From: Jonathan Reeves (JonathanR@mail.iclshelpdesks.com)
Date: Wed Feb 17 1999 - 08:39:34 MST
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.
>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?
To an observer in that frame, it will appear to slow down as it
approaches the event horizon - just like falling into a black hole. The
people in the ship however will not experience this and if they keep
accelerating they will move into a different inertial frame to the one
they started off in. Thus, they will be moving ftl relative to a point
in that original frame (although no one there will be able to see them
doing it)
Jon Reeves
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