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Michelle_Z comments on Harry Potter and the Methods of Rationality discussion thread, part 19, chapter 88-89 - Less Wrong
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My reaction upon reading these chapters was to scream. Naturally, no one within hearing range was pleased. And my thoughts are...
So, Dumbledore likely has the philosopher's stone.
And ok, I guess it COULD be hard to make the elixir of life, but... he has a phoenix. He can foof anywhere he likes. I can imagine Harry being horribly angry when he figures out Dumbledore had it the whole time and didn't even bother to use a timeturner, make the elixir, and save Hermione.
I think the elixir of life stops aging, not death from blood loss. Of course, if you can avoid paradoxes, traveling back in time and applying a tourniquet earlier would save her.
The problem with the Time-Turner approach is that (given what we understand of the Time-Turner's rules) he'd have to somehow fool first-iteration Harry (and Fred and George) in order to avoid a paradox. The Methods universe is full of tales of time-turning gone wrong; since saving lives is one obvious application of the Time-Turner, Dumbledore surely knows exactly what he can and cannot get away with in that respect.
All he would need to do is replace Hermione with a suitably transfigured/polyjucied/magicked rat to avoid the paradox.
The hard part would be accounting for what the killer will have did to prevent counter-turning.
I would imagine that "dying-soul-magic", or whatever that was, is impossible to fake (or, at least, really dang hard to) like prophecy magic.
No, this is what you'd do: You'd polyjuice another human into Hermione. Thus, when the imposter dies, there would still be the "dying-soul-magic" of a human dying. (Of course, there are the ethical objections of trading another's life for Hermione's, but to be honest, I don't think that would stop Harry at the moment in the state he is in.
Oh, and you'd use the Imperius curse or something to make the polyjuiced duplicate do the whole "Not your fault" thing. (Hey, if you're ignoring ethical objections, might as well...)
Does this sound like someone polyjuiced into Hermione to you?
Meh. I'd take the simpler route of confounding my own perceptions.
Find someone who's already about to die (a terminally ill patient suffering from the advanced stages of an incurable disease or a condemned prisoner in the ), and use them.
Harry is the only one to witness the 'dying-soul-magic' and he has no idea what it is supposed to look like. Adding any sort of magical disturbance to the dying magicked!rat would have the same result from Harry's point of view.
False memory charm?
I'm not sure if I love or hate time-travel grammar. A little of both, I think.
I can't figure out how tense I am when I think about it myself.
You don't have to trick out time. You can have it work the way you want from the beginning. Harry didn't have to trick his past self into not knowing that he was being pranked in order to prank himself. That wouldn't even make sense.
He did act in a manner which completely explained what he had previously experienced.
I also wouldn't put it past Harry to risk breaking time by refusing to lose to "do not mess with time" over Hermione.
Your argument is circular. The only reason that it applies here and not with pranking his past self is that he successfully pranked his past self but didn't go back in time here. It doesn't answer the question of why there's a stable time loop of him pranking himself, but not one of him saving Hermione.
Are you objecting to a time travel argument because it is circular?! Of course it's circular, it's time travel. That's the thing about time travel, it makes causal circles. That's why it drives you insane to think about it.
It's about fixed-point solutions.
Harry got "Do not mess with time" because he was willing, in that case, to send the same message back. If he hadn't been, he never would have received that message in the first place.
If Harry had been willing to write "101x101" after receiving "do not mess with time", he would have solved NP=P?
If he had been willing to do that, he wouldn't have received "do not mess with time".
Though I notice I'm confused as to how, exactly, the universe can figure out he'd create a paradox in this situation without actually running the computation to see what happens. Probably it can't. Probably time-travel is hilariously unethical.
The universe isn't limited to object-level proofs that exist in the universe, I guess. Perhaps the universe has access to the list of everything which is true about the universe?
I think you're inappropriately anthropomorphizing the universe.
I suspect he would have had an unfortunate encounter with someone else's stable time loop.
It's not entirely obvious what causes a given stable time loop, but that doesn't mean there is no way to predict it. Even if it's random, it has to have some kind of probability distribution. Time loops isn't an excuse for an author to do whatever they want. At least, not if they want it to take place in a universe based on rules and not narrative causality.
I'm asking why he didn't fail in an attempt to go back in time; it's obvious that he's going to try, using every means available to him less insane than assaulting Azkaban single-handedly.
It doesn't look like you were asking anything.
There was some miscommunication here. Please restate your original point.
... You can only travel back in time if you've already arrived. The mechanism by which the time-turner works is unclear, but if Harry didn't try and fail to use his time-turner simply because he already hadn't arrived earlier in time.
You only travel back in time if you've already arrived. I don't think "can" belongs there. You only travel to New York if you arrive, but you don't say that you only can travel to New York if you arrive, even though it's impossible to leave for New York and then disappear into the ether.
I can't seem to parse this sentence. Please restate.
We know that Harry won't successfully use his Time Turner from the fact that he hasn't arrived in the past, but we don't know why.
... That was lack of sleep talking.
And right now that we only know that Harry's attempts to travel back in time doesn't appear to stop Hermione's death. That could be because for some reason Harry is unable to convince or blackmail Dumbledore and unable to defeat a simple casing despite knowing partial transfiguration, it could be because of an as-yet unstated limitation on the use of time-turners (which would be the bad storytelling trope known as "ass-pull"), or it could be because the same enemy which buffed the troll also takes precautions against counter-turning (for example, by taking meaningless information from 1800, encoding it into the junk DNA of some yeast, and putting the yeast into dinner; I would expect a smart dark wizard to consider something very analogous to this, and it takes a master of stable time loops to go back in time BEFORE eating the food, thwart the troll and save Hermione, then set up a fake troll and fake Hermione so that you can convince the enemy that their plan failed so that they later spend their re-do on attempting to stop yours)
Hmm. You're right, that particular oddity ''did'' work. Has anyone here noticed conclusive rules about when a paradox will and will not form?
... Anyhow, though, if a Time-Turner could be used without paradox, it wouldn't be here. When Hermione was missing, it would have been very, very easy to make her missing somewhere safe, without changing anyone's observations. The fact that we got to the death scene without that happening, or any other visible Time-Turner intervention, tells me that it probably can't happen.
It's not clear what happens when there are multiple possible stable time loops. For example, why he ended up with a paper that says "DON'T MESS WITH TIME TRAVEL" instead of the semiprime factored, even though either would work. However, it can't do anything that results in a paradox. If Harry's going to go back and try to save Hermione whether or not he sees his future self save her, there is conceivable some loophole in which she is not saved, but it seems much more likely she'd just get saved.
This isn't like trying to factor a semiprime. This is like trying to write a specific phrase and send it back. You can mess it up, and if you don't get anything back you know you did, but it doesn't seem very plausible.
Because if he'd gotten back a number, he would have kept pushing until he did something that broke time, thereby causing a paradox. The only way to head off paradox was to cut his line of inquiry off then and there.
One of the established rules was that information can't be sent back more than six hours. Would he have broken time within six hours?
Also, there is always a way to head off a paradox. Consider the multiple universes model. What came out of the time machine in one universe is a function of what came out in the last universe. Furthermore, it's a continuous function. Theoretically, you could do something like send back what came out plus a mote of dust, but I think it can be assumed that there's a limit to whatever the time turner can bring back, meaning the domain of the function is bounded. Since every continuous function mapping a bounded set into itself has at least one fixed point, there must be at least one stable time loop.
Knowing HJPEV, yes, he would have broken time within six hours. He wouldn't have even had much trouble doing it.
And yes, there's a stable time loop. It's the one where he writes "DO NOT MESS WITH TIME".
He already went back in time once. He knows he's not supposed to go back more than two hours a day, and while he breaks that rule quite often, he wouldn't do it for something as minor as not wanting to wait until tomorrow.
If he was going to use the time turner again, he'd have just only gone a half-hour back from the beginning.
Addendum: Why would it be a continuous function? Human decisions can be binary. Consider, as a trivial example, "If I see 1 on the paper, I'll write 0 and send it back in time. If I see anything else on the paper, I'll write 1 and send it back in time".
Humans are made of atoms. Atoms behave continuously. Therefore, human decisions are continuous. A human can no more follow the algorithm you gave than Buridan's ass can follow the algorithm of "Eat the bigger bale of hay first, or the one on the left if you can't tell which is bigger".
There is the whole quanta thing with quantum physics, but when you get to that point there are bigger problems. Which future does the Time Turner come from? How can you have single universe time travel when the physics you're using already established more than one universe?
I think this is the compositional fallacy: Humans are made of atoms. Atoms are smaller than pennies. Therefore, humans are smaller than pennies.
I don't mean that your conclusion is false, just that your argument is (as read) invalid.