Cosmic acceleration rediscovered

[In a discussion of Type Ia SNe data, acceleration, etc.]

"k" == kurtan writes:

k How much of standard cosmology are you willing to sacrify ?

As much as it takes to fit the data.

More seriously, what do you mean by "standard cosmology"? This term
(or something similar) gets thrown around (both here and in
sci.astro).

Modern cosmology starts with general relativity. Making certain
assumptions (isotropy and homogeneity) one can derive equations that
should describe the evolution of the Universe. General relativity has
been quite well tested within the solar system, and to some extent in
other systems (e.g., the Hulse-Taylor binary). Obviously, there's a
huge extrapolation involved going from the scale of the solar system
to the Universe as a whole. Nonetheless, we need some way of
starting. GR has been so well tested, I think it would require a
*lot* of evidence for it to be "sacrificed."

The equations for the evolution of the Universe depend upon certain
parameters e.g., the Hubble constant and the cosmological constant.
With our current state of knowledge, we cannot derive these ab inito;
they must be measured. As measured values, their quoted values should
always be seen as tentative. Additional data certainly has the
possibility of changing what we think their current values to be. I
don't think this is in any way "sacrificing" standard cosmology to say
that new data have become available.

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"Phillip Helbig---remove CLOTHES to reply"
wrote in message ...
In article , "Bob Day"
writes:

No. The "alternative theory" I'm interested in is Tuomo Suntola's
Dynamic Universe theory, which explains not only the Ia supernova
redshift vs. distance modulus data, but also, for example, the
rotation of the perihelion of Mercury, the bending of light around
stars, and time dilation in gravitational fields, just as well as
general relativity.

These are all well known phenomena. Does the Dynamic Universe theory
make any predictions which differ from those of conventional wisdom?
Did it exist before the current supernova data and if so did it predict
them?

Mostly, the differences in the predictions of the Dynamic Universe
(DU) theory and GR are very slight. For example, at the surface of the
Earth, the gravitational correction for the frequencies of atomic
oscillators matches in the first 17 decimal places.

The DU theory did not predict how the redshift vs. distance modulus
data for Ia supernovae should look before early data was obtained;
however, as data has been obtained for redshifts greater than 1 (Knop's
and Riess's studies), the DU's model of it has continued to be accurate.

The DU theory does not predict gravitational radiation, and such
radiation has not been discovered.

The DU theory predicts that the expansion of the universe is not
accelerating, and no mechanism, such as dark energy, for such an
acceleration has been found.

The DU predicts that all gravitationally bound objects, such as galaxies,
are expanding along with space, and the data that has been obtained
does not contradict that.

For more information about the Dynamic Universe theory, go to
http://www.sci.fi/~suntola/DU%20libr...%20reprint.pdf, and
http://www.arxiv.org/ftp/astro-ph/pa...12/0412701.pdf

-- Bob Day

"Bob Day" wrote in message
...
No. The "alternative theory" I'm interested in is Tuomo Suntola's
Dynamic Universe theory, which explains not only the Ia supernova
redshift vs. distance modulus data, but also, for example, the
rotation of the perihelion of Mercury, the bending of light around
stars, and time dilation in gravitational fields, just as well as
general relativity.
-- Bob Day

[Mod. note: I'm sure Bob is aware of the speculativeness criterion for
s.a.r. postings, and so meant to say `purports to explain'. -- mjh]

If you mean that Suntola claims to EXPLAIN the GR, I can understand
your interest (and Mod's note). The other three examples are standard
verifications of the validity of GR itself. A new theory must have much
more to tell , before the scientific community is willing to give up the
Standard one! I suggest you take a closer look at Masreliez' SEC.
(He may be on limits of s.a.r.allowed speculation, when deriving
Quantum mechanics from modelling GR with a discrete conformal
time approach - in January -05 issue of Apeiron)
/Kurt

[Mod. note: (1) quoted text trimmed.
(2) to remind readers about the speculativeness criterion:
what we aim to avoid is people asserting as true
statements about observation or interpretation that aren't
generally accepted as true (or, worse, are generally
accepted to be false). We have no problem with discussing
non-standard astronomical theories so long as the
discussion is reasoned, referenced and open-minded. --
mjh]

In article , "Bob Day"
writes:

The DU theory does not predict gravitational radiation, and such
radiation has not been discovered.

How does it explain the slowdown in the binary pulsar? This is an
indirect detection of gravitational radiation.

The DU theory predicts that the expansion of the universe is not
accelerating, and no mechanism, such as dark energy, for such an
acceleration has been found.

I think you need to quantify what "find" means here. Certainly many
people think that it has been found.

"Joseph Lazio" wrote in message
...
[In a discussion of Type Ia SNe data, acceleration, etc.]
"k" == kurtan writes:
k How much of standard cosmology are you willing to sacrify ?

As much as it takes to fit the data.

More seriously, what do you mean by "standard cosmology"? This
term(or something similar) gets thrown around (both here and in
sci.astro).

Instead if saying the Big Bang or BB for short, which causes comments
as to whether you are referring to a dusty thing based on GR or a hot
version with inflation, or also including dark energy, dark matter etc,
i e referring to what is today generally accepted, that also modern text
books use to label "Standard Cosmology [Model]", SCM for short.

Modern cosmology starts with general relativity. Making certain
assumptions (isotropy and homogeneity) one can derive equations that
should describe the evolution of the Universe. General relativity has
been quite well tested within the solar system, and to some extent in
other systems (e.g., the Hulse-Taylor binary). Obviously, there's a
huge extrapolation involved going from the scale of the solar system
to the Universe as a whole. Nonetheless, we need some way of
starting. GR has been so well tested, I think it would require a
*lot* of evidence for it to be "sacrificed."

Certainly so, I totally agree. But had you just left a bit more of the
thread's context or even better up to Bob D's reply, we are faced
with two competing alternate theories claiming excellent fit to the Riess
et al data without accelerating expansion. Purporting other merits as
well both challenge the SCM. Masreliez' FRW solution is based on
GR, while Suntola's is not. Which means that Suntola has to stand up
to acount for GR's direct achievments as well.

The equations for the evolution of the Universe depend upon certain
parameters e.g., the Hubble constant and the cosmological constant.
With our current state of knowledge, we cannot derive these ab inito;
they must be measured. As measured values, their quoted values should
always be seen as tentative. Additional data certainly has the
possibility of changing what we think their current values to be. I
don't think this is in any way "sacrificing" standard cosmology to say
that new data have become available.

A quick glance att Suntola´s web page doesn't give a clue to how he
treates the the cosmological "constant", but Masreliez has chosen a
fixed value = 3H^2.

/Kurt

[This is perhaps more history of astronomy than discussion of modern
astronomy, so with the indulgence of the moderator....]
"PH" == Phillip Helbig---remove CLOTHES to reply writes:

PH I think it is important to realise that the Copernican Revolution
PH (nice pun, by the way) is NOT typical of how progress in science
PH takes place, at least not since the time of Galileo or, at the
PH latest, Newton. It's not usually a case of a new paradigm
PH replacing an old one, but rather a more general paradigm replacing
PH a less general one.

While generally true, it's also important to recognize that the
Copernican Revolution only looks revolutionary after 400 years. I'm
in the midst of a fascinating book, _Sun in the Church_, that
describes at least part of the process by which the Copernican
cosmology supplanted the Ptolemaic. It was by no means as
straightforward as usually presented. Part of it was the influence of
the Church, but Tycho Brahe had also developed his own cosmology and
there were heated arguments about whether a Ptolemaic or Brahian or
Copernican cosmology (or even some mixed version of two of these) fit
the observations better.

--
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In article , Joseph Lazio
writes:

While generally true, it's also important to recognize that the
Copernican Revolution only looks revolutionary after 400 years. I'm
in the midst of a fascinating book, _Sun in the Church_, that
describes at least part of the process by which the Copernican
cosmology supplanted the Ptolemaic. It was by no means as
straightforward as usually presented. Part of it was the influence of
the Church, but Tycho Brahe had also developed his own cosmology and
there were heated arguments about whether a Ptolemaic or Brahian or
Copernican cosmology (or even some mixed version of two of these) fit
the observations better.

Two points. First, I think that the original Copernican theory
(circular orbits) fit the observations LESS WELL than the Ptolemaic
theory with all its epicycles (a good example of Fourier
analysis/synthesis in practice). However, most people would say that
Copernicus was still "more right" than Ptolemy, so fitting the
observations isn't everything. (A model in which the Earth is enclosed
in a sphere and the planets are just projections, like in a planetarium,
moving according to a detailed table, would fit the observations in some
sense, but would not be very real.) Second, there is a common
perception that Tycho developed his theory beccause he couldn't fully
accept the Copernican view. Actually, he developed it because he didn't
know wave optics. (He assumed that the apparent angular size of stars,
about one minute of arc, indicated that they were about 30 times farther
away than the Sun (and intrinsically much dimmer, of course) and deduced
(correctly) that at this distance, he should see aberration, which he
didn't. We now know, of course, that the apparent angular size of stars
is determined by the size of our pupil etc and that the apparent
brightness of stars is a better estimate of their distance than their
apparent angular size (to the unaided eye).)