Paradox of Time Travel in PoA

[jlv230]

No: HPFGUIDX 132061

Wading in with two left feet and a physics degree... sorry! I 
shouldn't really be playing that card so early...

Looking at the time turner bit of PoA, I have to say that Steve, 
Heather, Del etc are right. The model of time travel they describe 
is not only what JKR seems to be describing (with the clues like the 
steps/doorslam in the hallway and the Patronus sequence), but is 
also actually (logically) possible. It is exactly the sort of time-
travel theory that Stephen Hawking and his contemporaries (although 
perhaps I should steer clear of temporal language) would consider 
possible. I'm afraid to say that 'the wheelchair guy' (as Homer 
Simpson named him) would not, however, consider your view to be even 
a candidate for a possible time travel scenario.

Davenclaw said:
> Let's think of it this way. Harry
> and Hermione experience the same three hour block of time in three
> different ways:
>
> - the original way, before time was changed
> - the altered way
> - as time-travelers
>
> Reading through it again, I realize that WE NEVER SEE THE ORIGINAL
> EVENTS. We only see the events as they were changed, and the events
> from the perspective of the time-travlers.

JLV:
I'm afraid this view is definitely logically impossible. If time 
went one way first, then Harry and Hermione went back and changed 
it, the new events would effectivly 'erase' the old ones, as you 
say, so Harry and Hermione could possibly *never* go back to change 
it in the first place. If you think everyone else's view is 
contradictory, you really have to look at your own first.
 
Davenclaw
> I understand what everyone is saying about how once events are
> changed, they are changed. But this ignores the basic fact that
> there were events that took place prior to Harry and Hermione going
> back in time - otherwise, what were they changing? 

JLV:
I really think you have misunderstood. Please re-read the replies 
above - I beg you! There is no `basic fact' about this at all. If 
you remove this preconception then it all makes sense. Not only 
that, you'll see how clever it all is! And I'm confident that many 
modern philosophers of time will heartily congratulate you when you 
do.

I'd  also like to point out that our best physical theory for the 
way space and time relate (General Relativity) actually gives 
different objects different timelines. What is happening now 
according to me will not be the same as what is happening now 
according to the person who is now-according-to-me in their car 
driving away. I could technically loop `back in time' according to, 
say, my house without contradicting any physical or logical laws. I 
*could* be in two places at once, but it just depends on who you 
ask. And if you think you can show that's impossible... well... I 
suggest you publish your paper in a Physics journal.

Who needs science fiction? Just pick up a book on the philosophy of 
time.

Of course, usual disclaimer, JMO ;-)
JLV xx