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  #1  
Old 13-01-2006, 07:15 AM
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iceman (Mike)
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Article: The Structure and Proportions of the Universe

Hi all.

The Cosmic Sentinel has kindly written a great article The Structure and Proportions of the Universe.

You can read the article at the IceInSpace Articles page, or directly by clicking on the link below:

The Structure and Proportions of the Universe

Thanks to The Cosmic Sentinel for his contribution.

If you'd like to submit an article/how-to/review for the site, please contact me.

Last edited by iceman; 16-01-2006 at 07:38 AM.
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Old 16-01-2006, 07:38 AM
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Placeholder replaced with article. Bumping.
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  #3  
Old 25-01-2006, 03:27 PM
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Howdy Iceman,
Interesting play on ratios.
Apart from a few numbers being debatably incorrect good article, 'cept for
one thing. Footnote 6. While I think I understand what "The cosmic sentinel" is getting at, this 'considered' theory suggests that the speed of light (1x) and the speed of expasion of the universe (say 1.2x for arguments sake) are cumulative? ie. 2.2x light speed? I don't believe so. The speed of light would simply be expansion (1.2x) minus light (1x) = .2x! Expansion wins. If the universe was collapsing, then the light would reach us, but still at the same speed. If we were talking about special theory, with light always going away from you at the same speed no matter your speed, then this is an effect of "Time Dilation", something light is not affected by, purely perception.
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Old 26-01-2006, 11:46 AM
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Yep, one or two figures incorrect, but it illustrates the point, and it does say

Footnote 6 also incorrectly suggests that the redshift caused due to the expansion of space is a doppler effect, which is quite wrong. Doppler is a described under Special Relativity, cosmological expansion under General Relativity.

I'm also confused about the authors interpretation of how light from superluminal objects still reaches us . It's either doesnt not understood or greatly oversimplified.

Cheers,
Andy.
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  #5  
Old 26-01-2006, 11:48 AM
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Ooops, please ignore the one or two grammatic errors in my last post. the kids were jumping all over me and I hit submit before a proof read. DOH!
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  #6  
Old 27-01-2006, 03:25 PM
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Also very true, good point AGarvin.

I hope it doesn't sound like we're "bashing" your efforts to supply some
useful information iceman, i for one am not.

But some points needed to be corrected as it is wrong to speculate with no solid grounds on which to correct the entire scientific community on their
horrible lack understanding on what is really a basic concept.

The other reason is that I personally love cosmology and welcome any chance
to dicuss it.
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  #7  
Old 27-01-2006, 07:55 PM
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Definately not trying to "bash" so I hope I havent offended anyone. There are some aspects of cosmological expansion that are quite counter-intuitive. I've even seen it wrong in books. Bit of a worry really.
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Old 27-01-2006, 08:23 PM
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The concept of recession at greater than light speed raises several problems. Including fringe mass being greater than the remainder of the universe - this implies unrestrained net energy growth - if we start fom a singularity this is not possible.

However the approaching light speed recession model doeas give explanation to unexplained dark mass.

The question is - do we expalin unaccounted dark mass with eisting theory or agree we've missed something entirely - yet to be discovered? !
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Old 28-01-2006, 09:54 AM
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I'm curious, why do you say that superluminal recession implies a "fringe mass" greater than the rest of the universe and a corresponding net energy growth?
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Old 28-01-2006, 10:58 AM
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Superluminal objects implies an increas in mass.
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Old 28-01-2006, 03:32 PM
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Your confusing Special Relativity with General Relativity. The whole mass-energy thing (aka e = mc2), and indeed the speed of light restriction is described under Special Relativity, which governs the motion of objects through space. Comsological expansion (aka the expansion of space) is derived from the Freidman-Robertson-Walker metric using General Relativity and there is no such restriction. This is probably the most misunderstood aspect of the whole big bang/expanding universe model. Think of it as one laying down the rules within the bubble, the other laying down the rules of the bubble.

Within any local frame of reference, the speed of light will always be constant (Special Relativity), even though to a distant observer an object might be receeding superluminally (General Relativity). But even the distant observer will still only see the light reaching them at the speed of light, just cosmologically (not Doppler) redshifted.

This stuff can really do your head in .
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Old 28-01-2006, 04:00 PM
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Looks to me that the outer edge of the"bubble" is then lost too us thanks to - Special Relativity?
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Old 28-01-2006, 04:57 PM
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Kinda. Here's how I'm understanding it.

The distance at which you pass from sub to superluminal recession is known as the Hubble distance. The Hubble distance is derived from the Hubble constant, but the Hubble constant however actually changes with time (not sure why yet, still digesting that one), so the Hubble distance is actually increasing. As a result, the light from these objects can eventually be "caught" by the increasing Hubble distance and cross from super to subluminal recession and begin it's forward journey towards us. I think the Hubble distance is believed to be at a redshift of about 1.5, but we have observed objects out to redshift of over 6.

You also have the case of objects that were within our Hubble sphere when they emitted the light we're now seeing, even though they are now receeding superluminal.

Having waffled on though, there is a point at which we cannot see beyond, called the particle horizon which defines our observable universe.

That got my head spinning . Hope it makes sense.
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Old 30-01-2006, 03:03 PM
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all good points, very interesting chaps.

If I can go back a point, i think the idea is that E=mc2 constraining the speed of the expansion is fine for our space-time as we know it, but, with the universe expanding, I would assume that it would be expanding into SOMETHING. That "something" we don't understand in the least and probably not meant to (yet). So we don't really know what rules govern the speeds in that place for lack of a better term. On the other hand, there must be a tremendous amount of energy involved in order to make the universe expand, in the right conditions, this may be allowing left-over energy to cross to matter, accelerating expansion, or at least allowing for the basic builing blocks to fill the void, a self sustaining cosmos yes/no?

Maybe a bit far fetched but i'm willing to entertain it for arguments sake.
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Old 30-01-2006, 04:27 PM
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I don't see the need for an expansion into SOMTHING - just what IS expanding. The amount of energy / mass in the universe is THE question - there appears to be too much mass - so the search is for this dark matter as yet undetected, which may even be greater than the sum of all known objects.
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Old 30-01-2006, 06:17 PM
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I have trouble...

even comprehending the simple things in Astrophysics - like 'Hubble's Constant'. If it is a constant, then why does it vary? Why shouldn't it be called Hubble's Variable instead? Or perhaps 'Hubble's Mostly Constant'. No wonder it's all very confusing...
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Old 30-01-2006, 08:29 PM
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Quote:
even comprehending the simple things in Astrophysics - like 'Hubble's Constant'. If it is a constant, then why does it vary?
Fair point. This is why it is often and more correctly referred to as the Hubble parameter, I think the term "constant" is more of an historical term. Hubble basically discovered that the universe was expanding, and determined a rate of expansion. The theories that determined its "variability" came later.

Quote:
If I can go back a point, i think the idea is that E=mc2 constraining the speed of the expansion is fine for our space-time as we know it
The speed of light restriction is a Special Relativistic "law" governing the movement of matter through space. It has nothing to do with the expansion if space itself, which is basically the geometry of space as described by General Relativity.

As far as what the universe is expanding into, it's really a philosophical question. If the universe is infinite, which I think current theory suggests, then there is no boundary. If it is finite, then the fact that we are confined to and can never see beyond the boundary means we will never know. It's an unanswerable question.
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  #18  
Old 31-01-2006, 06:30 PM
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Agree with Stinky....

dunno why anyone would get hung up on what the universe is expanding 'into'. I've always assumed it's expanding into nothing in particular. Seems to me that most of the universe is comprised of vast quantities of nothing, with occasional bits of something....

However, without wanting to aggravate any learned Astrophysicists out there, I'm very sceptical about many of the theories that have been evolving in this field for many years. Their very complexity smacks of people desperately trying to find 'answers' within the very confusing and contradictory observations that have been made over the years. I really can't comprehend string theories & multiple dimensions, dark energy/matter etc.

I find that E = Mc2 is much more elegant. I prefer to entertain the belief that eventually someone brilliant will stumble across an equally simple/complex & yet elegant unifying theory/formula to explain how it all works.

For example, if you look at the mathematical formula that generates a Mandelbrot Set, you will see that it appears relatively simple. But look at the absolutely incredible images it can generate, which it appears to do to an infinite level.

I think we are at the same sort of stage that Watson & Crick were before they finally hit on the correct structure for DNA. Did you ever see their first model of what they thought it looked like? You would laugh now, since we all know how symmetrical & elegant DNA actually looks, but then these pioneers persisted & finally figured it out. Maybe Astrophysics will be a similar situation.

But then, what the heck do I know about it? Nothing.... I'm the guy who thought that a 'quark' was the sound you get when you step on a duck....
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Old 31-01-2006, 06:51 PM
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Quote:
-There appears to be too much mass-
Thanks, i didn't know that the reason for the expansion is because there it a "little" too much matter.

In fact, expansion of the universe slowed for a time, probably once the original momentum from the big bang dissipated, and gravity took hold, then accelerated again, this must mean that matter is being produced / converted somehow and that is why this is happening. Dark matter fills a large portion of our universe (so the theory goes) i'm aware of that too.

Quote:
The speed of light restriction is a special relativistic "law" governing the movement of matter through space. It has nothing to do with the expansion of space itself, which is basically the geomentry of space as described by General Relativity
Thanks for the lesson, but it's actually not what I meant, my fault I suppose... I acutally understand Relativity theory quite well.

My point was in support of one of your earlier statements in a way,
Quote:
Think of it as one laying down the rules within the bubble, the other laying down the rules of the bubble
Is this not Special relativity? The speed of matter rule WITHIN the bubble?

Also (while i'm going on about it),
I disagree that beyond the universe is a philosophical question...
My assumption that the universe is "somewhere" is no more right or wrong than your assumption that the universe is "infinite". You just finished talking about the Hubble constant and not being able to see behind it, so how do you know that the universe is infinite? So you don't belive in the "Big Bang"? After this expolosion (which originated somewhere), the universe got bigger, then bigger, and bigger still until... It suddenly had no boundry and became infinte? Maybe I should continue to eat more junk food until I get so big that I become infinite too.

If there is no boundry, then what we are really taking about is the "Distribution of matter within an infinite universe", not expansion, which is what everyone is referring to. If there was too much matter in the universe to begin with then it would have continued to expand exponentially and would not have stopped to form stars and planets, Therefore it cannot be "infinite". In fact, it WAS pretty much perfect, that is why we are here discussing it. Something is changing, that is the issue, and if the "boundries" of the universe are not expanding then the cosmos is becoming denser. Is there any evidence that it is becoming denser? I don't think so. So, the universe is getting bigger.

So let's remove the previously mentioned SOMETHING that we apparently have no need for, and watch as the universe becomes denser, and finally collapses in on itself under the force of gravity all the while, counting the amount of atoms contained within it. Not that we''' be here to see it!
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  #20  
Old 31-01-2006, 07:00 PM
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Quote:
Originally Posted by rochler
dunno why anyone would get hung up on what the universe is expanding 'into'. I've always assumed it's expanding into nothing in particular. Seems to me that most of the universe is comprised of vast quantities of nothing, with occasional bits of something....
So the universe is not actually about 15billion years old, only the matter contained within it?
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