Ron McFarland wrote:
> On 3 Nov 2003 at 16:45, Joao Leao wrote:
> > Part II:
> > >It is not the distance that contributes, it is the
> > > relative rate of expansion that contributes to the apparent
> redshift
> > > (all other factors that can contribute to redshift being ignored
> for
> > > the purpose of concentrating only on the affect caused by
> inflation
> > > itself). The further something is away from us, relatively
> speaking,
> > > then the faster it is moving away from us. With inflation being
> on
> > > an
> > >
> > > ever increasing rate, there comes a point in finite time when the
> > > expansion rate reaches a level that causes the entire universe to
> > > appear dark and at absolute zero in temperature in reference to
> all
> > > its matter relative to itself.
> >
> > If the acceleration persists, which is may or not be the case, that
> is
> > surely a possibility, depending on some other features of the
> > concordance model being verified or not. But we are still not sure
> > that the acceleration is forever...
>
> That's both an astonishing and maybe just a little bit of a scary
> thought. Is there some hint of any kind that the acceleration of the
> universe might have a limiting factor?
Well the argument is that, because the onset of acceleration may
be more or less dated we may speculate that it will start decreasing
at some point in the future. Of couse not all "scenarios" allow for
this. The "eternal inflation" point of view is quite to the contrary...
>
> > > In other words, the redshift at all points within the universe
> will
> > > have shifted to a level of absolute zero observable energy at
> some
> > > future time because the universe is then expanding (at every
> point
> > > within itself) at or beyond a rate that would allow energy to
> find
> > > anything in the universe that it could be relative to.
> >
> > I don't quite understand this last sentence.
>
> Assume that at some distant time the inflation rate of space/time has
> exceeded the speed of light. At that moment, and forever thereafter,
> no particle within that inflation region could interact with another -
> - because the distance between particles is increasing faster than a
> particle can transverse any distance at the speed of light or below.
> That leads to the conclusion that the affected particle is then no
> longer relative to anything but itself. As far as that affected
> particle is concerned it IS the entire universe and nothing else
> exists. This of course is an illusion, from the larger viewpoint of
> the meta universe. But I argue that when the particle becomes in that
> way relative only to itself then it has in fact melded with the meta
> universe, meaning that its energy has in fact returned to the meta
> universe from which it was spawned during the big bang.
OK. I get your point. That "supersolipsistic" situation is rendered
somewhat unlikely by the fact that galaxies seem to be structuraly
stable (the dark matter issue), in other words, they do not seem to
berak apart with the accelerated expansion. The chances of every
particle becoming its own disconnected universe are also made
unlikely by what we know of microphysics. Gravitational collapse
is the way out of of space-time problems altogether.
> >But it may be worth
> > pointing
> > out that dark energy is uniformely and isotropically distributed so
> > that
>
> It is? That would infer a homogeneous distribution of energy that
> does not appear to hold true with any other observation of the
> universe. If the big bang had resulted in an observable universe that
> is uniform in structure or composition throughout then one might
> expect the same of dark energy, but this does not appear to be the
> case. I would argue that when/if we are able to measure (as opposed
> to just infer) dark energy then we will find it to be distributed in
> much the same way as is energy that we can now measure.
Well we can and have measured the dark energy distribution via
the luminosity distance of Type Ia supernovae and the CMB
background observations (recently WMAP) and it is smooth,
uniform and "tensional" (=feels like a negative pressure).
This is not an inference: it is as direct evidence as you can get
in the cosmological domain!
Dark Energy, if indeed originated in the Big Bang, could
have had a very different distribution than and that is part
of the problem: we don't know why it resulted in such a
small cosmological term if it is indeed the combined energy
of all the vacua of the interactions we know about...
>
>
> > it seems to be something akin to the largest scales of
> matter/energy
> > distribution, for example, inertial mass distibution (dark and lit)
> or
> > better still, curvature or torsion. There are several models of DE
> > proposed along these lines...
>
> Perhaps. As you say, it's too early to know. But our closed universe
> has of late been attributed to have a shape that is NOT a smooth
> spheroid. Amazingly, it appears to be composed of interlocking shapes
> that are not that of a sphere, but because the universe is closed the
> aggregate appearance is theat of a non smooth spheroid. Maybe this is
> not so amazing, since no perfect sphere seems to exist in nature.
You are talking topology, not geometry. As far as the later is concerned,
the shape is spherical, no doubt. There could be distant connected
pieces but the evidence so far is not conclusive of that...
> > > In that
> > > situation a particle would never be able to travel from any point
> A
> > > to any point B, although it might try to do so for as long as it
> > > existed. Eventually the particle could no longer exist, because
> it
> > > itself would loose coherency as its integral parts moved away
> from
> > > each other as a consequence of the space it occupies continuing
> to
> > > inflate, and thereby move its parts away from each other until
> > > nuclear forces could no longer maintain the attraction that keeps
> > > the
> > >
> > > particle (of any type whatsoever) from totally disintegrating.
> >
> > Well, I can't quite make out what you are saying here! I don't
> think
> > the "integrity of particles" is threteaned by universal
> acceleration.
>
> Perhaps not if indeed a particle, once the inflation rate has reached
> a rate relative to a particle so that the particle can no longer
> itneract with any other particle, then the particle has indeed melded
> with an thereby returned its energy to the meta universe from which
> it originated to begin with.
>
> But if it does not, then ALL points in space relative to that
> particle, including at all points within and exterior to the
> particle, keep increasing in expansion rate. In that case the
> distance between bound quarks (for example) keeps distancing, and at
> some point they suddenly become unbound because of a nuclear force
> being unable to influence a binding force over that much of a
> distance. The particle completely disintegrates.
I addressed this point you keep making above. This is really not
worth worrying about. Collapse is a much more likely end for
a particle than supreme loneliness...
>
> > That the Universe has causaly disconnected regions, as it stands,
> is
> > undeliable but Dark Matter seems to define the largest regions that
> > are able to be structured if that is what you are talking about.
>
> No, it's just that at this current stage of expansion rate we are
> only able to observe the expansion over cosmic distances. In time, if
> one lived long enough, it would be observable at quantum distance.
It isn't quite like that! If anything QM shows you that distant particles
interact in some manner or better, exhibit non-local correlations beyond
their time-like separation, so even between disconnected pices of the
Metaverse (Level 1 as the list lingo goes) there are residual bonds that
do not care about universal expansion...
> > The local inhomogeneities, such as you and I, do not betray the
> very
> > high degree of homegeneity the Universe displays at the Megaparsec
> > scale. The cosmological term may cease to be constant at some
> scale,
> > that is true, and it would be most interesting to know which one
> but
> > it is to early in the game for that.
>
> It is too early! But I argue that a high degree of homegeneity does
> not equate to homegenity. Our universe could not have planets, stars,
> and other items such as people if it were homogeneous.
I qualified it: at the Magaparsec scale...
>
> > A lot of the approaches to DE assume a cosmological term varying
> > with some cosmic scalar field (quintessence) or some clever
> equation
> > of state (quartessence). These address time variation rather than
> > spacial variation because that is where the weirdness remains...
>
> A varying comological term probably does exist in reality, although I
> might argue that the term is an effect rather than an affect. I think
> such a term would represent an exponential inflation rate factor (an
> observation at a point in space at a specific point in time).
It does indeed represent an "inflation rate". There are several ways to
argue that the Cosmological Term must be a varying field of some
sort but they remain unconvincing.
>
> > I am afraid I cannot offer much comment on what you say here. I
> > presumme you are expounding your own ideas but each one of your
> > paragraphs contains assumptions that are not quite consistent with
> > each other, beyond what is believe known. I have specail trouble
> with
> > your insistence on a "metauniverse of absolute temperature zero"
> and
> > your language of energy exchange between each universe and the
> > metauniverse!!! Not my thermodynamics there!
>
> I'm merely refering to a universe that has reached ultimate and total
> heat death, when I refer to a meta universe. A universe that is at
> 100% equilibrium throughout all of its points. I am not sure that
> there can be only one meta universe, but it seems to me that a meta
> universe by that definition must be a singularity of nature. Perhaps
> the only real singularity that ever has, does, or will exist.
Maybe! The worries that the Universe will reach a heat bath state
left people very worried 2 centuries ago. I think that all the dark
stuff,
ominous as it sounds is kinda reassuring that such end is quite
unlikely. But, if you want to be worried, I am sure you can find
plenty of reasons, still.
>
> There is no real energy exchange from the viewpoint of the meta
> universe, for it is at average and over infinite time at equilibrium.
> It is only due to quantum effects (however unlikely they are, they do
> still have an eternity to occur within) that the creation of virtual
> particles within the meta universe can lead to the (temporary)
> formation of a universe similar to ours. No matter if the resultant
> universe is open, flat, or closed ... by one way or the other those
> virtual particles are returned to the meta universe; those methods
> being via black holes and/or the expansion of a universe at an ever
> increasing rate (they are both really one and the same thing from the
> viewpoint of the meta universe). What we, bound in our universe,
> perceive as energy is but an illusion from the viewpoint of the MU.
Wow! I would not know about any of that...
>
>
> Ron McFarland
Take care,
-Joao
--
Joao Pedro Leao ::: jleao.domain.name.hidden
Harvard-Smithsonian Center for Astrophysics
1815 Massachussetts Av. , Cambridge MA 02140
Work Phone: (617)-496-7990 extension 124
Cell-Phone: (617)-817-1800
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"All generalizations are abusive (specially this one!)"
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Received on Fri Nov 07 2003 - 10:28:23 PST