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Good News for Big Bang theory



 
 
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  #21  
Old October 19th 06, 09:03 AM posted to sci.astro.research
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Default Good News for Big Bang theory

Phillip Helbig---remove CLOTHES to reply wrote:
In article ,
" writes:



So we have agreement on several important issues, but some remaining
differences, as discussed below.


There is an ongoing debate over whether the very large-scale distribution of galaxies is fractal,
or goes over into a homogeneous distribution.


It is ongoing, but not in serious circles. There IS a scale above which
there is large-scale homogeneity.


"Serious" cosmologists can say that as many times as they like, but it
is still a matter of faith, and I use that term literally. What
scientific proof do you offer for your claim of homogeneity? The
microwave background used to be the best supporting evidence, but many
strange anomalies (recently the possibility of a quadrupole anisotropy)
and correlations with the Solar System's ecliptic, etc. have clearly
shown that we probably have much more to learn about the large-scale
structure of the observable universe? As scientists, we need be sure
that the evidence is unambiguous before we declare an issue closed.


Ok, but quite simply: is there some prediction or test by which the
new, and heavily reworked, modified, adjusted, Big Bang paradigm can be
falsified, or does the present incarnation of the Big Bang paradigm not
meet Popper's criterion for science?


Certainly. But you have to define exactly what you mean first. Second,
it is a widespread misconception that disproving one aspect of a theory
also disproves the foundations. That is not necessarily the case.


Please show me at least one definitive prediction, by which we might
put the Big Bang paradigm to a rigorous, quantitative scientific test.
  #22  
Old October 19th 06, 09:04 AM posted to sci.astro.research
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Default Good News for Big Bang theory

wrote:
Phillip Helbig---remove CLOTHES to reply wrote:


Prediction, prior observation, prediction, assumption later verified by
observation.


By my accounting this list should read:


1. Background Radiation: prediction, but initially off by about 400%
and had to be adjusted to come into agreement with observations.


Your 400% seems way off -- Alpher and Herman's 1948 prediction was "about 5K."
Furthermore, you're not quite asking the right question. CMBR temperature
varies with time, so to predict the value "now" you need to know when "now"
is, relative to, say, primordial nucleosynthesis. Alpher and Herman used
(baryonic) matter density as a proxy for this, and got the correct relation;
their error in the exact value came from an imprecise knowledge of the
present matter density.

Remember also that the prediction was not just a temperature, but a spectrum.
Black body spectra are hard to make (since temperatures of different sources
get different red shifts); the observation of not only the temperature but
the spectrum is a very strong confirmation.

2. Global expansion: agreed, this was prior knowledge.


3. Abundances of light elements: definitely not predicted! We had good
approximate abundances prior to any BB paradigm.


Joseph Lazio has addressed this.

You shouls also add a number of other predictions:

-- red shift dependence of CMBR temperature (for observations, well after the
predictions, see Battistelli et al., astro-ph/0208027; Srianand et al.,
astro-ph/0012222; Molaro et al., astro-ph/0111589)

-- Tolman surface brightness test (predicted by Tolman in 1930; observed by
Lubin and Sandage, astro-ph/0106566)

-- time dilation of supernova light curves (predicted by Wilson, Ap. J. 90
(1939) 634; for observations, see Goldhaber et al., astro-ph/0104382)

-- three (and no more) light neutrinos (predicted by Yang et al., Ap. J. 227
(1979) 697; confirmed in accelerator experiments later -- see, e.g., ALEPH
Collaboration, Phys. Lett. B235 (1990) 399)

Steve Carlip
  #23  
Old October 19th 06, 12:55 PM posted to sci.astro.research
Oh No
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Posts: 433
Default Good News for Big Bang theory

Thus spake "
Phillip Helbig---remove CLOTHES to reply wrote:
In article ,
" writes:


. What
scientific proof do you offer for your claim of homogeneity? The
microwave background used to be the best supporting evidence, but many
strange anomalies (recently the possibility of a quadrupole anisotropy)
and correlations with the Solar System's ecliptic, etc. have clearly
shown that we probably have much more to learn about the large-scale
structure of the observable universe? As scientists, we need be sure
that the evidence is unambiguous before we declare an issue closed.


The large scale distribution of galaxy clusters is also observed to be
extremely homogeneous. But actually, what would be really difficult is
justifying the formulation of a theory which did not obey the
cosmological principle.

Ok, but quite simply: is there some prediction or test by which the
new, and heavily reworked, modified, adjusted, Big Bang paradigm can be
falsified, or does the present incarnation of the Big Bang paradigm not
meet Popper's criterion for science?


Certainly. But you have to define exactly what you mean first. Second,
it is a widespread misconception that disproving one aspect of a theory
also disproves the foundations. That is not necessarily the case.


Please show me at least one definitive prediction, by which we might
put the Big Bang paradigm to a rigorous, quantitative scientific test.


I think, notwithstanding possible anomalies, the microwave background is
such a test. It's overall character is well established and in
accordance with a big bang. Only some of the detail may need attention.

Another is the proton-neutron balance. This can be precisely calculated
as a product of big bang nuclear synthesis, and depends quite critically
on Hubble's constant. Observation and prediction fit extremely well.

But there are simpler and more obvious ones. Without a big bang we would
be caught up in Olber's paradox.

A big bang is the most natural solution of Einstein's field equation
(the same is actually true in Newtonian gravity). The fact that
scientists, including Einstein himself, did not tend to adopt a big bang
model had to do with theoretical prejudice, and had nothing to do with
whether cosmological expansion was a prediction of the model. It was
only when a prediction of the model was observed by Hubble, that the
model started to be adopted.

Einstein's theory of general relativity has also been put to a number of
rigorous experimental tests, and has passed all of them while
alternative models have failed. One must accept that any model must form
a self consistent mathematical whole. One cannot accept parts of it and
then accept other things which are mathematically inconsistent. It seems
to me that any scientific model must satisfy this criterion even before
one applies observational tests. In that regard, a big bang obeying
general relativity has no serious competitors. One can hardly say this
is not the result of rigorous scientific quantititive testing.




Regards

--
Charles Francis
substitute charles for NotI to email
  #25  
Old October 19th 06, 12:57 PM posted to sci.astro.research
John (Liberty) Bell
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Posts: 242
Default Good News for Big Bang theory

I think I would like to respond at this point, not because I am
challenging anybody, but because I don't know enough about this
subject, and hope that, by asking some questions (pertinent or
otherwise), the resultant responses will improve my own level of
understanding.

wrote:
wrote:
Phillip Helbig---remove CLOTHES to reply wrote:


Prediction, prior observation, prediction, assumption later verified by
observation.


By my accounting this list should read:


1. Background Radiation: prediction, but initially off by about 400%
and had to be adjusted to come into agreement with observations.


Your 400% seems way off -- Alpher and Herman's 1948 prediction was "about 5K."


The figure I seem to remember was a factor of 3 difference, but I
certainly couldn't quote references after all this time. I would guess
from the above that various people had a stab at this calculation, with
differing results. If so, cherry picking the best, after the fact,
would seem to be no more logical than cherry picking the worst.

Furthermore, you're not quite asking the right question. CMBR temperature
varies with time, so to predict the value "now" you need to know when "now"
is,


I don't think anyone could argue with that.

relative to, say, primordial nucleosynthesis.


Clarification here would be appreciated. I was under the impression
that CMBR is black body radiation at the transition from plasma physics
to the point where protons and electrons combine to form atomic
hydrogen, thus indicating the temperature at which this transition is
believed to take place.

Remember also that the prediction was not just a temperature, but a spectrum.
Black body spectra are hard to make (since temperatures of different sources
get different red shifts);


Hmm. Black body radiation is black body radiation, isn't it?. Different
elements give different spectra because of bound electron transitions.
Any plasma should give the same BB spectrum (with the peak intensity
defining the temperature of that plasma).

the observation of not only the temperature but
the spectrum is a very strong confirmation.


Surely observed intensity is at least as important?

You shouls also add a number of other predictions:


-- red shift dependence of CMBR temperature (for observations, well after the
predictions, see Battistelli et al., astro-ph/0208027; Srianand et al.,
astro-ph/0012222; Molaro et al., astro-ph/0111589)


Yes, that certainly confirms global expansion (which I don't think
anybody doubts). However, I dont see how this necessarily nails things
down any more precisely. Take, for example, Oh No's theory (which I am
definitely not claiming to support). In this you should still get such
changing T with changing z despite the timescales being radically
different.


John Bell
(Change John to Liberty to bypass anti-spam email filter)
  #26  
Old October 20th 06, 05:43 PM posted to sci.astro.research
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Posts: 40
Default Good News for Big Bang theory

"John (Liberty) Bell" wrote:
[...]

wrote:
wrote:
Phillip Helbig---remove CLOTHES to reply wrote:


Prediction, prior observation, prediction, assumption later
verified by observation.


By my accounting this list should read:


1. Background Radiation: prediction, but initially off by about 400%
and had to be adjusted to come into agreement with observations.


Your 400% seems way off -- Alpher and Herman's 1948 prediction was
"about 5K."


The figure I seem to remember was a factor of 3 difference, but I
certainly couldn't quote references after all this time. I would guess
from the above that various people had a stab at this calculation, with
differing results. If so, cherry picking the best, after the fact,
would seem to be no more logical than cherry picking the worst.


Alpher and Herman's 1948 Nature paper was, I believe, the first to make a
prediction. There was some variation after that, but it came from lack of
a good observational value for the present density of the universe (and
probably also from the fact that people were making order-of-magnitude
estimates of a quantity they didn't expect to be observable).

Furthermore, you're not quite asking the right question. CMBR temperature
varies with time, so to predict the value "now" you need to know when "now"
is,


I don't think anyone could argue with that.


relative to, say, primordial nucleosynthesis.


Clarification here would be appreciated. I was under the impression
that CMBR is black body radiation at the transition from plasma physics
to the point where protons and electrons combine to form atomic
hydrogen, thus indicating the temperature at which this transition is
believed to take place.


Right, but not relevant to the present issue. To compare a past value
to a present one, we need to be able to compare two independent quantities,
one to relate the times and the other to allow a prediction of temperatures.
At recombination, we know the temperature (from the ionization energy of
hydrogen), but don't know anything obvious that would tell us the time
between then and now. At primordial nucleosynthesis, though, we know both
the temperature and the baryon density. So we can start then, predict the
evolution of both temperature and density until recombination (which then
gives us a density at recombination), and then compare the density at
recombination to density now to calibrate the time.

Remember also that the prediction was not just a temperature, but a
spectrum. Black body spectra are hard to make (since temperatures of
different sources get different red shifts);


Hmm. Black body radiation is black body radiation, isn't it?


Black body radiation at a given temperature is all the same. But if you
combine two black body spectra at different temperatures, the result is
not a black body spectrum at some intermediate temperature -- it's not
black body at all. Observation of a uniform black body spectrum means
either that the universe was once a black body at a uniform temperature,
or that some huge series of implausible coincidences somehow combined a
bunch of different spectra to mimic a black body.

Steve Carlip
  #27  
Old October 20th 06, 05:43 PM posted to sci.astro.research
John (Liberty) Bell
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Posts: 242
Default Good News for Big Bang theory

I find myself largely agreeing with Oh No here, except for the
following paragraph.

Oh No wrote:
A big bang is the most natural solution of Einstein's field equation
(the same is actually true in Newtonian gravity).


I think you must mean gtr. EFE (as first published) contained a
cosmological constant for the explicit purpose of preventing any such
global geometrical dynamism.

The fact that
scientists, including Einstein himself, did not tend to adopt a big bang
model had to do with theoretical prejudice,


That is unfair. Every generation is a product of its educational
background. In Einstein's case that was in the 19th century, when the
thermodynamics of steam engines was still the 'state-of-the-art' in the
technological application pure physical principles.

Einstein supressed global geometrical dynamism within his mathematical
apparatus, in order to produce a general theory of relativity which was
consistent with the then known facts about the universe.

If that is prejudice, then we are certainly still guilty of it now.

Perhaps we would all be a little wiser if we learned from the lessons
of history, by recognising that nothing ever really changes, in that
respect.

John Bell
(Change John to Liberty to bypass anti-spam email filter)
  #28  
Old October 20th 06, 05:45 PM posted to sci.astro.research
Oh No
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Posts: 433
Default Good News for Big Bang theory

Thus spake "John (Liberty) Bell"
-- red shift dependence of CMBR temperature (for observations, well after the
predictions, see Battistelli et al., astro-ph/0208027; Srianand et al.,
astro-ph/0012222; Molaro et al., astro-ph/0111589)


Yes, that certainly confirms global expansion (which I don't think
anybody doubts). However, I dont see how this necessarily nails things
down any more precisely. Take, for example, Oh No's theory (which I am
definitely not claiming to support). In this you should still get such
changing T with changing z despite the timescales being radically
different.


In fact my proposal only affects quantum phenomena for which, by
definition, continuous observation is not possible, and for which,
incidentally, there is not an alternative existing theory. It gives
classical general relativity in the classical correspondence.
The cosmic microwave background is continuously observable, so it must
be treated classically and obeys the same redshift relationship as found
in the standard model.


Regards

--
Charles Francis
substitute charles for NotI to email
  #29  
Old October 20th 06, 05:45 PM posted to sci.astro.research
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Posts: 110
Default Good News for Big Bang theory

wrote:

Remember also that the prediction was not just a temperature, but a spectrum.
Black body spectra are hard to make (since temperatures of different sources
get different red shifts); the observation of not only the temperature but
the spectrum is a very strong confirmation.


This a good and important point. It is a crucial fact about nature,
and verfies that the BB paradigm offers a good approximation for what
is going on in the local Hubble Bubble. I regard the prediction of the
black-body spectrum and approximate temperature of the microwave
background as the best evidence for the BB approximation. I do not
accept that this means that it had to be the whole Universe that went
"pop!", or that even within the Hubble Bubble the physics is quite as
idealized as standard cosmology would have it.

Parenthetically, I have always been fascinated with the speculation
that the background radiation might be a result of the Unruh effect in
QFT, which causes an accelerated observer to observe an isotropic
black-body thermal "bath". See Schultzhold et al, PRL, 97, 121302,
2006. Low acceleration gives a low temperature.
This is a pretty far out idea, but one I am pursuing just for the fun
of it.


You shouls also add a number of other predictions:

-- red shift dependence of CMBR temperature (for observations, well after the
predictions, see Battistelli et al., astro-ph/0208027; Srianand et al.,
astro-ph/0012222; Molaro et al., astro-ph/0111589)

-- Tolman surface brightness test (predicted by Tolman in 1930; observed by
Lubin and Sandage, astro-ph/0106566)

-- time dilation of supernova light curves (predicted by Wilson, Ap. J. 90
(1939) 634; for observations, see Goldhaber et al., astro-ph/0104382)

-- three (and no more) light neutrinos (predicted by Yang et al., Ap. J. 227
(1979) 697; confirmed in accelerator experiments later -- see, e.g., ALEPH
Collaboration, Phys. Lett. B235 (1990) 399)

Ok, but again, the first 3 just verify global expansion within the
Hubble Bubble, and do not say anything more. Personally, I have to
admit that I treat many high-energy results with a wait-and-see
approach because of the numerous false "positives", the complexity of
what they are trying to do (Feyman's: 'It's like smashing two clocks
together, and from what falls out,...) and subtle but severe pressures
to get the "right" answers.

At any rate, let us see a prediction by the BB paradigm about something
that is currently unknown, but knowable in the foreseeable future. Can
the BB paradigm do this, or not?

Rob
  #30  
Old October 20th 06, 05:45 PM posted to sci.astro.research
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Default Good News for Big Bang theory

Phillip Helbig---remove CLOTHES to reply wrote:

Indeed. All the research on CMB inhomogeneities (and there is a lot of
research to do) has obscured two Very Important Facts in the popular
mind: the black-body spectrum, as Steve mentioned, and the fact that the
signal is very homogeneous. The latter doesn't just mean that the
inhomogeneities are small, but is in itself very important.


I agree that within the local Hubble Bubble the CMB is approximately
"homogeneous", but then there are the dipole, quadrupole and octopole
anisotropies. The difference between the Newtonian and GR predictions
for the precession of the perihelion of Mercury was "small" too. The
devil is sometimes in those "small" details, no?

Also, does the distribution of matter look homogeneous, with all those
very much unpredicted sheets, filaments and voids? I might go along
with a claim of statistical homogeneity, but claims of a more
idealized, literal homogeneity seem to me to be in conflict with
accepted observations.

Rob
 




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