# Re: starship-design: FTL

```L. Parker wrote:

>I don't really have a problem with relativity, unless it starts violating
>causality. Even Einstein had a problem with what he called "spooky action
>at a distance" and that was merely simultaneous - not an actual violation
>of causality. I just don't think it is possible to create a causality
>violation, with or without FTL. (If you can do it with FTL then FTL isn't
>possible.)

One thing is for sure--a _true_ causality violation is impossible.
It is a mathematical impossibility to truly kill your own grandfather
so he never fathered your father.

It's as impossible as assigning a true/false value to the statement,
"This statement is false." or finding a real number x such that x^2
is -1.

However, just as it is possible to invent logic systems with more
than true/false, and just as it is possible to extend to complex
numbers where i^2 = -1, it might be possible that the universe is
modeled by an extention of what we normally think of as causality
(the solution to a complex differential equation).  It's possible,
but not necessarily so.  And note that just as with the other
extensions I mention, this extension would be very bizarre compared
to the "normal" case.

BTW, the problem with differential equations is that sometimes
no solution exists.  What happens if the universe is modelled
by a differential equation where no solution exists?  Well...it
can't happen--it's like asking what happens if there were a rational
number whose square was 2.  What really could happen is that using
our understanding of physics, our best mathematical models which
best fit the universe might be a differential equation where no
global solution exists--and our best model is by definition
incomplete.
--
_____     Isaac Kuo kuo@bit.csc.lsu.edu http://www.csc.lsu.edu/~kuo
__|_)o(_|__
/___________\ "Mari-san...  Yokatta...
\=\)-----(/=/  ...Yokatta go-buji de..." - Karigari Hiroshi

```