From: scsd1005@altair.selu.edu (Terry Cooper)
Newsgroups: rec.arts.startrek.misc
Subject: Re: Modern THEORIES and Reality (was RE: S.O.S. signal!)
Date: 4 Oct 92 05:56:20 GMT
Organization: Southeastern Louisiana University

In article <1992Oct1.165014.17532@aplcen.apl.jhu.edu>, (jmhodapp@aplcomm.jhuapl.edu) writes:
> 
>> >Sorry Terry, but to a layman in physics like me, you did not at all say
>> >why travel backward would be impossible.
>> >
      [...deletion]
> 
> Don't forget Clarke's Laws 1 and 2:
> 
      [...deletion]
> 2) But when a distinguished, elderly scientist states that something is
> impossible, he is usually wrong.
> 
      [...deletion]
> Jon jmhodapp@aplcomm.jhuapl.edu
> ===============================
> Clarke's Third Law:"Any sufficiently advanced technology is indistinguishable
> from magic"

I should probably have addressed the prior-level statement when
it was posted, but I had pretty much decided then that I had said
all I wanted to on the subject. But perhaps I should give it
another try.

It is not necessary to use physics to show that backward time
travel is impossible. It is not a problem in physics. Really!
Before I address that, let me comment on 2). I agree with 2)
entirely! The operative word there is "usually." Believe it or
not, there are some things that ARE impossible. I usually avoid
declaring something "impossible" based on my understanding of the
physical sciences. As has been so often demonstrated, man's grasp
of the makeup and processes of "reality" and his ability to
manipulate that reality continue to advance. Yes, I subscribe to
Clarke's third law.

Now, having said all that, I still assert that backward time
travel is impossible. Can I prove it?  YES!

In order to prove my assertion, I have to say what I mean.
I can travel in space, but I cannot travel backward in time. I
can go to Seattle, interact with people there, and actually
affect the course of events in some manner, large or small. When
I do, Seattle doesn't split off, as far as I know, into multiple
Seattles. I and everyone else can still see the Seattle that I
interacted with.

THAT is the kind of backward time travel I'm talking about: where
you can travel back at will, interact with the past, and actually
affect the course of events so that people in THIS universe, in
THIS time line can actually observe those effects. We are not
talking about an action causing a branching of time lines where
one is affected, the other not. This is exactly what happened in
"Times Arrow." There was no indication of an alternate time line
(as was the case in "Yesterday's Enterprise."

I do not say that parallel universes or alternate time lines do
not exist. I simply do not know. All I know is that you cannot
travel back in time, interact with the past at will, and change
what has already happened. And THAT's what you open yourself up
to when you say that backward time travel is possible. In short,
backward time travel leads to a contradiction.

I cannot both exist and not exist. I can never go back into the
past and kill an earlier ME. Therein lies the proof that backward
time travel is impossible.

How do I prove that the square root of two is irrational? I
ASSUME it to be rational and show that the ASSUMPTION leads to a
contradiction. Likewise, I ASSUME that time travel backward is
possible and show that the ASSUMPTION leads to a contradiction.
There is NO physics involved!  As in the preceeding paragraph, if
I go back and kill the younger ME, then there will be no ME in
the present to go back. If that's the case, the earlier ME was
not killed so that there *is* a ME in the present which means
that I CAN go back and kill the earlier ME which means that I
don't exist in the present so that I can't go back ...  It's a
damn contradiction.  I cannot both exist and not exist.  Since
assuming backward time travel to be possible leads to a
contradiction, we have PROVED mathematically and scientifically
that backward time travel is NOT possible.

It's one thing to eschew the word "impossible." It's quite another
to suspend all rational thought and go berserk at the mention of
the word.

"Times Arrow" made for a nice story. (That's a matter of
opinion.) But, that's all it was: a story. If you *really*
analyze what happened, there *is* a contradiction. Why did they
go back 500 years to SF? Because they found Data's head! But why
was Data's head there to be found? Because they went back! I find
it astonishing that there are actually living, breathing,
sentient souls incapable of grasping the concept.  Oh, well!

    siempre,
      ...terry