Re: BOOKS: Pournelle's *A Step Farther Out*

Anders Sandberg (
17 Feb 1999 15:41:30 +0100

Jonathan Reeves <> writes:

> Anders Sandberg writes:
> >Jonathan Reeves <> writes:
> >> The energy needed to accelerate it from it's _starting_ point
> increases,
> >> but not the energy it needs to accelerate itself.
> >> An object/vessel which is capable of generating it's own thrust will
> not
> >> need to output more power to maintain a constant acceleration the
> >> further it gets from it's origin.
> > True. But an observer sitting at the origin will not see it pass c,
> > and neither will any other observer moving in an intertial frame with
> > a relative velocity to the origin less than c. A spaceship
> > accelerating at constant acceleration (as measured by the crew) will
> > describe a hyperbolic path in a Loretnz diagram; it will never break
> > c.
> Exactly. It will never appear to pass c (either in the original
> inertial frame or in a Lorentz diagram), but this does not mean it is
> not travelling ftl relative to it's start point.

Huh? This seems to be a contradiction, how can something move FTL relative to a point when in that point's frame it is moving sublight?

> What was the original point?

Of this discussion, or the example?

Anders Sandberg                                      Towards Ascension!                  
GCS/M/S/O d++ -p+ c++++ !l u+ e++ m++ s+/+ n--- h+/* f+ g+ w++ t+ r+ !y