starship-design: Re: More Symmetry Stuff

[TLG.van.der.Linden@tip.nl (Timothy van der Linden)]

>Thanks for your response, Tim!  I had the feeling this one was just 
>going to fall flat.  Instead, you've given me a chance for one more 
>iteration... 
>
>>What is a "FTL virtual particle drive"? How is it thought to work?
>
>My understanding was that because virtual particles are "seen" (or at 
>least inferred) to travel faster than light, some people think you can 
>get more momentum out of them with a given amount of energy than you 
>could with a real particle.  So a virtual-particle drive would use 
>Faster-Than-Light virtual particles as propellant, although the ship 
>itself would not travel faster than light.  

Hmmm, I never heard about virtual particles traveling faster than light,
unless they tunneled.
For example (static) electric fields are maintained by exchange of virtual
photons. If indeed the field between two charged plates would be maintained
by particles that move faster than light, we would have a very simple FTL
communication device.

>>What about black-holes? Aren't they coherent enough?
>
>Actually, (According to Mr. Price) they aren't.  In our forward-time 
>view, we wouldn't expect two photons converging on a black hole (coming 
>from different directions) to be correlated in any way.  However, two 
>photons emitted from a common source ARE considered to be correlated.  
>This is a time-asymmetric assumption; viewed in the opposite time-
>direction the reverse would be true.  Although we see the evidence of 
>this asymmetry all around us, there is no time-asymmetric law of physics 
>to explain it, and it is probably a result of the special boundary 
>conditions of Big Bang. 
>
>A coherent radiation sink would have correlations between all incoming 
>particles.  The correlation would be a result of their common Future, 
>although they would have no common Past.

Am I missing something? These seem to be exactly the properties of photons
being absorbed by a black hole. They often don't have a common past, but
they are likely to have a common future somewhere inside the black hole.

>We are used to seeing 
>correlations as a result of a common past, although viewed in the right 
>way the strange phenomenon of quantum mechanics can be seen as evidence 
>that certain correlations can be caused by a common future.  So a 
>coherent radiation sink would be very different from a black hole.
>
>>Hmm, how do you get the mass out of the radiation sink (and into the
>>conventional engine)? Would that not spoil the fun?
>
>Good point.  I suppose it all depends on what sort of object our 
>coherent absorber would be, and whether it would be possible to use 
>reverse-causal mass in a forward-causal engine.  I've been thinking 
>about this a little more and have come to a strange conclusion, based on 
>CPT symmetry.  CPT symmetry is a physical principle (in both quantum and 
>relativity) that any system with opposite Charge, opposite Parity 
>(mirror-image), and opposite Time-direction, must act exactly like the 
>original un-reversed system.  This would mean that if there was some 
>form of matter causally propagating backwards in time, it would most 
>likely be (mirror-image) antimatter.  The Big Crunch, when viewed from a 
>CPT-symmetrical standpoint, would then look exactly like the Big Bang, 
>with the same amount of antimatter then as we have matter today.
>
>The strange thing, though, is that the future boundary conditions would 
>not allow this backward-time antimatter to annihilate with forward-time 
>matter.  The antimatter Couldn't annihilate (in our temporal frame), 
>because it's constrained to exist at the end of the universe!  But this 
>would mean that antimatter "created" at the Big Crunch would be very 
>different from the antimatter that we create in particle accelerators.  

Aren't you looking at the problem with "forward-time"-view? It may be that
(mirror-image) antimatter annihilates with our forward-time matter, but that
in the future some effect (yet not know by us temporal creatures) creates
antimatter once again.
(If this makes no sense, it may be because I've lost track of all the
mirrors, forward/backward, anti/matters.

Tim