[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

starship-design: More Symmetry Stuff

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 

>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.  

>When talking about FTL (faster than light) I'm always a bit unsure, not
>because of the physics involved, but about what the the phenomenon 
>For example does travel trough perminent warped space also count as 
>Anyhow, regardless of how you call it, one day there may exist a 
>to create permanent "worm-holes" to travel to distant stars in a "no-
>This phenomenon will likely not depend on tunneling (forward causation) 
>instead on general relativity and thus still allows for FTL travel to 

Very true.  Of course, if we're worried about energy requirements NOW...

>>You'd get (from our perspective) Inverse
>>Stars that would be coherent radiation sinks, rather than coherent
>>radiation sources.  The laws of electromagnetics account for this
>>possibility in the equations; it just so happens that we never see
>>large, coherent radiation sinks--that's the radiation arrow of time.
>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.  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.  
One obvious difference is that antimatter that we create from matter 
would necessarily be causally propagating forward in time, because all 
of its Boundary Conditions could still be traced back to the Big Bang. 
But if they are fundamentally the same in all other ways, you'd still 
expect both types of antimatter to obey the same laws of physics; 
instead one annihilates with matter and one doesn't.  This contradiction 
either spells defeat for this theory, or points to some new law of 
physics.  One possibility is the mirror-image requirement I mentioned 
earlier; perhaps there is a unknown conservation-of-parity law in 
physics that only allows annihilation of similar-parity particles (i.e. 
particles that had the same causal direction).  Physics could not have 
discovered this law yet because all forward-causal particles would have 
the same parity.

Anyway, even if this backward-causal material exists, we'd have to find 
some.  I mentioned the problems with seeing radiation from these 
objects; they'd emit incoherently and absorb coherently.  But it would 
still be gravitationally attractive.  In fact, if this theory is true, 
it would most likely be some of the "missing" mass of the universe.  The 
Great Attractor between the Milky Way and Andromeda galaxies, a 
completely dark object with roughly 10 galactic masses, would be a 
likely possibility, but useless for us.  Instead, we'd have to hope 
there were chunks of this dark matter throughout our galaxy as well, and 
we'd have to come up with a way of detecting them.  As far as I know, no 
one is working on devices that detect when photons Leave an object (as 
opposed to arriving on a piece of film), but I don't see any fundamental 
reason why it couldn't be done.  Anyone have any ideas?