From: bjgaed@bb1t.monsanto.com
Newsgroups: rec.arts.sf.misc
Subject: Re: Free will and time travel
Date: 14 Aug 92 07:20:13 CST
Organization: Monsanto Company, St. Louis, MO

In article <1992Aug14.011312.13075@organpipe.uug.arizona.edu>, dave@cs.arizona.edu (Dave Schaumann) writes:

[Stuff Deleted]

> So whither time travel?  There are several possibilities:
> 
>   - The past is not immutable.  I'm not sure what you could do with
>     this.  The nature of free will suggests that there would be
>     continuous spontaneous changes in the past as people made different
>     choices, and thus, there would be little logical consistency to the
>     world.
 
Hmmm... I'm not sure either.  Can't seem to get my mind wrapped around 
that one.

>   - You can travel to the past, but if you do, you lose your free will.

Maybe this works if you only *observe* the past.  For example, through 
FTL travel you go some distance from earth.  Then with some incredibly 
sensitive detector you receive signals (light waves, for visual images) 
coming from earth that left there some time in the past.  But to 
physically return to the past, there is no way you can avoid changing 
the past.  By your very presence you displace air molecules, among 
other things.  If one of those displaced oxygen atoms was to have later 
wound up in a phosphorus-oxygen bond in an ATP molecule in *your* 
brain, it may not have been in the right place to have been breathed 
by you, or your mother, or your grandmother, or ...  (How incredibly 
sexist that we call it the "grandfather paradox".  Should be the 
"grandmother paradox".)  (Also, we *really* need some new verb tenses. 
 Can't remember when I last used past perfect passive subjunctive (I 
think.).  Glad this isn't in Russian.)


>   - You can travel to the past by "reversing" time, so everyone comes
>     along.  Then, the future you know of will only be one possibility.
>     The new one that is subsequently  played out will no doubt be
>     different...

Only works if everyone *forgets* their original timeline, in which 
case there is no way of detecting if this has happened.  All it takes 
is a few time travellers jerking everyone back and forth a few times 
and we would all go mad.  How would we know which set of experiences 
we "remember" is going to happen this afternoon?

>   - You can travel to the past, but as soon as you arrive, reality
>     "branches" ala `parallel universes'.  (Or, you can only travel
>     to alternate universes, but some of them would be indistinguishable
>     from our own except for being n years behind us).

This is the one I find easiest to deal with, but again, how does the 
traveller keep multiple experience lines straight after two such 
jumps?  If you "forget" your previous timeline this is indetectable.  
If there is "leakage" of the memory/awareness of an individual and her 
doppelgangerin (?) this may be indistinguishable from madness.  (See 
_Infinity's Web_ by Sheila Finch.)  

>   - You can't travel in time.

Party pooper. 8{)

> 
> That's all I can think of. 

Let's see... In Varley's _Millenium_  (the book, *not* the movie, 
*puh-leeze* 8{(      ) they tried to compensate for removing matter 
from the past by replacing it with exact replicas of that matter.  
This operates on the assumption that *little* changes don't make any 
significant difference.  This seems to be the basis of a lot of 
time-travel sf.

--Electric Monk            (Bruce Gaede); 
                            e-mail: bjgaed@ccmail.monsanto.com

"...and then time started seriously to pass."
--Douglas Adams, _Dirk Gently's Holistic Detective Agency_
Newsgroups: rec.arts.sf.misc