Re: CMBR and neutron stars

Dear Steve Willner:

"Steve Willner" <willner@xxxxxxxxxxxxxxx> wrote in message
news:430ce1f9$1@xxxxxxxxxxxxxxxxxxxxxxxxxx
> SW> Thus as of today (and barring an error somewhere), it looks
> as
> SW> though
> SW> stellar light is 3 to 10% of the total radiation in the
> SW> Universe.
>
> In article <sbxOe.124446$E95.76067@fed1read01>,
> "N:dlzc D:aol T:com \(dlzc\)" <N: dlzc1 D:cox T:net@xxxxxxxxxx>
> writes:
>> ... for a position similar to our own.
>
> No, the numbers in my previous post for "extragalactic
> background
> light" were for a position far from any local light source.
> From
> Earth, looking towards the Galactic pole, the brightness of
> stars
> fainter than mag 6 corresponds to about 110 nW m^-2 sr^-1 in
> visible
> light alone. You would have to add to that a considerable
> infrared
> contribution, and of course the brightness is much greater at
> lower
> Galactic latitudes.

Do you see the m^-2 in the number you cited? *IF* the number of
stars is approximately constant, but the area is expanding, the
stellar background will decrease also. Note how the "stellar
background" was sufficient to maintain the CMBRM plasma... and
then it wasn't.

>> Stellar light would likely be lower for a lone BH in deep
>> space,
>
> See above. The EBL is the minimum.

So you don't feel that "local to the galactic disk" dust would
contribute anything worth handling on a first pass? (Keep in
mind I am an engineer, so am used to using first approximations
to judge how much more effort is required, if any.)

>> > SW> Thus the relative contribution from stars increases with
>> > time.
>>
>> Actually no, it would not, since the Universe is expanding.
>
> You didn't read carefully. Expansion affects both the
> microwave
> background and existing starlight equally, but stars keep
> pumping out
> new light.

But from progressively further away. 1/r^2 wins over t...

> To see the result, imagine we could instantly "turn off"
> all stars in the Universe. Then at all future times, the ratio
> of
> stellar to CMWB energy density would be exactly the same
> as today, decreasing as the fourth power of the scale length.
> But we cannot turn off stars, and they will continue to add
> energy in the future. Thus the ratio of energy densities will
> increase with time until all stars have burned out.

Let's see if you still think that is true...
The percentage may increase, but the effect will be a decrease in
total intensity...

>> And "what I meant by this" is that we don't discover
>> entirely new galaxies where none existed before, say,
>> 10 or 20 years ago. We are only able to bring new
>> more-distant ones into focus.
>
> The number of galaxies is thought to be decreasing
> because of mergers, but I don't see what this has to do
> with any of your other claims.

I keep hoping that I can leave this as a "question", rather than
a "claim", Steve. Others have made the claim, and I am
(attempting to) add some observability to the claim.

> We see new stars forming in many locations, and we certainly
> expect existing stars to keep radiating for quite awhile.

.... and not balloon up into a red giant and cook us while we
argue about necessary funding for a space program (or anything
else necessary). Yes, I agree.

>> > SW> "Coalescence" into what?
>> >>
>> >> Proto-galaxies, for a start.
>> >
>> > How does this keep the Universe from being optically thick?
>>
>> It doesn't. It presents the inside of an event horizon as an
>> optically thick surface *also*.
>
> I guess I don't understand your model. If you have an
> optically
> thick plasma at a redshift of a few thousand, it will be very
> hard to
> observe anything at higher redshift.

Gamma might punch through. But it would be close to optical
now... And others have "pie in the sky" experiments that might
allow us to detect "early" neutrons.

> And if you don't have an
> optically thick plasma back then, I think you will have quite
> some trouble to explain where all the baryons were.

Gelled into proto-galaxies (or some close kin to small BHs, just
cooler than ~3000K), which would subtend very little compared to
the CMBRM.

>> No. A "way around it" is that the CMBRM is the inside
>> of the event horizon, a temperature TBD, and structures
>> exist right up to it.
>
> But where were all the baryons at z=2000? What was
> their density and temperature, and why didn't they create
> a medium that was optically thick? "Coalescence" is too
> vague. Exactly what state were these baryons in? What
> size objects with what average density? Hand waving is
> no good; let's see some numbers.

Then let's make the distant past look something like the present.
Galaxies of approximate size to what we see today. Quantities on
the order of 10% as "potentially visible", with the balance as
still waiting for differential momentum to equilibrate and
partition into stars. Bulk temperature for the 90% will likely
still be in the 3000 K range.

As a first pass, and only because you feel it is important to
have something more to attack.

> By the way, I share the standard GR view that an event horizon
> is not a physical singularity.

I understand. I appreciate the candor, but more than this, I
appreciate the "benchmarks".

> And certainly the event horizon is not a
> requirement for an accretion disk to exist. After all, neutron
> star
> accretion disks look pretty much the same as black hole
> accretion
> disks, so the disk and its radiation cannot depend on an event
> horizon. (If you compare the time variability in great detail,
> you
> can indeed find differences, but the existence and basic
> structure of
> the disks seems to be the same.)

Not to a "close enough is good enough" kind of guy like me! ;>)

I can never convince you or anyone else that the event horizon is
a physical singularity. You seem to define this as something you
can bounce a photon off of, and clearly no tool we have can ever
come back from "contact". So we will have to agree to disagree
here as well.

David A. Smith


.

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