New problems for current cosmology

In article ,
Robert L. Oldershaw wrote:
Ok. When theorists tell us what happened within the first 10^-30
sec after the Big Bang, are they talking science, or are they talking
something else. Does any modeling of what went on before recombination
qualify as science? If so, where exactly is the line between
untestable speculation and testable science?

Of course they're talking science. We have ample evidence that the
universe was hotter, denser and younger in the past, that galaxies and
the CMB evolve, and so on. One can take the laws of physics known in
the lab and say: what happens if we run the theory governing the
evolution of the universe back from the current observational limits?
What does that predict for the properties of the universe now? If the
answer is that it predicts something that is not observed, something
is wrong with the observations or the theory (either the local laws of
physics don't apply or you are not doing the extrapolation correctly)
and that is telling you something. Big Bang nucleosynthesis is a good
example of this; there's no way of directly observing it happening but
it must have done so if the BB model is correct, and the theoretical
predictions for primordial elemental abundances agree well (on the
whole) with reality, suggesting that (a) we understand the relevant
local laws of physics and (b) the extrapolation to those times works
well. Clearly as one extrapolates to earlier and earlier times there
comes a point where we don't actually know the relevant fundamental
physics very well from terrestrial observations, but it's still
interesting to think about, because you might find that certain
classes of model make predictions (say, 'the universe contains no
matter') which are clearly at variance with observation, and then you
have constrained fundamental physics without having to carry out an
experiment at the required energy.

Well.... don't other readers have thoughts on this question? I would
really like to hear from people who accept the something-from-nothing
beginning of the whole shebang. Surely these people are out there
because it is the prevailing story one reads in Nature, Sci Amer.,
NYT, ..., and from all the luminaries who are dutifully quoted in
the media.

The sensible position, supported by the observations of the CMBR, of
BBN and of the evolution of galaxies, is that the Universe went
through a phase where all matter contained in the currently observable
universe was extremely hot and dense and has been evolving from those
initial conditions ever since. There is not, and I think there is
never likely to be, any evidence to say for sure what happened before
that. Whether it all sprang into being ex nihilo or not is therefore
not a scientific question, so it's not one I personally lose any sleep
over.

(Note that people who say 'The universe *began* in the Big Bang' or
'*began* in a phase where all matter was extremely hot and dense' are
simply using a definition of 'began' to mean 'for practical purposes,
began' rather than taking a side on this question. Creation ex nihilo
is not assumed.)

Martin
--
Martin Hardcastle
School of Physics, Astronomy and Mathematics, University of Hertfordshire, UK
Please replace the xxx.xxx.xxx in the header with herts.ac.uk to mail me

Le 28/09/2015 05:10, Jos Bergervoet a écrit :
Well, at least the "soup of subatomic particles" phase did not
take too much of the total time in this process, I would expect.

In another message (in this same thread) I calculated that the CMB is
too hot for star formation until z=20 at least, i.e. 180 million years.
Since we already see galaxies at z=11 that leaves around 240 million
years to form a galaxy so big that we can see it through
13.2 billion years!!!

But this is no problem for BB theory OF COURSE!

To see the problem please read:
arXiv:1506.01377v1 [astro-ph.GA] 3 Jun 2015
THE IMPOSSIBLY EARLY GALAXY PROBLEM

The authors try to justify BB theory for galaxies up to z=8. Now, with
galaxies at z=11 the justifications falls down, but it is a good
introduction to the problem you do not want to see.


[[Mod. note -- I'm not confident that we understand star formation today,
never mind star formation in the early universe, well enough to rule out
stars forming before z=20. I am fairly confident that as of today, we
have precisely zero (published) observations of star formation at z15
(for example).
-- jt]]

In article ,
jacobnavia writes:
arXiv:1506.01377v1 [astro-ph.GA] 3 Jun 2015
THE IMPOSSIBLY EARLY GALAXY PROBLEM

A key phrase in the Abstract is "if halo mass to stellar mass ratios
estimated at lower-redshift continue to $z \sim 6-8$...." That's
certainly a reasonable assumption to start exploring, but I don't see
why anyone would be surprised if it turns out to be false. I've
mentioned
http://xxx.lanl.gov/abs/1504.00005
here before.

[[Mod. note -- lanl.gov urls for the arxiv have been obselete for
many years now. The current url is
http://arxiv.org/abs/1504.00005
and the paper is
Finkelstein et al,
"An Increasing Stellar Baryon Fraction in Bright Galaxies at High Redshift"
-- jt]]

--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA

[[Mod. note -- I have manually rewrapped over-long lines. -- jt]]

On 10/4/15 10/4/15 12:08 PM, jacobnavia wrote:
In another message (in this same thread) I calculated that the CMB is
too hot for star formation until z=20 at least, i.e. 180 million years.
Since we already see galaxies at z=11 that leaves around 240 million
years to form a galaxy so big that we can see it through
13.2 billion years!!!

But this is no problem for BB theory OF COURSE!

To see the problem please read:
arXiv:1506.01377v1 [astro-ph.GA] 3 Jun 2015
THE IMPOSSIBLY EARLY GALAXY PROBLEM

The authors try to justify BB theory for galaxies up to z=8. Now, with
galaxies at z=11 the justifications falls down, but it is a good
introduction to the problem you do not want to see.


[[Mod. note -- I'm not confident that we understand star formation today,
never mind star formation in the early universe, well enough to rule out
stars forming before z=20. I am fairly confident that as of today, we
have precisely zero (published) observations of star formation at z15
(for example).
-- jt]]

Is there an implicit assumption that galaxies are formed by stars?

It seems to me that galaxies are formed by mass, and aggregation
on the galactic scale can proceed even while the gas that will form
the stars has not yet done so.


Tom Roberts

On Thursday, October 8, 2015 at 11:17:17 AM UTC-6, Tom Roberts wrote:

[[Mod. note -- I have manually rewrapped over-long lines. -- jt]]

On 10/4/15 10/4/15 12:08 PM, jacobnavia wrote:

In another message (in this same thread) I calculated that the CMB is
too hot for star formation until z=20 at least, i.e. 180 million years.
Since we already see galaxies at z=11 that leaves around 240 million
years to form a galaxy so big that we can see it through
13.2 billion years!!!

But this is no problem for BB theory OF COURSE!

To see the problem please read:
arXiv:1506.01377v1 [astro-ph.GA] 3 Jun 2015
THE IMPOSSIBLY EARLY GALAXY PROBLEM

The authors try to justify BB theory for galaxies up to z=8. Now, with
galaxies at z=11 the justifications falls down, but it is a good
introduction to the problem you do not want to see.


[[Mod. note -- I'm not confident that we understand star formation today,
never mind star formation in the early universe, well enough to rule out
stars forming before z=20. I am fairly confident that as of today, we
have precisely zero (published) observations of star formation at z15
(for example).
-- jt]]

Is there an implicit assumption that galaxies are formed by stars?

It seems to me that galaxies are formed by mass, and aggregation
on the galactic scale can proceed even while the gas that will form
the stars has not yet done so.


Tom Roberts

It appears that the Milky Way is about 9 Gyr old, but there are a few stars
within it that are much older:

http://phys.org/news/2007-05-galacti...ion-years.html

http://www.cnn.com/2014/02/12/world/...tar/index.html

http://adsabs.harvard.edu/abs/2013ApJ...765L..12B

So some stars must have formed before galaxies. It appears that our
galaxy grew from older star formations, but its original structure
(as well as those it ate) may well have formed from an accretion disk.

Gary

Le 08/10/2015 19:17, Tom Roberts a écrit :
Is there an implicit assumption that galaxies are formed by stars?

It seems to me that galaxies are formed by mass, and aggregation
on the galactic scale can proceed even while the gas that will form
the stars has not yet done so.

1) Galaxies are formed by mass. We agree on that.

2) To be able to see a galaxy it must SHINE. I hope we agree with that too.

3) To be able to shine, a galaxy must have stars.

So, if we see a galaxy at z=11, 420 Million years after the supposed big
bang, that galaxy must shine, and shine considerably, since we are able
to see it 13.200 million light years away...

So, if that galaxy exists with so many stars that it can shine through
all that distance it must have started to make stars EARLIER.

If the CMB in the first 180 million years is too hot to form stars, (CMB
temperature is bigger than 50 kelvins) that leaves 420-180 --240
million years to build that galaxy.

You can start arguing that in those times stars would form somehow
anyway at 100 million years after the supposed bang or even earlier,
that makes you gain very little. Instead opf 240 Million years you could
have 340, what is actually almost the same at this scales.

On 10/11/15 4:39 PM, jacobnavia wrote:
Le 08/10/2015 19:17, Tom Roberts a écrit :
Is there an implicit assumption that galaxies are formed by stars?

It seems to me that galaxies are formed by mass, and aggregation
on the galactic scale can proceed even while the gas that will form
the stars has not yet done so.

1) Galaxies are formed by mass. We agree on that.

2) To be able to see a galaxy it must SHINE. I hope we agree with that too.

3) To be able to shine, a galaxy must have stars.

So, if we see a galaxy at z=11, 420 Million years after the supposed big
bang, that galaxy must shine, and shine considerably, since we are able
to see it 13.200 million light years away...

So, if that galaxy exists with so many stars that it can shine through
all that distance it must have started to make stars EARLIER.

If the CMB in the first 180 million years is too hot to form stars, (CMB
temperature is bigger than 50 kelvins) that leaves 420-180 --240
million years to build that galaxy.

You can start arguing that in those times stars would form somehow
anyway at 100 million years after the supposed bang or even earlier,
that makes you gain very little. Instead opf 240 Million years you could
have 340, what is actually almost the same at this scales.

Logic dictates the possibility of a much colder phase than CMBR
thermally distinct from CMBR
as the source medium for galactic formation.

On 10/8/2015 12:17 PM, Tom Roberts wrote:
[[Mod. note -- I have manually rewrapped over-long lines. -- jt]]

On 10/4/15 10/4/15 12:08 PM, jacobnavia wrote:
In another message (in this same thread) I calculated that the CMB is
too hot for star formation until z=20 at least, i.e. 180 million years.
Since we already see galaxies at z=11 that leaves around 240 million
years to form a galaxy so big that we can see it through
13.2 billion years!!!

But this is no problem for BB theory OF COURSE!

To see the problem please read:
arXiv:1506.01377v1 [astro-ph.GA] 3 Jun 2015
THE IMPOSSIBLY EARLY GALAXY PROBLEM

The authors try to justify BB theory for galaxies up to z=8. Now, with
galaxies at z=11 the justifications falls down, but it is a good
introduction to the problem you do not want to see.


[[Mod. note -- I'm not confident that we understand star formation today,
never mind star formation in the early universe, well enough to rule out
stars forming before z=20. I am fairly confident that as of today, we
have precisely zero (published) observations of star formation at z15
(for example).
-- jt]]

Is there an implicit assumption that galaxies are formed by stars?

It seems to me that galaxies are formed by mass, and aggregation
on the galactic scale can proceed even while the gas that will form
the stars has not yet done so.


Tom Roberts

There appears to be some debate about which came first in galaxy
formation ... the super massive black hole or the stars that form the
structures we see today.

If, in fact, the black holes came first then, it seems to me, the first
galactic light would come from the accretion disk and not from stars. A
quasar shining through the mass that will eventually form the stars of
the galaxy. I'm not sure how visible that would be from here now but I
can see how that might initiate a bulge forming starburst very quickly.

Le 13/10/2015 06:32, Richard D. Saam a écrit :
Logic dictates the possibility of a much colder phase than CMBR
thermally distinct from CMBR
as the source medium for galactic formation.


I have turned this sentence in many ways but I can still not make much
sense of it, sorry.

How can a colder phase exist if the CMBR is by definition coming from
all directions of space? How can this colder phase insulate itself from
the CMBR radiation?

Note that after the supposed bang there shouldn't be any dust around
that could shield a portion of the universe from the CMBR. The
condensation of the very first stars must have happened without the
protection of dust clouds that cool the gas and favor condensation into
stars.

[[Mod. note -- I think the whole topic of a "much colder phase than the
CMBR" falls under our newsgroup charter's prohibition on "excessively
speculative" material, and henceforth I'm going to apply that prohibition
rather more strictly than I have in the recent past. In particular,
unless there are new and not-excessively-speculative ideas or data
introduced, I think this posting is a good place to end the discussion
of this topic.
-- jt]]