How can we accurately determine the expansion rate of the Universe?

[heldervelez]

I also agree with the Mark Tegmarks arguments.

I tried to ask several times: if you believe that our universe is not completely equivalent to a purely mathematical structure then please provide an example of a purely *physical* axiom which can not be expressed in mathematical terms.

Nobody succeded...

This is a philosophical question and the answer must also be like like this:

We can ommit the observers (we) from the universe and it will continue (or go back in our past 10000 years).
Subtract the Universe and we (the owners of math concepts) will not survive.
Clearly one is not 'equivalent' to the other.

Idem reasoning I apply to the hipotetical 'space is topology'.
Topology is a math construct.

We humans use math concepts to make an understable framework of our knowledge.
The egyptians started to measuring (and triangulating...) to say "this is my land" but the land itself is there in the first hand.

 

[Chalnoth]

I do not understand which one you have in your mind.

None. I don't know which mathematical structure is isomorphic to our universe. Nobody does, yet. But it is enough to know that our universe must be isomorphic to some mathematical structure, because if it weren't, then it wouldn't be consistent. And we obviously can't have that.

 

[Carid]

Math as to serve Physics, and not the contrary.
Math is a mental construction not a reality of its own.

Physics is also a mental construct; in fact everything we know is a mental construct.
Yes, there is a reality out there, and we are part of it, and so are our mental constructs. Plato told us we see shadows on the wall; Newton told us he was picking up pretty shells in front of an ocean of knowledge, etc..

However, the real point of this post is so that I can lay claim to inventing the term "Snowflake Universe" to describe the unique mathematical form that each of Professor Tegmark's universes will adopt.

 

[Sundance]

Hello

What do the actual images tell us?

a) Of all the images that we see the common behaviour is clustering effect.

Matter is drawn into a gravity sink, such as stars and black holes.

Dwarf galaxies cluster around larger galaxies, these cluster and form local cluster of galaxies, these local clusters cluster to form super clusters of clusters of galaxies.


b) That compact objects such as Stars, neutron stars, the theoretical quark stars and black holes form jets that reform their surroundings even effecting the formation of stars and galaxies.

So what we actually see is at random a process that expands and contracts. This is simple enough and yet we try to complicate the observations.

 

[Chalnoth]

So what we actually see is at random a process that expands and contracts. This is simple enough and yet we try to complicate the observations.

It's not complicating the observations. It's just attention to detail.

 

[Sundance]

Hello

Chalnoth said

It's not complicating the observations. It's just attention to detail.

Detail has been the issue for hundreds of years.

Some create a model and try to fit the data to the model and in many cases with ad hoc ideas. EG: Big Bang Theory

 

[heldervelez]

Hello
..
Some create a model and try to fit the data to the model and in many cases with ad hoc ideas. EG: Big Bang Theory

(my bold)

'Had Hoc' is very appropriate, even in the case of BB beeing correct.
It was born after the 'discovery that galaxies are moving apart'. Then all matter had to be in some point of space at the same instant.
If Hubble findings (measure) can be interpreted differently than BB is out.

 

[Chalnoth]

Hello

Chalnoth said

Detail has been the issue for hundreds of years.

Some create a model and try to fit the data to the model and in many cases with ad hoc ideas. EG: Big Bang Theory

So when one single added parameter to the theory not only explains the original observation it was originally used for, but also half a dozen other observations made since, we gain some confidence that it is at least approximately accurate.

 

[Sundance]

Hello


heldervelez said:

'Had Hoc' is very appropriate, even in the case of BB beeing correct.
It was born after the 'discovery that galaxies are moving apart'. Then all matter had to be in some point of space at the same instant.
If Hubble findings (measure) can be interpreted differently than BB is out.

Did I miss something. Actual images show a clustering effect and that galaxies move towards an attractor, a gravity sink so to speak. We see this in the Milky way little group of dwarf galaxies rotaing and gravity bound to the Milky Way. This little group is part of the local group of galaxies with M87 as the centre and this local group is moving towards the great attractor.

If you see galaxies moving away from each other its because they belong to a different group with a different attractor.

 

[Chalnoth]

Did I miss something. Actual images show a clustering effect and that galaxies move towards an attractor, a gravity sink so to speak. We see this in the Milky way little group of dwarf galaxies rotaing and gravity bound to the Milky Way. This little group is part of the local group of galaxies with M87 as the centre and this local group is moving towards the great attractor.

If you see galaxies moving away from each other its because they belong to a different group with a different attractor.

If your supposition here were correct, then galaxies on opposite sides of both attractors would appear to be moving toward one another.

 

[Sundance]

Hello Chalnoth

The movement and clustering is not my idea, its general info.

 

[Chalnoth]

Hello Chalnoth

The movement and clustering is not my idea, its general info.

It appears you have mangled it, then. The idea is that the nonlinear effect of clustering can provide the appearance of an accelerated expansion. It wasn't proposed to explain all expansion, just as an alternative explanation to dark energy. However, so far all such attempts to explain the effect in this way have failed to do so when examined in detail. It is difficult to do the analysis properly, so it isn't yet certain that this is entirely wrong, but it seems unlikely.

 

[Sundance]

Hello Chalnoth

Have a look at as many images as you like

Eg

http://www.spacetelescope.org/news/html/heic0810.html

As for expansion and acceleration, I have questions.

 

[Chalnoth]

Hello Chalnoth

Have a look at as many images as you like

Eg

http://www.spacetelescope.org/news/html/heic0810.html

I don't understand what images of colliding galaxies have to do with your discussion. I mean, they're cool and all, but I really don't see what you think they indicate.

As for expansion and acceleration, I have questions.

Okay...

 

[Sundance]

Hello Chalnoth

The link NASA/ESA has many images

Look at the observation and maybe than you will see what I'm trying to explain.

Expansion and acceleration is in spacetime.

Now look at reality.

You are trying to observe a clustering effect of all star objects.

This does not mean that expansion does not occur, this occurs at the same time throughout the universe. Eg Compact matter as in Black holes and exotic stars such as Neutron Stars in the formation of jets and ejecting matter.

 

[Chalnoth]

Hello Chalnoth

The link NASA/ESA has many images

Look at the observation and maybe than you will see what I'm trying to explain.

Yes, well, this is what I do for a living. And simply glancing at telescope images doesn't provide any significant information about the universe, except that it's pretty. You need to go much deeper than simply glancing at a few images to extract meaningful information.

Expansion and acceleration is in spacetime.

Now look at reality.

You're showing your bias right there. Spacetime is reality.

 

[Sundance]

Hello Chalnoth

Than explain the expansion and acceleration by observation.

I just do not look at nice pics, I also read astrophysics papers.

====================

So tell me about your work

 

[Chalnoth]

Hello Chalnoth

Than explain the expansion and acceleration by observation.

You've got things backwards. Observations do not explain things. Theories explain observations. And one possible explanation, that is so far consistent with all explanations, is that there is a small but non-zero cosmological constant.

So tell me about your work

I've worked on ways to distinguish between varying dark energy and constant dark energy, I've worked on estimation of the power spectrum of the cosmic microwave background, as well as foreground cleaning techniques for the CMB.

 

[Sundance]

Hello Chalnoth

Your work sounds fantastic.

What is the difference between dark matter and dark energy?

 

[Sundance]

Hello Chalnoth

May I have your opinion on this paper

http://arxiv.org/abs/gr-qc/0601033
A darkless space-time

Authors: A. Tartaglia, M. Capone
(Submitted on 9 Jan 2006 (v1), last revised 25 Apr 2007 (this version, v5))

Abstract: In cosmology it has become usual to introduce new entities as dark matter and dark energy in order to explain otherwise unexplained observational facts. Here, we propose a different approach treating spacetime as a continuum endowed with properties similar to the ones of ordinary material continua, such as internal viscosity and strain distributions originated by defects in the texture. A Lagrangian modeled on the one valid for simple dissipative phenomena in fluids is built and used for empty spacetime. The internal "viscosity" is shown to correspond to a four-vector field. The vector field is shown to be connected with the displacement vector field induced by a point defect in a four-dimensional continuum. Using the known symmetry of the universe, assuming the vector field to be divergenceless and solving the corresponding Euler-Lagrange equation, we directly obtain inflation and a phase of accelerated expansion of spacetime. The only parameter in the theory is the "strength" of the defect. We show that it is possible to fix it in such a way to also quantitatively reproduce the acceleration of the universe. We have finally verified that the addition of ordinary matter does not change the general behaviour of the model.

 

[Chalnoth]

Hello Chalnoth

Your work sounds fantastic.

What is the difference between dark matter and dark energy?

Dark matter is an as yet unknown form of matter that has no electrical charge. It is very normal in the sense that it behaves much like stuff that we already know about: neutrinos. But it has to have much more mass than neutrinos to explain our observations. Its existence is strongly evidenced and extremely likely, and many searches to discover its exact nature are currently underway.

Dark energy is a proposed mechanism to explain the expansion of the universe. A number of potential quantum mechanical fields have been proposed that would behave so as to cause an accelerated expansion. There are also initiatives to investigate whether or not this just means that gravity is different at extremely large scales. So far, we just don't have enough data to say much about dark energy, and it should be considered largely hypothetical.

 

[Chalnoth]

Hello Chalnoth

May I have your opinion on this paper

http://arxiv.org/abs/gr-qc/0601033
A darkless space-time

Authors: A. Tartaglia, M. Capone
(Submitted on 9 Jan 2006 (v1), last revised 25 Apr 2007 (this version, v5))

One of many attempts to explain dark matter/dark energy in other ways. These proposals are a dime a dozen. Nearly all are certainly wrong. As for me, I'm just going to be paying attention to the ground-based dark matter searches that are currently underway. I'm hopeful that we'll have a result from them within ten years. Furthermore, our observations of the universe will, within ten years, be to the point where we can start saying some definitive things about the dark energy. Until we have a significant experimental discrepancy to explain, I just don't see any reason to bother entertaining any particular one of the vast array of hypothetical theoretical models that attempt to explain these things.

 

[Sundance]

Hello Chalnoth

I agree with you to some degree.

Why not consider dark matter/energy as a ultra dense degenerate matter found in compact objects. Such as Neutron matter, quark matter, neutrino matter and the preon particles.

I will get back onto this topic when I'm fully awake.

I'm off to sleep.

 

[Chalnoth]

Hello Chalnoth

I agree with you to some degree.

Why not consider dark matter/energy as a ultra dense degenerate matter found in compact objects. Such as Neutron matter, quark matter, neutrino matter and the preon particles.

If I'm understanding you correctly, you're talking about normal, baryonic matter that has collapsed into dense objects as potentially being the dark matter. The are two primary problems with this that I can think of off-hand. The first is that these collapsed objects will primarily form in the areas where normal matter is the most dense, i.e. the center of galaxies. But the distribution of velocities of the matter orbiting the centers of galaxies demonstrates that most of the mass is evenly distributed throughout the galaxy. So the idea just doesn't make a whole lot of sense.

The second major issue comes in from the cosmic microwave background: we can already see the effects of dark matter in the statistical properties of the cosmic microwave background, which was emitted long before any stars were formed, back when our universe was almost completely uniform (uniform to one part in 100,000). It doesn't make much sense for there to be large numbers of collapsed objects that early in our universe.

 

[Sundance]

Hello Chalnoth

In my opinion you are quite wrong.

4% of all matter is ordinary matter the rest is in the form of ultra dense matter.

On The Nature of the Compact Dark Mass at the Galactic Center
http://arxiv.org/abs/astro-ph/0512211
Authors: Avery E. Broderick (1), Ramesh Narayan (1,2) ((1) Institute for Theory and Computation, (2) Harvard University)
(Submitted on 8 Dec 2005 (v1), last revised 31 Mar 2006 (this version, v2))

Abstract: We consider a model in which Sgr A*, the 3.5x10^6 M_sun supermassive black hole candidate at the Galactic Center, is a compact object with a surface. Given the very low quiescent luminosity of Sgr A* in the near infrared, the existence of a hard surface, even in the limit in which the radius approaches the horizon, places severe constraints upon the steady mass accretion rate in the source, requiring dM/dt < 10^-12 M_sun/yr. This limit is well below the minimum accretion rate needed to power the observed submillimeter luminosity of Sgr A*. We thus argue that Sgr A* does not have a surface, i.e., it must have an event horizon. The argument could be made more restrictive by an order of magnitude with microarcsecond resolution imaging, e.g., with submillimeter VLBI

.

and

Compact Objects and Accretion Disks
Authors: Roger Blandford (1), Eric Agol (1), Avery Broderick (1), Jeremy Heyl (2), Leon Koopmans (1), Hee-Won Lee (3) ((1) Theoretical Astrophysics, Caltech, (2) Harvard-Smithsonian Center for Astrophysics, (3) Yonsei University, Seoul, Korea)
(Submitted on 13 Jul 2001)

Abstract: Recent developments in the spectropolarimetric study of compact objects, specifically black holes (stellar and massive) and neutron stars are reviewed. The lectures are organized around five topics: disks, jets, outflows, neutron stars and black holes. They emphasize physical mechanisms and are intended to bridge the gap between the fundamentals of polarimetry and the phenomenology of observed cosmic sources of polarized radiation, as covered by the other lecturers. There has been considerable recent progress in spectropolarimetry from radio through optical frequencies and this is producing some unique diagnostics of the physical conditions around compact objects. It is argued that there is a great need to develop a correspondingly sensitive polarimetric capability at ultraviolet through gamma-ray energies.

These are not a dime a dozen.

other papers by the writer

Avery Broderick
http://arxiv.org/find/astro-ph/1/au:+Broderick_A/0/1/0/all/0/1

 

[Chalnoth]

Compact objects like those only comprise a minuscule fraction of the total mass of the normal matter. Most matter hasn't yet had the time to collapse into dense objects.

 

[Sundance]

Hello Chalnoth

I do not know where you get your infromation from.

Maybe a bit of reading on the subject

Quantum cosmology 2008
http://lanl.arxiv.org/find/all/1/all:+AND+2008+AND+quantum+cosmology/0/1/0/all/0/1

and

Higgs boson astrophysics
http://arxiv.org/find/all/1/all:+AND+astrophysics+AND+higgs+boson/0/1/0/all/0/1


and

Quarks 2008
http://arxiv.org/find/all/1/all:+AND+quarks+2008/0/1/0/all/0/1

and

Ramesh Narayan
http://arxiv.org/find/astro-ph/1/au:+Narayan_R/0/1/0/all/0/1


This is just a tip of the iceberg.

also

Neutron Matter 2008
http://arxiv.org/find/all/1/all:+AND+2008+AND+Neutron+matter/0/1/0/all/0/1

I do not mean for you to read these papers, just get a gist of it.

 

[Chalnoth]

Hello Chalnoth

I do not know where you get your infromation from.

As I said, it comes straight from the cosmic microwave background. The CMB demonstrates that dark matter was gravitationally active before the emission of the surface of last scattering, when the universe was uniform to one part in 100,000. There's not really much way for large compact objects to have existed in quantity during that era.

There are, of course, some rather exotic theoretical ideas that might work, but they tend to be rather contrived.

Personally, I suspect that we'll get a positive detection of particle dark matter within 10-20 years.

 

[Sundance]

Hello Chalnoth

Mate do you read scientific papers or you talk off the bat?

To begin with read up on CMB.

 

[Chalnoth]

Hello Chalnoth

Mate do you read scientific papers or you talk off the bat?

To begin with read up on CMB.

Yes, I do. What, pray tell, do you think I am misunderstanding with respect to the CMB?

 

[Sundance]

Hello Chalnoth

You write well and sound very humble.

With due respect, either you or me are on opposite sides of the fence.

This is the type of reading I do

Degenerate matter black holes
http://adsabs.harvard.edu/cgi-bin/nph-basic_connect?qsearch=Degenerate+matter+black+holes&version=1

CMB 2008
http://arxiv.org/find/all/1/all:+AND+CMB+2008/0/1/0/all/0/1

=======================

The thing is this.

You are asssuming that the BBT is correct and relating this to CMB.

Maybe taking one step back and get to know a bit of the workings of the parts within the universe.


This link is quite interesting

NEW THEORY OF NON-EXPANDING UNIVERSE
http://sharma-upt.com/NonexpandingUniverse.aspx

Also the link By Eric Lerner, although questioned is still quite interesting on the science side of things.

Evidence for a Non-Expanding Universe: Surface Brightness Data From HUDF
http://arxiv.org/abs/astro-ph/0509611

Maybe I'm barking up the wrong tree.

 

[Chalnoth]

Hello Chalnoth

You write well and sound very humble.

With due respect, either you or me are on opposite sides of the fence.

This is the type of reading I do

Degenerate matter black holes
http://adsabs.harvard.edu/cgi-bin/nph-basic_connect?qsearch=Degenerate+matter+black+holes&version=1

CMB 2008
http://arxiv.org/find/all/1/all:+AND+CMB+2008/0/1/0/all/0/1

Okay. And what supports your claim that there existed large, compact objects in the early universe?

The thing is this.

You are asssuming that the BBT is correct and relating this to CMB.

No. I'm inferring from the consistency of a wide variety of evidence that the BBT is at least approximately accurate.

This link is quite interesting

NEW THEORY OF NON-EXPANDING UNIVERSE
http://sharma-upt.com/NonexpandingUniverse.aspx

Also the link By Eric Lerner, although questioned is still quite interesting on the science side of things.

Evidence for a Non-Expanding Universe: Surface Brightness Data From HUDF
http://arxiv.org/abs/astro-ph/0509611

Maybe I'm barking up the wrong tree.

Indeed. This would be pseudo science. Here is one clear indication that this is so (from the website):

Since the individual red shifts have never been found to increase with time, the galaxies are not flying away to generate an expansion of the universe.

Apparently this hack is of the opinion that because an experiment has not been performed, he gets to decide what the outcome of such an experiment would be.

But just fyi, such an experiment has been proposed, and we'll probably get a confirmation of the time rate of change of redshift within a few years. It does require an extremely high-resolution spectrometer and large signal-to-noise to perform, so it just can't be done immediately.

And from his paper, he is taking data about the time-evolution of galaxies and using it to attempt to claim it supports his model, when the time-evolution of galaxies is well-supported by a wide range of data: it's not just their brightness that changes, but also the general properties (things like ratio of spirals to ellipticals and the frequency of quasars vary tremendously with redshift).

So yeah, pseudo scientist hack. I see no reason to pay any attention to his statements.

 

[blighty]

If all the matter in the universe that we see came from 1 point in space and that this 1 point in space was a super massive black hole, this super massive black hole would have exploded at almost the same time as it was formed, caused imho by the large amount of mass coming together from the gravitational pull plus the inertia at which the mass was traveling towards this 1 point. there`s no way in my mind that mass was ripped out of another dimention or anything out of the ordinary. It was there before the big bang.

 

[Sundance]

Hello Blighty

The BBT is very theoretical. Here is some information on it. This does not mean that I agree with the BBT. It's more like information.

Big Bang Theory - The Premise
http://www.big-bang-theory.com/

Five Ages of the Universe
http://www.fathom.com/course/10701055/index.html

THE BIG BANG:
http://www.umich.edu/~gs265/bigbang.htm

NASA
Foundations of Big Bang Cosmology

Please avoid the following common misconceptions about the Big Bang and expansion:

The Big Bang did not occur at a single point in space as an "explosion." It is better thought of as the simultaneous appearance of space everywhere in the universe. That region of space that is within our present horizon was indeed no bigger than a point in the past. Nevertheless, if all of space both inside and outside our horizon is infinite now, it was born infinite. If it is closed and finite, then it was born with zero volume and grew from that. In neither case is there a "center of expansion" - a point from which the universe is expanding away from. In the ball analogy, the radius of the ball grows as the universe expands, but all points on the surface of the ball (the universe) recede from each other in an identical fashion. The interior of the ball should not be regarded as part of the universe in this analogy.
By definition, the universe encompasses all of space and time as we know it, so it is beyond the realm of the Big Bang model to postulate what the universe is expanding into. In either the open or closed universe, the only "edge" to space-time occurs at the Big Bang (and perhaps its counterpart the Big Crunch), so it is not logically necessary (or sensible) to consider this question.
It is beyond the realm of the Big Bang Model to say what gave rise to the Big Bang. There are a number of speculative theories about this topic, but none of them make realistically testable predictions as of yet.
To this point, the only assumption we have made about the universe is that its matter is distributed homogeneously and isotropically on large scales. There are a number of free parameters in this family of Big Bang models that must be fixed by observations of our universe.

The most important ones are: the geometry of the universe (open, flat or closed); the present expansion rate (the Hubble constant); the overall course of expansion, past and future, which is determined by the fractional density of the different types of matter in the universe. Note that the present age of the universe follows from the expansion history and present expansion rate.

As noted above, the geometry and evolution of the universe are determined by the fractional contribution of various types of matter. Since both energy density and pressure contribute to the strength of gravity in General Relativity, cosmologists classify types of matter by its "equation of state" the relationship between its pressure and energy density. The basic classification scheme is:

Radiation: composed of massless or nearly massless particles that move at the speed of light. Known examples include photons (light) and neutrinos. This form of matter is characterized by having a large positive pressure.

Baryonic matter: this is "ordinary matter" composed primarily of protons, neutrons and electrons. This form of matter has essentially no pressure of cosmological importance.

Dark matter: this generally refers to "exotic" non-baryonic matter that interacts only weakly with ordinary matter. While no such matter has ever been directly observed in the laboratory, its existence has long been suspected for reasons discussed in a subsequent page. This form of matter also has no cosmologically significant pressure.

Dark energy: this is a truly bizarre form of matter, or perhaps a property of the vacuum itself, that is characterized by a large, negative pressure. This is the only form of matter that can cause the expansion of the universe to accelerate, or speed up.

One of the central challenges in cosmology today is to determine the relative and total densities (energy per unit volume) in each of these forms of matter, since this is essential to understanding the evolution and ultimate fate of our universe.

 

[blighty]

The space fabric that is there now was there before is what I am saying, as was the mass. but what the current theory is trying to suggest ( unless I'm not reading it right ) is that the mass appeared as if by magic along with time and space? time can only be measured as long as something moves and how can a zone infinate in all directions be born alongside something that obviously has boundrys? I'm not buying this space is growing, balloon theory that's causing matter to drift apart. it just makes me laugh :P If it is ever proved then i might believe it, all i see is different types of matter & different types of magnetism. maybee i`m just stuck in the past.

 

[Chalnoth]

The space fabric that is there now was there before is what I am saying, as was the mass. but what the current theory is trying to suggest ( unless I'm not reading it right ) is that the mass appeared as if by magic along with time and space?

No, this is incorrect. I think that the NASA summary does indicate this, but it is being somewhat misleading. The beginning it's talking about seems to be the boundary between cosmic inflation and where the classical big bang theory takes over.

If we want to talk about the absolute beginning of our universe, the event that started off the expansion, the fact of the matter is that we just don't know. There are many ideas, but we don't yet know which, if any, are accurate. Currently the earliest epoch of the universe which we can detect is known as cosmic inflation. Unfortunately we don't yet know much about cosmic inflation, but many experiments are underway. If we are able to nail down what cosmic inflation was, it may turn out that there is an unambiguous prediction for how it began. But we just don't know that yet.

It is unlikely that we will ever be able to obtain direct experimental evidence of the beginning. But we don't yet know for sure, and the indirect evidence may be enough to understand it. If we're lucky.

I'm not buying this space is growing, balloon theory that's causing matter to drift apart. it just makes me laugh :P

Well, this is just the way that gravity works.

 

[blighty]

Ok, I will do some reading because I wan`t to know why everybody thinks that if you could somehow stop our galaxy moving with an imaginary hand, then let go again and it will begin to move again, this sounds crazy to me, but then again so does a broken star that can spin 600+ times a second. :)

 

[Chalnoth]

Ok, I will do some reading because I wan`t to know why everybody thinks that if you could somehow stop our galaxy moving with an imaginary hand, then let go again and it will begin to move again, this sounds crazy to me, but then again so does a broken star that can spin 600+ times a second. :)

It's not so mysterious. If you're in an expanding universe, and moving with respect to the background, you'll tend to catch up with the surrounding matter after a time, eventually becoming basically stationary with your surroundings again.

 

[blighty]

It's not so mysterious. If you're in an expanding universe, and moving with respect to the background,

What background are we talking about here? maybe this is were I am becoming confused, the way i`m interpreting the balloon theory is that it`s this background that is expanding and carrying the mass with it, ( hope i`m not annoying you here, But I wan`t to understand it all the same as the next person ) that is the part I disbelieve/find hard to believe.

Many thank you for your time Chalnoth :)

 

[Chalnoth]

What background are we talking about here? maybe this is were I am becoming confused, the way i`m interpreting the balloon theory is that it`s this background that is expanding and carrying the mass with it,

Please don't call it a balloon theory. The balloon is an analogy, and is not precisely representative of the theory.

With that out of the way, consider a one-dimensional case. Imagine a simple number line like so:

-4 -3 -2 -1  0  1  2  3  4

Imagine that the above numbers represent positions. Now, if H₀ is equal to 2 in these units, then the velocities associated with each of these points will be:

-8 -6 -4 -2 0  2  4  6  8

This is what uniform expansion looks like: the recession velocity is proportional to distance. Now, then, what happens if I move over to the right one step? I'll re-write the position number line so that the "zero" point is now one position to the right:

-5 -4 -3 -2 -1  0  1  2  3

See how it looks the same, just shifted? And what happens if I'm also now at rest with respect to the new point, so that the local velocity is zero? Then I just shift the velocity number line by subtracting the velocity at one position to the right, which is equal to +2:

-10 -8 -6 -4 -2 0  2  4  6

Again, it looks exactly the same, just shifted.

So, then, what happens if I'm sitting at some "zero", but am moving with respect to the background? I could measure this by comparing the recession velocities in one direction to those in another: if I'm not moving with respect to the background, the recession velocities should be identical (on average) in every direction. If I am moving, then they won't be. So if I look around, and the recession velocities are much bigger in one direction, then I'm moving with respect to the "cosmic rest frame".

This would be the equivalent of having a position number line that looks like:

-4 -3 -2 -1  0  1  2  3  4

...but a velocity number line that looks like:

-10 -8 -6 -4 -2 0  2  4  6

In this situation, we would be seen to move towards the right on the number line (since at the local point, the velocity of stuff in the universe is -2, the universe is moving to the left, which is the same as us moving to the right). And as we move to the right, stuff will be moving a little bit less to the left and more to the right, so we slow down. This continues until we slow to the point where we're stationary with respect to everything else. Until when we measure the positions and velocities of stuff around us and see something like:

-4 -3 -2 -1  0  1  2  3  4

-8 -6 -4 -2 0  2  4  6  8

Did that help?

 

[Sundance]

Hello

The observable universe does not show expansion or acceleration one way or another.

It does show a clustering affect.

The clustering produces areas of high density such as large galaxies and centres of clusters of galaxies that produce extremely large jets and Star that produce extremely small jets. This process of ejecting matter and reforming star and galaxies is a main player in the universe.


A Jet is a Jet, Big or Small: Scale Invariance of Black Hole Jets
http://www.mpa-garching.mpg.de/HIGHLIGHT/2003/highlight0308_e.html


The blowtorch jet in the radio galaxy NGC 6251
http://www.astr.ua.edu/keel/agn/ngc6251.html

One important lesson from radio galaxies is that the central engine continues to eject material in nearly the same direction for at least several million years, based on the fact that the tiny parsec-scale jets in the core regions point in the same direction as the very extended radio structure which may stretch several million light-years (and thus took at least that many years to form).

Photo Release - heic0804: Gargantuan galaxy NGC 1132 - a cosmic fossil?
http://www.spacetelescope.org/news/html/heic0804.html

The Origin of the Brightest Cluster Galaxies
http://www.cita.utoronto.ca/~dubinski/bcg/

Giant Galaxy's Violent Past Comes Into Focus
http://chandra.harvard.edu/press/04_releases/press_051004.html

and

Spectacular X-ray Jet Points Toward Cosmic Energy Booster
http://chandra.harvard.edu/press/00_releases/press_060600pic.html

M87:
Chandra Reviews Black Hole Musical: Epic But Off-Key
http://chandra.harvard.edu/photo/2006/m87/

The processes show a two part one part contracting pulling in star matter into dense regions and the other part ejecting the matter back into space reforming not just star areas but galaxies afar.

 

[Chalnoth]

Hello

The observable universe does not show expansion or acceleration one way or another.

It does show a clustering affect.

And your evidence for this is? Because nothing you posted after this has any relevance whatsoever to any of these claims you have made.

 

[Sundance]

G'day Chalnoth

I have given you information and you come back with such a statement.

The question is do you want to understand what's happening?

If you do than start reading

This topic, it has the key to many issues.


Magnetic Reconnection
http://arxiv.org/find/all/1/all:+AND+Magnetic+Reconnection/0/1/0/all/0/1

If you do not read it so be it.

 

[Chalnoth]

G'day Chalnoth

I have given you information and you come back with such a statement.

The question is do you want to understand what's happening?

If you do than start reading

This topic, it has the key to many issues.


Magnetic Reconnection
http://arxiv.org/find/all/1/all:+AND+Magnetic+Reconnection/0/1/0/all/0/1

If you do not read it so be it.

I suspect I understand the issues at hand much better than you do. It is not enough to simply throw a few papers out there and claim that they support your case. Make your case, and I will respond.

 

[Sundance]

Hello Chalnoth

You said

I suspect I understand the issues at hand much better than you do. It is not enough to simply throw a few papers out there and claim that they support your case. Make your case, and I will respond.

Its OK, do not worry about. You know all.

 

[Chalnoth]

Its OK, do not worry about. You know all.

No, I don't. I'm just saying I am likely aware of a fair fraction of the evidence you are presenting. At least as it relates to cosmology. So make your case already. Why, specifically, does this evidence endorse your view?

 

[Sundance]

Hello Chalnoth

My view is not that important. It's what science can prove and give us some understanding of the working parts of the universe.

I keep on reading knowing that I know very little and yet what I know tells me that you lack understanding of critical issues.

Here is another topic I want you to read.

Sort By date
Neutron Star Cores
http://adsabs.harvard.edu/cgi-bin/nph-basic_connect?qsearch=Neutron+Star+Cores&version=1

 

[Chalnoth]

Hello Chalnoth

My view is not that important. It's what science can prove and give us some understanding of the working parts of the universe.

Okay...

I keep on reading knowing that I know very little and yet what I know tells me that you lack understanding of critical issues.

But you keep throwing out stuff about the astrophysics of particular objects in the universe. The astrophysics of these objects has no direct bearing upon cosmology. So why do you think these are 'key' issues? What makes them key? Why are they important?

Because as far as I'm concerned, I'm really only interested in understanding astrophysics so far as it helps me to understand cosmology. Cosmology is what interests me the most. And you haven't even attempted to draw a logical line between the astrophysics of these particular objects and cosmology. So what are you trying to say?

 

[Sundance]

G'day Chalnoth

Those topics are Key topics. I think you missed the boat in understanding astrophysics and cosmology.

Understanding the parts that make up the larger parts is quite important.

What triggers a Supernova?

What triggers a Jet small or large?

What evolution path do galaxies take?

How do galaxies form small or large?

Since you find no value in those topics so be it.

 

[Chalnoth]

G'day Chalnoth

Those topics are Key topics. I think you missed the boat in understanding astrophysics and cosmology.

Understanding the parts that make up the larger parts is quite important.

What triggers a Supernova?

What triggers a Jet small or large?

What evolution path do galaxies take?

How do galaxies form small or large?

Since you find no value in those topics so be it.

There is value in these topics, to be sure, but they're not things I personally find interesting.

Except perhaps for the supernova part. At least for Type IA supernova, the supernova occurs when a white dwarf that is accreting matter exceeds the Chandrasekhar limit. I like to have at least some understanding of these as they directly impact cosmology (as they're used as distance measures).

The other points you bring up are, as yet, very poorly-understood. Many astrophysicists are extremely interested in those questions. I am not. I'm interested in the large-scale behavior of the universe, not the details of objects within it. And none of these topics are key topics for understanding the large-scale behavior.