Red shift and homogeneity

Google seems to be unable to show threads with more
than 250 posts so I'm reposting my reply to Jim as
a new thread at Jim's request. My apologies to those
of you who have seen it before.

George


"Jim Greenfield" wrote in message
om...

... I tried it myself on the good old graph paper, as follows:
I marked 10 x 10 boxes with 2 blanks between each marked box.
I then on page 2 repeated with 3 blanks- Expanded by 50% OK? (still
homogenous)

You have filled in some squares and left others blank, right?
If so the distance between the centres of filled squares has
increased from 3 units to 4 units or 33.3% but the approach
is fine. If you had marked dots at every second or third
intersection then it would be 50%.

I placed page 1 over page 2, and poked a pin through each spot.
Then I drew lines from each original position, to the expanded
position---- and put the razor away! Because without making a
selection, the expansion had shown by default all proceeding from the
center.(all lines point to it)

But you did make a selection ;-) I didn't se you do it but I
can make some guesses: Firstly, I guess you lined up the edges
of the paper. Secondly, when you had to match a square on one
sheet to the corresponding square representing the same cluster
of galaxies on the other sheet, I guess you selected the centre
square on one to correspond to the centre square on the other.

So somehow by making your red and green selections, and expanding from
them, you are (accidently) nominating those as the center, before
beginning.

Yes (deliberately), just as you (perhaps accidentally) nominated
the square at the centre of the paper to be the square at the
centre of the observable universe.

Now the essential feature of this demonstration is not that
you can find a single centre, it comes from comparing two
sets of lines made under different assumptions. You have
your first set but nothing to compare so now you need to
do the rest of the experiment. Get a different coloured pen
and draw another set of lines but this time assume that the
centre filled square on the first sheet corresponds to a
filled square about eight squares from the centre on the
second sheet, or, if you want to have the sheets represent
the observable universe, assume we are moving and offset one
sheet by eight squares when laying it over the other. It
might be harder to keep track of which squares to join but
I'm sure you can handle it.

Of course the green and red were still separating in my diagram, but
as I had expanded the whole (Universe) they were not at the indicated
center. Red and green would still exhibit red shift, but it would be a
vector of the real situation (if expansion was occuring)
So I am still leaning to the view that red shift and expansion are the
product of an intriguing illusion.
(For now take it that my 100 spots represent the entire 13.7 universe,
so taking a piece of it arbitrarily wont wash)

But the 13.7 (whatever) that we can see is already just
a tiny piece of the whole, an infinitesimal piece if the
universe is infinite.

I'm
afraid I am still stuck with the conclusion that if distant galaxies
are moving away faster than closer ones, then our (observed) universe
is getting less dense further out, and isotropy, but NOT homo can be
preserved under expansion.

Ned Wright: "To say that the universe is homogenous means that any
measurable property of the universe is the same every where".
(Which brings us back to that red shift cause, as expansion causes
lessening of density, and if galaxies further out are moving away
faster than those close to us, then there is a differential in density
occurring)

While you are looking at these sheets Jim, there is
something else you can do since they are nicely regular.
I want you to draw a square box roughly in the centre of
your first sheet 12 units on each edge. If I understand
your description there should be 16 filled squares inside.
Draw another box the same size at the centre of the second
sheet and there should be 9 filled squares inside. The
density (squares per box) has reduced to 9/16 of the
earlier value (in 3D it would have reduced by 27/128). The
lines should show that 7 squares have moved outside but
the 9 remaining were previously inside.

Now try that at the edge of the paper with the same size
of boxes. You should find the same change in density but
this time (depending on the size of the paper) most of
the 16 original squares will have 'moved' out of the box
to be replaced by 9 new squares that have moved in. The
clusters represented by these squares are moving quickly
out from your chosen centre but the density change is
identical. Now imagine your sheet was just a sample of a
whole sheet a billion miles on each edge. If you consider
two boxes the same size as those you have drawn but nearly
a billion miles away can you see the density before and
after would still be the same as at the centre? I hope
that illustrates that expansion maintains homogeneity.

That is the BB model but when you then take into account
the speed of light what we observe of course should be
squares with three blanks between nearby and only two
blanks between at greater distances. Other aspects make
it a difficult thing to measure though.

Jim, I may not be able to reply for a few days, we have
an exhibition that will tie us up until Sunday.

best regards
George

"George Dishman" wrote in message ...

Thanks very much for troubling to get restarted (I've missed a few
posts 280/300, but our discussion is about where I was cut off)
"Jim Greenfield" wrote in message
om...

... I tried it myself on the good old graph paper, as follows:
I marked 10 x 10 boxes with 2 blanks between each marked box.
I then on page 2 repeated with 3 blanks- Expanded by 50% OK? (still
homogenous)

You have filled in some squares and left others blank, right?
If so the distance between the centres of filled squares has
increased from 3 units to 4 units or 33.3% but the approach
is fine. If you had marked dots at every second or third
intersection then it would be 50%.

Yes to both

I placed page 1 over page 2, and poked a pin through each spot.
Then I drew lines from each original position, to the expanded
position---- and put the razor away! Because without making a
selection, the expansion had shown by default all proceeding from the
center.(all lines point to it)

But you did make a selection ;-) I didn't se you do it but I
can make some guesses: Firstly, I guess you lined up the edges
of the paper. Secondly, when you had to match a square on one
sheet to the corresponding square representing the same cluster
of galaxies on the other sheet, I guess you selected the centre
square on one to correspond to the centre square on the other.

This may be going to the philosophical. I was trying to picture the
'whole' universe on my graph paper- I can't go 'outside the box',
because there is nowhere to go. IIUC, the CMBR origin is claimed to be
the outer limit of the universe, originating from the BB before the
formation of the first galaxies.

So somehow by making your red and green selections, and expanding from
them, you are (accidently) nominating those as the center, before
beginning.

Yes (deliberately), just as you (perhaps accidentally) nominated
the square at the centre of the paper to be the square at the
centre of the observable universe.

Now the essential feature of this demonstration is not that
you can find a single centre, it comes from comparing two
sets of lines made under different assumptions. You have
your first set but nothing to compare so now you need to
do the rest of the experiment. Get a different coloured pen
and draw another set of lines but this time assume that the
centre filled square on the first sheet corresponds to a
filled square about eight squares from the centre on the
second sheet, or, if you want to have the sheets represent
the observable universe, assume we are moving and offset one
sheet by eight squares when laying it over the other. It
might be harder to keep track of which squares to join but
I'm sure you can handle it.

As above, if I was considering a portion of the universe, you are
probably correct, and I, as did you, made a defacto selection for 'the
center'.

Of course the green and red were still separating in my diagram, but
as I had expanded the whole (Universe) they were not at the indicated
center. Red and green would still exhibit red shift, but it would be a
vector of the real situation (if expansion was occuring)
So I am still leaning to the view that red shift and expansion are the
product of an intriguing illusion.
(For now take it that my 100 spots represent the entire 13.7 universe,
so taking a piece of it arbitrarily wont wash)

But the 13.7 (whatever) that we can see is already just
a tiny piece of the whole, an infinitesimal piece if the
universe is infinite.

If BBs are accepting the possibility of an infinite (3D) universe,
doesn't that kill off the CMBR arguement as evidence? If there is more
'out there' beyond the origin of the perceived (til now) CMBR, that
theory is destroyed.

I'm
afraid I am still stuck with the conclusion that if distant galaxies
are moving away faster than closer ones, then our (observed) universe
is getting less dense further out, and isotropy, but NOT homo can be
preserved under expansion.

Ned Wright: "To say that the universe is homogenous means that any
measurable property of the universe is the same every where".
(Which brings us back to that red shift cause, as expansion causes
lessening of density, and if galaxies further out are moving away
faster than those close to us, then there is a differential in density
occurring)

I want you to draw a square box roughly in the centre of
your first sheet 12 units on each edge. If I understand
your description there should be 16 filled squares inside.
Draw another box the same size at the centre of the second
sheet and there should be 9 filled squares inside. The
density (squares per box) has reduced to 9/16 of the
earlier value (in 3D it would have reduced by 27/128). The
lines should show that 7 squares have moved outside but
the 9 remaining were previously inside.

Now try that at the edge of the paper with the same size
of boxes. You should find the same change in density but
this time (depending on the size of the paper) most of
the 16 original squares will have 'moved' out of the box
to be replaced by 9 new squares that have moved in. The
clusters represented by these squares are moving quickly
out from your chosen centre but the density change is
identical. Now imagine your sheet was just a sample of a
whole sheet a billion miles on each edge. If you consider
two boxes the same size as those you have drawn but nearly
a billion miles away can you see the density before and
after would still be the same as at the centre? I hope
that illustrates that expansion maintains homogeneity.

That is the BB model but when you then take into account
the speed of light what we observe of course should be
squares with three blanks between nearby and only two
blanks between at greater distances. Other aspects make
it a difficult thing to measure though.

As above, my original "Popping" was aimed at the idea of the universe
being a certain size, and formed my arguements around that. If we are
going to step "outside the box" in order to understand the
implications and views of being at other locations, then I am inclined
to feel my position vindicated.
How is this?
I marked adjacent boxes ABCDEF on my graph paper. Then I moved B one
space. But red shift indicates that when F was at position B (before
expansion) it was moving a lot faster (say 2 squares in the same
interval- which is of course exagerated). Now when I do this exercise
a few more times, using all the letters, I find that density of ABCD,
is less than CDEF (larger spread)
So I am afraid that I still have this (belief?) that an expansion,
considering ALL the universe, by default would cause a change in
homogeneity.

Other posters refer to light being at a different velocity when the
universe was 'smaller', which is claimed to upset this view. Also that
the expansion of space drags the galaxies along, rather than them
travelling through space. You might have to try convincing me along
those lines, in order to overcome my current skepticism ref expansion.

Best regards,
Jim G
(I may add/subtract some of this before your return)

"Jim Greenfield" wrote in message
...
"George Dishman" wrote in message
...

Thanks very much for troubling to get restarted (I've missed a few
posts 280/300, but our discussion is about where I was cut off)

No problem.

I placed page 1 over page 2, and poked a pin through each spot.
Then I drew lines from each original position, to the expanded
position---- and put the razor away! Because without making a
selection, the expansion had shown by default all proceeding from the
center.(all lines point to it)

But you did make a selection ;-) I didn't se you do it but I
can make some guesses: Firstly, I guess you lined up the edges
of the paper. Secondly, when you had to match a square on one
sheet to the corresponding square representing the same cluster
of galaxies on the other sheet, I guess you selected the centre
square on one to correspond to the centre square on the other.

This may be going to the philosophical. I was trying to picture the
'whole' universe on my graph paper- I can't go 'outside the box',
because there is nowhere to go.

It is not philosophical in the least, it is fundamental. Seeing the
map as the 'whole' doesn't work because the fact that you have a
finite piece of paper imposes edges on the map where there are no
edges in an infinite universe. No matter how far you go, there is
always an infinite amount beyond the limit of your map, or to put
it another way, outside your box is just more of the same as is
inside.

IIUC, the CMBR origin is claimed to be
the outer limit of the universe, originating from the BB before the
formation of the first galaxies.

Yes and no. It is the limit of how far we can see but not the
limit of the universe. It does come from before the earliest
galaxies were formed but not from further away. More on this
later.

So somehow by making your red and green selections, and expanding from
them, you are (accidently) nominating those as the center, before
beginning.

Yes (deliberately), just as you (perhaps accidentally) nominated
the square at the centre of the paper to be the square at the
centre of the observable universe.

Now the essential feature of this demonstration is not that
you can find a single centre, it comes from comparing two
sets of lines made under different assumptions. You have
your first set but nothing to compare so now you need to
do the rest of the experiment. Get a different coloured pen
and draw another set of lines but this time assume that the
centre filled square on the first sheet corresponds to a
filled square about eight squares from the centre on the
second sheet, or, if you want to have the sheets represent
the observable universe, assume we are moving and offset one
sheet by eight squares when laying it over the other. It
might be harder to keep track of which squares to join but
I'm sure you can handle it.

As above, if I was considering a portion of the universe, you are
probably correct, and I, as did you, made a defacto selection for 'the
center'.

Exactly, but because you have a finite piece of paper,
mapping only a small portion is the best you can do.

If BBs are accepting the possibility of an infinite (3D) universe,

It's not a question of accepting it, Eddington came up with
the balloon analogy in 1933, I guess because he was fed up
trying to explain that there wasn't a centre or bounds. The
possibility that space is infinite has been part of the idea
since the start and astronomers have been trying to explain
that to people since before you were born (unless you are
over 70)!

doesn't that kill off the CMBR arguement as evidence? If there is more
'out there' beyond the origin of the perceived (til now) CMBR, that
theory is destroyed.

Not at all, it is still consistent with the model. I cribbed
this from Ned Wright's page:

http://www.dishman.me.uk/George/Cosm...nsion/cmbr.gif

The original is from this page:

http://www.astro.ucla.edu/~wright/cosmo_03.htm#MSTD


I want you to draw a square box roughly in the centre of
your first sheet 12 units on each edge. If I understand
your description there should be 16 filled squares inside.
Draw another box the same size at the centre of the second
sheet and there should be 9 filled squares inside. The
density (squares per box) has reduced to 9/16 of the
earlier value (in 3D it would have reduced by 27/128). The
lines should show that 7 squares have moved outside but
the 9 remaining were previously inside.

Now try that at the edge of the paper with the same size
of boxes. You should find the same change in density but
this time (depending on the size of the paper) most of
the 16 original squares will have 'moved' out of the box
to be replaced by 9 new squares that have moved in. The
clusters represented by these squares are moving quickly
out from your chosen centre but the density change is
identical. Now imagine your sheet was just a sample of a
whole sheet a billion miles on each edge. If you consider
two boxes the same size as those you have drawn but nearly
a billion miles away can you see the density before and
after would still be the same as at the centre? I hope
that illustrates that expansion maintains homogeneity.

That is the BB model but when you then take into account
the speed of light what we observe of course should be
squares with three blanks between nearby and only two
blanks between at greater distances. Other aspects make
it a difficult thing to measure though.

As above, my original "Popping" was aimed at the idea of the universe
being a certain size, and formed my arguements around that. If we are
going to step "outside the box" in order to understand the
implications and views of being at other locations, then I am inclined
to feel my position vindicated.

If it was of a finite size and bounded then yes you would
have been correct all along, but the BB has always been
unbounded.

How is this?
I marked adjacent boxes ABCDEF on my graph paper. Then I moved B one
space. But red shift indicates that when F was at position B (before
expansion) it was moving a lot faster (say 2 squares in the same
interval- which is of course exagerated). Now when I do this exercise
a few more times, using all the letters, I find that density of ABCD,
is less than CDEF (larger spread)

Suppose you marked every third square with a letter on your
first sheet. That becomes every fourth square on the second
sheet. Now suppose we align B like this:

A B C D E F
A B C D E F

Clearly the letters more distant from B seem to be moving
faster. C is moving at speed 1, D at 2 and so on. Now think
of that as two groups, ABC and DEF, and think of the change
as being composed of two effects, motion and expansion of
the groups. Group ABC has not moved as a whole since the
speeds are 1 to the left, 0 and 1 to the right, average 0.
The group is expanding since A and C are moving away from
B at speed 1 in opposite directions.

Group DEF on the other hand is moving at speed 3, 2 for D,
3 for E and 4 for F so 3 on average. DEF is also expanding
because D is moving away from E at speed 1 to the left while
F is moving at speed 1 to the right.

The key here is that both groups are expanding at the same
rate, 1 square in the interval for A/C and D/F even though
group DEF is moving rapidly but group ABC is not.

Now align E:

A B C D E F
A B C D E F

This time it is group ABC that is moving rapidly to the left
while group DEF is static. In fact it doesn't matter what
letter you align, A and C will be expanding away from B in
exactly the same way that D and F are expanding away from E.

The density has gone down for 0.33 letters per square to
0.25 letters per square everywhere and no choice of alignment
will affect that.

So I am afraid that I still have this (belief?) that an expansion,
considering ALL the universe, by default would cause a change in
homogeneity.

Try to imagine your piece of paper as just a fraction of the
whole. No matter how big it is it is no different anywhere to
what you see on your sample. Think of a letter as far away as
you can imagine, the letters adjacent to it will be expanding
away from it by 1 square in the interval and the density in
that region has gone down from 0.33 to 0.25.

If it was 0.33 everywhere and it is now 0.25 everywhere,
homogeneity has been preserved.

Other posters refer to light being at a different velocity when the
universe was 'smaller', which is claimed to upset this view.

There has been speculation about that but nothing believable.
The possibility exists so people do tests to look for any
variation when the opportunity arises but so far it is mainly
cranks pushing their own ideas.

Also that
the expansion of space drags the galaxies along, rather than them
travelling through space. You might have to try convincing me along
those lines, in order to overcome my current skepticism ref expansion.

If you ever become conversant with GR, I will have to backtrack
on some of what I am saying. Until then, I feel it is better to
explain it in terms you understand, as close to Newtonian physics
as I can manage. However, I will be open about this and suggest
you read the following threads. These are experts who know the
subject well, the question is not the theory but how to explain
it:

http://makeashorterlink.com/?V5C032776

http://makeashorterlink.com/?U2D051776

The essence is that the different ways of explaining it can
be considered equivalent under certain circumstances.

George

"George Dishman" wrote in message ...

It's not a question of accepting it, Eddington came up with
the balloon analogy in 1933, I guess because he was fed up
trying to explain that there wasn't a centre or bounds. The
possibility that space is infinite has been part of the idea
since the start and astronomers have been trying to explain
that to people since before you were born (unless you are
over 70)!

I admit I still cant quite understand the BB argument as it seems to
have contradictions. Recently I read a quote saying something like
this... that in a picture of the universe at a certain era early in
the big bang the universe was only 183,000million miles across.etc.. I
forget the source but it was a reputable theorists describing the BB .
Yet how could he give a definite width to the universe when your
argument and indeed now it seems a lot of different people are saying
the universe was and is always infinite in size? The two explanations
seem contradictory. (I`m sorry that I cant remember the quote and its
source ) Also I am certain that the eddington ballon idea used to be
explained in terms of the whole ballon being a finite size starting
off as a singularity of infinitely small size and expanding within a
empty vacuum. Hence the point at which the calculated density at so
many million miles in width became less dense enouigh for emr to
propogate.
Sean

"sean" wrote in message
om...
"George Dishman" wrote in message
...

It's not a question of accepting it, Eddington came up with
the balloon analogy in 1933, I guess because he was fed up
trying to explain that there wasn't a centre or bounds. The
possibility that space is infinite has been part of the idea
since the start and astronomers have been trying to explain
that to people since before you were born (unless you are
over 70)!

I admit I still cant quite understand the BB argument as it seems to
have contradictions.

Since it has to use GR, some of it may seem unintuitive. It is
certainly difficult to explain it in a Newtonian style (as will
become apparent as the conversation if Jim moves on). If you
think there are problems, this a reasonable place to ask. You
may even find you are right, there is much that is not yet known.

Recently I read a quote saying something like
this... that in a picture of the universe at a certain era early in
the big bang the universe was only 183,000million miles across.etc.. I
forget the source but it was a reputable theorists describing the BB .

They are using "the universe" in the sense of "the observable
universe" which in a way is quite scientific. Discussion of
things that cannot be observed tends to be classed as
speculation and science is restricted to what can be measured,
but cosmology models the whole based on what can be seen (the
angular power spectrum of the CMBR for example) so crosses the
usual bound.

Yet how could he give a definite width to the universe when your
argument and indeed now it seems a lot of different people are saying
the universe was and is always infinite in size? The two explanations
seem contradictory. (I`m sorry that I cant remember the quote and its
source )

He just means the bit we can see within the whole.

Also I am certain that the eddington ballon idea used to be
explained in terms of the whole ballon being a finite size starting
off as a singularity of infinitely small size and expanding within a
empty vacuum.

No, the 2D surface of the balloon has always represented the
3D volume of the vacuum.

Hence the point at which the calculated density at so
many million miles in width became less dense enouigh for emr to
propogate.

It is like the expansion of the gas in the cylinder of a car,
as it expands, it cools and when it becomes like the exhaust
gas it is transparent. I believe early expansion was adiabatic
in fact.

George

"George Dishman" wrote in message ...


Recently I read a quote saying something like
this... that in a picture of the universe at a certain era early in
the big bang the universe was only 183,000million miles across.etc.. I
forget the source but it was a reputable theorists describing the BB .

They are using "the universe" in the sense of "the observable
universe" which in a way is quite scientific. Discussion of
things that cannot be observed tends to be classed as
speculation and science is restricted to what can be measured,
but cosmology models the whole based on what can be seen (the
angular power spectrum of the CMBR for example) so crosses the
usual bound.

Yet how could he give a definite width to the universe when your
argument and indeed now it seems a lot of different people are saying
the universe was and is always infinite in size? The two explanations
seem contradictory. (I`m sorry that I cant remember the quote and its
source )

He just means the bit we can see within the whole.

To me though that implies that for the earlier universe when it was
183,000million light years across and denser it must have had a
different smaller value for infinity. As it has expanded since then it
is now larger according to BB and therefore is bigger than the
infinity of the earlier universe. That gives two values for infinity.
How can infinity be larger than infinity? The BB argument can only
work if the earlier universe was smaller than the infinite universe we
have now. And if it was smaller than it could not have been infinite
nor could it for that matter have expanded fast enough to have become
infinite now as it is impossible to go from a finite value to an
infinite value. (except maybe in an abstract mathematical world)
It is the trick of giving two values of infinity that I find to be
contradictory.
Sean

"sean" wrote in message
m...
"George Dishman" wrote in message
...


Recently I read a quote saying something like
this... that in a picture of the universe at a certain era early in
the big bang the universe was only 183,000million miles across.etc.. I
forget the source but it was a reputable theorists describing the BB .

They are using "the universe" in the sense of "the observable
universe" which in a way is quite scientific. Discussion of
things that cannot be observed tends to be classed as
speculation and science is restricted to what can be measured,
but cosmology models the whole based on what can be seen (the
angular power spectrum of the CMBR for example) so crosses the
usual bound.

Yet how could he give a definite width to the universe when your
argument and indeed now it seems a lot of different people are saying
the universe was and is always infinite in size? The two explanations
seem contradictory. (I`m sorry that I cant remember the quote and its
source )

He just means the bit we can see within the whole.

To me though that implies that for the earlier universe when it was
183,000million light years across and denser it must have had a
different smaller value for infinity.

You cannot place a value on infinity. If it could be given
a value, it would be finite.

As it has expanded since then it
is now larger according to BB and therefore is bigger than the
infinity of the earlier universe. That gives two values for infinity.
How can infinity be larger than infinity? The BB argument can only
work if the earlier universe was smaller than the infinite universe we
have now. And if it was smaller than it could not have been infinite
nor could it for that matter have expanded fast enough to have become
infinite now as it is impossible to go from a finite value to an
infinite value. (except maybe in an abstract mathematical world)
It is the trick of giving two values of infinity that I find to be
contradictory.

As Jim said, many people have trouble handling the concept
of the infinite. If space 'goes on forever' in the sense
of distance, you cannot have bigger and smaller versions
of 'forever'. Space never ends and you cannot have degrees
of never.

Let me also just note that this is still just a possibility
and there are other variants of BB model that are not
infinite, we really don't know.

George

"George Dishman" wrote in message ...

As Jim said, many people have trouble handling the concept
of the infinite. If space 'goes on forever' in the sense
of distance, you cannot have bigger and smaller versions
of 'forever'. Space never ends and you cannot have degrees
of never.

Let me also just note that this is still just a possibility
and there are other variants of BB model that are not
infinite, we really don't know.

George

Yes I agree we cant have bigger and smaller versions of infinity.
Thats actually the point I am trying to make.It is the BB concept that
seems to suggest that there are bigger and smaller versions of
infinity by saying that space is expanding in the BB model (hence the
redshift) from an already infinite singularity.But how can an infinite
space expand? We both agree that foever (infinity) cant be bigger or
smaller.
Sean

"sean" wrote in message
om...
"George Dishman" wrote in message
...

As Jim said, many people have trouble handling the concept
of the infinite. If space 'goes on forever' in the sense
of distance, you cannot have bigger and smaller versions
of 'forever'. Space never ends and you cannot have degrees
of never.

Let me also just note that this is still just a possibility
and there are other variants of BB model that are not
infinite, we really don't know.

George

Yes I agree we cant have bigger and smaller versions of infinity.
Thats actually the point I am trying to make.It is the BB concept that
seems to suggest that there are bigger and smaller versions of
infinity by saying that space is expanding in the BB model (hence the
redshift) from an already infinite singularity.But how can an infinite
space expand? We both agree that foever (infinity) cant be bigger or
smaller.

Why shouldn't it expand? The only way it could be stopped
would be if the most distant parts were up against
something, but for an infinite universe there is always
more space beyond. The words bigger and smaller just don't
apply, it starts infinite, it expands and it is still
infinite.

If you want to take a Newtonian view, I explained to Jim
some time ago, every galaxy moves away from us to a place
recently vacated by a more distant galaxy. There is never
a galaxy that doesn't have an infinite number of more
distant galaxies already beyond it.

I think it's one of those things that needs a bit of time
for your mind to adapt to. We are not accustomed to meeting
the infinite in real life.

George

"George Dishman" wrote in message ...
"Jim Greenfield" wrote in message
...
"George Dishman" wrote in message
...

IIUC, the CMBR origin is claimed to be
the outer limit of the universe, originating from the BB before the
formation of the first galaxies.

Yes and no. It is the limit of how far we can see but not the
limit of the universe. It does come from before the earliest
galaxies were formed but not from further away. More on this
later.

In which discussion I will ask, why then can we not see beyond 14bly?

Now the essential feature of this demonstration is not that
you can find a single centre, it comes from comparing two
sets of lines made under different assumptions. You have
your first set but nothing to compare so now you need to
do the rest of the experiment. Get a different coloured pen
and draw another set of lines but this time assume that the
centre filled square on the first sheet corresponds to a
filled square about eight squares from the centre on the
second sheet, or, if you want to have the sheets represent
the observable universe, assume we are moving and offset one
sheet by eight squares when laying it over the other. It
might be harder to keep track of which squares to join but
I'm sure you can handle it.

As above, if I was considering a portion of the universe, you are
probably correct, and I, as did you, made a defacto selection for 'the
center'.

Exactly, but because you have a finite piece of paper,
mapping only a small portion is the best you can do.

If BBs are accepting the possibility of an infinite (3D) universe,

It's not a question of accepting it, Eddington came up with
the balloon analogy in 1933, I guess because he was fed up
trying to explain that there wasn't a centre or bounds. The
possibility that space is infinite has been part of the idea
since the start and astronomers have been trying to explain
that to people since before you were born (unless you are
over 70)!

doesn't that kill off the CMBR arguement as evidence? If there is more
'out there' beyond the origin of the perceived (til now) CMBR, that
theory is destroyed.

Not at all, it is still consistent with the model. I cribbed
this from Ned Wright's page:

http://www.dishman.me.uk/George/Cosm...nsion/cmbr.gif

The original is from this page:

http://www.astro.ucla.edu/~wright/cosmo_03.htm#MSTD


I want you to draw a square box roughly in the centre of
your first sheet 12 units on each edge. If I understand
your description there should be 16 filled squares inside.
Draw another box the same size at the centre of the second
sheet and there should be 9 filled squares inside. The
density (squares per box) has reduced to 9/16 of the
earlier value (in 3D it would have reduced by 27/128). The
lines should show that 7 squares have moved outside but
the 9 remaining were previously inside.

Now try that at the edge of the paper with the same size
of boxes. You should find the same change in density but
this time (depending on the size of the paper) most of
the 16 original squares will have 'moved' out of the box
to be replaced by 9 new squares that have moved in. The
clusters represented by these squares are moving quickly
out from your chosen centre but the density change is
identical. Now imagine your sheet was just a sample of a
whole sheet a billion miles on each edge. If you consider
two boxes the same size as those you have drawn but nearly
a billion miles away can you see the density before and
after would still be the same as at the centre? I hope
that illustrates that expansion maintains homogeneity.

That is the BB model but when you then take into account
the speed of light what we observe of course should be
squares with three blanks between nearby and only two
blanks between at greater distances. Other aspects make
it a difficult thing to measure though.

As above, my original "Popping" was aimed at the idea of the universe
being a certain size, and formed my arguements around that. If we are
going to step "outside the box" in order to understand the
implications and views of being at other locations, then I am inclined
to feel my position vindicated.

If it was of a finite size and bounded then yes you would
have been correct all along, but the BB has always been
unbounded.

How is this?
I marked adjacent boxes ABCDEF on my graph paper. Then I moved B one
space. But red shift indicates that when F was at position B (before
expansion) it was moving a lot faster (say 2 squares in the same
interval- which is of course exagerated). Now when I do this exercise
a few more times, using all the letters, I find that density of ABCD,
is less than CDEF (larger spread)

Suppose you marked every third square with a letter on your
first sheet. That becomes every fourth square on the second
sheet. Now suppose we align B like this:

A B C D E F
A B C D E F

No. My letters spread as A B C D E F
(exagerated, but in yor spread, B is travelling the same speed as F,
which is not red shift observed)

Clearly the letters more distant from B seem to be moving
faster. C is moving at speed 1, D at 2 and so on. Now think
of that as two groups, ABC and DEF, and think of the change
as being composed of two effects, motion and expansion of
the groups. Group ABC has not moved as a whole since the
speeds are 1 to the left, 0 and 1 to the right, average 0.
The group is expanding since A and C are moving away from
B at speed 1 in opposite directions.

Group DEF on the other hand is moving at speed 3, 2 for D,
3 for E and 4 for F so 3 on average. DEF is also expanding
because D is moving away from E at speed 1 to the left while
F is moving at speed 1 to the right.

The key here is that both groups are expanding at the same
rate, 1 square in the interval for A/C and D/F even though
group DEF is moving rapidly but group ABC is not.

Now align E:

A B C D E F
A B C D E F

This time it is group ABC that is moving rapidly to the left
while group DEF is static. In fact it doesn't matter what
letter you align, A and C will be expanding away from B in
exactly the same way that D and F are expanding away from E.

The density has gone down for 0.33 letters per square to
0.25 letters per square everywhere and no choice of alignment
will affect that.

I think that you have placed your galaxies at distances dictated by c,
but have changed your observation points (from galaxy to galaxy)
INSTANTLY. This has allowed the appearance that the view would be the
same anywhere, when if the relocation was done similarly to the
arriving images (at c), I don't think your spread of maintained
homogeneity stands up.

So I am afraid that I still have this (belief?) that an expansion,
considering ALL the universe, by default would cause a change in
homogeneity.

Try to imagine your piece of paper as just a fraction of the
whole. No matter how big it is it is no different anywhere to
what you see on your sample. Think of a letter as far away as
you can imagine, the letters adjacent to it will be expanding
away from it by 1 square in the interval and the density in
that region has gone down from 0.33 to 0.25.

If it was 0.33 everywhere and it is now 0.25 everywhere,
homogeneity has been preserved.

Other posters refer to light being at a different velocity when the
universe was 'smaller', which is claimed to upset this view.

There has been speculation about that but nothing believable.
The possibility exists so people do tests to look for any
variation when the opportunity arises but so far it is mainly
cranks pushing their own ideas.

Also that
the expansion of space drags the galaxies along, rather than them
travelling through space. You might have to try convincing me along
those lines, in order to overcome my current skepticism ref expansion.

If you ever become conversant with GR, I will have to backtrack
on some of what I am saying. Until then, I feel it is better to
explain it in terms you understand, as close to Newtonian physics
as I can manage. However, I will be open about this and suggest
you read the following threads. These are experts who know the
subject well, the question is not the theory but how to explain
it:

http://makeashorterlink.com/?V5C032776

http://makeashorterlink.com/?U2D051776

These guys seem to chuck out the Doppler red shift for cosmological
scales. We spent considerable time in a certain railway station which
was supposed to be very sound evidence for BB per this very Doppler
red shift............

The essence is that the different ways of explaining it can
be considered equivalent under certain circumstances.

George

I'm afraid that I am still with Sean on this (or vice versa), in that
the term "expanding infinity" is oxymoronic and contradictory. There
may "appear" to have been some form of BB, but appearances can be
deceptive!
Can you perhaps give me link to Super Nova information which is
claimed to be heavy support for BB?
Thanks George

Jim G