Pottermore in an essay on Time Turners. She tells us through the voice of Saul Croaker, who studies time with the Department of Mysteries:
“As our investigations currently stand, the longest period that be relived without the possibility of serious harm to the traveller or to time itself is around five hours. We have been able to encase single Hour-Reversal Charms, which are unstable and benefit from containment, in small, enchanted hour-glasses that may be worn around a witch or wizards neck and revolved according to the number of hours the user wishes to relive.” (Pm)
So why in the world would Hermione Granger, a third year student at Hogwarts, be allowed to use such a power magic item? Rowling explains that as well:
Even the use of the very limited amount of Time-Turners at the Ministry’s disposal is hedged around with hundreds of laws. While not as potentially dangerous as skipping five centuries, the reuse of a single hour can still have dramatic consequences and the Ministry of Magic seeks the strictest guarantees if it permits the use of these rare and powerful objects. It would surprise most of the magical community to know that TimeTurners are generally only used to solve the most trivial problems of time-management and never for greater or more important purposes, because, as Saul Croaker tells us, “just as the human mind cannot comprehend time, so it cannot comprehend the damage that will ensue if we presume to tamper with its laws.”
So why didn’t Harry just go back and save Sirius or Dobby or his parents? Because he can’t. It’s extremely dangerous, it would probably kill him, and all the Time Turners were destroyed in the Battle of the Department of Mysteries in 1996.