Subject: Re: (urth) chems on Urth and a FTL Whorl
From: matthew.malthouse@guardian.co.uk
Date: Tue, 19 Aug 2003 08:54:27 +0100

>Okay. Are ya'll saying that a generational ship *would* be required for 
FTL
>travel?

No.  But there would likely be a minimum duration involved.

To make things simple assume a Newtonian universe and that the ship 
accelerates at 1 g - ie in your cigar-with-fins space ship the nose goes 
forward and the decks are perpendicular to the axis of the ship 
experiencing a comfortable 1 "gravity"

If a "starship" accelerates at a rate of 1 G , its speed is increasing by 
10 m/sec each second. If we divide the speed of light, 300,000,000 m/sec, 
by 10 m/sec^2, we find that the time to reach the speed of light is 347 
days.

So to get to our closest neighbour, Proxima Centauri which is 1541 light 
days away you have

    347 days accelerating
    1194 days cruising at the speed of light
    347 days decelerating.

that's 1880 days or five years and two months.   In the external time 
frame

Now the universe isn't Newtonian but I don't have the maths to work out 
the relativistic effects.  However simplest case, at the speed of light 
there is no duration so (crudely ignore the acceleration phases) the 
travelers don't experience those 1194 days cruising so internally on the 
space ship it's something approaching  690 days.  [and I have also 
entirely ignored the fact that at tSoL mass is infinite and would require 
infinite energy to accelerate to it]

Certainly a generation ship is not required, just something large enough 
that the passengers don't go mad. 

With such a means of transport the establishment of colonies would be 
eminently practical.  But I seriously doubt that an effective empire could 
be maintained once those colonies were productive.  If it takes more than 
10 years to send an envoy to the closest star and back political control 
will fail.

Sidebar:  thinking about this it occurs to me that Severian experiences 
decks with useful gravity _parallel_ to the axis of movement of The Ship 
Tzadkiel but I can't recall any indication of noticing the Ship's forward 
motion/acceleration.  If that is below the threshold of perceptibility 
then it's low and attaining the speed of light would be inordinantly long 
- unsurprising for a light-sailing vessel.  Yet although aboard some time 
- long enough to re-write his manuscript - it doesn't seem to me that it 
was a remarkably extended voyage so I'd have to conclude the Tzadkiel does 
not rely on attaining the speed of light in order to either travel in time 
or make the crossing between Briah and Yesod.  Therefore there must be a 
mechanism that is both esoteric and hidden from him (and us).  I don't 
think there is any adequate explanation of Tzadkiel to be had, a wand has 
been waved.  That being the case I suspect that it is entirely reasonable 
to assume supra-luminal space-flight for the Empire of Man as an 
inexplicable given - perhaps the backswing of the same wand. 

Matthew


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