| Subject: Netiquette Date: Fri, 10 Aug 2007 17:23:32 +0300 From: Dimi Chakalov <dimi@chakalov.net> To: <matt.visser@mcs.vuw.ac.nz> Cc: <bsk2@york.ac.uk>, <melia@physics.arizona.edu> Hi Matt: I mentioned your "The quantum physics of chronology protection", gr-qc/0204022, at http://www.god-does-not-play-dice.net/Trautman.html#continuum The solution is highly non-trivial, but is known since the time of Aristotle. Ignore it at your peril. Take care, Dimi ============== Subject: Absolute Reference Frame? Not Just
Yet... Dear Professor Visser, Let me tell you about my smart daughter. She's only 10, and last week she asked me a very simple question: do people in New Zealand walk upside-down? I immediately recalled that you're living there and could explain the issue professionally, but I tried to offer the following answer: no, they do not walk upside-down, because there is no place in the universe where you could go and find out who is "up" or "down". If there was such very special unique place, you could have gone there, look around, and not only tell everybody who's up or down, but also look at your watch, and imagine that it runs backwards, and then after just 13.7 billion years you will be right in the center of The Beginning. She didn't get it, I'm afraid. Maybe my explanation was wrong. I only wanted to tell her about the absolute reference frame, and why we can't get to it, although we all bear imprints from it: all our clocks have originated from The Beginning, but none of then can be used to trace back this Very Special Animal.:-) Am I wrong? I will appreciate your help. I also tried to read your latest paper, "Jerk, snap, and the cosmological equation of state", gr-qc/0309109 v3 [Ref. 1], and noticed that you've encountered some problems with the cosmological equation of state (EOS). However, it seems to me that you're optimistic, or at least you didn't mention any theoretical obstacle in determining the values of all time-dependent derivatives -- deceleration, jerk, snap, crackle and pop [Ref. 1]. You also quoted (ref. [19] in [Ref. 1]) a very interesting article by Sarah Bridle et al. [Ref. 2], which too is sort of optimistic. My impression is that you all are waiting for "forthcoming observations to substantially reduce the current uncertainty" [Ref. 2]. I'm wondering, what if the problem is of fundamental nature? What kind of time do you imply by "time-dependent derivatives" [Ref. 1]? Can you prove mathematically that all ambiguities in your paper [Ref. 1] do NOT originate from the missing absolute reference frame and therefore MIGHT be solved by future observations? For example, it seems to me that the issue of dark energy cannot be resolved since this Very Special Animal lives also in the absolute reference frame, http://members.aon.at/chakalov/Tajmar.html#2 http://members.aon.at/chakalov/Granik.html#note The future holds promise of greater mathematical advances that will uncover further cosmological surprises. Maybe the universe has a dual age. I believe you can figure it out on a plain sheet of paper. You're so good in math! And you never walk upside-down. Best regards, Dimi Chakalov http://members.aon.at/chakalov/faq.html Pritie amzanig huh? References [Ref. 1] Matt Visser, Jerk,
snap, and
the cosmological equation of state, gr-qc/0309109 v3, Fri, 5 Dec 2003
02:35:32
GMT, "Determining the first three Taylor
coefficients of the
equation of state at the current epoch requires a measurement of the
deceleration,
jerk, and snap -- the second, third, and fourth derivatives of the
scale
factor with respect to time. "Jerk [the third time derivative] is also
sometimes referred
to as jolt. Less common alternative terminologies are pulse, impulse,
bounce,
surge, shock, and super-acceleration. Snap [the fourth time derivative]
is also sometimes called jounce. The fifth and sixth time derivatives
are
sometimes somewhat facetiously referred to as crackle and pop. "The key result is that even at the linearized
level,
determining the slope of the EOS requires information coming from the
third
order term in the Hubble law. Unfortunately, while the experimental
determinations
of the parameters appearing in the Hubble law are certainly improving,
we are nowhere near being able to say anything significant concerning
the
third-order term. Despite the fact that some parameters in cosmology
are
now known to high accuracy, other parameters can still only be crudely
bounded [19]. The jerk is one of these parameters, and
as a consequence direct observational constraints on the cosmological
EOS
are likely to remain poor for the foreseeable future." [Ref. 2] S.L. Bridle, O.
Lahav, J.P. Ostriker
and P.J. Steinhardt, Precision Cosmology? Not Just Yet...,
astro-ph/0303180, "The recent announcement by the WMAP satellite
team of
their landmark measurements of the cosmic microwave background (CMB)
anisotropy
(1-3) has convincingly confirmed important aspects of the current
standard
cosmological model. The results show with high precision that space is
flat (rather than curved) and that most of the energy in the universe
today
is "dark energy", which is gravitationally self-repulsive and
accelerates
the expansion of the universe. The evidence is independent of
supernovae
results (4,5). "We also do not know whether dark energy is due to an
unchanging, uniform, and inert "vacuum energy" (also known as a
cosmological
constant) or a dynamic cosmic field that changes with time and varies
across
space (known as quintessence). "Dark matter", which is gravitationally
self-attractive, also remains mysterious: We do not yet know its
nature,
nor are we certain about its density or the amplitude of the initial
ripples
in its distribution. "Here we see that the high likelihood regions (solid lines) do not all overlap well, suggesting a problem with one or more of the measurements, or their interpretation, or, more interestingly, that the underlying model may be wrong. "Perhaps adding only select measurements to WMAP data will prove to be the correct strategy. On the other hand, given the issues raised in the second figure, it may be that the real uncertainty is much greater. We will have to wait for forthcoming observations to substantially reduce the current uncertainty. "Thus, even after the historic WMAP breakthrough, there remain unresolved issues, and so there is plenty of room for surprises. Only 5 years ago, breakthroughs in technology and astronomical technique led to the discovery that the expansion of the universe is accelerating. The future holds promise of even greater technological advances that will uncover further cosmological surprises."
Note: I've argued on numerous occasions about a dual age of the universe; the simplest ways to explain the case are here and here. We should never conflate the two times -- local, as read by a physical clock, and global, pertaining to the universe as a whole -- nor try to eliminate the input from the global time, by suggesting a cosmological equation of state (EOS) exclusively in the local mode of time. Why not? Because the resulting picture will be very ambiguous, to say the least: "direct observational constraints on the cosmological EOS are likely to remain poor for the foreseeable future", says Matt Visser. He has not yet replied to my third question above: "Can you prove mathematically that all ambiguities in your paper [Ref. 1] do NOT originate from the missing absolute reference frame and therefore MIGHT be solved by future observations?" I believe this ambiguity is generic and cannot be removed, not even constrained, in principle. It originates from the fact that the local time, as read by a physical clock, contains an imprint from the global time pertaining to the universe as a whole; hence the unique absolute reference frame of 'the universe as a whole'. Phrases like "shortly after the big bang" and "immediately before/after the measurement" are bona fide examples of such efforts to eliminate the input from the global mode of time and cast the whole story exclusively in the local mode of time. The result from these efforts is total mess. The most recent example is Lee Smolin's loop quantum gravity, in which the Planck time and the "number" of atoms of space are assumed to be accessible from the local mode of time. Has anyone managed in the past 2060 years to actually reach the atom of Lucretius? If you were able to reach it, you would immediately divide it into two pieces (recall Zeno's first paradox and Thompson's lamp paradox), so the true atom cannot be reached from the local mode of time. It is the ultimate cut-off, thanks to which we enjoy finite values of physical quantities, but the atom does not live in, and cannot be reached from, the local mode of time. That's why we need the global mode of time to accommodate the atom: the ultimate minimum of Nature exists without all parts. It's a Holon. All this is a very old story about the nature of continuum; sorry for repeating it here. How do physicists respond to the absolute reference frame of the global mode of time? The most frequent reaction I've had is "this doesn't make sense". Surely it doesn't make sense to talk about the size of the universe "after" some fixed instant called 'big bang', say, a "microsecond after the Big Bang, when the exploding fireball of the newborn Universe was only a few kilometres across, ..." (New Scientist, 11 June 2003). In order to grasp the size of the universe (just a few kilometers across, after a microsecond), you need to be placed in an absolute reference frame in the global mode of time: fixed values of physical quantities, which pertain to the whole universe -- age, size, spin, etc.-- can be ascribed only to the global mode of time. From the perspective of a local observer confined inside the universe, the size of the universe 13.7 billion years "after" the Beginning is indistinguishable from what it had been just a microsecond "after" the Beginning; it's all a matter of shrinking/expanding the rulers measuring the "size" of inside-the-universe. A local observer confined inside the universe cannot detect the increment of spacetime metric: he lives in a perfect spacetime continuum and the "gaps" needed for the elementary step of the "expansion of spacetime" are hidden in the global mode of time. Following the well-known balloon analogy, we can say that the reason why we cannot directly observe/measure the global mode of time is that we live in a perfect spacetime continuum, only in order to enjoy this perfect continuum we need a global mode of time. In other words, the "size" of the universe refers to 'the universe as a whole' in one single instant of time. What time? The local time, since you measure it with your clock. Also the global time, since it pertains to the universe as a whole, although, as you might say, "this doesn't make sense". What does make sense, however, are the imprints from the global mode of time, which refer to 'the universe as a whole'. The expansion of the universe and the microwave background radiation are two such global features of the universe. For more on this issue, click here and here. Perhaps the best way to explain the difference between the local and global modes of time is to recall the issue of negative energy and the beautiful example of Adam Helfer: the cat named Macavity. This invisible cat shows up only when no one is looking at it, and if we look at it we won't really see it. Only an imprint from it, left on the normalized, local values of physical quantities, as measured in the local mode of time. For more puzzles, see Matt Visser's gr-qc/0205066 and gr-qc/0204022. Once I hear from Matt, I'll be happy to elaborate.
Dimi Chakalov ===== Regrettably, Matt Visser did not reply to the third question above, and his paper (gr-qc/0309109 v4, 31 March 2004) will soon be published. It will contain an incredible mystery of the absence of any catastrophic events caused by the so-called exotic matter: "Exotic matter is powerful stuff: Apart
from possibly destroying the universe in a future "big rip" singularity
[7], if the exotic matter clumps to any extent there is real risk of
even more seriously bizarre behaviour -- everything from violations of
the positive mass condition (that is, objects with negative asymptotic
mass), through traversable wormholes, to time warps [4, 14, 15, 16,
17]."
Anyway, I don't like things like "exotic matter", it's much too close to parapsychology. There could be a very simple explanation of this so-called powerful exotic stuff, as I tried to outline above. But I cannot offer much math, while Matt Visser does prefer math. I think he is very good in math, as well as in parapsychology, and is perhaps drinking a Budweiser. Is there any other explanation for his dark powerful exotic silence?
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