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With the use of a time turner, that opens a whole "Pandora's Box" of possibilities. While the use of one can be problematical, when the Ministry of Magic found out how dangerous Voldemort was, why didn't they simply use a time turner to go back and stop him before he became dangerous?

(I know this does open a lot of plot holes, but witches and wizards don't seem to worry about laws of science, so it would seem strange that magic that seems to easily supersede laws of physics (like brooms that fly without propulsion) would worry about the problematical issues of time travel.)

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Do you mean, this way youtu.be/YsYWT5Q_R_w ? ;) –  ykombinator Feb 26 '12 at 9:11
The only answer is that here is no answer, other than "that's how the author wrote it". Hence the reason I pretty much hate any science fiction involving time travel, as it almost inevitably leads to ridiculousness like this. The only show I've ever seen that wasn't ruined after introducing time travel was "Misfits" and that's only because it's supposed to be ridiculous anyway. –  Kevin Apr 13 '12 at 19:21
@Kevin: Are you daring to imply that time travel has ruined Doctor Who? How dare you! –  Tango Apr 13 '12 at 23:00
I always wonder instead : Why Voldemort did not use a Time Turner? –  Matemáticos Chibchas Apr 19 '13 at 0:15
More than a year after this was asked, and I still read it "Why couldn't Tina Turner have been used to stop Voldemort". –  Avner Shahar-Kashtan May 30 '13 at 7:13

16 Answers 16

up vote 35 down vote accepted

I wasn't able to find a canonical answer to this, but I found one that is logical and lines up with the effects of Time-Turners in the books here.

Quoting from that page:

Luckily, time travel in Harry Potter doesn’t exactly work that way. The time traveler cannot change the past because what is experienced in the past has already been changed.

So the Ministry would be unable to go back in time and destroy Voldemort unless they already went back in time and destroyed Voldemort, thus negating the need to do so.

This lines up perfectly both with the book and movie versions of the events involving the time-turners. Remember in the movie, that Harry, Ron, and Hermione were alerted to the coming of the Ministry officials and Dumbledore when a rock mysteriously flew though the window and hit Harry. Later on, we see Hermione throwing the rock.

The book also falls into this pattern.

Note added for all of those that this doesn't make sense to

In science fiction, there have been several different ideas about what time travel entails. Wikipedia covers them. The time travel described in the Potterverse is described in the first theory listed here. It's not unique to the Potterverse at all.

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@Casebash, those things had already happened too. Recall that they didn't actually see Buckbeak get executed; they just saw the executioner swing his axe and heard a thud. Later we learn that he was just taking out his frustration on a pumpkin. Sirius' escape is even easier: he was locked in the tower, with nobody keeping watch. They actually helped him escape shortly before Dumbledore talked to Harry & co. in the hospital wing, they just didn't know it yet. –  Joe White Feb 26 '12 at 13:47
@JoeWhite but that's still a closed time loop! –  Pureferret Apr 11 '12 at 11:07
This "already happened" philosophy is actually not really true, and here is why: remember that Hermione explained Harry that meeting yourself is dangerous and a lot of wizards killed their past or future selves. Killing your past self is definitely not consistent with the "already happened" theory because if you are killed in the present, you won't be able to travel in time in the future. So apparently there's more to the theory. –  Malcolm May 24 '12 at 21:30
@NominSim - they don't go back to change the past, they go back to save Sirious & Buckbeat, something they'd already done at that past point, so effectively they just go back to the past to "fulfil" that bit of their future. It makes perfect sense if you assume that you can't change history - read the link David Stratton posted in his edit. –  Nick Shaw May 25 '12 at 8:03
No, the history is the way it is because they came back and affected it, which locks them into doing it again. really, this is standard fixed, unalterable, time travel. It's the only one that allows an orderly universe that obeys rules, and does not allow for alternate realities. Once you allow for alternate realities, you star wondering if earth 1218 is the only one, I mean what if Wolverine doesn't have a healing factor in another universe because of something Spartacus did to eliminate the mutant gene? –  David Stratton May 26 '12 at 0:09

From JK Rowling's entry on time-turners on Pottermore:

According to Professor Saul Croaker, who has spent his entire career in the Department of Mysteries studying time-magic:

'As our investigations currently stand, the longest period that may be relived without the possibility of serious harm to the traveller or to time itself is around five hours.

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That's JK's entry in what? –  Tango Aug 5 '13 at 4:22
Ooo, that's interesting! I must catch up on Pottermore. Here's a well-written article on time travel in Harry Potter that I've read quite a few times when time-turner questions have come up. Thanks for leaving this new information. +1 –  Slytherincess Aug 5 '13 at 14:42

I finally found the answer to this question today. I was reading the books again and saw this passage in Order of the Phoenix, during the Battle at the Ministry:

Harry stuck his head out of the door and looked around cautiously. The baby-headed Death Eater was screaming and banging into things, toppling grandfather clocks and overturning desks, bawling and confused, while the glass-fronted cabinet that Harry now suspected had contained Time-Turners continued to fall, shatter and repair itself on the wall behind them.

Then in Half Blood Prince, after Aragog dies, Hermione mentions this in a conversation with Hagrid:

‘... I don’ reckon it’d be safe fer anyone but me ter go near the colony at the mo’,’ Hagrid finished, blowing his nose hard on his apron and looking up. ‘But thanks fer offerin’, Hermione ... it means a lot ...’
After that the atmosphere lightened considerably, for although neither Harry nor Ron had shown any inclination to go and feed giant grubs to a murderous, gargantuan spider, Hagrid seemed to take it for granted that they would have liked to have done and became his usual self once more.
‘Ar, I always knew yeh’d find it hard ter squeeze me inter yeh timetables,’ he said gruffly, pouring them more tea. ‘Even if yeh applied fer Time-Turners –’
‘We couldn’t have done,’ said Hermione. ‘We smashed the entire stock of Ministry Time-Turners when we were there in the summer. It was in the Daily Prophet.

So the reason they couldn't use Time-Turners to fight Voldemort is simply that there weren't any more. The entire stock was destroyed. They couldn't even turn back time to before they were destroyed, because there wouldn't be any left with which to turn back time to begin with. :)

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But why didn't they use them before Harry was born or when he was young? If the only reason is because they were destroyed, seems to me they waited way to long to use them. If they were going to use them shouldn't they have done so when he first came to power? –  xecaps12 Apr 7 '12 at 2:36
Because they didn't know the extent of his power yet. They knew he was a really powerful dark wizard, but assumed he died when he attacked Harry. Remember, the Ministry controlled the Time-Turners. They were really hard to get. By the time Dumbledore knew Voldemort had returned, the Ministry refused to acknowledge it until after the Time Turners were destroyed. Fudge certainly wouldn't just hand a Time-Turner out to go back and stop someone who already was dead, especially when considering the difficulty of doing so without creating a paradox. –  Gabe Willard Apr 7 '12 at 2:48
That is only a stock of un-used time turners though. What about ones already out in the world? +1 anyway for a clear and canon answer. –  balanced mama Dec 8 '13 at 1:23

Remember what Reg says in Douglas Adams' Dirk Gently's Holistic Detective Agency? He claims he's tried to fix some similar problems in history by using time travel, but that those attemts have always backfired and have turned something else much worse.

Remember this conversation of Harry and Dumbledore in the Prisoner of Azkaban?

‘But – I stopped Sirius and Professor Lupin killing Pettrigrew! That makes it my fault, if Voldemort comes back!’

‘It does not,’ said Dumbledore quietly. ‘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 … […] You did a very noble thing, in saving Pettigrew's life.’

If Harry is effectively helped Voldemort rise again with what seemed like a noble action, would you dare to go back in time several decades to kill the young Riddle and bear all the consequences of your action? Could you be sure you're acting for the better in the end?

Remember what Gandalf says about ordering to keep Gollum captive instead of killing him? He says, there are so many people deserving death that live and so many that die innocently, you have to be very careful before you demand to kill people for their sins.

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I love this answer!! except that then, perhaps, using the time turner in the first place should not have happened. –  balanced mama Dec 8 '13 at 1:19
This reminds me of a large number of sci-fi universes where they try to go back in time and kill Hitler to stop WW2 from ever happening, and then something even worse happens (like the Soviets getting too strong and starting a war even more horrible than WW2, etc.) –  vsz Jan 4 at 14:00

Time turners are for strictly academic use. It would be incredibly dangerous to go back and kill someone that we knew existed. See every story dealing with time travel.

Hermione was able to use one because she didn't interact with herself. If she ever was found to use it in some other way, she could get in huge trouble, and not just from the law. Time travel is very dangerous stuff, not worth risking, even for such a noble cause.

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Who said anything about killing him? If it were early enough, Azakaban would have done the job. Do you have a reference about the "only for academic use" issue? –  Tango Feb 26 '12 at 4:34
@TangoOversway: No, other than that's the only purpose they are even hinted at in the series. And even tossing him in Azkaban would have been just as dangerous... –  PearsonArtPhoto Feb 26 '12 at 4:35
Of course, they do interact with themselves by throwing the rock through the window at Hagrid's. –  Ken Liu Apr 11 '12 at 16:04
Time travel is very dangerous stuff, not worth risking, even for such a noble cause. But it is fine to take a few more classes in high school ^_~ –  Sardathrion Apr 12 '12 at 9:50
Of course, they do interact with themselves by throwing the rock through the window at Hagrid's and let's completely ignore the patronus? –  Rob Apr 12 '12 at 15:29

Harry Potter and the Prisoner of Askaban "Horrible things happen to wizards who meddle with time, Harry."- Hermione Granger to Harry Potter

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Because this would create a paradox (http://en.wikipedia.org/wiki/Bootstrap_paradox).

Let's say Dumbledore went back in time to kill Voldemort when he was a child. Once he killed Voldemort, Voldemort would obviously no longer exist. Therefore, the reason why Dumbledore went back in time (i.e. Voldemort) wouldn't exist either - making this scenario impossible.

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If you remember when the existence and use of the time-turner was introduced in Book 3, Dumbledore said in the hospital wing to Hermione, "three turns should do it" for three hours. Now I don't think it was addressed ever that you could set it for hours, days, weeks, etc so I believe it was only in hours. Now say they went back in time to stop Tom Riddle when he was in Hogwarts, 50 years ago. 365 days in a year, 24 hours per day so to go back in time one day they would need to turn it 24 times. 50 years, 365 x 50 = 18,250 days. 18,250 x 24 for the hours = 480,000. Goodluck turning it 480,000 times. Same concept even if they went back a little earlier than that.

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Yes, you're right. It would be really difficult for Harry and Hermione to use the Time Turner at that point, but someone could have used it waaaaay earlier on - like when Voldemort first started to come to power. –  phantom42 Oct 15 '13 at 20:23
Someone's been watching HISHE :) –  DVK Oct 15 '13 at 21:41
Gee, if only there was some sort of supernatural force the characters could command to turn it 480,000 times for them.... –  jwodder Oct 15 '13 at 21:43
Nobody said it had to be turned by hand and not by a spell or some other contrivance. But, even more so, there's no indication that time turner (or others) cannot be set for a day - or that a turn isn't an hour and that the amount each turn lasts is linear and not logarithmic. But if it would save many lives, I'm sure there are those who would have been willing to turn it half a million times to bring back a loved one. –  Tango Oct 16 '13 at 6:18

Because it only goes back a few hours.

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Where do you get that information? I didn't see anything limiting its range. –  Tango Feb 26 '12 at 4:22
My wife told me. :) But, Dumbledore did turn it back three times for three hours. Seems like it would take quite some time to turn it back over and over and over to go back to when he went bad. He might have been able to prevent one event, but I doubt one event would have been enough. –  xecaps12 Feb 26 '12 at 4:26
That is clearly wrong. I have evidence that proves you can go much further back: youtube.com/watch?v=YsYWT5Q_R_w. –  Dason Feb 26 '12 at 4:32
That was awesome. Never saw that before. –  xecaps12 Feb 26 '12 at 4:41
I agree with everyone that it's not mentioned in the text. However, there's no evidence against it. Besides, if one turn turns back just an hour, this is already an indication that it's not meant to turn back much time. The problem when people take all these "how it should've ended" too seriously is that they assume that there's nothing more than it is told in the books or films, which could absolutely not be the case. –  Malcolm Jul 13 '13 at 20:27

Things you do in the present change the future. Thing you've done in the past changed the present. In the theory of multi-history, history will change toward what you've done in the past. Every decision will make a different history. May be someone tried to go to the past and kill Voldemort, and the history went another route. Our story goes to another history route where they didn't do it. Just enjoy the movies and books :)

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I couldn't find anything called the theory of multi-history -- is this a scientific theory? Did you possibly mean the Chaos Theory? :) –  Slytherincess Apr 14 '12 at 2:54
Yah, a scientific theory. I don't remember who is creator of hits. Please try 'Brief History of Time', author: Stephen Hawking, I lost my book years ago. May be it's one you mentioned. Not sure what it called in English, I read one in my native language, sorry :) –  Shinigamae Apr 14 '12 at 8:51
Well, it's not really my responsibility to authenticate the sources in your answer :) IMO, if you're going to cite a specific theory, you need to be prepared to provide a source for the works that you're basing your answer on. Sources are important at this site because anyone can claim a theory or quote is authentic. Unless you have something to back it up, it's really only conjecture. :) –  Slytherincess Apr 14 '12 at 14:10
Oh got it. I'm just passing by because the topic about HP :) really my knowledge of science is narrow, just say what I think about the topic, not to instruct anyone to a theory. But I really got what you want to tell 'Sources are important at this site'. I'm new here and it is the first rule I know. –  Shinigamae Apr 14 '12 at 18:02
I think that source was Back to the Future. –  Cees Timmerman May 25 '12 at 13:33

From Harry Potter and the Half Blood Prince:

"'Ar' I always knew yeh'd find it hard ter squeeze me inter yeh timetable," [Hagrid] said gruffly, pouring them more tea. "Even if yeh apploed for Time-Turners -"

"We couldn't have done," said Hermione. "We smashed the entire stock of ministry Time-Turners when we were there in the summer. It was in the Daily Prophet."

  • Chapter 11, Page 218, Paragraphs 4-5

Stop bringing up this argument. They smashed every single time turner in the battle at the end of book 5, time turners (I'm assuming) are too complicated for some average Joe to make, and I doubt a Voldemort-controlled Ministry would be allowed to make any. This is not a plot hole, even the 'How It Should Have Ended' Harry Potter parody caught this non-plot-hole when Harry said "Hermione, something might conveniently destroy the time turners making that the last one, you'd got to keep it"

(the scene I'm quoting is at about 0:58)

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This was already mentioned in GabeWillard's answer, and comments in there even bring up the issue of, why weren't they used before Voldemort tried to kill Harry as a baby? –  Izkata Apr 18 '13 at 2:25

paradox theory is the simple reason and used in many scifi to explain this same issue. see time machien for me. pretty much if you go back in time to change the event that made you go back in time int he first place then you never go back in time to alter the event. it makes a wibbly wobbly loop known simpley as a paradox and it writes itself out.

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In the Harry Potter Series the Time-turner can be Dangerious you could unravel Existence itself. now if you read the book. Hermione Granger explained it to Harry Potter when they went back in time to save Harry Potter's Godfather That if you went back in time and yourself saw yourself (Lol that sounds confussing) That you'd think some serios DArk Magic was going on. And You can't kill a little kid, He has no idea what he does in the future and im sure that if you killed him the story would suck. AND IF YOU WENT BACK IN TIME TO KILL TOM RIDDLE/VOLDEMORT/HE WHO MUST NOT BE NAMED/YOU KNOW WHO YOU COULDN't COME BACK TO THE FUTURE.

P.S. I'm Twelve and I LOVE HARRY POTTER!!!

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In Harry Potter and the Prisoner of Azkaban, when Harry and Hermione go back in time, what they did had already happened. Had someone gone back in time to stop Voldemort and succeeded, Voldemort would never have killed Lily and James, and the series would never have happened. However, someone would have had to have enough awareness of this to go back in time and stop Voldemort.
I hope this helps; I don't think I phrased it very clearly.

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While not explained in the books in much detail, we can guess at its functionality from the ways it was used. It seems that time turners have two major laws governing their functionality:

  1. Their range is limited, they can only take you back a few hours at most (confirmed in an interview what Treborcram mentioned in another answer)

  2. They cannot violate causality, in the sense they don't allow you to change anything which was observed. So if you look at a glass for an hour, you can't go back in time an hour an smash it. Had they witnessed the hippogriff's execution, they could have probably been unable to go back in time and save it.

If we want to be really picky, we can even define "observed" in a quantum physics kind of way. There is a fan fic which greatly expands on the use of time turners, and remains consistent with the original books in their capabilities.

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Even if it has a limited "range", that doesn't explain why someone did/could not use a time turner more immediately after Voldemort began his attacks. Similarly, someone who was not present at, say a murder, could go back and stop the murder. –  phantom42 Jan 4 at 16:20
phantom42 : in this case we have to go with the "all time turners were destroyed in the battle at the ministry" concept. It happened before it was officially acknowledged that Voldemort is back. –  vsz Jan 4 at 18:05
In HPMOR, time turners are used tactically to call for aid any time, anywhere. You are attacked, you call for help, and the aurors can go back in time, mount broomsticks, and arrive at the exact time when you were attacked (so they don't violate causality) –  vsz Jan 4 at 18:08

It could be used to kill voldemort, the time Turner has no limit to how far back it can go. A paradox is easily avoidable, say Dumbledore went back in time and killed voldemort when he was a child, all he needs to do after this is to tell his past self when he's his age go back to that date and kill Tom riddle. Even if this resulted in many people not being born, voldemort killed over a million people throughout the war. He would have to do this before 1996 (relative to the books) as in that year all time Turner's were in the time room and they got knocked off the shelf, one of which fell in such a way they got stuck in an infinite loop of falling and un-falling and rendered useless.

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The maximum time you can go back is only 5 hours. –  Monty129 Aug 8 at 21:19

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