Researchers Using Hubble and Keck Telescopes Find Farthest Known Galaxy in the Universe

Bart Mathias wrote:

Bjoern Feuerbacher wrote:
Luigi Caselli wrote:

"Bjoern Feuerbacher" ha scritto nel
messaggio ...

Luigi Caselli wrote:

But "rushing away" does cause a Doppler shift, does it not?

In the standard big bang theory Doppler shift is the reason for "rushing
away".

Sorry, but this makes no sense. Did you want to say:
"In the standard big bang theory 'rushing away' is the reason for
Doppler shift"?

If yes: that would make sense, but would be wrong nevertheless..

You're right (is the "rushing away" that creates Doppler shift), but why is
wrong?


That's a popular misconception about the cosmological red shift. It
isn't called by galaxies actually moving - it is caused by the space
between galaxies expanding.

I think part of the reason that misconception remains popular is that it
is hard for us laymen to see why space expands between galaxies, but not
between the stars within galaxies and between the molecules that make up
our yardsticks (and analogically, the "yardsticks" by which we measure
wavelengths).

Was this a question? Or did you only want to point out that many people
don't understand this?

If this was a question: the space between stars within galaxies and
molecules in a yardstick does expand, too - but this is more than made
up by the gravitational attraction between the stars resp. the
electromagnetic attraction between the molecules.

Only on very large scales (say, 10 Mpc or more - I don't know the exact
number off hand), the gravitational attraction is weak enough that it
can be "overrun" by the expansion.


Bye,
Bjoern

Bjoern Feuerbacher wrote:
Bart Mathias wrote:
...
I think part of the reason that misconception remains popular is that it
is hard for us laymen to see why space expands between galaxies, but not
between the stars within galaxies and between the molecules that make up
our yardsticks (and analogically, the "yardsticks" by which we measure
wavelengths).


Was this a question? Or did you only want to point out that many people
don't understand this?

If this was a question: the space between stars within galaxies and
molecules in a yardstick does expand, too - but this is more than made
up by the gravitational attraction between the stars resp. the
electromagnetic attraction between the molecules.

It is a question for me. Back in my youth I read an analog of the
expanding universe (might possibly have been in George Gamow's _One Two
Three Infinity_) with dots on a balloon that was blown up.

That analogy has space expanding but the "galaxies" expand as well. So
if there was 100 galaxy diameters of space between two galaxies before
the balloon was blown up much, there would still be 100 bigger galaxy
diameters of space between them when it was puffed up big.

If space itself is expanding, then the distances between ever-larger
galaxies should look the same--be measured in the same number of now-
longer lightyears--as when they and the universe were smaller. And with
the expanded angstrom, blue light should still be blue no matter how
long it has traveled.

Obviously that's not how it works. But to people who don't have an
awful lot of special education (about gravitational attraction?), it
must seem to be the way it should work.

Bart Mathias

Bart Mathias wrote:

Bjoern Feuerbacher wrote:
Bart Mathias wrote:
...
I think part of the reason that misconception remains popular is that it
is hard for us laymen to see why space expands between galaxies, but not
between the stars within galaxies and between the molecules that make up
our yardsticks (and analogically, the "yardsticks" by which we measure
wavelengths).


Was this a question? Or did you only want to point out that many people
don't understand this?

If this was a question: the space between stars within galaxies and
molecules in a yardstick does expand, too - but this is more than made
up by the gravitational attraction between the stars resp. the
electromagnetic attraction between the molecules.

It is a question for me. Back in my youth I read an analog of the
expanding universe (might possibly have been in George Gamow's _One Two
Three Infinity_) with dots on a balloon that was blown up.

Yes, that's a common analogue. Unfortunately many people confuse this
analogue with reality and thus take it too far...


That analogy has space expanding but the "galaxies" expand as well.

The analogy would be better if you wouldn't point dots on the balloon,
but glue cent pieces to it.


So
if there was 100 galaxy diameters of space between two galaxies before
the balloon was blown up much, there would still be 100 bigger galaxy
diameters of space between them when it was puffed up big.

Right. The analogy is false, plain and simple.


If space itself is expanding, then the distances between ever-larger
galaxies should look the same--be measured in the same number of now-
longer lightyears--as when they and the universe were smaller.

But light years don't get longer. A light year is the distance light
travels in one year. The length of a year stays the same, light speed
stays the same, hence the length of a light year stays the same.


And with
the expanded angstrom, blue light should still be blue no matter how
long it has traveled.

The angstrom doesn't expand, too.


Obviously that's not how it works. But to people who don't have an
awful lot of special education (about gravitational attraction?), it
must seem to be the way it should work.

Yes - as in most topics of complex science, the popular science accounts
of it are often so oversimplified that they become simply wrong. Just
like David A. Smith in this thread, I often get angry at popular science
articles because they have *again* written something which simply isn't
true - and thereby confused the public only more.


Bye,
Bjoern

Bjoern Feuerbacher wrote:
Bart Mathias wrote:
... Back in my youth I read an analog of the
expanding universe (might possibly have been in George Gamow's _One Two
Three Infinity_) with dots on a balloon that was blown up.


Yes, that's a common analogue. Unfortunately many people confuse this
analogue with reality and thus take it too far...



That analogy has space expanding but the "galaxies" expand as well.


The analogy would be better if you wouldn't point dots on the balloon,
but glue cent pieces to it.

But then we're seemingly back to it being not space per se that is
expanding, but we're getting more units of intergalactic space: the
galaxies are moving apart and there are more light years between them.
Consider if a line representing a light year had been painted on the
balloon. Doesn't work--you have to glue on a piece of thread.

There's another common analogy that doesn't work, the one for
visualizing curved space-time. You imagine a large ball on an elastic
sheet, That makes the sheet curve down, so if you roll a small ball
across the sheet it will roll down around the big ball.

How would that work in the space station? According to the analogy,
gravity is caused by gravity!

Bart Mathias

Bart Mathias wrote:

Bjoern Feuerbacher wrote:
Bart Mathias wrote:
... Back in my youth I read an analog of the
expanding universe (might possibly have been in George Gamow's _One Two
Three Infinity_) with dots on a balloon that was blown up.


Yes, that's a common analogue. Unfortunately many people confuse this
analogue with reality and thus take it too far...



That analogy has space expanding but the "galaxies" expand as well.


The analogy would be better if you wouldn't point dots on the balloon,
but glue cent pieces to it.

But then we're seemingly back to it being not space per se that is
expanding, but we're getting more units of intergalactic space:

Huh? Where do you see the difference between these concepts?


the
galaxies are moving apart and there are more light years between them.

Or, alternatively, the space between the galaxies is expanding!


Consider if a line representing a light year had been painted on the
balloon. Doesn't work--you have to glue on a piece of thread.

Yes, obviously.


There's another common analogy that doesn't work, the one for
visualizing curved space-time. You imagine a large ball on an elastic
sheet, That makes the sheet curve down, so if you roll a small ball
across the sheet it will roll down around the big ball.

How would that work in the space station? According to the analogy,
gravity is caused by gravity!

Yes, that's another analogy I don't like very much, for precisely this
reason.

It can be improved of you don't take only one elastic sheet, but two,
between which the small ball is "trapped". I think in this case, the
small ball would roll around the big ball even without gravity pulling
it down.


Bye,
Bjoern

My understanding is nature showed us a galaxy 13.4 LY away by gravity
lensing. Bert

"N:dlzc D:aol T:com (dlzc)" N: dlzc1 D:cox wrote in
message news:z%yYb.1578$4K3.274@fed1read06...
Dear OG:

"OG" wrote in message
...

"N:dlzc D:aol T:com (dlzc)" N: dlzc1 D:cox wrote in
message news:0MeYb.435$C21.161@fed1read07...

Events that occur on the surface of the Sun are red-shifted. They are
red-shifted because the density of the space they occur in is higher
than
where the events are measured... namely on Earth.

Density of space ? What are the units of that then?? cubic metres per
cubic metre???

Density of the Universe, like the density of anything else is typically
mass/volume^3. So an ancient Universe that was only tens of light years in
diameter (based on the CMBR), and the Universe today would have different
densities. Assuming the amount of mass has not changed.

So to say that those
events (on the Sun) are red-shifted because they are rushing away, is
incorrect. The ancient Universe had a much higher density. The red
shift
we perceive of the ancient Universe as compared to the here&now is due
primarily to the density of the two Universes.

That seems a very odd thing to say. Surely if you were right, then the
red
shift of distant objects would go as the third power of distance, rather
than linearly with distance as observed.

Two things...
Dark Matter was not evident at the time of the CMBR, and
the relationship between "time rate" and density may not be linear.

I find the simplified relationship:
/\T/T = g/\R/c^2 at
URL:http://www.pact.cpes.sussex.ac.uk/~markh/GR/node24.html

Substituting...
g = GM/R^2

/\T/T = G*M/c^2 * /\R/R^2

It's not third order in radius...

Allowing rho = M/R^3

/\T/T = G*/\R*R/c^2 * rho

It appears first order in density, but it leaves the extra R term as a
nasty.

David A. Smith

Hi David, I've been away - otherwise I would have replied earlier.

I think you are mistaken in talking about 'density' in respect of red
shift - if by that you mean the density of the gas producing the spectral
features.
The spectral lines in the solar spectrum are created in the photosphere
which is very much lower density than the earth's atmosphere. So in your
model the spectral lines would be 'blue shifted' as they moved from the low
density photosphere to practically zero density space between the sun and
the earth and back into the 1300g/m^3 Earth's atmosphere.
Now, maybe you meant something other than 'density', but that's what you
said.

Going back to the website you referred to; that gives an equation for
calculating time dilation between two points in a radial gravitational
field - I would be surprised if it can be straightforwardly applied to
derive a 'cosmolological red shift' in the way you hope.

For instance - the term R in the formula is used to give a distance from the
centre of gravity, and I don't accept that it can be used to represent a
scale size of the universe in the way you have done.

If you can provide any good references I would be interested to read further
about this.

Owen

Hi Owen Photons from the sun's core are gamma photons. There absorbing
and emission this way and that before coming to the sun's surface some
100,000 years later changes the overall wave lengths of photons to be in
the middle of the spectrum,and that means white light. If all photons
came right to our eyes without this time lapse from the sun's core. It
would be gamma.(invisible) Some of it is. Lots of photons are in the
inferred. X-ray. etc Nature saw to it that the middle of the spectrum
would be better for our brain to recieve light. Bert

"G=EMC^2 Glazier" wrote in message
...
Hi Owen Photons from the sun's core are gamma photons. There absorbing
and emission this way and that before coming to the sun's surface some
100,000 years later changes the overall wave lengths of photons to be in
the middle of the spectrum,and that means white light. If all photons
came right to our eyes without this time lapse from the sun's core. It
would be gamma.(invisible) Some of it is. Lots of photons are in the
inferred. X-ray. etc Nature saw to it that the middle of the spectrum
would be better for our brain to recieve light. Bert

DO YOU MIND I was talking about something else.

Dear OG:

"OG" wrote in message
...

"N:dlzc D:aol T:com (dlzc)" N: dlzc1 D:cox wrote in
message news:z%yYb.1578$4K3.274@fed1read06...
Dear OG:

"OG" wrote in message
...
....
So to say that those
events (on the Sun) are red-shifted because they are rushing away,
is
incorrect. The ancient Universe had a much higher density. The
red
shift
we perceive of the ancient Universe as compared to the here&now is
due
primarily to the density of the two Universes.

That seems a very odd thing to say. Surely if you were right, then
the
red
shift of distant objects would go as the third power of distance,
rather
than linearly with distance as observed.

Two things...
Dark Matter was not evident at the time of the CMBR, and
the relationship between "time rate" and density may not be linear.

I find the simplified relationship:
/\T/T = g/\R/c^2 at
URL:http://www.pact.cpes.sussex.ac.uk/~markh/GR/node24.html

Substituting...
g = GM/R^2

/\T/T = G*M/c^2 * /\R/R^2

It's not third order in radius...

Allowing rho = M/R^3

/\T/T = G*/\R*R/c^2 * rho

It appears first order in density, but it leaves the extra R term as a
nasty.

Hi David, I've been away - otherwise I would have replied earlier.

No issues.

I think you are mistaken in talking about 'density' in respect of red
shift - if by that you mean the density of the gas producing the spectral
features.

The spectral lines in the solar spectrum are created in the photosphere
which is very much lower density than the earth's atmosphere. So in your
model the spectral lines would be 'blue shifted' as they moved from the
low
density photosphere to practically zero density space between the sun and
the earth and back into the 1300g/m^3 Earth's atmosphere.

Now, maybe you meant something other than 'density', but that's what you
said.

I refer to the density of the entire Universe, at two different times. The
instant of emission occured in a Universe with a mass M_u, and a size R_u.
Absorption occured in a Universe that is likely close to M_u, but R_u is
now larger. So the "time base" for the absorbing Universe is short,
compared to the "time base" at emission.

Going back to the website you referred to; that gives an equation for
calculating time dilation between two points in a radial gravitational
field - I would be surprised if it can be straightforwardly applied to
derive a 'cosmolological red shift' in the way you hope.

For instance - the term R in the formula is used to give a distance from
the
centre of gravity, and I don't accept that it can be used to represent a
scale size of the universe in the way you have done.

It would be naive to think it could be that easy. And it would be a pretty
boring Universe if everything were that easy. But my point was only that
the time base might not have to vary by 1/r^3. I am not up to a reasonable
attempt at what the quantitative relationship should be.

If you can provide any good references I would be interested to read
further
about this.

I do not find any web sites that have my "unique" interpretation of red
shift. This one is always good:
URL:http://www.astro.ucla.edu/~wright/cosmo_02.htm. Anyway, think Shapiro
time delay, if you are concerned about light passing through empty space.

I will only offer that we are moving at 200-300 km/sec wrt the Universe at
large, and likely have done so since we were embedded in the CMBR. If
"rushing away" from the ancient Universe is the correct terminology, then
we do so along the time axis. I just don't think "rushing away" is the
right terminology, which is why I was bitching. It has the baggage of
describing "where did the energy come from" to make us "rush away", faster
and faster.

Are you OK with "rushing away" to describe the red shift? Maybe I'm just
being too critical...

David A. Smith