ethan@utastro.UUCP (05/07/84)
[It was a dark and stormy night. Suddenly a bug rang out!!!!!] This article is a reply to two questions by Jerry Aguirre and a reply by Doug Gwyn. First the questions: >>1 - Is there any thing besides red shift to indicate that the universe is receding from us? >>2 - Have any alternate theories been proposed to account for the red shift? Now the first answer: >1 - No, there is nothing other than the Hubble effect to indicate that >distant objects are receding from us at a speed proportional to their >distance from us, and then only if the assumption is made that the >observed red shift is a Doppler effect. > The "assumption" that the observed red shift is a Doppler effect is just the assumption that physics as we know it locally applies globally to the universe. Probably not a bad assumption inasmuch as the spectral lines of distant objects are understandable in terms of familiar physics. >2 - Yes, alternative explanations of the Hubble effect have been >proposed. Please note that the Hubble effect is predicted for the >DeSitter cosmological model, which is the natural solution for the >Einstein-Schr"odinger field equations. The nice thing about this >cosmology is that it describes a static universe (no expansion in any >real sense) obeying the "perfect cosmological principle" (i.e. the >universe looks the same (on a large scale) everywhere AND everywhen). The DeSitter cosmological model has the property that two nearby particles, separated by a spacelike interval and traveling along geodesics, will exponentially diverge from one another. This is as real an expansion as you could possibly want. This expansion is the reason that a Hubble effect will appear in a DeSitter cosmology. The "static" nature of the DeSitter model is an illusion caused by an inappropriate set of coordinates introduced by DeSitter. The perfect cosmological principle is an attractive suggestion. However the discovery of quasars (indicating that the universe used to contain a whole class of conspicuous objects that no longer are common) and the blackbody background (indicating a earlier phase of the universe's existence in which radiation and matter had a much greater mean density) made it seem highly unlikely. Whether or not the singularity at the beginning of the universe (the big bang) has any real meaning is open to question. Presumably quantum effects (which would be important during the first 10^^-43 seconds of the big bang) remove the singularity. >Down with the Big Bang! Down with monday mornings! ( See. Anyone can talk like this :-) ) >Down with blindly applying General Relativity >in domains where we know the field equations are wrong! We have every reason to believe that after the first 10^-43 seconds of the universe's history we are on safe ground. In any case the standard model of the universe's early history does a bang-up job of predicting the primordial abundances of elements. Primordial nucleosynthesis happens at an age of about 3 and a fraction minutes. "Just another Cosmic Cowboy" Ethan Vishniac {ut-sally,ut-ngp,kpno}!utastro!ethan Department of Astronomy University of Texas Austin, Texas 78712
ethan@utastro.UUCP (Ethan Vishniac) (05/08/84)
[In the name of Yag-Soggoth begone bug!!!!!]
This newsgroup has been awfully quiet. In an attempt to liven
things up I'm posting a summary of some of the highlights of
the last conference on cosmology I've been to. I'm also posting
it to net.physics since the material is probably of equal relevance
to that newsgroup. The meeting was the
Inner Space/Outer Space conference at Fermilab May 2 - 5.
The conference included various notables in particle physics
and cosmology and a large number of active researchers in these
fields. Talks were about evenly divided between particle theories
and their effects on cosmology and extragalactic astronomy and its
implications for the initial conditions for the universe (and therefore
for cosmology). What I've listed below is by no means a complete
(or even fair) listing of the talks. These are just the points that
struck me as particularly interesting.
1) G. Steigman and B. Pagel both gave talks on the primordial
element abundance. The bottom line is that the standard model
fits quite well if the present baryon density (as a fraction of
the density required to produce a marginally bound universe)
lies between
0.01 h^-2 and 0.035 h^-2 . (Pagel favored a narrower range
with an upper limit of about 0.02). The upper limit
comes from primordial lithium 7. The lower limit comes from
primordial Deuterium plus primordial He3. "h" is, as usual,
Hubble's constant in units of 100 km/sec/Mpc. The primordial
Helium 4 abundance appears to be consistent with the this
picture. However, the range of reported values is large enough
to include anomalously low values. In the numbers quoted above
I have assumed that the present blackbody background temperature
is 2.7 degrees. More on this later.
2) There are still no reported instances of baryon decay. This
probably rules out the minimal SU(5) models of grand unification
(theories which unify strong, weak, and electromagnetic forces).
3) B. Cabrera's reported possible detection of a magnetic monopole
has not been repeated. Various experiments are underway to improve
the upper limits on the local monopole flux. Various astrophysical
constraints are probably much more sensitive than any experiment
now in the cards if monopoles catalyse nucleon decay.
4) Particle physicists are now working on various ways to
a) cause the universe to expand exponentially at some
early epoch
b) cause the "inflationary" epoch to end gracefully
and quietly
c) produce (during the exponential expansion) just enough
cosmological perturbations to explain the large scale
structure of our universe without disturbing its overall
homogeneity.
d) reheat at the end of exponential expansion just enough to
create the matter-antimatter asymmetry in the universe.
e) avoid various monsters whose energy density in the present
universe would be prohibitive large (monopoles, gravitinos etc).
Not much progress was evident in the sense that there exists no
"natural" unification theory which would accomplish these things
or anything else. Nevertheless many ideas were presented.
The expectation remains quite firm that if these schemes are correct
than the present universe is "flat" (i.e. the average energy density
at present is just what is required to produce a critically bound
universe. Compare this to item # 1 to see an obvious problem.
5) Polite (and otherwise) disagreement continues on the subject
of the value of Hubble's constant (which determines the rate of
expansion of the universe).
6) The microwave background spectrum was discussed by P. Richards
The results are now consistent with a blackbody spectrum whose
temperature is about 2.75 degrees (plus or minus somewhat less
than a degree). Other speakers reported that the microwave
background continues to show no anisotropies. The lowest limit
quoted was a fractional temperature variation of less than
5.6x10^-5 on scales of a few arc minutes. (There is a dipole
moment due to our own motion).
7) The Russian measurement of a neutrino mass stands alone and unconfirmed.
New experiments are coming on line to test this result. The latest
fit to the Russian data looks bad for any neutrino mass. The Russians
are suggesting at least two massive neutrinos. Other people are
somewhat (or entirely) skeptical.
8) Preferred models for the formation of structure in the universe
now rely on some massive, collisionless particle to dominate the
structure of the universe. It must be very massive (probably at
least a Kev). Dynamical measurements of the mass density of the
universe give a density which is only about 20% (at most) of the
critical density. There was considerable discussion of having
galaxies form only at unusual density peaks so that galaxies do not
trace the mass density of the universe well. This has problems of
its own.
9) S. Weinberg gave a synopsis of his own hopes for the unification of
all forces in nature. He wants to use a graded Lie algebra in an
N-dimensional space (where N is large). To create a universe
in which space is locally Euclidean in 3+1 dimensions (our familiar
universe) but in which other directions exist in which we have
almost no freedom of motion. These other directions possess
different symmetries than those we normally associate with space.
Distortions of space-time in all these dimensions then generate
the sets of particles and forces we observe.
"Just another Cosmic Cowboy"
Ethan Vishniac
{ut-sally,ut-ngp,kpno}!utastro!ethan
Department of Astronomy
University of Texas
Austin, Texas 78712gwyn@brl-vgr.ARPA (Doug Gwyn ) (05/08/84)
utastro!ethan has summarized the consensus viewpoint on cosmology fairly well. I would like to expand on a minority viewpoint: The Hubble effect does not have to be Doppler (involving relative longitudinal velocities) in nature. The same spectral line shifts etc. can be explained in other ways, e.g. gravitational red-shift, tiring photons, and others harder to explain simply. The idea that quasars are ancient objects is entirely based on the idea that they are far away and that there is some form of global time frame. I don't know whether the Burbidges ever changed their minds about the matter, but they used to think that quasars are relatively close (in which case their energy output is no longer so hard to explain, nor is the periodicity of the pulsars). The idea of a global time frame is so repugnant to the relativist that it must be seriously challenged. This matter of the 3-degree K blackbody background radiation is interesting. The blackbody spectrum does not appear to be invariant even under Lorentz transformation (I would appreciate any proof to the contrary), so if it really is (a) blackbody-spectral and (b) isotropic as observed from Earth, then it singles out the Earth as a privileged reference frame. Not impossible, but highly suspicious. I bet there would be some alternative explanations if people really sought after them. Similarly, I don't think that only the "big bang" is capable of explaining the current abundances of the elements. It seems likely that any cosmic cataclysm would produce similar results (I would like more discussion on this since I don't know that much about the current ideas on this topic). The claim that the general theory of relativity is safe to use except within the first 10^-43 sec. of the "big bang" is simply incorrect. Einstein was well aware of the deficiencies of the symmetric gravitational theory when applied to cosmological issues. Although he is often quoted as saying that the "cosmological constant" was the biggest mistake he ever made, I think that is taken out of context. I believe his intention was more to say that the WAY in which he fudged his theory in the original introduction of this constant, because he didn't like what his theory seemed to be predicting without it, was inappropriate. The drastic effect on one's cosmological models of introducing such a "minor" change in the field equations should make one cautious about applying the simple, special-case general theory. In fact, if one carefully removes some of the special assumptions of the general theory (as did Schr"\odinger in the late 40's and early 50's), the field equations when cast into a form comparable with those of classical general relativity NATURALLY ACQUIRE A "COSMOLOGICAL CONSTANT" TERM. The "cosmological constant" appears in such a way that it definitely cannot be exactly zero, and a careful analysis of its meaning ties it to one's choice of measurement units relative to the natural cosmological scale; thus it is NOT "arbitrary" but is susceptible of measurement in terms of our conventional laboratory system of units (e.g. cm^-2, in terms of which it is a very small number). For the same reasons that cosmologists normally assume that they can apply general relativity to the problem of the large-scale structure of the universe, one can use the generalized theory for a wider range of possibilities for cosmology. I for one am extremely dissatisfied with the way in which only one point of view on these (by no means settled) issues are taught in our universities. The only thing to be said for the consensus point of view in science is that future developments will almost surely make it "obviously" wrong. I attribute a large part of the intellectual stagnation to the way in which research funding is centralized in a bureaucracy, so that the good opinion of one's "peers" becomes more important than the cogency of one's ideas. The lack of a guiding philosophy founded in reality also shows quite heavily in some of the theoretical work now fashionable.. Sorry if I have stepped on any toes or bored anyone with this long note, but I would rather see discussions of fundamental issues in the field in this list than questions about how thermostats work (kudos to the guy who finally took one apart to find out!).
dzd@cosivax.UUCP (05/13/84)
<>
Let me begin by stating that I favor a minority view and tend to
agree more with brl-vgr!gwyn than utastro!ethan. My reasons are
not so much based on simple physics or astrophysics as they are
on plain aversion to singularities, whether big bangs,
renormalizations or (relatively) small whimpers -- black holes.
Such a principle is clearly "meta-physical" but I believe we too
sharply discriminate between physical science and philosophy
anyway. [note the newsgroups to which I have posted this]
I would like to cite three references on several sides of these
issues:
1) A. Eddington, "Universal Theory" <why fool around?>
2) Kantor, "Information Mechanics"
3) ?, "Cosmology, Physics and Philosophy"
The third is by an Israeli professor at U of Haifa but I can't
remember his name.
When published, Eddington's book was considered trash, probably
the result of senility. Eddington was inconsiderate enough to die
with this book only half done and, I believe it was Wittaker (of
Wittaker & Watson) who finished it as best he could from
Eddington's notes etc. A major theme is the connection between
cosmological theories, data, etc. and microscopic ones. This was
an extremely unpopular view in that day though very faddish now.
It tries to take seriously several things:
1) Einstein knew what he was doing in looking for Unified Field
2) Einstein did not reject completely the Cosmological Constant
but rather his too hasty evaluation of it. In particular, he
wanted to keep open the possiblity of a gravitating vacuum
energy. I believe this is what his pursuit of Unified Field
Theory was all about. I wish they would get on with
publishing his notes, letters etc.
3) All the "negative" principles -- uncertainty, finite speed
of light, etc. and *finite current size* of universe.
Notice that under all variation of big bang theories, current
universe is of finite size. This point seems to me to be
under-appreciated by the "standard" cosmologists nowadays.
Reference 3) is by a proponent of the current "mainstream" in the
sense that he is a big banger but also he is somewhat out of that
stream in advocating a tighter union of physics and philosophy. I
think his book is an excellent summary of the evidence, ideology
and philosophy of big bangers plus it has some interesting and
provocative speculations toward Unified Field Theory. But it
seems to me to ignore the finiteness of the universe and what
that might mean for metrology, especially wrt a standard for
length. Eddington had a lot to say on this but it is so obscured
within counting possible states of high-order tensors that I have
never been able to figure out what he means. BTW, I don't think
Wittaker figured it out either, but just reproduced it as best he
could.
Finally, there is reference 2) which came out about four years
ago and has been completely ignored as far as I can find out. It
is either completely crackpot or the **ANSWER**. It proceeds from
simple assumptions including finiteness of universe and the
implications of this in terms of Non-Relativistic Quantum
Electrodynamics (NRQE), i.e., the most accurately verified branch
of physics by many orders of magnitude. This leads to a
self-gauging universe with a vacuum energy that gravitates -- in
particular, the vacuum gravity affects the STANDING WAVES
associated with at least two photons so as to bind them such that
the quantum states of the result are determined by allowed
wavelengths devired by boundary conditions from finite universe.
This bound bunch of photons are what we call a particle. From
this, he goes on to derive mass, charge, spin, etc. properties of
various "elementary" particles from first principles. [Eddington
did some of this too, but to a lesser extent]. Of course, this is
a Super Grand Unified Theory since it subsumes all four "forces".
Its main appeal to me is that it contains *NO* singularities.
Also, it deals with position, what it means, its quantification,
quantization and relation to gravity and the "forward" coupling
from mass to geometry.
I would particularly be interested to hear from anybody who has
read Information Mechanics and what they think of it. I think
both IM and Eddington's stuff have great merit but, for
Eddington, was too far ahead of its time. I summarize my
understanding of these approaches by asking this critical
question:
"How does an electron know how big it's supposed to be?"
Answer in the spirit of Eddington and Info Mech:
"By sitting at the center of the universe, reaching out and
pushing against the edges"
Answer in the current "consensus" view:
AHEM!
-----------------------------------------------------------------
BTW: If you think this question is dumb, remember that modern
scientific cosmology began when somebody [Hubble?] asked:
"Why is the sky dark at night?"
-----------------------------------------------------------------
Dean Douthat
[All opinions are my own. I have no connection with COSI except
as a guest on their vax.]
UUCP: ...!sb1!mb2c!uofm-cv!cosivax!dzd | Mail: Zahntron, Inc.
Ma: (313) 995-9762 | 330 E. Liberty
MCI Mail: DDOUTHAT 187-3270 | Suite 3B
TWX/TELEX: 6501873270 | Ann Arbor, MI
Answerback: 6501873270 MCI | 48104dzd@cosivax.UUCP (05/13/84)
<>
Let me begin by stating that I favor a minority view and tend to
agree more with brl-vgr!gwyn than utastro!ethan. My reasons are
not so much based on simple physics or astrophysics as they are
on plain aversion to singularities, whether big bangs,
renormalizations or (relatively) small whimpers -- black holes.
Such a principle is clearly "meta-physical" but I believe we too
sharply discriminate between physical science and philosophy
anyway.
I would like to cite three references on several sides of these
issues:
1) A. Eddington, "Universal Theory" <why fool around?>
2) Kantor, "Information Mechanics"
3) ?, "Cosmology, Physics and Philosophy"
The third is by an Israeli professor at U of Haifa but I can't
remember his name.
When published, Eddington's book was considered trash, probably
the result of senility. Eddington was inconsiderate enough to die
with this book only half done and, I believe it was Wittaker (of
Wittaker & Watson) who finished it as best he could from
Eddington's notes etc. A major theme is the connection between
cosmological theories, data, etc. and microscopic ones. This was
an extremely unpopular view in that day though very faddish now.
It tries to take seriously several things:
1) Einstein knew what he was doing in looking for Unified Field
2) Einstein did not reject completely the Cosmological Constant
but rather his too hasty evaluation of it. In particular, he
wanted to keep open the possiblity of a gravitating vacuum
energy. I believe this is what his pursuit of Unified Field
Theory was all about. I wish they would get on with
publishing his notes, letters etc.
3) All the "negative" principles -- uncertainty, finite speed
of light, etc. and *finite current size* of universe.
Notice that under all variation of big bang theories, current
universe is of finite size. This point seems to me to be
under-appreciated by the "standard" cosmologists nowadays.
Reference 3) is by a proponent of the current "mainstream" in the
sense that he is a big banger but also he is somewhat out of that
stream in advocating a tighter union of physics and philosophy. I
think his book is an excellent summary of the evidence, ideology
and philosophy of big bangers plus it has some interesting and
provocative speculations toward Unified Field Theory. But it
seems to me to ignore the finiteness of the universe and what
that might mean for metrology, especially wrt a standard for
length. Eddington had a lot to say on this but it is so obscured
within counting possible states of high-order tensors that I have
never been able to figure out what he means. BTW, I don't think
Wittaker figured it out either, but just reproduced it as best he
could.
Finally, there is reference 2) which came out about four years
ago and has been completely ignored as far as I can find out. It
is either completely crackpot or the **ANSWER**. It proceeds from
simple assumptions including finiteness of universe and the
implications of this in terms of Non-Relativistic Quantum
Electrodynamics (NRQE), i.e., the most accurately verified branch
of physics by many orders of magnitude. This leads to a
self-gauging universe with a vacuum energy that gravitates -- in
particular, the vacuum gravity affects the STANDING WAVES
associated with at least two photons so as to bind them such that
the quantum states of the result are determined by allowed
wavelengths devired by boundary conditions from finite universe.
This bound bunch of photons are what we call a particle. From
this, he goes on to derive mass, charge, spin, etc. properties of
various "elementary" particles from first principles. [Eddington
did some of this too, but to a lesser extent]. Of course, this is
a Super Grand Unified Theory since it subsumes all four "forces".
Its main appeal to me is that it contains *NO* singularities.
Also, it deals with position, what it means, its quantification,
quantization and relation to gravity and the "forward" coupling
from mass to geometry.
I would particularly be interested to hear from anybody who has
read Information Mechanics and what they think of it. I think
both IM and Eddington's stuff have great merit but, for
Eddington, was too far ahead of its time. I summarize my
understanding of these approaches by asking this critical
question:
"How does an electron know how big it's supposed to be?"
Answer in the spirit of Eddington and Info Mech:
"By sitting at the center of the universe, reaching out and
pushing against the edges"
Answer in the current "consensus" view:
AHEM!
-----------------------------------------------------------------
BTW: If you think this question is dumb, remember that modern
scientific cosmology began when somebody [Hubble?] asked:
"Why is the sky dark at night?"
-----------------------------------------------------------------
Dean Douthat
[All opinions are my own. I have no connection with COSI except
as a guest on their vax.]
UUCP: ...!sb1!mb2c!uofm-cv!cosivax!dzd | Mail: Zahntron, Inc.
Ma: (313) 995-9762 | 330 E. Liberty
MCI Mail: DDOUTHAT 187-3270 | Suite 3B
TWX/TELEX: 6501873270 | Ann Arbor, MI
Answerback: 6501873270 MCI | 48104gwyn@brl-vgr.ARPA (Doug Gwyn ) (05/14/84)
Very interesting references. Eddington's "Fundamental Theory" (not "Universal Theory") was indeed brought out by Whittaker (first name Edmund, I think), who also wrote his own book critiquing Eddington's. I tried to understand this work when I was younger and smarter but had only limited success. My impression is that much of Eddington's theory is valid but that he was trying too hard to extract patterns where there might not be any. It is quite certain that if you take the (Einstein flavor) unified field theory seriously, then a closed universe will produce field quantization. Indeed the "displacement field duality" of such a theory also embeds a discrete symmetry in the field. I have much to say about this in my Masters' thesis. It seems to me that the Grand Unified Field Theorists of today are working "inward" from quantum symmetries while Einstein and his small band of followers started close to the core with the expectation that they could eventually work their way "outward". Whether either is extensible into the complete picture is unclear. I prefer the Einstein-Schr"odinger approach because it can be built on explicit philosophical grounds that I happen to agree with, although this was not made explicit in the original work. Philosophy is important, folks.