[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
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.
>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
means.
>For example does travel trough perminent warped space also count as
FTL?
>Anyhow, regardless of how you call it, one day there may exist a
possibility
>to create permanent "worm-holes" to travel to distant stars in a "no-
time".
>This phenomenon will likely not depend on tunneling (forward causation)
but
>instead on general relativity and thus still allows for FTL travel to
be
>possible.
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?
Ken