Re: starship-design: FTL Navigation

[Zenon Kulpa <zkulpa@ippt.gov.pl>]

> From STAR1SHIP@aol.com Fri Aug 24 18:56:43 2001
> 
> In a message dated 8/24/01 6:54:19 AM Pacific Daylight Time, 
> zkulpa@ippt.gov.pl writes:
> 
> >I, for one, am not particularly interested 
> 
> (in FTL discusion?).
> 
Exactly.

> > Partly because any
> >mention of this subject here starts an avalanche of gibberish from
> >some <STAR1SHIP@aol.com>, who is not even able to edit his posts
> >so that they are moderately readable...
> 
[...]
> Trip length: 4.25 light years.Acceleration: 1.0 g.
> Time on earth: 5.8780560467144 years.
> Time on ship: 3.544401860293398 years.
> Bon Voyage!
> 
> Average Velocity(V)= distance traveled/time traveled.
> Relativistic subscript:= rel.
> Lorentz velocity: Vrel.=distance traveled/proper time;
> Vrel.=D/T
> Einstein Velocity: Vreal=distance traveled/ship time; 
> Vreal=D/Trel
> Note: Ship time is not considered improper time aboard ship.
> Vrel.=4.25 light years / 5.878 years = .723 C
> Vreal=4.25 light years / 3.544 years = 1.20 C
> 
> Since a universal law of physics requires it be true that nowhere in the 
> universe is a case found in violation of the law, the law is held to be, 
> by  virtue, a self evident truth.
> 
> Therefore in the above case is found a single C + V velocity 
> and no Universal law forbidding C + V velocities or math proof 
> of any limit to C velocity of  objects of mass, can exist.
> 
> I rest my case by summarizing: Any claim other wise is held to be without 
> virtue and clearly false and those making the claim are seen from this 
> rest observer viewpoint as without virtue, truth or other redeeming 
> qualities.
>
I have written on that already, long ago, let me quote:

> From owner-starship-design@lists.uoregon.edu
> Date: Mon, 21 Feb 2000 21:43:43 +0100 (MET)
> From: Zenon Kulpa <zkulpa@zmit1.ippt.gov.pl>
[...]
> It seems there is some misunderstanding.
> Tom receives "FTL" by dividing the distance in the Earth reference frame
> by the time in the starship reference frame. For relativistic speeds,
> due to time dilation, one indeed obtains from this division
> a "velocity" larger than c. However, this is not a velocity 
> in physical sense - for which one should measure time and distance 
> in _the same_ reference frame.
> 
Your "Vreal" is not a _speed_, since "D" and "Trel" are measured
in different reference frames. The fact that such a formula
gives the "speed" greater than c was, and is, well-know to anybody
having even a cursory knowledge of relativistics.
It was also since long ago explained in most popular
literature on the subject, showing that because of that time
dilation in the fast traveling starship, if only it contained
enough fuel allowing it to travel in constant acceleration, say 1g,
it would be possible to reach the farthest galaxies within
the lifetime of those aboard - though, of course, on Earth
would then pass billions of years.
So boasting around about discovering that miraculous fact,
and presenting it as an argument against that stupid physiscist
that claim FTL is impossible, is silly and annoying, 
hence the disgust I expressed.

May be a simple thought experiment will show that your trick
of juggling reference frames does not produce _real_ FTL.
Consider that there is some mirror in Alpha Centauri system.
You start from Earth in your relativistic ship accelerating
with that 1g, and at the same time a laser impulse is send to
your destination yonder. The light goes on with c, is refelected
in the mirror and returns back to Earth. It arrives after exactly
8.5 years, right? Your ships ploddes on, stops at Alpha, 
immediately returns back and arrives on Earth as well.
Of course, according to your (quite correct) calculation
its "Vreal" will be 1.20 c approx. So, the ship should arrive 
back on earth earlier than the laser impulse, since it traveled,
as FTL acronym means - "Faster Than Light", right?  Nohow. 
Actually it will be much late, arriving 3.26 years _after_ 
the light impulse.
So, did it _really_ traveled faster than light??
Nice feat - to claim that who arrived later, actually went faster...

Of course, the crew will be 4.67 year younger (physically 
and subjectively) than if they stayed back on Earth, but this 
is not FTL, only relativistic time dilation.

Note: Of course, the argument works as well without returning back. 
The light impulse arrives at Alpha after 4.25 years,
while the ship, going along identical route and allegedly traveling 
faster than that light, arrives there 1.63 years _after_ 
the light impulse. I used the return trip example to ease somewhat
the problem of shifting refence frames...

And that is about all that I would like to say about the subject.

-- Zenon Kulpa