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

Jonathan Reeves (JonathanR@mail.iclshelpdesks.com)
Wed, 17 Feb 1999 14:27:29 -0000

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Anders Sandberg writes:

>Jonathan Reeves <JonathanR@mail.iclshelpdesks.com> 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.

What was the original point?


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Anders Sandberg writes:

>Jonathan Reeves = <JonathanR@mail.iclshelpdesks.com> 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.


What was the original point?