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

Jonathan Reeves (JonathanR@mail.iclshelpdesks.com)
Thu, 18 Feb 1999 09:08:47 -0000

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Anders Sandberg writes:

> I think you mix up things a bit. If I jump into my spaceship and blast
> off from Earth (I have an urgent meeting at Aldebaran) with a constant
> acceleration (as measured with an accelerometer onboard) you will see
> my ship recede with a speed (as measured from Earth, for example by
> observing the rate I pass regular milestones along my way) that
> initially increases linearly with time, but gradually the increase
> slows down and after a long while I appear to move near c. No FTL
> there.
>
> Properly speaking the ship is in no inertial frame - it is defined as
> a frame of reference experiencing no accelerations - but it is
> possible to speak of instantaneous inertial frames for each
> moment. However, in neither the ship frames or the Earth's frame is
> anything seen moving beyond c.

I'm not actually talking about ftl in the strict interpretation of the term.
I think the main point of disagreement is the time dilation effect and whether it is possible to overcome it.

The fact that a ship can blast around the galaxy in within the crews lifetime is not much use to anyone else if they cannot communicate any information faster than a direct light signal.

You may like to look at Eric Baird's relativity pages

which contain a lot of very interesting ideas about ftl travel and communication.

Jon Reeves

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Anders Sandberg writes:

> I think you mix up things a bit. If I jump into = my spaceship and blast
> off from Earth (I have an urgent meeting at = Aldebaran) with a constant
> acceleration (as measured with an accelerometer = onboard) you will see
> my ship recede with a speed (as measured from = Earth, for example by
> observing the rate I pass regular milestones = along my way) that
> initially increases linearly with time, but = gradually the increase
> slows down and after a long while I appear to = move near c. No FTL
> there.
>
> Properly speaking the ship is in no inertial = frame - it is defined as
> a frame of reference experiencing no = accelerations - but it is
> possible to speak of instantaneous inertial = frames for each
> moment. However, in neither the ship frames or = the Earth's frame is
> anything seen moving beyond c.

I'm not actually talking about ftl in the strict = interpretation of the term.
I think the main point of disagreement is the time = dilation effect and whether it is possible to overcome it.

The fact that a ship can blast around the galaxy in = within the crews lifetime is not much use to anyone else if they cannot = communicate any information faster than a direct light = signal.

You may like to look at Eric Baird's relativity = pages

http://ourworld.compuserve.com/homepages/eric_baird/ho= mepage.htm

which contain a lot of very interesting ideas about = ftl travel and communication.

Jon Reeves