Dear George Dishman,
"George Dishman" wrote in message
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Dear George Dishman:
"George Dishman" wrote in message
...
I had written a more extensive reply but it got trashed
when a virus checker update locked up and has mostly
been superseded so I'll trim this severely.
OK.
....
even though it may no longer be able to make it
around the size of the Universe now. So the stated
condition "A photon created at t=0 gets exactly
half way across the universe when the crunch
arrives." is obviously not met in this Universe.
Currently a closed universe seems highly unlikely
as we have discussed.
Agreed. You asked me "why" and I was answering that.
Then I still don't understand why you said "Which
doesn't work too well, since we have photons
arriving in all directions from even ~300,000 y
after the Big Bang". They were produced everywhere
so would be arriving from all directions even 1s
after the bang.
And how they could have NOT been aroud the early
Universe *at least once*, when it took ~300,000 years
to get to a size of 6300 ly. Maybe I'm being too
Newtonian about it...
No, I think it's more basic. The size in such a
universe would not be static. The radius first
increases then decreases. slice through it and
stack different slices at different times and
you get a shape like an american football
standing on one end. The path of a photon would
be a variable radius helix starting at the base
and winding round to the top. Looking down from
the top it turns through only 180 degrees total.
*That* went right over my head! I know the light cone, which
could remotely be called one end of a football (Amercian
football, yes?), and the expansion of the Universe could be
called the other end... but the spiral?
My figure of 6300 LY would suggest it was opaque at
372,700 years and transparent at 379,000 years. "In
an instant" doesn't seem inappropriate in cosmological
terms.
... but it does to a mechanical engineer! Is the
"thickness" being the same order of magnitude as the global
"quench" meaningful?
What do you mean by "global 'quench'"?
What was completed by "379,000 years". The plasma was
quenched to a normal matter state. If we were expanding
compressed air as an analogy, it the point at which water
vapor (as opposed to steam) would form.
OK, but then 6300 years is two order smaller
than that, not the same order of magnitude.
379,000 - 372,700 = 6,300
.... looks like the same order of magnitude.
The z of the CMBR can be thought of as produced
by motion of the source away from us but it can
also be considered as similar to gravitational
redshift or a stretching of the wavelength of
the photon while it was travelling through space
that was being stretched.
That sucked when Paul Lutus was feeding it to me.
It is a standard way of expressing it. I'm not
keen myself but I think the three descriptions
are effectively equivalent while appearing
different in the same sense as wave/particle
duality.
But it requires that the photon give up some of its
energy, yet retain the vector portion of its mometum
entirely intact. We don't know how to do that.
Both energy and momentum are proportional to
frequency, and both values are frame-dependent.
"We don't know how to do that."
Stretching is what we don't know how to do. What we do see right
here/now is gravitational time dilation, which is sufficient also
to describe the redshift of ancient light.
Ignoring my 'proper motion' part, the kinetic
motion and the "expansion velocity" are one and
the same.
I think that I will stick with Ned Wright's defintion,
wherein
"kinetic motion" is kept separate form expansion. "Let
each man lay his dead according to his own fashion."
Can you give me a pointer to this in his tutorial,
I wasn't aware he used the terms. I'll search
later but if you have bookmarked the section it
would save me some time.
I swear it was there explicitly. Any way, as close I can find
is Part 2:
http://www.astro.ucla.edu/~wright/cosmo_02.htm
(without the URL:...)
Works perfectly :-)
QUOTE
Note that the redshift-velocity law is not the special
relativistic Doppler shift law
1+z = sqrt[(1+v/c)/(1-v/c)]
which only applies to special relativistic coordinates, not to
cosmological coordinates.
END QUOTE
neither a search for "kinetic" nor "motion" yielded as clear a
delineation as I'd like.
I think we have lost the thread on this, that
is just "the velocity" and doesn't draw any
distinctions.
It does, George. It delineates between velocity in Minkowski
spacetime, and expansion velocity. And the point is moot, since
it wasn't as clearly phrased on his pages as I "remembered".
They keep talking about "recombination",
It is a misnomer, it should be just "combination",
it's a bit of an in-joke actually.
Perhaps. But many still believe that it started from some
"central singularity", some complex (perhaps) ordered
(certainly bound) state, it had to "de-order" to "get out",
then *recombined* to simpler diffuse forms.
I've never seen anything like that suggested.
Like a white hole (or evaporating black one), which is hotter
than the Universe that contains it.
It is, but being hotter means the contents are
ionised. "Recombination" implies something cold
has been ionised by heating and is now becoming
cold again.
OK.
Then that is 'new physics'
No, it isn't.
I'll continue to disagree on that.
I provided three links that indicate that it isn't "new
physics",
but a prediction of GR, quantum mechanics, or some
combination thereof. You may continue to disagree.
I just think you are looking at those pages with
a preconceived notion and are seeing what you
expect. I respect Steve Carlip's knowledge on GR
so I'll read what he says with great interest.
You indicated that you felt the same way about John Baez. Two of
the citations I provided were his, and the third was Chris
Hillman. Steve Carlip is also a very smart cookie.
Consider a young Universe, some 6300 ly "across", with
mass sufficient to achieve a "curvature coefficient" of 1079
(compared to today).
Lots of confusion there, the optical thickness
of the period of recombination was 6300 ly but
that happened at 380,000 years so the part of
the universe which is _currently_ observable
might have been 760,000 LY across and the
whole universe would have been billions of
light years across or perhaps infinite.
The plasma would be too thick to fill 760,000 ly,
I have no idea what that means!
and still generate the spectrum.
Or that!
It is based on the words you provided, which came from your
understanding of the topic when you said it. So maybe a timeline
will reveal my confusion:
BB - 366,000 - 372,300 - 379,000 - 14 Gy
.... you say the CMBRM is 6300 ly thick, so I assumed 366,000 is
the start of it (or the beginning of the end).
Perhaps this is another lesson for another day...
The universe appears to be flat and would have
been then too. The figure of 1079 is the redshift
compared to today, not the curvature.
An indication of the curvature of the Universe that
emitted the light, vs. the Universe that detected it.
Again your words mean nothing to me. I believe z
is a measure of the angle between two normals to
a surface that has curvature between them, but I
also suspect that's too simplistic. However, I
don't see how you could compute the angle between
two points on curved surfaces in different
universes. How do you calculate across the
discontinuity?
It is continuous between them, isn;t it?
That may be a small beginning, but it no less massive.
It still held only 4% of the required matter in
baryonic form.
Sufficient to produce a redshift many orders of magnitude
greater than our Sun does, and by similar means. Last I
heard, there was no Dark Matter at the time of the CMBRM.
Where does this stand now?
Where did you hear that? I thought the WMAP results
supported dark matter.
I "heard that" here on sci.astro. Since I don't catch every bit
of late breaking news, and since I frequently get my memories
rearranged, I was asking you. So Dark Matter is evident in the
CMBRM?
For the CMBR, use this link
http://lambda.gsfc.nasa.gov/product/...prod_table.cfm
Yes. This would be good (as a start) for a free BH, or one
near our position in a "largely spiral" galaxy.
I intended that as a good start for the CMBR after
the removal of all stars. You need individual stellar
spectra separately. A free BH has no spectrum since
it is black !
The detector of a satellite can behave like a "differential
area" on an event horizon.
Again I have no idea what you mean. If we point a
satellite at a black hole, we don't see the hole,
only the universe behind distorted a bit.
Sigh...
George, I am going to use the recorded spectra, as detected by
"detectors", and infer from that via the magic of integration,
what the EH of a black hole would ingest over its surface, over
its lifetime. I thought I said this more than once.
You believe that the images will come in spectrally, I do not.
That would be inside, we are outside all the black
holes we can use for a reference.
This is what you are comfortable in believing, yes George. I
have seen "non-beginner" solutions to GR that indicate that
perhaps our Big Bang is the inside of an event horizon of a black
hole that contains our Universe. I propose to test this by the
above mentioned integration.
Then I need to come up with a spectrum for a BH consuming
a companion,
Try Cyg X1
A good search ("Cygnus X1"). I'll see what I can find. Is it
"close" and/or is the line-of-sight pretty clear?
http://en.wikipedia.org/wiki/Cygnus_X-1
2500 parsecs.
http://www.oa.uj.edu.pl/research/cygx1.html
.... spectral references. Much more suitable.
http://astrophysics.sr.unh.edu/mccon...26_v4_p119.pdf
.... and graphs!
line-of-sight is clear. So I will assume the spectrum ingested
is pretty close to the same, adjusting for the difference in
distance and angular size (using Einstein ring #1 as the outer
boundary).
and to somehow infer the influx to the BH at the center of
our own galaxy.
It appears to be in a relatively clear region so
is invisible.
Vaccum cleaners are like that! How about the center of
Andromeda? Is it pretty quiet there also?
These may be of more use
http://www.astr.ua.edu/keel/agn/
In particular
http://www.astr.ua.edu/keel/agn/spectra.html
http://heasarc.gsfc.nasa.gov/docs/ob...n/agntext.html
http://en.wikipedia.org/wiki/Active_Galactic_Nuclei
Here is a problem in modelling. Would you say that the
percentage of active galactic nucleii vs. non-active (Milky Way
and Andromeda) would be and indication that this behavior might
be periodic. In other words, my black-hole-in-galactic-center
model should be sometimes active, and sometimes not, roughly like
the percentage above?
Thanks, it's nice to know you appreciate it. I could
tell you do the same and while we may disagree I hope
you feel you benefit as much as me from reading the
cited resources.
What fun would it be if everyone agreed with me? I wouldn't
get to learn anything. ;)
Now if I just can...
A few more links to keep you going ;-)
If only I had the time to study them all myself
I won't blindside anybody. Anything I find will be on the
internet.
Thanks to all.
David A. Smith