Dear Tom Roberts:

"Tom Roberts" wrote in message
. ..
N:dlzc D:aol T:com (dlzc) wrote:
Dear Tom Roberts:
"Tom Roberts" wrote in message
...
N:dlzc D:aol T:com (dlzc) wrote:
The CMBR appears to have a perfect blackbody emission
curve, at least from what is left after passing through
intergalactic and interstellar "stuff". Normal matter does
not produce the kind of emission curve that the CMBR
produces (apparently).

Sure it does, as long as it is black.

I find no reference that supports this claim, Tom.

Look in elementary textbooks on thermodynamics and/or
quantum mechanics. You'll have a difficult time finding a
reference for 1+1=2 also.

Thanks for your efforts, Tom. Bilge provided the missing (for
me) piece with the plasma, excited beyond the absorption/emission
energies.

Any black object will emit a black body spectrum.
And virtually all astronomical objects are very close
to black (with some absorbtion/emission lines added
-- ignore them). That's why the black body model is
so useful.

I have always imagined the thermal emissions of normal
matter as the typical material "emission bands", smeared
by thermal velocities (gamma factor from individual atomic
motions). Neutrons don't have emission bands. I
suppose their "atmospheres" do... iron.

There is more to it that that. You are just considering atomic
emission for atoms that to not ionize. But in many materials
there are free electrons (i.e. electrons not bound to any
particular atom), and for hot enough objects some/most
atoms will ionize -- both of these contribute a continuous
spectrum. The combination of all of the radiation from a black
object reproduces the blackbody spectrum because
of the thermodynamics of the situation.

Tom, I am given to understand that the CMBR was
produced by an opaque "medium" (CMBRM).

Yes. In the early universe no atom could remain an atom
very long because the high temperature gave other particles
enough kinetic energy so a simple collision often/usually
would ionize the atom. So between a few seconds and
~300k years after the big bang the universe was filled with a
charged plasma consisting primarily of electrons
and protons. When the temperature had been reduced
enough so most collisions did not have enough K.E. to
ionize the atoms the electromagnetic attraction between
protons and electrons quickly caused them to form
hydrogen atoms. The charged plasma was essentially
opaque to all types of EM radiation (hence it was black),
but the hydrogen is transparent to most EM radiation.
So in a short time the radiation emitted by the plasma could
suddenly propagate over large distances. It is
remnants of this radiation we see as the CMBR.

But the CMBR is free of the absorption bands of "cooler"
hydrogen. Let's pretend a timeline, with "CMBRM stops glowing"
at 300,000 pBB (post-Big Bang). What about this Universe
filling, formerly opticaly dense, hydrogen at 301,000 pBB? Does
this mean that it all coalesced to "structures" in
next-to-no-time?

I am further given to understand that the CMBR shows an
intensity vs. frequency curve that
is NOT reproducable by hydrogen at 3000 K "locally".

Right. Because it was not generated by hydrogen, it was
generated by the charged plasma, and modified by
transmisstion through the subsequent universe....

The CMBRM filed the early Universe. The CMBRM emitted
blackbody radiation. The radiation was not absorbed by the
same Universe-filling hydrogen because...

Because hydrogen is transparent to most of the CMBR
radiation. The CMBR was emitted as a continuous blackbody
spectrum ~3000 K; hydrogen can only absorb discrete lines
from it, and the large redshift and Doppler shifting of the
hydrogen in the early universe smeared out the bands so much
they are not prominent (or perhaps not apparent at all,
I don't know).

Not detectable at all.

At some point the CMBR had redshifted enough so it could
not be absorbed at all by hydrogen, and since then the
universe has been transparent to it (except for isolated
objects we call stars).

Let me ask a related question. The CMBRM has been described as
opaque and isothermal. Presumably "opaque" could be defined as
no emissions detectable from beyond a certain place (watch my
terms). So let me ask this question about the Universe that
contains ours... It would be certainly opaque, since we cannot
see beyond the Big Bang, but would the container Universe appear
isothermal? Rather than the CMBRM being some intermediate matter
state on *this* side of the Big Bang, could it simply be
infalling light?

I gave you a couple of "days off" so hopefully I don't elicit an
ulcer on your part...

David A. Smith