Questions about the inverse square law and dark matter

Dear Steve Willner:

On Jul 14, 2:48*pm, (Steve Willner) wrote:
On Jul 12, 9:52=A0am, eric gisse wrote:

That's the problem with invoking things like black holes,
dust, etc. It has to have existed at decoupling, while true
for the case of neutrinos

Why did any of these things have to exist at decoupling?

Evidence of neutrinos were seen in the CMBR glow.
http://arxiv.org/abs/astro-ph/0310198

Galaxies form around black holes it appears, and there are fully
formed galaxies at 500 My after recombination...

*They had to exist well before recombination, and I
suppose before decoupling is the natural time to have made
them if they exist, but I don't see why "existed at decoupling"
is strictly necessary.

In article ,

*dlzc writes:
And helium, and metals missing lots of electrons...

Metals didn't exist at recombination, let alone at decoupling.

How do you know? High initial density, lots of energy, and the "three
forces" were in effect. We see *lots* of bare protons and oxygen
missing 5 electrons in the depths of intergalatic space. Do you
really feel it sourced only from supernovae and galaxies that formed
later? Note that "oxygen" = "metal" in my "dissertation", anything
more complex than helium is a metal.

You are challenging Eric and I on our certainty, why not your own?

What is it about a significant portion of interstellar hydrogen being
able to hold on to its electrons that makes you think friction could
not have helped form stars, and fusion was impossible?
http://www.huffingtonpost.com/2011/0...n_814391..html

David A. Smith

dlzc wrote in
:


[...]

*dlzc writes:
And helium, and metals missing lots of electrons...

Metals didn't exist at recombination, let alone at decoupling.

How do you know?

Nucleosynthesis.

Different abundances would show up in WMAP and direct observations of
metalicity.

[...]

On Jul 15, 11:33*am, eric gisse wrote:
dlzc wrote :

[...]

dlzc writes:
And helium, and metals missing lots of electrons...

Metals didn't exist at recombination, let alone at decoupling.

How do you know?

Nucleosynthesis.

Possible.

Different abundances would show up in WMAP and direct
observations of metalicity.

[...]

If recombination was a "pure black body", and is as opaque as it would
have to be, there could be a galaxy-sized red DeSoto in there, and we
might not see it.

http://arxiv.org/abs/1011.0722
http://arxiv.org/abs/1007.0466

I think it is just hasty to say "no way" (except for an actual DeSoto,
of course).

David A. Smith

On Jul 12, 9:01*am, "Androcles" .
2011 wrote:
[snip]
If one photon arrives in one square eyeball every second,

Heh heh. Square eyeball. Heh heh.
Socks

In article 00,
eric gisse writes:
I've seen decoupling both refer to when during nucleosynthesis when the
neutrinos got kicked out, and during recombination when the universe
became transparent.

On looking around some more, I see that "decoupling" is indeed used
for many different stages. I'm used to having it mean "decoupling
betweend radiation and baryons," i.e., during the early stages of the
Big Bang.

So I guess for specificity I mean 'at recombination'

We don't have any scientific disagreement, then. Whatever caused the
microwave background fluctuations had to exist some time before
recombination but not necessarily as early as the epoch of
nucleosynthesis.

SW Metals didn't exist at recombination, let alone at decoupling.

Does lithium count?

Are you saying lithium was made in the Big Bang? If so, that's news
to me. I thought the "mass 5 barrier" prevented synthesis of
anything heavier than helium. I don't suppose that means literally
zero nucleons, but I thought the numbers were trivial compared to
present abundances. (And the present abundance of lithium is pretty
low!) Do people now think BBNS produced metals? Or are you
proposing some way they were produced later but before recombination?

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

(Steve Willner) wrote in news:ivq61i$poo$1@dont-
email.me:

In article 00,
eric gisse writes:
I've seen decoupling both refer to when during nucleosynthesis when
the
neutrinos got kicked out, and during recombination when the universe
became transparent.

On looking around some more, I see that "decoupling" is indeed used
for many different stages. I'm used to having it mean "decoupling
betweend radiation and baryons," i.e., during the early stages of the
Big Bang.

So I guess for specificity I mean 'at recombination'

We don't have any scientific disagreement, then. Whatever caused the
microwave background fluctuations had to exist some time before
recombination but not necessarily as early as the epoch of
nucleosynthesis.

Yeah. My point is any invocation of something as a dark matter
explanation has to have existed at some point prior to the creation of
the CMB.


SW Metals didn't exist at recombination, let alone at decoupling.

Does lithium count?

Are you saying lithium was made in the Big Bang? If so, that's news
to me. I thought the "mass 5 barrier" prevented synthesis of
anything heavier than helium. I don't suppose that means literally
zero nucleons, but I thought the numbers were trivial compared to
present abundances. (And the present abundance of lithium is pretty
low!) Do people now think BBNS produced metals? Or are you
proposing some way they were produced later but before recombination?


Ned Wright explains it better. With some pictures.

http://www.astro.ucla.edu/~wright/BBNS.html

It looks like with the current parameter set, Lithium production was in
the parts-per-billion regime.

On Fri, 15 Jul 2011 12:48:23 -0700, Puppet_Sock wrote:
On Jul 12, 9:01Â*am, "Androcles" wrote:
[snip]
If one photon arrives in one square eyeball every second,

Heh heh. Square eyeball. Heh heh.

It's in that book about the anatomy of spherical cows. -- RLW

On Jul 15, 6:28*pm, "Androcles" .
2011 wrote:
[Androclese-has-leprosy announcement snipped]

I'm so amused to hear that.
Socks

On 15 juil, 22:19, eric gisse wrote:
(Steve Willner) wrote innews:ivq61i$poo$1@dont-
email.me:





In article 00,
*eric gisse writes:
I've seen decoupling both refer to when during nucleosynthesis when
the
neutrinos got kicked out, and during recombination when the universe
became transparent.

On looking around some more, I see that "decoupling" is indeed used
for many different stages. *I'm used to having it mean "decoupling
betweend radiation and baryons," i.e., during the early stages of the
Big Bang.

So I guess for specificity I mean 'at recombination'

We don't have any scientific disagreement, then. *Whatever caused the
microwave background fluctuations had to exist some time before
recombination but not necessarily as early as the epoch of
nucleosynthesis.

Yeah. My point is any invocation of something as a dark matter
explanation has to have existed at some point prior to the creation of
the CMB.



SW Metals didn't exist at recombination, let alone at decoupling.

Does lithium count?

Are you saying lithium was made in the Big Bang? *If so, that's news
to me. *I thought the "mass 5 barrier" prevented synthesis of
anything heavier than helium. *I don't suppose that means literally
zero nucleons, but I thought the numbers were trivial compared to
present abundances. *(And the present abundance of lithium is pretty
low!) *Do people now think BBNS produced metals? *Or are you
proposing some way they were produced later but before recombination?

Ned Wright explains it better. With some pictures.

http://www.astro.ucla.edu/~wright/BBNS.html

It looks like with the current parameter set, Lithium production was in
the parts-per-billion regime.

That is a good point, but the CMB is also affected by the inverse
square law and the way measurements are made.

I have noticed that the cubic term mentioned: ex^2 ex/t is really just
quadratic, always, because ex/t would be equal to n, the number of
particles.

In cases where the incoming light rays are relatively collimated, the
"excess term" will be of several orders of magnitude less (thousands
to millions or more) with respect to the other term (and irrelevant).
In the case of gravity in the solar system that would be the case
given the diameter of the sun and the distance to it. But for near
clusters of galaxies, the "excess term" could be of the same order of
magnitude to the normal term, which depends on the distance to the
cluster. A problem could also arise when measuring light from smaller
structures that are far from the center of a single portion of sky
captured by a CCD.

The size of areas in the CMB could also be affected, but it depends on
how big are the portions of the sky being captured at a time. The
smaller the portion of the sky captured, the more collimated the
incoming rays are.

A problem with the equations in the original post is that the apparent
brightness is treated as an average. The bigger the portion of the sky
captured by a CCD, the less the equations apply. But as the portions
of sky captured get smaller, the better the equations apply. When the
captured area tends to be a point, the more homogeneous its apparent
brightness will be, and the "excess term" will tend to zero.

So it seems that the math on the original post is correct with
restrictions. The conclusion would be that scanning the sky using
small patches, in which rays will be acceptably collimated, will
reduce a possible error in measurement of big structures (or groups of
structures) that may fit in a single CCD exposure.

In article 0,
eric gisse writes:
Ned Wright explains it better. With some pictures.
http://www.astro.ucla.edu/~wright/BBNS.html

It looks like with the current parameter set, Lithium production was in
the parts-per-billion regime.

Yes, the graph at http://www.astro.ucla.edu/~wright/BBNS-sm.gif shows
Li-7 produced in the Big Bang at a fraction of a part per billion by
number. I'm slightly surprised it's that high, but I'm sure Ned has
used good references.

For comparision, the Li abundance in meteorites is a couple of parts
per billion (http://lanl.arxiv.org/abs/0901.1149) or about an order
of magnitude higher than the BB calculations. Unless meteorites are
somehow enriched in lithium relative to cosmic abundances, about 90%
of the lithium in existence today was produced subsequent to the BB.
Cosmic ray spallation used to be considered the dominant process, but
this is not a subject I follow (as should be obvious from this
thread!).

Just as a side note, lithium is destroyed in stars, so you can't in
general use stellar abundances to estimate the cosmic abundance for
lithium. The solar lithium abundance, for example, is about 150
times lower than the meteoritic abundance.

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