From: ingles@engin.umich.edu (Ray Ingles)
Subject: Re: Is omniscience impossible?
Date: Fri, 13 Nov 92 09:46:15 EST
Organization: University of Michigan Engineering, Ann Arbor

In article <2B039669.16698@news.service.uci.edu> cnc@balboa.eng.uci.edu (Christopher Christensen) writes:
>cnc = (me)
>ingles = ingles@engin.umich.edu (Ray Ingles)
>
>[deleted assertions by Dave Weaver about extra dimensions allowing
>omniscience]
>
>cnc:
["Relativity should apply to any extra dimensions that might exist."]
>ingles:
>>Of course, we have no reason to suppose that relativity *does* apply,
>>either... and some reason to suppose not.
>
>I'm assuming that the extra spacial dimensions are just that--spacial
>dimensions no different than the 3 we know of, only for some reason
>we can only percieve 3 of them at a time.  If relativity does not apply
>to the extra spacial dimensions, then perhaps we'd be better off calling
>them by a different name to distinguish between the two types of spacial
>dimensions.  I had the "flatlander" parable in mind which I'm sure you've
>heard of (i.e. flatlanders live in a 2D world, can only see in 2D, are
>ignorant of the third spacial dimension, etc...).

 Well, if we're talking about a second time axis orthogonal to the first,
it is possible for the whole four-dimensional "3space+time" system to
evolve. E.g. in one hypermoment the universe exists in a state where you were
born, lived your life and died, in the next hypermoment you were not born.

>>Or, at least that it might not be relevant.
>>Heard of the wormhole idea?
>
>I'm somewhat familiar with the idea of wormholes.  Basicallly, an
>object's mass distorts the timespace close to an object.  The greater
>the mass, the more distortion of timespace there is.  A wormhole is
>where the distortion somehow creates a connection between 2 points
>in timespace.  The 2 points can allow stuff to travel from one point
>to the other, permitting time travel forwards or backwards and faster-
>than-light travel.  (Please correct me if any of that is wrong..)

 Pretty much. If our comfortable 3-dim space is folded (like a crumpled
ball of paper, to borrow an anology from Robert Heinlein) then two
points that are distant in normal space might be close in that fourth
direction.
 But, if one end of the wormhole is moving relative to the other, it
experiences normal relativistic effects. It's possible to leave one
end 'before' you entered the other.

>cnc:
>>Additional dimensions of time sounds like nonsense to me.  Time is a
>>fundamentally different dimension than space.
>
>ingles:
>>Uh, you *are* aware of four-vectors, where the lorenztian transforms
>>are characterized as rotation in a four-dimensional space of which
>>time acts as the fourth spatial dimension?
>
>I don't doubt that time and space are related and interact.
>Nevertheless, the dimension of time is quite different from the
>dimensions of space (at least from our point of view).

 Whether and to what degree time and space are truly distinct is still a
matter of some debate in the brainy circles. Also, Hawking for one has
proposed a rather massive alteration in our conception of time by including
an imaginary component. Things get weird when you talk to cosmologists and
high-energy physicists and such.

>cnc:
>>We can move freely
>>through space, but not time.  Time has a direction, we can only move
>>"forward", to move "backward" through time introduces logical
>>impossibilities.
>
>ingles:
>> I have sitting here in my desk a number of papers...
[deletions]
>>"Global Structure of the Kerr Family of Gravitational Fields," by Brandon
>>Carter (Phys. Rev., Vol 141 #4, Jan. 1966) & "Quantum Mechanics Near Closed
>>Timelike Lines" by David Deustch, Phys. Rev. D, Vol 44, #10, 15 Nov. 1991
[...]

>Well I'm glad to have in this discussion someone who knows something about
>this.  Are these "closed timelike lines" not considered a paradox under QM?
>If the paradoxes cannot be resolved, doesn't that indicate a problem with
>the theory?

 They are (at least according to Deutsch) not paradoxical. He essentially
argues that the "Many Worlds" interpretation of QM can account handily for
the physics of CTC (closed timelike curves) and no other interpretation can.
 Me, I have some personal prejudices about this, but hey...

>As an example of a paradox, let's assume that we have a wormhole with
>the endpoints spacially close but separated by a time of 1 hour.  I jump
>into the wormhole and travel backward in time by an hour to await my own
>arrival.  When the 1-hour younger "me" arrives to jump in the wormhole I
>stop him from going in.  Is there any consensus among theorists as to what
>happens?

 Deutsch covers this one in his paper. As you note, most theorists stick
with two possible outcomes...

 1) PARADOX! The universe comes crashing down about us. God picks up her
marbles and goes home.
 2) A separate universe is created/entered, and in one you aren't stopped
(because one universe over you were prevented from coming) and in one you
are (because one universe over you weren't prevented from coming back.)
 Deutsch argues for #2. I'm not really qualified to evaluate his argument...

>  There may be other possibilities, but I can't think of any.  I'd
>love to hear an alternate explanation.. :-)

 Well, now, then there's my own personal favorite. Ever see the movie "The
Terminator?" In essence, argue that if you travel back into the past, it
is *the* past you are travelling into. The same past that gave rise to you.
So, you were 'already' there in the past. You won't go back and prevent
yourself from entering the machine... because you *didn't.*
 Lots of people object to this one, because of how they perceive its effects
on free will. Also, it requires that the future 'already' exist. You and I
are 'already' there tomorrow, composing our next round of replies to this
thread. (Doubtless a frightening thought to other readers... :-> )
 Also, it allows you to essentially create information from nothing. Suppose
a time traveller gives me the data I need to invent a tme machine, and then
I hire the time traveller to use this machine and go back to give me the
data I needed...
 However, it is (by definition) consistent. And it allows me to know what
someone will do before they do it.

>cnc:
>>By the time you get information about a part of
>>the universe, you have moved inexorably forward on the time axis and
>>your information is out of date. [...]
>
>ingles:
>> As the papers above show, there can be regions where, by moving forward in
>>your own subjective time, you can essentially move into the past relative to
>>the rest of the universe. Maybe. If we're right about general relativity.
>
>Perhaps a formal version of this "subjective time" could be the extra
>dimension in my "5-space" hypothesis above.  I just can't accept the
>paradoxes inherent in time travel in a 4-dimensional universe.

 Well, paradoxes are in the eye of the beholder.

>cnc:
>>Besides, there is no reason to assume the existence of additional
>>dimensions of space or time unless there is some way for us to interact
>>with them.  The dimensions that we know of seem to have a great deal of
>>interaction between them.  Seeing no evidence for interaction with
>>extra dimensions, I have to assume they do not exist.
>
>ingles:
>> We don't generally hang out in highly stressed spacetime such as
>>around a rapidly rotating black hole, either.
>
>True.  What I meant is that we should not postulate additional dimensions
>unless they help explain the evidence at hand.  Occam's razor..

 Well, the reason these dimensions and such are postulated is generaly
because they flow naturally out of general relativity, a particularly
good explanation for certain things...

[deletions]

>|  Christopher  |  Computer Engineering graduate student, UC Irvine  |


Sincerely,

Ray Ingles                  || The above opinions are probably
                            || not those of the University of
ingles@engin.umich.edu      || Michigan. Yet.
Newsgroups: alt.atheism,talk.religion.misc