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starship-design: Re: FTL idea

Kyle writes:

>What happens when you have negative mass? This
>has only been observed between casimir cavities, and they certainly
>don't exceed the speed of light, yet light speeds up in the cavity.
>Maybe negative mass particles travel faster than light? Or speed up

Negative mass particles wouldn't travel faster than light.

For a while it was speculated that perhaps antimatter had negative mass; 
no one had observed anitmatter's response to gravity, because there 
wasn't enough of it.  But recently experiments have been done that show 
that antimatter has "positive" mass just like regular matter; it falls 
down, not up.

If there was something with negative mass, perhaps it would be 
gravitationally repulsed by objects with positive mass.  You could 
perhaps make anti-gravity ships, but not FTL.

>Causality violation:
>Stephen Hawking has speculated that at FTL speeds, particle-antiparticle
>anhialations dampen out chronal distortions, thus preventing causality
>violation. Perhaps FTL IS allowed in this way, preventing causality
>violation. In effect, the "naughty" part of your trip is prevented from
>creating CV's since it is hidden behind an event horizon.

Maybe, but you need to define "naughty", and in my opinion the "naughty" 
part is the FTL itself.

>This brings me back to my question: What happens if you surround a
>normal object with a spherical shell casimir cavity? I don't know if I
>would want to be the one to try it.

In principle, a spherical casmir cavity would seem to be much more 
effective than a planar one; for a given volume in space you "damp" more 
modes of virtual photons in you can damp with 2-D plates.  But, when you 
look at it more closely, it doesn't work.  Casmir cavities need to be 
extremely small or they have no effect; a small 3-D cavity would be SO 
small that the "walls" couldn't really be called conducting at all, so it 
might not damp ANY virtual photons.  Also you couldn't fit anything 
inside if you wanted it to be small enough to have any noticable effect 
on the vacuum.

>P.S: If two objects APPROACH, each one travelling .99C, what is their
>combined velocity of approach? Is this done the same way as the regular
>velocity addition?

Relative velocity = (0.99 + 0.99) / (1 + 0.99^2) = 0.99995c