From: ken@dakota (Kenny Chaffin)
Newsgroups: sci.physics,sci.astro,sci.philosophy.tech
Subject: Re: Fossil Paradox (was: Structure of Time)
Date: 13 Aug 92 16:01:37 GMT
Organization: U S WEST Advanced Technologies

In article <41256@ogicse.ogi.edu> shobaki@gummo.cse.ogi.edu (Khaldoun Shobaki) writes:
>In article <1992Aug12.164703.4068@wdl.loral.com> mab@wdl39.wdl.loral.com (Mark A Biggar) writes:
>>In article <1992Aug12.091957.14414@vax5.cit.cornell.edu> cpyy@vax5.cit.cornell.edu writes:
>>
>>I've heard this called the "fixed point" theory of why ther are no vistors
>>from the future.  Now all we have to do is show that the sheaf of universes
>>where noone every get around to inventing time travel is an stable 
>>attractor and we're done.
>>
>>--
>>Mark Biggar
>>mab@wdl1.wdl.loral.com
>
>Well, I'm no physicist, yet....but that is going to be my major, so I 
>am going to take a whack at this one...
>
>First a bit of set-up:
>
>The situation: 	-Fred lives in the year 1992 (call this PRESENT #1)
>		-Fred goes into the past of PRESENT #1 and kills his father
>		 (call the past of PRESENT #1 PAST #1)
>		
>What will happen (I think ;-)):
>
>		At the exact moment when Fred kills his father, he will be,
>		in effect creating a new reality (call the point where his
>		father dies PAST #2, with a corresponding PRESENT #2)
>		So, in PRESENT #2, there is no Fred, or Fred's dad, since
>		Fred's dad is dead in PAST #2.  Unfortunately for Fred, he 
>		cannot go to PRESENT #2 since he cannot exist there, so Fred
>		can only return to PRESENT #1, or some permutation of PRESENT
>		#1.  This would mean that if it IS possible to travel in time,
>		that even if you change a point in your past, that altered 
>		past does not take effect for you, since by changing it, you 
>		have created a new reality/universe.  Now if it you COULD move
>		"up" a time/space permutation that you create...

	This may be true, but it might not be either. Perhaps the events are
changed such that you actually return to PRESENT 1, but there is a slight 
alteration in the events of the past such that Fred was born before his father
was killed etc. It doesn't have to be all or none, there can be other 
possibilities. I mean what we are talking about is changing the events of the
past. It seems likely that you couldn't change one thing and leave all the 
rest the same. There would be shifting and changing until things reached
equilibrum again. This of course assumes that there is only one physical
reality. If there are multiple realities then your Present 1 and 2 might be
true, but if that were true we wouldn't actually travel into "our" past or
future, but into a different version of it.

>
>I basically have alot of trouble accepting time travel if it has to fit within
>our current understanding of the Universe.  Some of the things that bug me 
>about it are:
>
>-If you move anything back in time, then you are in effect creating new matter,
> and altering the Universe's total matter content...which is currently a no-no

	What if the theory requires that masses be exchanged, not simply moved?
On theory in a recent sf book is that as one person moves into the past someone
else _must_ move into the future to balance it.

>
>-Also, the movement of ANYTHING through time will create a paradox, since all
> matter is in existance somewhere all the time. eg If i went back 2 billion
> years, the matter in my body may be part of an asteroid, a puddle, and a
> breeze....
	good point, but as before what if those piece parts must move into
the future as you move into the past, thus balancing one another.
>
>I guess this could all be explained by the infinite reality idea, since any 
>irregular movement between times would just create a new reality with more mass
>etc....
>
>I probably just confused the subject more than I helped anything, but hey,
>thats my job ;-)

	No these are all good points.
\
KAC


Kenny A. Chaffin                      {...boulder}!uswat!ken
U S WEST Advanced Technologies         ken@dakota.uswest.com
4001 Discovery Drive  Boulder, CO 80303	     (303) 541-6355