Free Will and Time travel

[Brooks R]

No: HPFGUIDX 1309

--- In HPforGrownups at egroups.com, Kathleen Kelly MacMillan 
<kathleen at c...> wrote:

> .... and then what I call the "Prime 
Directive 
> approach" (i.e. we can't change the past, because it will have all 
kinds of 
> unwanted repurcussions, and if we do meddle with the past, it
should 
only be 
> to change the damage we have done by meddling with it in the first 
place.  
> This second one seems to be pretty common, though the only example
I 
can think 
> of right away is "Back to the Future".  

The _Superman_ comics actually took a slightly different approach
than 
that - ANY attempt to alter history is foredoomed, as the universe 
itself will intervene in some way to keep you from making a real 
change; if you come from the future, 'history' is predestined.  

(Probably first expressed in a classic Superboy story where Superboy 
decides to try to prevent the assassination of Abraham Lincoln, only 
to be frozen in place by a device wielded by Lex Luthor, who has gone 
into hiding in the past - coincidentally in Washington DC in the 
spring of 1865.  When Superboy shows up, Luthor thinks that Superboy 
is after him, and only after witnessing Lincoln being carried from 
Ford's Theater does he realize that there was perhaps another 
explanation for Superboy's presence in that time, and is stricken
with  
a fit of conscience (this is the 1950's-written teenage Lex Luthor).
This approach actually seems to be used in the majority of the _Star 
Trek_ writings; time travel by any means other than "the Guardian of 
Forever" puts you in a past that no matter what you do, it is in fact 
what did happen and history has already recorded it.  _Star Trek: 
First Contact_ is less clear on whether they were sticking with the 
Predestination rule they seem to have had in Trek Classic.

There is also Niven's hypothesis - If a time machine can be created 
in a universe, and a traveller to the past can change history, then a 
time machine will NOT be created in that universe.  The reason for 
this is that at some point a time traveller will alter the past in 
such a way that the time machine is never invented, at which point 
there is no further push to change the past, so the universe reaches
a 
path of stability and stays on that - because a change to allow a
time 
machine to be invented can no longer be made, as there is no further 
possibility of a time traveller to make it!

-Brooks