Cosmic acceleration (from back-reaction)

melroysoares@hotmail.com

I am surprised that there has not been even a single post on this forum
even though this eems
to be the hottest topic in gr-qc over the past one year. for those who
came late, the set of papers
I am talking about is
http://cosmocoffee.info/viewtopic.php?t=218
starting from Kolb et al's . Since this paper there have been many
claims and counter-claims.
Would people on this like to add to that whether they think that this
mechanism for cosmic acceleration is feasible.
Inetersted to hear your thoughts and opnions.

Phillip Helbig---remove CLOTHES to reply

In article <1147646225.945339.82670@j55g2000cwa.googlegroups.com>,
melroysoares@hotmail.com writes:

> I am surprised that there has not been even a single post on this forum
> even though this seems
> to be the hottest topic in gr-qc over the past one year. for those who
> came late, the set of papers
> I am talking about is
> http://cosmocoffee.info/viewtopic.php?t=218
> starting from Kolb et al's . Since this paper there have been many
> claims and counter-claims.
> Would people on this like to add to that whether they think that this
> mechanism for cosmic acceleration is feasible.
> Inetersted to hear your thoughts and opnions.

See the comments (and references to papers refuting the claim) at

http://www.astro.ucla.edu/~wright/cosmolog.htm

In particular, "This could be a case where the effects of good Italian
wine overwhelmed the scientific super-ego of Kolb et al.".

As I mentioned, Wright cites some papers refuting the claim.

Of course, the claim has to be addressed on its own terms, but in
deciding how to spend our precious time, we have to take into account
whether the authors have an axe to grind. Kolb definitely does.

Omega = Omega_matter in what follows.

About 8 years ago at a Moriond conference on cosmological parameters,
Kolb and Ray Carlberg both gave concluding remarks. This was around the
time when even theorists started realising that the observational
evidence for Omega < 1 is overwhelming. Carlberg gave an honest
assessment of how, though (for whatever reason) he would have liked to
believe that Omega = 1, observations showed otherwise. Kolb was more
"Omega = 1, next question". Extremely arrogant. (The published version
in the proceedings tones down his remarks somewhat.)

He's been dead long enough that we can criticise him. Check out the
arrogance of Schramm in Dennis Overbye's book LONELY HEARTS IN THE
COSMOS where Schramm criticises a student for even considering Omega < 1
in some numerical simulations. "You are thinking like an astronomer and
not like a physicist" was his scathing commentary. Kolb operates in the
same manner. (Note that Schramm wrote a famous paper, together with
Gott, Gunn and Tinsley, not only saying that observations support
Omega=1, but also promoting an unbiased look at the data. But that was
at the beginning of the 1970s, before inflation reared its head.)

It seems to me that Kolb is clutching at straws here in order to try to
save face. There is of course nothing wrong in revising one's opinion
in the face of better data (see Carlberg), but of course it is more
difficult if, as in the case of Kolb, his opinion was always presented
with a "holier than thou" attitude.

Don't get me wrong---Rocky Kolb is an entertaining speaker, a nice guy
and has done some good work. But I think he has been too confident
about things which are not certain (nor even agreed on within the
community), which is a) in itself not good and b) adds fuel to the fire
of those who think that observations can falsify an entire paradigm,
when in practice they only refine what has gone before. (Copernicus is
a bad example, since the previous paradigm was supported by torture, not
by science.)

Jim Peebles, by contrast, has also played with various non-orthodox
scenarios (often to have Omega=Omega_baryon), but in his case my feeling
is that he plays devil's advocate and that such things do much more harm
than good. Of course, this is supported by the fact that his
alternative scenarios don't always have the same goal. And he's not
arrogant about it.

Phillip Helbig---remove CLOTHES to reply

In article <1147646225.945339.82670@j55g2000cwa.googlegroups.com>,
melroysoares@hotmail.com writes:

> I am surprised that there has not been even a single post on this forum
> even though this seems
> to be the hottest topic in gr-qc over the past one year. for those who
> came late, the set of papers
> I am talking about is
> http://cosmocoffee.info/viewtopic.php?t=218
> starting from Kolb et al's . Since this paper there have been many
> claims and counter-claims.
> Would people on this like to add to that whether they think that this
> mechanism for cosmic acceleration is feasible.
> Inetersted to hear your thoughts and opnions.

See the comments (and references to papers refuting the claim) at

http://www.astro.ucla.edu/~wright/cosmolog.htm

In particular, "This could be a case where the effects of good Italian
wine overwhelmed the scientific super-ego of Kolb et al.".

As I mentioned, Wright cites some papers refuting the claim.

Of course, the claim has to be addressed on its own terms, but in
deciding how to spend our precious time, we have to take into account
whether the authors have an axe to grind. Kolb definitely does.

Omega = Omega_matter in what follows.

About 8 years ago at a Moriond conference on cosmological parameters,
Kolb and Ray Carlberg both gave concluding remarks. This was around the
time when even theorists started realising that the observational
evidence for Omega < 1 is overwhelming. Carlberg gave an honest
assessment of how, though (for whatever reason) he would have liked to
believe that Omega = 1, observations showed otherwise. Kolb was more
"Omega = 1, next question". Extremely arrogant. (The published version
in the proceedings tones down his remarks somewhat.)

He's been dead long enough that we can criticise him. Check out the
arrogance of Schramm in Dennis Overbye's book LONELY HEARTS IN THE
COSMOS where Schramm criticises a student for even considering Omega < 1
in some numerical simulations. "You are thinking like an astronomer and
not like a physicist" was his scathing commentary. Kolb operates in the
same manner. (Note that Schramm wrote a famous paper, together with
Gott, Gunn and Tinsley, not only saying that observations support
Omega=1, but also promoting an unbiased look at the data. But that was
at the beginning of the 1970s, before inflation reared its head.)

It seems to me that Kolb is clutching at straws here in order to try to
save face. There is of course nothing wrong in revising one's opinion
in the face of better data (see Carlberg), but of course it is more
difficult if, as in the case of Kolb, his opinion was always presented
with a "holier than thou" attitude.

Don't get me wrong---Rocky Kolb is an entertaining speaker, a nice guy
and has done some good work. But I think he has been too confident
about things which are not certain (nor even agreed on within the
community), which is a) in itself not good and b) adds fuel to the fire
of those who think that observations can falsify an entire paradigm,
when in practice they only refine what has gone before. (Copernicus is
a bad example, since the previous paradigm was supported by torture, not
by science.)

Jim Peebles, by contrast, has also played with various non-orthodox
scenarios (often to have Omega=Omega_baryon), but in his case my feeling
is that he plays devil's advocate and that such things do much more harm
than good. Of course, this is supported by the fact that his
alternative scenarios don't always have the same goal. And he's not
arrogant about it.

John Bell

Phillip Helbig---remove CLOTHES to reply wrote:
>
> Don't get me wrong---Rocky Kolb is an entertaining speaker, a nice guy
> and has done some good work. But I think he has been too confident
> about things which are not certain (nor even agreed on within the
> community), which is a) in itself not good and b) adds fuel to the fire
> of those who think that observations can falsify an entire paradigm,
> when in practice they only refine what has gone before. (Copernicus is
> a bad example, since the previous paradigm was supported by torture, not
> by science.)
>
Whilst I would not dream of contradicting your comments about Kolb (You
obviously are much better read on this subject than me), your
Copernican comment does seem to suggest some historical inaccuracy. The
use of torture to support the geocentric theory did not start until
some 50 years or so after the death of Copernicus. If I remember
correctly, the work of Copernicus was actually encouraged during his
lifetime by the then Pope Clemence.

I would suggest that the subsequent use of torture to support the
geocentric theory was a consequence of Copernican theory being so
revolutionary when interpreted as physically meaningful, not the cause.

John Bell
http://global.accelerators.co.uk
(Change John to Liberty to respond)

Phillip Helbig---remove CLOTHES to reply

In article <1148033051.053137.61290@u72g2000cwu.googlegroups.com>, John
Bell <john.bell@accelerators.co.uk> writes:

> Copernican comment does seem to suggest some historical inaccuracy. The
> use of torture to support the geocentric theory did not start until
> some 50 years or so after the death of Copernicus. If I remember
> correctly, the work of Copernicus was actually encouraged during his
> lifetime by the then Pope Clemence.
>
> I would suggest that the subsequent use of torture to support the
> geocentric theory was a consequence of Copernican theory being so
> revolutionary when interpreted as physically meaningful, not the cause.

In one sense, of course, one can't be tortured for supporting a rival
theory unless there IS a rival theory, so torture in support of the
Copernican theory could not take place until after it had been
published. However, Copernicuus himself literally waited until his
death to have it published, certainly out of a FEAR of torture.

Heliocentric ideas had been around since the time of the ancient Greeks,
but everything which didn't fit into the digest version of Greek thought
prepared by Thomas Aquinas etc WAS subject to torture, which is probably
why it took until Copernicus to actually get something like this
published.

In any case, the point I'm trying to make is that the idea of a
"Copernican revolution" as a paradigm for how ideas change in science is
not a good idea if based on the actual Copernican revolution, since in
this case we don't have a new idea replacing an old idea as a
consequence of science as we know it today, but rather of the old idea
dying because the unscientific defenses of it became less of a problem.

John Bell

Phillip Helbig---remove CLOTHES to reply wrote:
> In article <1148033051.053137.61290@u72g2000cwu.googlegroups.com>, John
> Bell <john.bell@accelerators.co.uk> writes:
>
> > Copernican comment does seem to suggest some historical inaccuracy. The
> > use of torture to support the geocentric theory did not start until
> > some 50 years or so after the death of Copernicus. If I remember
> > correctly, the work of Copernicus was actually encouraged during his
> > lifetime by the then Pope Clemence.
> >
> > I would suggest that the subsequent use of torture to support the
> > geocentric theory was a consequence of Copernican theory being so
> > revolutionary when interpreted as physically meaningful, not the cause.
>
> In one sense, of course, one can't be tortured for supporting a rival
> theory unless there IS a rival theory,

Quite so. However, the heliocentric theory was not new when Copernicus
conceived it. It had first been thought up by the Greek philosopher
Aristarchus, some 2000 years earlier.
In fact, Copernicus was greatly relieved to discover this, since, at
the time, nothing was considered genuinely scholarly or scientific
unless it DID have a precedent in Greek philosophical literature.

> so torture in support of the
> Copernican theory could not take place until after it had been
> published.

You presumably mean here torture to support the Ptolomaic theory.

However, torture to support the Ptolomaic system was not even invoked
after Copernicus published. All I can find is a THREAT of torture to
Galileo, half a century later, after he made himself a lot of political
enemies.

> However, Copernicuus himself literally waited until his
> death to have it published, certainly out of a FEAR of torture.

I doubt this, given aforementioned Papal encouragement. He probably
waited out of fear of ridicule, rejection, and perhaps even loss of his
direct ecclesiastical means of support. However, that was also true of
Darwin (for 20 years), until he was warned that somebody else was about
to publish substantially the same theory of evolution. (The Anglican
church definitely did not threaten torture in the 19th century.)
>
> Heliocentric ideas had been around since the time of the ancient Greeks,
> but everything which didn't fit into the digest version of Greek thought
> prepared by Thomas Aquinas etc WAS subject to torture,

I am not so sure. Can you quote any specific example?
http://www.fordham.edu/halsall/source/inquisition1.html , for example
suggests that the inquisitions were primarily concerned with matters of
spiritual heresy, and, even then, were more concerned with returning
heretics to the fold. Even Galileo was not actually tortured. He was,
at worst, just threatened with torture if he did not recant. In fact,
http://www.uwgb.edu/dutchs/WestTech/evili.htm suggests that Galileo was
treated remarkably sympathetically in practice, given the overall
political situation at the time.

> In any case, the point I'm trying to make is that the idea of a
> "Copernican revolution" as a paradigm for how ideas change in science is
> not a good idea if based on the actual Copernican revolution, since in
> this case we don't have a new idea replacing an old idea as a
> consequence of science as we know it today, but rather of the old idea
> dying because the unscientific defenses of it became less of a problem.

Again I disagree. The Catholic ban on Copernicus was not revoked until
the 20th century, and this caused no real problem, from the start, in
Protestant countries (and less of a problem than one might imagine in
Italy). The initial appeal of Copernican theory was that it was more
conceptually elegant - certainly a consideration that is still
important today (or, at least, should be). It then got indirect support
from observations made with scientific instruments - still relevant
today. It finally got completely vindicated when subsumed into Newton's
universal theory of gravitation. Until then, it was probably still no
more accurate than the old Ptolomaic system, for describing planetary
motions.

Perhaps more importantly, this paradigm illustrates that there is
always a political dimension to scientific revolutions, whether overt
or hidden. Perhaps the conservatives amongst us no longer threaten
torture to promote their point of view, but there are still such things
as job security and research funding to worry about. Such
considerations only become irrelevant for advances that are
evolutionary as opposed to revolutionary. (Even with the discovery of
oxygen, phlogiston theorists remained remarkably recalcitrant until it
had been proven that phlogiston had to have both negative volume and
negative mass, as well as being lethal to all living organisms.)

John Bell
http://global.accelerators.co.uk
(Change John to Liberty to respond)

Phillip Helbig---remove CLOTHES to reply

[ Mod. note: Unless followups concern themselves with the physics of
of Galileo or others, this discussion should be wrapped up. -ik ]

In article <1148300615.447569.50350@38g2000cwa.googlegroups.com>, John
Bell <john.bell@accelerators.co.uk> writes:

> > In one sense, of course, one can't be tortured for supporting a rival
> > theory unless there IS a rival theory,
>
> Quite so. However, the heliocentric theory was not new when Copernicus
> conceived it. It had first been thought up by the Greek philosopher
> Aristarchus, some 2000 years earlier.

Yes, as I mentioned:

> > Heliocentric ideas had been around since the time of the ancient Greeks,
> > but everything which didn't fit into the digest version of Greek thought
> > prepared by Thomas Aquinas etc WAS subject to torture,

> You presumably mean here torture to support the Ptolomaic theory.

Yes.

> However, torture to support the Ptolomaic system was not even invoked
> after Copernicus published. All I can find is a THREAT of torture to
> Galileo, half a century later, after he made himself a lot of political
> enemies.

Legally, threatening someone with torture is the same as torture, at
least in many legal systems. Of course, Giordano Bruno was burned at
the stake. To what extent this was due to his belief in "other worlds"
and Copernicanism is not completely clear (at least, it isn't completely
clear to me; I'm not a historian); certainly many have suggested that
it played a roll in his downfall.

> > but everything which didn't fit into the digest version of Greek thought
> > prepared by Thomas Aquinas etc WAS subject to torture,
>
> I am not so sure. Can you quote any specific example?

I suspect the moderators might deem this tangent as not having enough
physics content. :-)

> http://www.fordham.edu/halsall/source/inquisition1.html , for example
> suggests that the inquisitions were primarily concerned with matters of
> spiritual heresy,

Of course, but in those days, much more was considered "spiritual" than
is the case today.

> and, even then, were more concerned with returning
> heretics to the fold.

Perhaps, but if so, then they failed in the many cases of documented
deaths.

> Even Galileo was not actually tortured. He was,
> at worst, just threatened with torture if he did not recant. In fact,
> http://www.uwgb.edu/dutchs/WestTech/evili.htm suggests that Galileo was
> treated remarkably sympathetically in practice, given the overall
> political situation at the time.

Of course, he got better treatment than the average heretic.

> > In any case, the point I'm trying to make is that the idea of a
> > "Copernican revolution" as a paradigm for how ideas change in science is
> > not a good idea if based on the actual Copernican revolution, since in
> > this case we don't have a new idea replacing an old idea as a
> > consequence of science as we know it today, but rather of the old idea
> > dying because the unscientific defenses of it became less of a problem.
>
> Again I disagree. The Catholic ban on Copernicus was not revoked until
> the 20th century, and this caused no real problem, from the start, in
> Protestant countries

Of course not, because the whole point of protestantism is avoiding
allegiance to the Pope. That's why Galilo published in Holland.

> (and less of a problem than one might imagine in
> Italy). The initial appeal of Copernican theory was that it was more
> conceptually elegant - certainly a consideration that is still
> important today (or, at least, should be). It then got indirect support
> from observations made with scientific instruments - still relevant
> today. It finally got completely vindicated when subsumed into Newton's
> universal theory of gravitation. Until then, it was probably still no
> more accurate than the old Ptolomaic system, for describing planetary
> motions.

Actually, it was LESS accurate, at least less accurate than the
Ptolemaic system with all the epicycles. Of course, we know today that
an arbitrary periodic motion can be described by a large enough number
of epicycles (it's called Fourier synthesis), if one ignores things like
the distance to the planet, which wasn't known then. However, it was
still a better theory, because more elegant. And, as you say, when
better observations became available, it (or, rather, it's Keplerian
variant) was confirmed. (Ptolemaic theory makes testable predictions,
such as the variation in the distance of a planet from the Earth, which
were later falsified.)

> Perhaps more importantly, this paradigm illustrates that there is
> always a political dimension to scientific revolutions, whether overt
> or hidden.

Certainly, in the past, this has been the case. Today, it is still the
case as far as the treatment of science by the outside world goes (see
the creationism debate in the USA). Within science, not any more, not
in the sense you describe...

> Perhaps the conservatives amongst us no longer threaten
> torture to promote their point of view, but there are still such things
> as job security and research funding to worry about.

...but of course whoever pays the piper calls the tune, and it IS a
political decision what research to fund etc. However, this tends to be
concerned with priorities rather than suppressing an idea for
ideological (as opposed to other) reasons.

Oh No

Thus spake Phillip Helbig---remove CLOTHES to reply <helbig@astro.multiC
LOTHESvax.de>
>> (and less of a problem than one might imagine in
>> Italy). The initial appeal of Copernican theory was that it was more
>> conceptually elegant - certainly a consideration that is still
>> important today (or, at least, should be). It then got indirect support
>> from observations made with scientific instruments - still relevant
>> today. It finally got completely vindicated when subsumed into Newton's
>> universal theory of gravitation. Until then, it was probably still no
>> more accurate than the old Ptolomaic system, for describing planetary
>> motions.
>
>Actually, it was LESS accurate, at least less accurate than the
>Ptolemaic system with all the epicycles. Of course, we know today that
>an arbitrary periodic motion can be described by a large enough number
>of epicycles (it's called Fourier synthesis), if one ignores things
>like the distance to the planet, which wasn't known then. However, it
>was still a better theory, because more elegant. And, as you say, when
>better observations became available, it (or, rather, it's Keplerian
>variant) was confirmed. (Ptolemaic theory makes testable predictions,
>such as the variation in the distance of a planet from the Earth, which
>were later falsified.)

Actually there seem to be huge myths about Copernicus. The idea that the
sun was at the centre was due to Aristarchus, and had become known to
the educated of Europe after the fall of Constantinople. Aristarchus
based his ideas firmly on observation, and estimated the ratio of the
diameter of sun and moon, (though his result was not accurate it is, I
think, the first recorded measurement of an astronomical body).
Copernicus simply reproduced a Ptolemaic system of wheels within wheels,
and had the sun not at the centre, but near it. It was no more elegant
than Ptolemy, and was really just a variant on it. His book was full of
calculations which no one wanted to read, but they wanted to believe the
sun was at the centre, so the word went out that he had "proved it".
This was probably helped by the fact that he lived so far from anyone
else that no one knew what he had proved. In fact, not a lot. Copernican
theory also made testable predictions, which were falsified by Tyho
Brahe at the same time as he falsified Ptolomeic theory. As far as I
recall, Copernicus was slightly the less accurate of the two.

Regards

--
Charles Francis
substitute charles for NotI to email