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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 thrustwill
>> 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 framewith
>> > 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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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