# Re: starship-design: FTL

```Steve VanDevender wrote:

>First of all, I'm not entirely sure what you mean by a negative time
>value.  The only observer-independent notion of time in relativity is
>"proper time", i.e. the time that an object experiences itself.  In at
>least one (probably oversimplified) analysis, FTL motion requires that
>the object experience _imaginary_ proper time.

It is an oversimplified analysis.  It starts off with the very erroneous
assumption that FTL frames of reference are enough like STL frames of
reference that the equations derived about STL frames of reference can
be applied to FTL frames of reference without modification.

In particular, some of you are familiar with Einstein's derivation
in special relativity of how the passage of time is measured--it's
measured by using a clock.  The one he uses is a simple "light
clock" (two parallel mirrors have a photon bouncing between them
and the number of times the photon bounces ticks off time), but
the passage of time on even this simple clock reflects the passage
of time for everything else (like mechanical clocks, atom clocks,
chemical reaction times, etc).

The shocking thing about FTL frames of reference is that not even
this simple light clock works!  In an STL frame of reference, the
miracle is that with a Lorentz transformation, the light clock
will measure time the same no matter how it's rotated (e.g. whether
they are perpendicular to or parallel to the direction of motion
is irrelevant).  In an FTL frame of reference, the light clock
measures time differently depending on how it's rotated--in some
angles, time doesn't seem to pass at all (the photon can't catch
up to the other mirror)!

Therefore, the equations for time dilation, which are derived
from the light clock and the Lorentz transformation, simply are
not valid for FTL frames of reference.  No wonder they spit out
a nonsensical notion like time passing in an imaginary direction!

In order to analyze FTL frames of reference, you have to go back
to basics--the Lorentz transformation.
--
_____     Isaac Kuo kuo@bit.csc.lsu.edu http://www.csc.lsu.edu/~kuo
__|_)o(_|__
/___________\ "Mari-san...  Yokatta...
\=\)-----(/=/  ...Yokatta go-buji de..." - Karigari Hiroshi

```