How can we see anything from 13 billion light years away?

"Wilhelm" wrote in message
om...

So you mean that the Big Bang didn't occur in a point but in a huge
space, so that the object from which the light has travelled 13 Gly
was already at the time of the BB about 13 Gly away?

Not necessarily huge. Maybe as large as a grapefruit just
a moment after the creation event. The whole thing expanded
at rates far exceeding the speed of light for a short time,
before settiling down into a more sedate expansion/acceleration
phase that we see now.

The point though, is that the expansion occurred everywhere
and carried the contents with it. The contents are still
being carried along by the ongoing expansion.

An object that we see now whose light took some 13 Billion
years to reach us, may have been less than a billion light
years distant when the light was emitted. As the space
between it and us expanded, the light took longer to reach
us and was red shifted (stretched).


How is it possible to keep ahead of light? I though the whole idea of
SR is that light travels at the same speed so that if we at some stage
were only 0.7 Gly away from the galaxy, it should have arrived here in
0.7 Gy. Besides the speed of 10-14 Mly in 13.4 Gy wouldn't keep us
anywhere ahead of the light even if we were thinking of this without
taking into account SR.

The locally measured speed of light is always c. That's the
speed of light in empty space. But space itself can be
moving, carrying its contents, including embedded light, along
for the ride. Distant regions of the universe can be moving
away at greater than light speed, so that light from such
regions will never be able to reach us, and vice versa. Thus
we have a "cosmic horizon" centered on our location beyond
which we cannot see.

Wilhelm wrote:

Bjoern Feuerbacher wrote in message ...
Wilhelm wrote:

So you mean that the Big Bang didn't occur in a point but in a huge
space, so that the object from which the light has travelled 13 Gly
was already at the time of the BB about 13 Gly away?

No reason that that needs to be entirely false. It is believed that
everywhere is the center, but only one "when" was the center. Expansion
means that what appears as 13 Gy now was *less*, when the light was
emitted. The Universe is NOT a static structure. Us flatlanders have
real
difficulties in imagiing just how many dimensions this Universe really
has.

But if the Universe was already a large place at that time, then it
would mean that objects must have travelled MUCH faster than light
from the BB to reach their positions at 13 Gy ago. Otherwise there
would have been not enough density just after the BB to generate the
CMBR, right?

Imagining the cosmological expansion as "objects traveling away from
each other" is often problematic. It's wiser to see this as "objects
hold their places (their coordinates), but they space between them
expands". This can *look* like if objects recede from each other at
superluminal speeds - but essentially they aren't - merely the space
between them expands very fast.

Ok, I understand.

Don't be to sure about that - it's a rather slippery terrain. ;-)


And light can't beat this expansion, it actually
needs to travel a much longer distance and this is why we can see
something 13.0 Glys away.

Yes. I don't know if a cosmologist would fully agree with this, but as a
model of what's going on, it certainly makes sense.


If the object that we see is expanding to
exactly opposite direction,

Opposite of what?

(and, BTW, it's not the object which is expanding, it's the space
between us and the object)


it might actually be already 13+13-2*0.7 =
24.6 Glys away by now supposing that BB was 13.7 Gys ago.

Sorry, I couldn't follow your calculation...

Have you read the following?
http://www.astro.ucla.edu/~wright/cosmology_faq.html#DN


Now I just
need to decide whether I believe in this expansion or not.

If you accept that General Relativity is the "right" theory of gravity,
this expansion is an almost straightforward conclusion.


However,
humans always have made the mistake that they think they are in some
kind of unique place.

Well, the *basis* of the Big Bang theory is the so-called "cosmological
principle": the universe is homogeneous and isotropic, i.e. looks the
same everywhere and in every direction. That's exactly the *opposite* of
"we are in a kind of unique place".


My bet is that there are several billion other
universes

How do you define "universe"?

The standard definition for "universe" is "all that exists". Using that
definition, the term "other universes" makes no sense.


and in couple of decades there's new telescope which can
actually detect something 100 Glys away with a blueshift.

That's very unlikely - the "object" with the highest red shift we can
see (z ~ 1000) is the CMBR. Do you suggest that somehow "behind" this
CMBR, the red shift begins to decrease again, gets to zero and turns
into a blue shift? Even if this would happen, we couldn't see it -
because the stuff which produced the CMBR was optically think, i.e. no
light could pass through it.


[snip]


If I understand correctly, it seems that there are two kinds of
expansion, one is the slow one that we can measure, ie 10-14Mly in
13.4 Gy

No, the 10-14 Mly have nothing to do with expansion. That's just the
distance our galaxy moved in these 13.4 Gy "with respect to space", i.e.
wrt to that frame of reference where you see the CMBR without any
Doppler shift (this is often called the "peculiar motion", AFAIK).


and the other much faster one is the imaginary expansion which
has been invented to explain CMBR.

There is nothing imaginary about the cosmological expansion, and it
wasn't invented to explain the CMBR.

But without the expansion (if we look backwards) there would never
have been a time with sufficient density to create CMBR.

Right.


So in this
respect the expansion is necessary to explain the CMBR, isn't it?

Yes. However, "A is necessary for B" does not imply "A was invented to
explain B". It was the other way round: the BBT was invented based
essentially on General Relativity and Hubble's measurements of red
shift, and only about 20-30 years later, people realized that we should
see microwave radiation from an earlier epoch of the cosmos. And around
that time, the CMBR was indeed detected. So the CMBR is evidence for the
validity of the BBT.


Bye,
Bjoern

lid (John Savard) wrote in message ...
On 14 Mar 2004 10:51:59 -0800, (Oriel36)
wrote, in part:

You are being just plain silly,if the Sun in 9 minutes light distance
away,it means it takes 9 minutes for the light to reach us,the terms
are interchangeable

Not quite. The sun doesn't move very far in nine minutes. In 13
billion years, what we are looking at may have moved somewhere else.


A star goes supernova in a distant galaxy in M81 at a distance of 10
million light years.

http://www.nature.com/cgi-taf/DynaPa.../364600a0.html

Here is the position of M81 to our local Milky Way stars.

http://www.ast.cam.ac.uk/~ipswich/Ob...Ursa_Major.jpg

The local Milky Way stars are rotating around the galactic axis and in
principle the position of M81 changes its position over time to local
galactic rotation or what amounts to the same thing,the rotation of
our local star along with the billions of others circling a distant
axis.

The difference between the actual supernova occurence and the observed
supernova occurence is 10 million years,the local stars have rotated
10 million years and subsequently the position of the parent galaxy to
a local Milky Way star has changed by 10 million years of Milky Way
rotation.

Now you have to decide in which direction M81 changes its position to
the rotation of the local Milky Way stars noting that there is a
'Polaris' or stellar circumpolar obstacle obstructing our discernment
of the true change in orientation.

In summary,it is not a question of " may have moved somewhere else"
but a certainty with a known value for that motion,namely the stellar
rotation around the Milky Way axis.

Further complicating matters,local stellar rotation around the Milky
Way axis generates a cosmological version of the polaris effect on the
scale of galaxies but this is another matter.






John Savard
http://home.ecn.ab.ca/~jsavard/index.html

You site is excellent,truly !.

The tendency of natural forms to generate a particular geometry is
what brings me to this forum and especially Penrose tiles.I recognise
that many are not suitable to go down this avenue but there is always
a chance that the outlines may resonate with an individual.

432 deg
/
/
/
/
/
/
324 deg ////////////////////// 108 deg
/ / /
/ / / 36 deg
/ / /
/ / /
288 deg / / 72 deg / 144 deg
/
216 deg



If the above graphic does not interest you then just leave it be but
it represents the tendency of natural forms towards simplicity rather
than complexity via the mathematics and forms associated with the Phi
proportion hence Penrose tiles, their angles and the myriad of other
forms which come under the heading of Fibonacci,golden mean,divine
proportion,ect.

In attempting to justify 432 degrees within Euclidean geometry in
1990,I turned to a cosmological resolution and specifically stellar
collapse.The only copyright (1990) I possess contains two graphics,the
one above and the other presenting stellar collapse as two large outer
rings and a smaller one at intersection,I cannot represent it here but
I will show you an image from 1994.

http://www.ps.uci.edu/~superk/pic/sn1987a.gif

There is an natural geometric limit to stellar collapse which keeps
its remnants from developing further into a so-called Black Hole,part
of that explanation relies on the fact that no arrangement of Penrose
tiles or the 3 dimensional quasicrystals can form a periodic
pattern,they have a tendency towards a particular geometry but that is
as far as it goes,likewise with stellar collapse and the geometric
nature of that collapse.

Bjoern Feuerbacher wrote in message ...
Oriel36 wrote:

"N:dlzc D:aol T:com \(dlzc\)" N: dlzc1 D:cox wrote in message news:y%S4c.31300$Zp.999@fed1read07...
Dear Wilhelm:

"Wilhelm" wrote in message
om...
"N:dlzc D:aol T:com \(dlzc\)" N: dlzc1 D:cox wrote in
message news:xCG4c.30603$Zp.8461@fed1read07...
...
Supposing that the Universe is 13.7 billion years old, how can the
Hubble ST see a galaxy 13.0 billion lightyears away?

I just wish I could get a simple answer to a simple question.

So your first lesson needs to be that HST did not resolve an object "13.0
billion lightyears away". It resolved an object from which light had been
travelling for 13.0 billion years.

You are being just plain silly,

No, he is just plain right.


Well,well,well,if it is'nt Bjoern.




if the Sun in 9 minutes light distance
away,it means it takes 9 minutes for the light to reach us,
the terms are interchangeable

Not if the space in between is expanding.


Hey,be my guest,expansion is a property of geometry, and volume
specifically,the poor fools who come here trying to visualise
'expanding space' deserve everything they get.



and carry the information that there is an object
at that distance if you choose light distance as a measure where
light covers 186 000 miles in one second.

Wilhelm or anyone else should not be forced into drawing a distinction
and more importantly he is correct,you are not.

No. It's you who is wrong.




The CMBR is older still than this
(about 13.4 Gy), and we have been mapping it for decades. Based on our
current velocity, we are just 10-14 Mly from our "starting point" at the
Big Bang. And every other object is likely equally close to its
beginning.


Well you shifted ground here

No, he is still talking about the same topic. Your statement that he has
shifted ground shows quite nicely that you didn't understand what he was
saying.


and now speak of cosmological evolution from the BB

No, he wasn't. Why do you think so?


You are a ball of information,are'nt you.



and drop physical distances altogether based on the
distance light covers in a second.

Huh?



There is no way of telling if
Wilhelm noticed the shift

There was none.


but he was speaking in terms of distance
while you are now talking in terms of BB evolution and of things being
calendrically older than others.

You are making no sense.


Hey,it is all documented historically that finite light distance
generates an illusion in the anomalous motion of Io because of the
variation in the distance between Earth's orbit and Jupiter.

Even the shadow Io casts on Jupiter is part of that illusionary
motion,we are just fortunate enough to recognise that the effect is
known in terms of 186 000 miles per sec through Ole Roemer.

http://antwrp.gsfc.nasa.gov/apod/ap021207.html

No offense,but if you can't handle anomalous motion and its non local
geometric resolution within the solar system by way of finite light
distance perhaps you should take up stamp collecting or gardening.




Your last sentence proves the point that you are wasting people's
time.

Well, all your sentences so far proved this about you.


The "13.0 billion lightyears" is comparing "there then" to "here now".

Because the awful relativistic epoch still prevails

What's the "relativistic epoch"?


An enormous wordplay on Newton.




there is little
reliable information on how the anomalous motion of Io was resolved by
a geometric solution insofar as it relies on actual physical
variations in distance between the orbit of Jupiter and the Earth.The
irregularity in the appearance of Io in terms of time differences
emerge as variations in distance differences.

http://history.nasa.gov/SP-349/p6c.jpg

Astronomically,Roemer did not concern himself with 'then and now' but
with 'where and why' , the where is the difference between apparent
position and actual position of Io and the why is explained as finite
light distance.

How is this relevant to the size of the universe?


My turn,how would you know the Milky Way stars are rotating around a
central axis.Your answer should be that they change their position to
the remaining galaxies which collectively is known as the
Universe.Now,if you recognise Milky Way rotation and gives the local
stars rotational motion you cannot assume that this rotation is
against background galaxies or a 'celestial sphere' made of galaxies
unfortunately this is what you do by not taking stellar rotation
around the galactic axis into account.




The same applies to cosmological structure in terms of
galaxies but where the effects are tiny within the solar system they
are almost total on a cosmological scale.

Well, yes, the cosmological expansion is onyl relevant on cosmological
scales. OTOH, I don't know what effects *you* are talking about.


Here,let me show you that picture of Io again

http://antwrp.gsfc.nasa.gov/apod/ap021207.html

Io has an irregular motion when seen from Earth,this motion is an
effect of finite light distance due to the variation in distance
between the orbits of Jupiter and Earth,again,the irregular motion is
not caused by finite light distance,it is caused by physical
variations in distance .There are no forces involved in calculating
the true motion of Io from its apparent irregular motion so a
gravitational treatment is useless,likewise in dealing with the
effects on a cosmological scale of galaxies,these effects would be
almost total and skew the position of galaxies to our observed
position and to each other




The point is that the observed position of galaxies and the actual
positions of galaxies are two different things

Complete agreement. I think every cosmologist and even every astronomist
would agree with that.


Hardly,recognising a reference for the observed positions and the
actual position of galaxies should naturally fall to the
changing orientation of Milky Way stars to the remaining galaxies and
that involves recognising a cosmological stellar center removed from
our position namely the Milky Way center or axis.

Simple stuff that becomes rapidly complex.


and it should open up
great challenges for the future,far greater than those which occupied
astronomers who presented us with the basics derived from heliocentric
modelling.

Huh? Cosmology has nothing to do with heliocentricity.


As far as I can see it cosmology has nothing to do with anything
..Astronomy is knowing how to read observations of the night sky,few
appear to be capable of actually removing themselves from paper
theories and going outside and recognising what the illusions are and
placing the discoveries of Copernicus,Kepler,Roemer and Newton in
context.





They are incrementally different Universes, different sizes, and different
time rates (hence the red shift). And yes, expansion had kept us "ahead"
of the light from that particular galaxy, until HST spent 400 orbits
capturing enough light to resolve it.

Adding sci.astro, so that wiser heads might be able to give you a simpler
answer than "visit Ned Wright's Cosmology webpage and here's the link"...

David A. Smith

More like old frogs croaking in their swamps,let Wright suffer a
newsgroup for a while and I will show you how intellectually weak
these 'experts' are never mind the cannon fodder which goes to support
them.

I don't think that you could stand up to Wright in a discussion even one
minute.


Bye,
Bjoern

There is just as many Wrights as there are Wilhelms,one no better than
the next and all pretending to see Albert's odd curved universe.For me
it is easy,Albert tells you how he likes his universe and even gives
his reason for why he thinks it is 'curved'and uses his flatlanders to
support it.I can have a good chuckle at it while others attempt
develop it notwithstanding that his view would only amount to a latter
day Ptolemy.

Here you go,have Wright deal with Albert's 1920 dreamworld and in the
same terms.

"If we ponder over the question as to how the universe, considered as
a whole, is to be regarded, the first answer that suggests itself to
us is surely this: As regards space (and time) the universe is
infinite. There are stars everywhere, so that the density of matter,
although very variable in detail, is nevertheless on the average
everywhere the same. In other words: However far we might travel
through space, we should find everywhere an attenuated swarm of fixed
stars of approximately the same kind and density.
This view is not in harmony with the theory of Newton. The latter
theory rather requires that the universe should have a kind of centre
in which the density of the stars is a maximum, and that as we proceed
outwards from this centre the group-density of the stars should
diminish, until finally, at great distances, it is succeeded by an
infinite region of emptiness. The stellar universe ought to be a
finite island in the infinite ocean of space.
This conception is in itself not very satisfactory. It is still less
satisfactory because it leads to the result that the light emitted by
the stars and also individual stars of the stellar system are
perpetually passing out into infinite space, never to return, and
without ever again coming into interaction with other objects of
nature. Such a finite material universe would be destined to become
gradually but systematically impoverished."

This guy deserved an oscar for best screenplay and maybe they should
combine it with the Nobel prizes in future.