Re: starship-design: FTL idea and paradox

["Kevin 'Tex' Houston" <hous0042@tc.umn.edu>]

Timothy van der Linden wrote:

<some math snipped>

> Conclusion:
> They saw a bullet nose pointed forward coming from B, the opposite direction
> of your measurement!
> Of course this isn't surprising since spacelike coordinates may reverse the
> ordering of events, but at least we know that those who could influence the
> events didn't see any reversal of events.
> 
> Knowing this, I would conclude that in the frame of the initiator, FTL
> cannot influence his past. Or in other words he cannot influence his past
> using FTL.
> 
> Timothy

In a Sci-fi story I read (Thrice upon a time by <James?> P. Hogan,  the
problem of 
killing your mother was addressed rather well.  The gist of it was this:

TIME               EVENT                                 Age of A
1965            Person A born                                0
1990            Person A invents time machine               25
1991            Person A travels back in time to 1960       26

1960            Person A arrives in past                    26
1961            Person A kills progenitor                   27
1990            no one invents time machine                 56

There is no paradox, because for all intents and purposes, the person
who arrives in 1960 is from a different universe.  His arrival in 1960
is historical fact, no amount of killing in 1961 can change that.  So
what we have is a person who arrived in our universe without being
born.  Strange yes, but not forbidden.  

BTW, in the story, there is only one universe, but it gets re-written
when a past altering event takes place.

example 1:

1) time machine recieves random message from future.
2) time machine stores message without looking at it.
3) time machine generates random number and sends it back.
4) time machine compares two numbers (they match 100%)

conclusion:  Time machine works perfectly.

example 2:

1) time machine recieves random message from future.
2) time machine stores message without looking at it.
3) time machine generates random number but doesn't send it.
4) time machine compares two numbers (they match 99%)

Conclusion: some quantum variation (I told you this was sci-fi) changed
the random number generator a little bit and the error was not
"corrected" by sending the data back in time.


example 3:
1) time machine recieves random message from future.
2) time machine reads message.
3) time machine attempts to send different number back.
4) time machine suffers breakdown 100% of time.

conclusion:  Universe entered infinite loop that was only broken when
the machine suffered some random breakdown.  number of iterations
unknown (days, weeks, months, years?).  Messages were actually sent and
re-sent, but we don't know about that because the universe was
re-written many times.  It's only the breakdown of the machine that we
remember, because that allowed us to go foreward with intact memories.

All in all, I wouldn't worry about the time travel aspects of FTL, It is
possible to have a self-consistent set of rules which allow time-travel
but not paradoxes.  But woe be unto you who tries to generate a pardox
involing yourself, you are most likely to suffer some random aliment
(heart attack, stroke whatever) before you can complete your task (at
least, that's what we will all remember, even though you may actually
have succeeded many times.


-- 
Kevin "Tex" Houston 		http://umn.edu/~hous0042/index.html
Webmaster			http://www.urly-bird.com/index.html
"Whoever undertakes to set himself up as a judge of Truth and
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