# Re: starship-design: FTL idea

```Steve VanDevender wrote:
> One observer fires a projectile that travels at 3 c, and strikes a
> target 3 light-years away.  Consider the firing of the projectile as
> event A and the projectile striking the target as event B.  What is the
> spacetime location of event B relative to event A as seen by an observer
> travelling at 0.1 c relative to the first observer?  At 0.5 c?
> observer?  At 0.9 c?  At what velocity does a moving observer have to
> travel to measure those events as simultaneous in his reference frame?
>
> Now repeat this exercise for the case where the projectile travels at
> 1/3 c and strikes a target 1 light-year away, and determine the measured
> spacetime locations as seen by the same three moving observers.

Can you please explain why the backwards in time travel occurs? If the
Causality violation has to do with the light arrival from the object, I
have a solution you might want to consider. Time travel in FTL might not
occur- see my earlier mention of Stephen Hawking's time protection
theory. Causality violations do not accur if you do not travel LOCALLY
FTL, which is not what I'm suggesting doing. If you construct the
spacetime metric correctly, proper time will be EXACTLY THE SAME as
apparent time. Causality violations would not occur either since the
respective light cone would be carried along with the object travelling
FTL. Not local FTL, GLOBAL FTL. The object would actually not be moving
FTL, but be stationary. This is real stuff, and I know it. I'm not just
making this up.

P.S.: Tipler's infinite rotating cylinder has to have no ends?? How is
that possible? (sudden thought comes to my mind...)

Kyle Mcallister

```