Space is NOT expanding. Where are the holes in this simplistic view?

[ckollerer]

No expansion of space, per se? Sure, all galaxy groups appear to be traveling away from ours. But does that mean the universe is inexplicably expanding, like a loaf of raisin bread, as some have likened it? I think not exactly. I think it is expanding, in that all objects appear to be moving away from each other, leaving ever greater space between them. But pardon me if I hesitate to subscribe to the widely-accepted hypothesis that "actual space" is expanding like a loaf of raisin bread.

Here is my simpler explanation:

The origin point of the big bang is the point from which all things have been driven in all directions for some 14 billion odd years. (Discounting incidental cross-vectoral forces.) So even objects relatively close to our galaxy group, having been blown away from that origin at very, very, very nearly the same vector as ours, are continuing to separate away from us exponentially, as that ever-so-slight vector differential evolves into an ever greater physical separation.

I really hope I'm just naive about this. I'd hate to think the whole of astrophysics has been derailed on a false notion. Please set me straight.

 

[schroder]

Let’s say there are two particles along the 1 degree line that are separating as they move forward, and two particles along the two degree line doing the same thing. Then you would have as many particles moving closer together as you have moving farther apart. In order for all particles to be moving away from each other, it seems space must be uniformly expanding in all directions.

 

[ckollerer]

Let’s say there are two particles along the 1 degree line that are separating as they move forward, and two particles along the two degree line doing the same thing. Then you would have as many particles moving closer together as you have moving farther apart. In order for all particles to be moving away from each other, it seems space must be uniformly expanding in all directions.

I think we agree, except on the definition of space expansion.

Local particles conglomerated into local galaxies and galaxy groups. The spokes of big-bang vectors diverged over the 14 billion years. In current time, these galaxy groups are continuing to fly far apart enough to be beyond each other's gravitational influence. So far out from the epicenter, space becomes vaster and vaster exponentially.

My simple view seems more able to account for the dilution of mass to space to me. I need better convincing. Call me hard-headed.

 

[russ_watters]

Your view requires there to be an edge. There isn't one.

You also either misunderstood what shroder was saying or have an incorrect understanding of what is observed. The point schroder was trying to make is that the velocity distribution would be different from what we observe if the Big Bang were like an explosion. This is easiest to see the further back you look. The Hubble Deep Field pictures would reveal very different views because they were shot in different directions. And if the Big Bang happened at a single point, in one direction, then there would be no CMB. The CMB is essentially radiation left over from the big bang and we see it from all directions, which means everywhere we look, the big bang happened there.

 

[Hurkyl]

My simple view seems more able to account for the dilution of mass to space to me.

How do you figure? You have made no quantitative predictions to be tested. Heck, I don't think you've even made any qualitative predictions! Upon what grounds can you possibly make your claim?

 

[ckollerer]

Your view requires there to be an edge. There isn't.

No requirement for an edge, just an epicenter. The only discernable edge would be this moment in time. But that has more to do with perspective than edge.

 

[russ_watters]

No requirement for an edge

How could something that looks like an explosion not have an edge?

just an epicenter.

Like I said: there isn't one. We'd see evidence of it if there was. Instead, we see evidence of the big bang in every direction.

The only discernable edge would be this moment in time. But that has more to do with perspective than edge.

That doesn't make any sense. Could you rephrase?

 

[ckollerer]

How do you figure? You have made no quantitative predictions to be tested. Heck, I don't think you've even made any qualitative predictions! Upon what grounds can you possibly make your claim?

I thought I was asking a just asking a question. My comment states I am not persuaded by schroder's quick response.

But you raise an interesting point. Rather than giving me a reason why I am wrong, you put the onus on me to prove I am right. And in so doing you have given implied merrit to my simple question. I thought it was a very simple question. Now it is something else, a problem.

 

[ckollerer]

How could something that looks like an explosion not have an edge? Like I said: there isn't one. We'd see evidence of it if there was. Instead, we see evidence of the big bang in every direction. That doesn't make any sense. Could you rephrase?

Of course the outer reaches of what we know of the initial energy wave of the big bang are all exterior to us. We are within that "expanding bubble". If you need an edge defined for my question to make sense to you. That would be it.

However, I am concerned with the galaxy clusters which we agree are all moving away from each other within that bubble.

 

[ckollerer]

If my question is being taken seriously, then it behooves us to look for evidence of the big bang's epicenter. How should that be done? Instead we are looking for explanations of actual-space expanding.

(I will not be making any more real-time responses in this thread today. I will review the thread tomorrow. Thank you for helping me clarify my question.)

 

[atyy]

In Milne's model space is not "expanding", and particles move away from each other because of an initial explosion. However, Milne's model requires that the particles be massless. This article discusses the Milne and Friedmann models.

Is space expanding in the Friedmann universe models?
Oyvind Gron, Oystein Elgaroy
http://arxiv.org/abs/astro-ph/0603162

 

[marcus]

expansion of space, per se...widely-accepted hypothesis that "actual space" is expanding like a loaf of raisin bread...

widely-accepted by whom? not in standard mainstream cosmology.
I think what is confusing you is somebody's straw man.

This is just my experience talking with astronomers and reading the research literature, but my impression is what they mean by expanding universe in standard cosmology is best thought of as a pattern of increasing distances, which behave to some extent as if they were distances on a sheet of rubber balloon being expanded. That analogy merely helps visualize the pattern of increasing distances. But don't push the analogy too far. Don't confuse space with rubber or any other material.

I think probably one should reserve phrases like "space itself expands" for talking to journalists, laymen, children and other people needing a nonmath verbal surrogate

I never heard anyone (in lecture or among professionals) say "actual space expands" or "space, per se, expands". That would be assuming space to be some sort of material. Like dough or rubber.

So I tend to think people who pretend that astronomers say "space itself" or "space per se" or "actual space" expand as promoters of or hoodwinked by a cheap straw man tactic aimed at misrepresenting what the mainstream cosmology picture actually is. Intentionally or not, they mislead us into thinking that the mainstream community re-ifies space, thinks of space as a substance. And then often as not they offer some patent medicine as a cure.

 

[cepheid]

So I tend to think people who pretend that astronomers say "space itself" or "space per se" or "actual space" expand as promoters of or hoodwinked by a cheap straw man tactic aimed at misrepresenting what the mainstream cosmology picture actually is.

Okay...so what is that picture? What does it mean to say that the universe is expanding?

 

[marcus]

Okay...so what is that picture? What does it mean to say that the universe is expanding?

cosmology is a mathematical science. the basic components are mathematical objects, not verbal statements. the thing to focus on is the metric----essentially a distance function---and in cosmology it's typically the FRW metric

and typically in cosmology the model is given by a couple of simple differential equations (Friedmann eqns) that determine the evolution of a function a(t) called the scalefactor which is a key factor in the FRW metric.

expanding universe just means that a(t) is an increasing function of time.
Hubble law which derives from the Friedmann eqn model is just a pattern of increasing distance between stationary points

stationary essentially means wrt CMB (same temp in all directions, no doppler hotspot). universe time is time measured by stationary observers.
=====================
You might try reading the Balloon Analogy sticky thread.

Thanks for asking the question!

One thing that is often omitted is that as of 1915 GR taught us that geometry is dynamic. It is changeable. You have no right to expect that a triangle always adds to 180 degrees, or that distances between stationary points always stay the same. That is what curvature is all about.

Gravity is geometry. The gravitational field is identical to the metric and the metric is what determines the geometry. If the gravitational field is dynamic then so likewise is the geometry and you have to be skeptical of Euclidean prejudice. So it is no big deal for distances to increase. What else are they going to do? You don't suppose they'll stay the same do you?

 

[Hurkyl]

I don't know how accessible this is, but it's certainly fun (IMHO):

http://math.ucr.edu/home/baez/gr/

 

[gonegahgah]

Russ I understand the assertion that there is no epicentre and no edge to the universe.

Sorry, I prefer 'assertions' instead of 'statements' because we can only see our part of the universe and despite any CMB data that will always be the case.

That's fine. Not my question.

No edge means I guess that there was never an edge at any time.

What is your view then if we were able to stop the universe in time and travel forever.
Will we get back to where we start? or
Do we travel on forever finding unknown galaxies as we go forever and ever?

I guess the question is: at this moment are there a finite number of galaxies or is there an infinite number of galaxies?

 

[russ_watters]

Of course the outer reaches of what we know of the initial energy wave of the big bang are all exterior to us. We are within that "expanding bubble". If you need an edge defined for my question to make sense to you. That would be it.

Well ok then: there is no edge and no epicenter. So that's pretty simple and clear evidence that your idea is wrong.

If my question is being taken seriously, then it behooves us to look for evidence of the big bang's epicenter. How should that be done?

We point telescopes of all types at the sky and actually look for them. Not finding them and instead finding things that preclude the possibility of their existence proves they don't exist.

You are implying that we see only what we want to. That just isn't the case. It is you who are not taking seriously the thousands of scientists who have/are researching this. They aren't the idiots you are assuming them to be.

 

[russ_watters]

Russ I understand the assertion that there is no epicentre and no edge to the universe.

Sorry, I prefer 'assertions' instead of 'statements' because we can only see our part of the universe and despite any CMB data that will always be the case.

That's fine. Not my question.

That doesn't make a lot of sense, but ok...

No edge means I guess that there was never an edge at any time.

What is your view then if we were able to stop the universe in time and travel forever.
Will we get back to where we start? or
Do we travel on forever finding unknown galaxies as we go forever and ever?

I guess the question is: at this moment are there a finite number of galaxies or is there an infinite number of galaxies?

AFAIK, the universe is believed to be finite, so if you could freeze the expansion, you could travel "around" it and end up back where you started, kinda like traveling around the earth.

 

[Chronos]

. . . The origin point of the big bang is the point from which all things have been driven in all directions for some 14 billion odd years.

Aye, there is the rub. The big bang had no 'point' or origin. It happened 'everywhere'. There is no evidence suggesting the presence of any preexisting space or time when the BB occured. This is a common misperception.

 

[gonegahgah]

AFAIK, the universe is believed to be finite, so if you could freeze the expansion, you could travel "around" it and end up back where you started, kinda like traveling around the earth.

So the expanding expansion was the thing that was generated at the time of the 'big bang' and it just happened to have materials present in it. These exotic materials weren't blowing away from each other as part of the 'big bang'; they were just caught up in the expanding expansion. However these TOE materials then began to form sub-particles and exotic particles while still being 'dragged' with the expansion and somewhere along the line 'gravity particles' (matter and dark matter)' and 'antigravity something' (dark energy) formed and began to exert their influence on each other and the expansion itself; there being more dark energy influence the expansion is accelerating.

(Just a side question: does dark energy shun everything including other dark energy?)

Are there any suggestions also as to the trigger for these expansions to occur? I imagine you could get other expansions of different initial speeds and different quantities of exotic material? I wonder what causes the initial speed of expansion and the quantity of finite exotic material? Stephen Hawking gave us evaporating black holes (bless his soul) so I imagine everything evaporates down to the smallest possible expanded form? What is the form of this fully expanded and evaporated material?

Why did the exotic material bother to form into sub-particles in the first place? How did it form before 'gravity particles' existed to pull it together?

So the expansion must have a physical presence to be able to carry things along with it in its expansion? Yet it is not formed of any particles or material itself is it? Or strings? That is correct isn't it?

 

[ckollerer]

This thread has had a lot of arguments for me to respond to individually. I will instead, summarily state the holes and misconceptions of the simplistic question have been well-exposed by the profound contributions to this thread. Excellent referrences too! I graciously thank all who responded.