More on time travel in PoA

[qaztroc]

No: HPFGUIDX 43661

For those who still feel confused by the apparent time 
travel paradox in PoA, I suggest you have a look at the 
latest issue of _Scientific American_ which happen to
be a special issue devoted to time. 

There is a paper on page 50 by Paul Davies about time 
machines ("How to build a time machine"). If you look 
on page 54, you'll see a nice diagram that illustrates 
the notorious time travel paradox with a billiard ball 
falling into a wormhole. You can also go on the _Scientific 
American_ website www.sciam.com to see the article, 
the figure I'm talking about is at this URL:

http://www.sciam.com/article.cfm?articleID=0004C31
F-B4E0-1D4E-90FB809EC5880000

Now replace the billiard ball by Harry, and the wormhole 
by the time-turner, and you have something similar to the 
PoA time paradox. The "paradox resolved" (right panel) shows
that it is entirely consistent for Harry to be rescued from
the dementors by his future self. The fact that he is saved
then allows him to use the time turner, and go back in time to
save his past self. The loop is then closed. There is absolutely
no need to invoke a "parallel universe" or "alternate realities"
scenario.

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qaztroc