starship-design: Something Different...

[wharton@physics.ucla.edu (Ken Wharton)]

Hello all...

I just finished a fascinating book; Time's Arrow and Archimedes' Point, 
by Huw Price, and Australian Philosopher/Mathematician.  The main (and 
convincing) argument is that while practically all of the physical laws 
of nature are time-symmetric, our position as beings with a particular 
temporal orientation--we sense the "future" being distinctly different 
from the "past"--has interfered with taking Time-Symmetry to it's 
logical Conclusion.  In particular, he argues that the inherent Time-
Asymmetry of the Copenhagen Interpretation of Quantum Mechanics is 
flawed, and we need to pick a time-symmetric quantum theory, such as 
Cramer's Transactional Interpretation or another possible option he puts 
forward.  Indeed, he sees the *ONLY* reason that we even perceive an 
"arrow" of time is because of the low-entropy boundary conditions of the 
Big Bang, and the fact that consciousness has to move in the same 
direction that entropy increases.  (He argues that the radiation arrow 
of time also stems from the special conditions of what we call the Big 
Bang.)

So--assuming he's correct--what does this all mean as far as this group 
is concerned?  First of all, it would seem to rule out FTL virtual 
particle drives.  The concept of "faster than light" virtual particles, 
along with non-local quantum effects, stem from our forcing our 
subjective time-asymmetry onto physics as a whole.  Basically, what 
looks like a faster-than-light occurrence in our temporal frame is 
actually a combination of a "forward" time causation and a "backward", 
or advanced causation.  Huw Price shows that any attempt to use a 
backward causation to set up a paradox will fail; the measurement itself 
will destroy the correlation you're looking for.  In fact, it looks like 
you can derive all of modern quantum mechanics from two axioms; 1) 
Nature is Time-Symmetric, and 2) You can never set up a true paradox.

But a more interesting idea I had is this:  Assume that the universe is 
closed; i.e. that it will recontract into something we call the Big 
Crunch.  In fact, given symmetry arguments we have no reason to expect 
that one "edge" of the universe will be any different from the other.  
But the Big Crunch will come with its own Boundary Conditions that will 
propagate in the reverse time direction from what we're used to.  
Indeed, on the other side of the universe, Entropy would be increasing 
in the opposite direction!  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.  
Anyway, my idea revolves around this question: what happens to an object 
that survives the transition from an expanding to a contracting 
universe?  There are two possible answers here, and one of them kills my 
idea.  If that object is equally constrained by the Boundary Conditions 
of the two ends of the universe (The Big Bang and the Big Crunch) then 
it's entropy would start to move in the other direction.  If that's the 
case, this idea won't work.  BUT - If some objects are ONLY constrained 
by the boundary conditions at ONE end of the universe, and they pass 
each other in the middle, then they would continue to be affected by the 
more distant end of the universe rather than the closer one they were no 
heading toward.  If this is a possibility, then in OUR side of the 
universe there might be objects that "originated" from the boundary 
conditions of the Big Crunch; perhaps there might be large-scale 
radiation sinks of the kind I mentioned earlier.  This would have 
profound implications for a starship propulsion system, if we could ever 
get our hands on one.

An objection here might be that there aren't such objects; we don't see 
them.  Nowhere have astronomers ever seen light coming from all 
directions and converging on an object in a coherent fashion.  But COULD 
we even see such a thing?  Think of the situation in the reverse-time 
perspective, where the "inverse-star" is radiating outward, shining 
photons on our eyes.  Now, back in our time perspective, we don't see 
any light; photons are Leaving our eyes, not arriving at them.  (This is 
also true for a photographic plate, of course...)  So in our time frame, 
we have to spin our head around and look AWAY from the inverse-star in 
order to see the radiation coming toward it.  But now the back of our 
head is blocking the light!  Photons would be emerging from the back of 
our head and going to the inverse-star; our eyes would miss the whole 
thing.  I think it's possible to see such an object, but it would 
require a completely new type of detector that would somehow be able to 
detect that photons were Leaving, rather than arriving, but do so it a 
way that wouldn't disturb the photons themselves.

Anyway, the point is that a large, coherent radiation sink would get rid 
of a rather painful asymmetry in spaceship engines.  Because there are 
only coherent radiation sources, we have to Expend mass to gain 
momentum.  But why not the opposite case; gain momentum by Receiving 
mass?  A coherent radiation sink would allow this possibility; matter 
would converge upon it coherently and possibly give momentum to the ship 
while Adding to the mass of the ship, rather than subtracting from it.  
A more conventional engine could then operate in tandem, keeping the 
mass of the ship constant while we gained momentum.

A little farfetched, perhaps.  But things have been awfully quiet 
lately, so I thought I'd toss it out and see what happens.

Ken