Paradox of Time Travel in PoA

[jlv230]

No: HPFGUIDX 132138

> Davenclaw: 
> I think it is logically impossible to say that Harry was ALWAYS 
> saved by a time-travelling Harry, when Harry didn't get the 
> opportunity to go back in time until after the encounter with the 
> dementors.

I think to understand this you really do need to think four-
dimensionally. Harry's timeline is distinct from the timeline of, 
say, Hogwarts, Sirius, Buckbeak and Dumbledore just like these are 
distinct in a three-dimensional sense. Harry's timeline *relative 
to* pretty much everyone else (but Hermione) loops back on itself, 
yes, but nothing else has this fold. We only see `the same time 
twice' according to Harry, *relative to* the timeframe of Hogwarts. 
Harry doesn't actually `experience' time twice – he's older when he 
casts the Patronus than when he sees it – and Hogwarts doesn't 
experience time twice. The only thing is that *relative* to Hogwarts 
time, Harry is only going back in time in a sense. He *doesn't* undo 
what is already done according to his timeline. It has passed and he 
can't jump back into his old skin and redo the day – or at least not 
with the time-turner as described by JKR.

I really really hope you can see the distinction I'm making here 
because it is crucial. Really think about what you mean when you 
say `back in time'? Think about *relative* timelines. This is the 
basis of Einstein's Theory of Relativity and accepted universally by 
Physicists in the real world. Any accusations of logical absurdity 
aren't going to cut it here. I have the big guys on my side (so 
ner!). I know it isn't easy to grasp but it isn't absurd. Please 
don't dismiss it because you can't see it right away. It took me a 
long while to sort this stuff out, but now it's second nature so 
excuse me if I don't explain well enough! I'm not a great teacher 
(as you can tell!) but I really am passionate about this stuff. I 
think it is the most interesting physics thing there is to know 
about.

Right, now you've got this far, one problem you seem to have is the 
apparrent 'backwards' causation in HARRY's timeline. Note that there 
is no apparrent backwards causation in the timeline of Hogwarts. In 
Harry's timeline, he sees the Patronus a long time before he casts 
it. Now, this is a problem (i.e. philosophers talk about it alot), 
but there is actually no *logical* contradiction in this 'backwards' 
causation at all. The causes are continuous, it's just that Harr's 
timeline happens to overlap at some point. This doesn't even defy 
the laws of Physics! This sort of thing would be perfectly 
acceptable if space-time curved in a certain way. Ever heard of worm-
holes? The problem comes when you define causation and time first 
then find that reality doesn't fit. Sometimes you have to step back 
and let your preconceived ideas go. Look at the facts. Question your 
beliefs. *I* had to. And I love the fact I did. I see everything in 
a different way now.

> Davenclaw:
> As JKR presents the risks of time-travel, I think she makes it 
clear 
> that the past CAN be interfered with.  Otherwise, there is no risk 
> of encountering your past-self if you have no memory of already 
> doing so when you were your past self.

JLV:
I am totally in agreement with the `Hermione didn't present the 
facts' brigade here. You argue that Hermione's words are actually 
more reliable than the testimony of actual events that occurred that 
night. Remember Harry *did* see himself cast the spell across the 
lake. Harry knew he could cast the patronus *because* he had already 
seen that he could do it.

> Davenclaw:
> The moment that you do something that alters the course of events, 
> it erases any memory of how things had occurred the first time 
> around, so although you are ACTUALLY causing events, you only 
THINK 
> that you are participating in events that already happened.

JLV:
I have no idea where you got this idea from. Where in the book is it 
even suggested that Harry's time-turning changed his memory or 
changed the past? This is something that you have constructed 
yourself. Let go of this idea and you'll see that there is a far 
simpler explanation – no conspiracy – no omniscient headmaster. Just 
the events from the book.

> Davenclaw:
> Heck, this basically means that if you go back to fix a problem, 
> after having fixed the problem, you're going to say "Wait, this is 
> how it always happened - so why did I have to go back in time in 
the 
> first place?  Huh, I guess that it didn't happen this way the 
first 
> time... weird."  (This is sort of like the scene in Quantum Leap 
> where we learn that Sam has saved Jackie Kennedy's life, but 
didn't 
> realize it because to him, that's how it always happened.)

JLV:
Ah – there's the problem – Quantum Leap! The show where they go back 
in time – right inside someone else's skin – and fix their life. 
Remember this is nothing like what Harry and Hermione actually do.

You are assuming that Harry and Hermione time-turned to /change/ 
time, so of course you expect something to have changed. I contend 
that they do not change time. It is this assumption that is causing 
the confusion. Time didn't need changing, they just needed an extra 
set of hands with a perfect alibi to do the rescuing. Let go of 
the `change time' assumption and you find your problem just 
vanishes, *poof*, into thin air. Now, that's magic!

> Davenclaw:
> Consider this:
> 
> TT-H&H are watching normal H&H walking in a field. Hermione 
> says "don't interfere."  But Harry has no memory of seeing himself 
> as a time-traveler, so he thinks there is no risk.  So he runs out 
> into the field screaming like a banshee.  IMMEDIATELY TT-Harry 
only 
> remembers seeing the events that he is now causing, back when he 
was 
> normal-Harry, who is now watching himself screaming.  As every 
> moment goes by, the events occurring become the only timeline 
anyone 
> ever knew.  But this doesn't change the fact that we, as 
omniscient 
> observers to the entire situation, are aware that things were 
> different before the time traveling took place.

JLV:
This problem falls into the free-will category. This is a *big* 
issue in the philosophy of time which I won't pretend to be able to 
explain to you here (because I don't really understand it all). 
Basically, given my view of events, Harry has *no* 'free will' to go 
running about in front of himself as you describe. Again, there is 
no *logical* contradiction here. You assume we have free will, 
whereas I don't – I take the facts as I see them. Of course, you 
just have to carefully consider what I mean by free will. Don't just 
say `of course I'm free' – how free is free? I have to obey the laws 
of physics and logic - so do you.  Is that free? If I'm not free 
should I just give up? Of course not!

Consider this:
If we were free to go `back' and erase the past of ourselves where 
we decided to go `back', we would never have got `back' to actually 
do it! I can't emphasise this enough. If you *could* change the past 
then you *would* erase the future when the past-changing was 
originally initiated, thus you have a logical absurdity. Please try 
to understand this – I feel terrible that we can't seem to impress 
this on you!

> Davenclaw:
> Perhaps that is the disconnect here: everyone else is describing 
> events as they are understood within the Potterverse, whereas I am 
> complaining that we, as outside observers, are left out of the 
> series of events that were not tampered with.

Why think that there was another series of events that were erased 
when there is a much simpler explanation – one that fits with the 
laws of logic and (to some extent) physics? Why introduce a set of 
events that isn't even hinted at in the book. Remember that if there 
is *no* evidence for something there is no logical reason to suppose 
that it exists. (Occam's razor)

Please don't dismiss this off-hand. You don't have to agree with 
everything I say, but I really think the explanation that myself and 
my fellow posters propose is simpler and contains fewer logical 
contradictions and assumptions than your own.

Of course, that is JMO...
JLV xx