Centre of the Universe

[Robh]

How often have I read that the universe is expanding and that there is no centre.
Every point is expanding away from every other point.
Sorry, but I just don't get it!

Let's assume the Big Bang was the origin of the Universe.
Everything is "blowing out" from where the Big Bang occurred.
The sum total of matter and energy is expanding in a shell which is itself getting thicker.
A bit like an expanding balloon (however the balloon's skin is actually thinning). An often used analogy but the balloon does have a centre!
The major part of the matter and energy will occur in any direction roughly tangential to the shell (we are somewhere in the shell).
Radially from the expansion point, the amount of matter and energy is only the thickness of the shell.
There should be two directions, outwards and inwards where the amount of matter and energy is minimal.
Looking in any direction tangentially to the shell, matter and energy should be maximum.

So here's my first idea ...
Is the thickness of the shell still within the cosmic event horizon?
If yes, then there should be a radial direction at which matter and energy should end.
This point will be closer than where matter and energy seems to end in any tangential direction at the cosmic event horizon.
If not, then we cannot see this difference.

My second idea ...
Tangentially to the shell in any direction, gravity should be strongest.
You would expect strings of galaxies to line up in directions tangential to the shell i.e. seemingly in a plane.
Does anyone know whether the filaments of galaxies in large structures like the Great Wall and the Sloan Great Wall appear to lie in the same plane?

We may still be able to check whether our Universe has a centre.

If you've ploughed through this, you deserve a medal!
Does our Universe have a centre?
Curious, Rob.

[Kal]

Because of inflation after the big bang the observable universe which we can see is smaller than the actual size of the universe. This is why the universe appears fundamentally flat.

[Robh]

Andrew, I agree with you on this point.
I've created some confusion using the word "width" instead of "thickness".
I've changed the words "wider" to "thicker", "width" to "thickness".
Thanks for the input,
Rob

[omnivorr]

I think the idea is that in the beginning, everywhere was the same place.... there is still nothing 'outside' it... there's just more 'inside'.

there was no space... now space is growing....

???

[sjastro]

Rob,

There is no centre, radial or tangential components as the Universe is not expanding into existing space.

Regards

Steven

[rogerg]

I would recommend listenning to this series of podcasts from AstronomyCast:

Where is the centre of the universe:
http://www.astronomycast.com/astronomy/ep-77-where-is-the-centre-of-the-universe/

What is the shape of the universe:
http://www.astronomycast.com/astronomy/ep-78-what-is-the-shape-of-the-universe/

How big is the universe:
http://www.astronomycast.com/astronomy/ep-79-how-big-is-the-universe/

... and... a question show:

Questions on the shape, size and centre of the universe:
http://www.astronomycast.com/astronomy/ep-81-questions-on-the-shape-size-and-centre-of-the-universe/

:thumbsup:
Roger.

[NotPrinceHamlet]

I think that that is about right. You need to step out of a euclidean mindset.

The 3K residual microwave radiation from the big bang is almost completely uniform no matter where the radio telescopes are pointed.

[Robh]

rogerg (Roger), I looked at your links.
Found them very interesting.
The first link has a section "Where is the Centre of the Universe ?
It states ...
It is less well known that Lemaître found a more general class of solutions which describe a spherically symmetrical expanding universe. These solutions, now known as Lemaître-Tolman-Bondi (LTB) models describe possible forms for the universe which could have a centre.
... although the standard big bang models describe an expanding universe with no centre, and this is consistent with all observations, there is still a possibility that these models are not accurate on scales larger than we can observe. Our ignorance about the real answer to the question "Where is the centre of the universe?" is complete.
I think things have just got a whole lot more complicated!
Thanks, Rob

[Archy]

:) One of the difficulties with the concept that the universe is expanding, is that one has to ask what is it expanding into?
We can avoid that problem by assuming instead that length and time are changing so as to correspond to the redshifts that have been observed. If this postulate (or model or paradigm) is correct, then there is no need for the universe to be expanding into anything and there is no need for it to have a centre.

[Robh]

Archy (George),
You make a good point. There may in fact be other explanations for the red shift of light. Although, the "tired light" hypothesis has been somewhat discredited, I've read recently of a different approach.

String Theory predicts the existence of gravitons (see Wikipedia: Gravitons). Scientific experiments are currently underway in an attempt to detect gravitational waves which "carry" gravitons (analagous to light waves and photons). The experiments cannot detect individual gravitons. However, if gravitons have any mass, then fields of gravitons might cause light to lose energy over large distances i.e cause a red shift.

[OneOfOne]

I always think of the balloon analogy in terms of a two dimensional representation of 3 dimensional space. The whole of the current universe is represented by just the surface of the balloon itself. Think of the "thickness" of space as being squashed into the balloon surface, so no matter which direction we are looking, we are always looking along the surface of the balloon. Therefore there IS no central point of expansion. Looking "into the balloon" would be like looking back to how the universe was at some previous time, but not in the way we usually think of looking back in time when looking billions of light years away, in this case we are still looking along the surface of the balloon, but just at something a long way away...if you get what I mean.

[Robh]

Trevor, I get what you mean with this model. Your explanation is well put.
But I wonder, does it actually reflect reality?
Consider this proposition.
Suppose the Universe we see is actually a very large bubble or void (Giant Cosmic Bubble), which is part of the larger Universe beyond.
Suppose, the mass density within our bubble is much lower than the average mass density of the Universe at large.
The gravitational effect of this would be to mimic an expansion towards the areas of higher mass outside.
There is of course a centre to this bubble.
http://www.newscientist.com/article/mg20026821.200-is-earth-at-the-heart-of-a-giant-cosmic-void.html?page=1

Regards, Rob.

[OneOfOne]

I must admit, I have often thought that even though our universe may exist in our "space and time" and there may be parallel universes as well in a different "space and time" that we can never see, but, equally, maybe there could be a multitude of other universes that are not part of ours, but given enough time we may actually "see" or come under the influence of. Perhaps the gravity from these universes is causing some effect on ours which we are interpreting as something else? And struggling to find a theoretical solution to because we can't think outside the "sphere"?

[bloodhound31]

Who was it that has that wonderful signature?...."In the beginning there was nothing....and then it exploded."

Get your head around that.

I love this type of thinking an expanding universe provokes. It really stretches the mind. If your imagination is expanding, where is the centre of your imagination, and what is it expanding into?

Will imagination continue indefinately, speed up and end in an imagination rip, or slow down and stop, only to collapse and explode again?

[xelasnave]

This is a most wonderful thread and it is great to read the views.

Firstly as hard as it may be to realise the Big Bang Theory is exactly what it says of itself...a theory...and as close to being an established reality, with a limitless supply of supporting observation, it can only remain an idea presented by a human in an effort to explain "everything"... be it fact well really who knows..other than those of such arrogance that thery believe they actually know everything.

Having determined the Universe was expanding... (and such a proposition is presented as a reality and no alternative offerred such that there can be no reason to exclude expansion as an established fact).... an extrapolation backwards reasonably establishes that the Universe started at a point and expanded from that point..,

firstly I say that such an extrapolation is unreasonable ...why should we jump at the conclusion drawn here... is the human brain not capable of any other reasoning other than to fit any observation into a similar human experience...I hint at our experince that all things growing come from a seed and that creation of something from nothing is indeed most reasonable (Well it is not reasonable but comes from a hang over from the fisrt book of the bible that God created all we see)...

The big bang requires a God to place the seed as there is no reasonable science that can give us everything from nothing...

The big bang requires the theory of inflation to support it in its current form..without inflation we have a major worry as to how to get everything the same...so rather than bite the bulet and wonder how to answer such a question with reason and facts gained from observation Mr Guth put forward "the theory of inflation".. a theory with out scientific support,,no experiment or observation..but it sounds good and as it saves our favorite theory ..the big bang..it was accepted wirth no reasoning as to why it sounds incredibly lame...

The theory lets the Universe grow from a basket ball to over 100, maybe 150 billion light year diameter in some 30 seconds...

if one can accept such one should find the Bible very easy to accept for one must have extrodinary powers of acceptance of unsupported fact...

So could it be that the expansion is simply nonsence??? could it be that the Universe is not expanding, could it be that for what ever reason although we think it is in fact it is not... be it tired light or some part of science that is hidden from us that leads us down this riddiculous reasoning that the Universe is like an animal..born of a seed and grows till it is big..and presumably will then die.

This is Science on human experience seeking a result that soothes human desires to have a purpose.

Why should the Universe be anything other than infinite?.

All the talk of geometry does not get past this little point... if it is expanding it must expand into something... technical manoverings will not let that aspect settle in a spot where it seems reasonable or a provable reality.

The big bang has run away with, and excludes opportunity to consider data other than its usefulness to support the big bang theory...and that is not doing anyone any good at all...

The most exciting thing to come out of the sky is the fact that galaxies line up like buttons on a string..and yet as this has no bearing on support for the big bang we ignore this most amazing piece of info to be presented to us... why is it so...why do the galaxies line up so..the only comment I ever heard was... well one could expect this structure as a result of the big bang.... well sadly this is where though is focused.

Is this discovery not hinting of things we know nothing of??? well lets not even look at it...it is irrelevant to big bang notions...

But other than the big bang why do they lie up this way..what is going on... to answer this question is important but to sideline it as mere support for the "big bang structure" is simply not science.

And for all those folk who say the background radiation proves the big bang I say yes sure it does ...but if one did not have the "theory" to support could we not have alternatives to explain the observation... COULD WE NOT SEE DATA AS AVAILABLE TO SUPPORT OTHER STUFF NOT JUST bb...sorry caPS MISTAKE..NOT SHOUTING..

So my view (and no one needs to know it I well recognise) as to the UNiverse having a center is ...it can not have a center as infinity knows of no center... as to the observable Universe its center is and always will be ones self... yes the word observable makes the Universe a personal thing and as observer you have the privelledge of always being at the center..of everything really.. and that is the way each human will see themselves and indeed the total Universe..they are and will always be at the center....and be right and correct about everything they observe from thier priveleged place.

If you sdupporet the big bang idea that is ok but save it and replace Mr Guth's wild fancy re inflation... I mean how can that idea still fly.. no logic mixed with no science to support a belief....


alex:):):)

[Robh]

Xelasnave (alex),
Fascinating read. You've covered a heap ... from God, to the theory of inflation, an infinite universe, galaxies "on a string", the CMBR, no physical centre, a subjective centre. Ideas, don't you just love it!
I was a great fan of the Big Bang until the concept of Dark Energy was mooted to explain the accelerated expansion. Got to be something wrong somewhere.:shrug:
Rob.

[Shnoz]

Very interesting thread!:D

With the centre of the universe; the other day my computing teacher was explaining wormholes to me.
He said that they are theoretically formed because spacetime is curved like a ball, and black holes create infinitely deep pits in the surface of the ball. Each of these pits leads to the centre and can connect to other black holes somewhere else on the surface of the ball. Would the place where the black holes connect be the gravitational centre of the universe?

And if this ball was expanding, every point on the surface of the ball would be moving away from every other point. Could we then replace the 2D surface of the ball with our 3D space?

I think I may have raised more questions than I solved.:lol:

[Robh]

I think you have opened up a can of worms here!!!
Seriously though, Sophie, I don't know whether we know enough (or I should say I know enough) to promote or discount this idea. It sounds entirely feasible and an attractive idea (that was unintentional)- blackholes connecting via a gravitational centre. Maybe someone else here on IIS can comment on this possibility.
Thanks for the input.:thumbsup:
You have got us all thinking here on IIS!:help:

Regards, Rob.

[Barrykgerdes]

This is a lovely thread and most of the posts are based on the theories put forward by thinkers to explain something that the human mind cannot comprehend. Remember they are only theories.

There is no centre of the universe. The universe is infinite. Infinity is what it says no beginning no end so therefore no centre. Try putting that into the theories. What we call the universe is only what we have so far been able to see. A Big bang may have started our universe. It may not have. If there was one big bang, then in infinity there has been an infinite number of big bangs.

I can say no more. I know what infinity means but my mind cannot comprehend that in a finite environment, can anyone's.

Barry

[xelasnave]

Infinite is a most interestring proposition.
We can not arrive at infinite by doubling a finite ..so if we electect for a infinite universe it can not be made from a seed that is doubled and doubled etc etc.. such a process will never arrive at infinite ...so if we elect for big bang our universe will always be finite..and if finite there must always be something else out there..think about that it is so simple one can miss the enormous implication of such on our current cosmological philosophy.
Still no one seeks an answer or a speculation in respect to the galaxy line up, observed, and as I present above ..forget looking for a center and ask why do they line up like buttons on a string..for what purpose... is there no one who will engage the opportunity of cosmological speculation, the correct answer to which may well provide most of all we need to know about our universe? Why do galaxies line up like buttons on a string????

alex

[Robh]

Who am I to say, but here's my bits worth ...
Assuming the Big Bang started it all, matter and energy were more than likely not evenly distributed through space. Like a paint bomb will never work to evenly paint a room. There must have been "strings" of hot spots of matter and energy over very large distances. Along these "strings" there were also variations in matter and energy. In time, not only did matter coalesce into stars and then galaxies in one section of the "string" but also into filaments of galaxies along the "string". An effect something like a random fractal. Even though, the cosmic microwave background radiation is fairly even across the sky there must be slight variations to account for this effect.
I'm also going for a bounded, finite mass universe.
Regards, Rob.

[xelasnave]

Great stuff Rob...
There seems to be more to the "string" part as it seems some matter is passed between galaxies... I think we pass stuff to M31... or the other way...
Yes a finite Universe is managable..look at the math..hard to argue with that...
Thank you sincerely for your well considered reply.
alex

[Robh]

Alex, you're probably right here. As matter an energy are interchangeable, maybe energy gradients between nodes (where stars and galaxies form) cause energy/matter movements which seed the nodes or galaxies on the "string". Just hypothesising.
Regards, Rob.

[Chippy]

And there definitely are strings between the Milky Way and the Magellanic Clouds. I remember reading about it last year. I think they're known as the "Magellanic strings" but I could be wrong. I suspect there are probably strings to M31 as well, although I haven't actually read of that.

[Barrykgerdes]

I am afraid I don't understand "string theory". The term string is very confusing. I get distracted when I think of string because the first connotation of string is something you tie round your finger to jog your memory. However I think it is something to do with the transfer of energy/matter. Something more like transverse progressive waves describing electromagnetic energy though a vacuum against longtitudinal progressive waves describing transmission though some other media by compression and expansion like the sound from a vibrating violin string through air.

Maybe if a different terminalogy was used I would be able to grasp it.

Further to a finite universe as most seem to believe in, the question always arises but never answered "If the universe is finite what lies beyond ?"

Barry

[xelasnave]

Yes and it is a matter that demands more thought simply because we will seek to explain our observations...and that is what it is all about.

Barry I should not have used the term string I guess in so far as folk will think it has something to do with "String theory" and it does not..in a general sence.

Buttons on a thread certaily may seperate it for you.

But my point is simply there is something going on that we fail to look at but if such is going on attempts to explain it may open new doors in our knowledge... where does the thread end??? is stuff passing back and or forth...:shrug::shrug::shrug:
It is new ground so there is an opportunity for someone to come up with something new and maybe bag a special prize;).
alex:):):)

[Robh]

Tracked down your info.
It's called the Magellanic Bridge and is a stream of neutral HI hydrogen with some stars linking the SMC and LMC. There is also a Magellanic Stream of HI gas linked to the SMC and LMC. Some twisting of the filaments may indicate that the Magellanic Clouds are tumbling about one another on their way into the halo of the Milky Way.
http://apod.nasa.gov/apod/ap980826.html
Again illustrates the complex relationship between gravitational forces and the formation (and destruction) of stars and galaxies.

Regards, Rob.

[Shnoz]

I had heard somewhere that the bridge of stars meant that the Magallenic Clouds and the Milky Way were going to collide (or had already), and that's what was causing the link. Perhaps one day the Milky Way will have one of those odd ripple effects seen in collided galaxies, which would be cool.:thumbsup:



I think the temperature of the early universe had a lot to do with the structure of it today, but I also heard that dark matter and dark energy helped keep the shape of the strings. However I may just be thinking of galaxies and dark matter haloes. Interesting theories though.:)
Although because things tend to get more jumbled up as time goes on, maybe the strings will one day fall apart?

[Chippy]

Thanks Rob, I remember now - it was the Magellanic "Stream" that I was referring to (and read about). As I recall, the Magellanic Stream actually connects the MC's with the Milky Way, and is essentially the result of gravitational interactions between the 3 galaxies. Basically the Milky Way has stripped some matter from the MC's and the Magellanic Stream is the wispy remains of those interactions I think.

[Robh]

Sophie, I agree with you on this point and this provides me with a cue to hypothesise/speculate again ...

At the Big Bang, energy/particles disperse randomly into an inflated space. The universe overall consists of an extremely high temperature plasma and other elementary particles. Although fairly uniform overall, the chaotic nature of the temperature results in hot-spots and a convective plasma with an uneven density of particles. As regions of temperature drop below one billion Kelvin, protons form Hydrogen and some protons and neutrons combine to form He. Gases and particles begin to congregate through gravitational forces but form weaving interconnected streams throughout space. Analogous to smoke streams due to convection currents around a fire.

As cooling continues, localized regions of much higher density accrete more gases and particles due to gravitational forces. Eventually, the mass in a local region is high enough for gravitational pressures to cause nuclear reactions and stars are formed. Uneven distributions of stars causes galaxies to form by gravitation in star dense regions. The original streams of gases and particles have now congealed to form an irregular fabric of filaments or threads of galaxies throughout space. The whole mesh of filaments is more or less in equilibrium but with some expansion due to gravitational forces. The end result is a bit like a random three-dimensional cobweb.

Increasingly large filaments are now becoming evident around us. Each filament is a large thread-like structure consisting of gravitationally bound galaxies and superclusters of galaxies. A filament of significant length and width is called a galaxy wall.
Examples are the Coma Supercluster which lies within the Coma Filament and forms part of the CfA2 Great Wall.
The Sloan Great Wall is the largest known structure discovered so far at 1.37 billion light-years in length. :eyepop:
See ...
http://en.wikipedia.org/wiki/Galaxy_filament

Anyone else with any ideas as to how these superstructures formed?
:juggle: ideas, Rob.

[KenGee]

Ok I’ll bite Alex,
“The big bang requires a God to place the seed as there is no reasonable science that can give us everything from nothing...”
Er no , apart from that not being right, invoking a God only moves the goal posts, Where did God come from? That’s the last I’ll say of God. BTW as an “New Atheist” I must say I like Barry@A.S.I.G.N (Barry@A.S.I.G.N). Tag line “We all Fall short”. We may have different worldview but it’s always good to remind one’s self that we are not all we could be.
You forget Alex that energy is a construct, it can easily be said that it doesn’t really exist. If you take that view then something coming from nothing is easy to shown to be true.
Robh say he can’t “believe in” dark energy why is dark energy anymore fanciful then plain old energy. What is potential energy? The mass of a ball is no different when it’s rolled down the hill, yet it has lost its potential energy, where did it go?
Alex currently the distribution of matter within the universe is of intense interest to cosmologist so I don’t understand where your coming from.
I’ve got no interests in pulling people thoughts apart, beside there are people on this sight more knowledgeable then me on this subject, what I do want to talk about is how science works.
You often hear it’s only a theory.
Theory in science circles means something different then it does in the normal world. In the normal world a theory is an Idea that may or not be supported by the facts. In Science that is called a conjecture. A science will come up with a conjecture and test it against the know facts, if it fits all then know facts then that’s great, if it can make testing predictions even better. It has now become a scientific theory. So basically a theory is an Idea that is supported by all the know facts (it’s plain silly to say it’s only a theory not a fact). Now here is the kicker if it doesn’t fit all the know facts, the theory must be changed or thrown out altogether. You need to keep these Ideas in mind when you read or listen to scientist, they are human being just like us their common language more often than not will not include all these caveats, but they are there. Now if scientist waited until all the facts where in, before developing hypotheses and grinding out theories then we wouldn’t then we would still be in the caves. Newton ideas on gravity fitted all the know facts, when facts where found that it didn’t fit the search was started, Relativity fitted all the know facts. No know observation contradicts relativity, however we have doubts about it because it doesn’t fit another really well supported theory. That for me is the really interesting part. All of our ideas about reality maybe wrong it all could have been created by the flying spaghetti monster last Wednesday.
Alex as I understand current thinking is during the inflation period ripples were formed by some porcess, these areas of increase density went on to become the seeds of galaxies and that is why they appear to be in vast chains.

[Robh]

Kenny, thanks for your input.
As I've stated before, I am just hypothesizing about the nature of events that led to the current universe we see.
To me the universe consists basically of matter and energy. One being continuously converted to the other. Energy doesn't just come from nowhere. It always has a source e.g. nuclear reactions within the sun produce radiated energy (electromagnetic radiation). Matter stores energy and also produces gravitational forces. Perhaps there is a particle that transmits gravity (graviton) similar to the photon with light. When a ball rolls down a hill its gravitational potential energy from its height is converted to a kinetic energy of motion. Total energy remains the same.
If the universe is finite it may well have a fixed total energy, with energy being continuously converted from one form to another. It appears gravitational forces are storing a lot of this energy in stars, galaxies and filaments of galaxies. And perhaps dark matter.
My comment about dark energy is a question about its source. It is believed to be homogeneous and to make up 74% of all the mass-energy of the universe. It's mass is calculated at a density of roughly 10^-29 grams/cubic cm and no-one has any idea how to find its physical composition. It "interferes" with gravity causing an accelerated expansion of the universe.
There could be some other explanation for the apparent accelerated expansion. Maybe the red shifting is caused by fields of gravitons in space, which cause light to lose energy over large distances.
Regards, Rob.

[KenGee]

Robh, if the higgs particle is found there maybe some hope to shed some light on this, but if they don't it is going to cause some head scratching, just as the failure to detect gravity waves. It will mean our two best but different theories on how gravity works are not quite there yet. My comments about energy was only to show that different ways of looking at things can cause different questions but not ones that have answers.
The example I gave is one in which Alex’s pushing gravity can give a good account of what is happening. Queue Alex.
.

[xelasnave]

Sorry I have been busy playing pool and training for my first cage fight:)
Thanks for your input Kenny:thumbsup:.

My annoyance with "inflation theory" is simply ..in my humble opinion..that it does not fit the requirements of a "theory" I am reasonably aware of the meaning of "theory" in science...and say that inflation theory is no more than a fancy idea and deserves no more than perhaps being labled a hypothisis:D... a layman can call it a theory but I feel a scientist if he looked at the "theory" would say yes nice idea but it is not a "theory"... yet they call it so...

Inflation theory askes us to accept everything grew to all that it is now in 30 seconds... that is a big idea but why it gets called a theory I can not fathom... even God took near a week to get the job done:D


I think the HB may well be found ... and one would think they must be very findable if it give mass to er stuff...well they must be everywhere and in large numbers... but I think they have gone down the wrong path with speculating upon its existence... it crept in because of the notion of massless particles and I doubt if it works that way... but if they do find it I say it is the gravity rain I have been seeking all these years:lol::lol::lol: and it will be smaller..just a guess as is the way I do science:lol::lol::lol:

Kenny said......Alex currently the distribution of matter within the universe is of intense interest to cosmologist so I don’t understand where your coming from....and I can only reply... yes of course that is so:) however I have not come across anything ( not saying it is not out there) on the line up thing and matter/energy transfer between galaxies.

alex:):):)

[Archy]

I agree

[Archy]

If you believe energy is a construct, stand in front of a moving car.

The potential energy has changed into kinetic energy and heat.

[KenGee]

LOL, no thanks but does that mean you can tell the rest of us what energy is then, I'd love to hear it.
Alex it's important to remember what you are calling inflation theory is in fact a flavour of the big bang model of creation.
Inflation was included into the big bang theory to keep it in line with the know facts, as I said before a theory has to be consistent with all the know facts. http://map.gsfc.nasa.gov/universe/bb_cosmo_infl.html
What is it that you don't like about it, the rate of expansion or the bonding of the amount of "energy" within the universe. It seems to me that the very thing you seem not to like about Inflation is one of the things it explains really well. Can you expand please on what your thoughts are.

[xelasnave]

Well I feel unqualified to stand up to the current views but to nail down my specific complaint re inflation I feel my previous post says it all... I do not call my ideas a theory and frankly the inflation theory seems to have less basis for its place in the big bang theory than my push ideas should replace anything out there to date..I know an idea and call it so..inflation is no more than an idea...

I did think inflation was part and parcel of the big bang idea..however you say it is but one flavour... my understanding is that without inflation or a suitable alternative big bang dies as there is no way to fix why everything is the same...simply put...I am not sure but we need it to expalin why we have all laws the same...now it does not worry me at all other than it seemed to me that because it saved big bang it got thru the hypothesis to theory stage with out the demands placed upon other hypothisis...

So given "they" found the "problem" and given it was a fair one to examine I would have thought the demand from the "saving" idea may well have needed something in the way of supporting observation or evidence and not simply a math construct without "real" evidence to support the placement of it in the gutz of the main theory and as I understand saw inflation as crutial for its (bb) very survival.

alex:):):)

[xelasnave]

I do have a problem to imagine all energy could be concentrated in such a small space as the "seed" flavour BB would suggest. Who /how could achieve this?
alex

[Archy]

I don't have the energy to do that at present, but you may look it up in Wikipedia.

[g__day]

I feel uncomfortable defining the entire universe like a very big room full of stuff moving around and hearing someone asking where is the centre of the room.

Saying well no - imagine inflating a very large balloon super fast - surely it must still have an epicentre - isn't the universe like that?

Let me give you another scenario - you have a sheet of 10 dimensional "paper" crushed by tremendous force and on a spring trigger to explode. Suddenly it expands - so fast that its own 10 dimensional structure ruled its rate of expansion - the physics of relativity didn't apply here and spacetime itself as we know it got defined some where/when during this epoch.

Now at a point things cooled down and got less energetic until relativity phased in as the dormant force shaping the macro universe, and a 3 dimensional spacetime and fourth dimension of time dominated how most of spacetime continues to evolve. But in that first instant spacetime didn't exist, wasn't predominantly 3 dimensional and geometry or field curvature of a higher dimensional reality reigned. So what we have today is a remenant of the creation scenario - it certainly does not have to be 3 dimensional given the anomonally of its birth.

If all spacetime today was 3 dimensional - it would be simple to reconcile relativity with quantum mechanics, or SuSy with string theory or answer what is the topology of of our Universe or is our universe finite or is spacetime fractal not quantised.

Black holes are an interesting example where instead of a singularity at there core according to relativity (and noting relativity doesn't apply below the event horizon) the event horizon may simply be a dimensional transition zone where we move from 4 dimension space-time to a higher lever dimensional spacetime governed by quantum gravity or some other set of forces that dominant higher dimenisonal membranes of existence.

[avandonk]

It is still legitimate to still ask the BIG questions. We can only have answers by real observations. As primitive mammals we are just beginning to scratch the surface of what is reality. We can only rely on real evidence that leads to some sort of coherent theory. We do not yet know how our brains work and yet we contemplate the Universe! Science is a verb not a noun. It is the only thing that seems to really work so far.

Bert

[g__day]

Those seven sentences are incredibly hard to parse and glean any meaning from, harder still to link it in any way to the central themes of this thread.

I guess I agree / dis-agreed / don't know - can't understand what you are trying to get to, reminds me of...

http://members.optushome.com.au/mowglhi/piccys/lightningbottle_001.jpeg

[Karls48]

There are speculations, speculations squared and then there is a Cosmology. Find the point in our Universe where an object will have a zero potential energy and you will have centre of Universe.

[mswhin63]

Funny if Dark Matter or Dark Energy is the centre. Wouldn't see it :D

[g__day]

Our main contending models are nowhere near well enough developed to describe the topology of the universe - that's maybe 50 - 100 years away. So the debates we are having now are topical - but the science and technology necessary to rule in or out models doesn't yet exist (even as an idea) and the models themselves are so incomplete as to have almost no predictive power yet to be validated.

We don't understand dark energy yet well enough to even begin theoretically speculating what it is or isn't. Personally I ponder whether spacetime could have far more complicated and subtle interactions with matter and energy in it than we have allowed for - the curvature of spacetime could open up whole branches of science in itself if hidden dimensions at a Planck level are shown likely to exist. CERN and GRB studies are likely to be the labs showing data supporting this. Space is thought of as a large, most empty room - that is itself neutral to things in it - but what if that is very, very far from the reality? MOND looks at this very slightly, scale relativity delves alot further saying at a Planck level spacetime isn't quantised but fractal. Dark energy may be for instancey hidden geometries of spacetime interacting with energy or matter in it. If that is discovered to be the case well it will be a real inflection point for our physical understanding of reality.

Until we reach that point - there is a whole lot of unknowns - without even a theoretical framework to speculate against.

Example - imagine the universe is either far larger than we thought - or infinite. Secondly image our big bang was just a minor, local area event - a minor burp overall. Well there could be trillions of these events happening every second - like bubbles bursting or forming in the foam of a very, very large universe. Large bubbles of existence would form - large to our scale of thinking yes - but these bubbles would not be anywhere near all of creation and each would really be infinitesmally tiny compared to the entirety of the universe. If each little bubble had its own local physical parameters and the geometry of that bubbles spacetime could vary slightly (e.g. weight and charge of a proton, speed of light etc just slightly different) well eventually some bubbles would be capable of sustaining intelligent life. Where would the centre of this reality be - we in our bubble can have no way of knowing. So what such a bubble universe moves in - or what's outside our Hubble bubble that may be cause its overall expansion well we have no models to ponder this seriously yet.

String theory could model this - but string theory can model over 10 ^ 384 possible realities without preference for any (yet) so it has basically no predictive power (yet).

Stay tuned!

[Robh]

Matthew,

Your estimation of our current knowledge (or lack of it), and the possibility of a universe much more complicated than we know, illustrates just how fragile our current models and theories actually are. Thanks for taking the time to describe your views in such detail.
String theory. Lets hope they can narrow down some of the parameters. Multi-dimensions ... is man smart enough to get his head around it all?
I'm hoping that our universe is just the one unique bubble and that perhaps it is understandable, at least post-inflation. If there are trillions of such bubbles out there then perhaps we will never know due to the cosmic event horizon. And no model will ever truly describe our universe with any certainty. Hopefully, this is not our fate.

I find this amusing ...
Not long ago, we were happy to accept the Big Bang and inflation, which explains the homogeneity and isotropy of the observable universe. And initially, the WMAP satellite supported a flat universe, homogeneous and isotropic, to one part in 10000.
Well, WMAP also found patterns of hot and cold spots in the CMB that are not random. They seemed to be aligned along the "axis of evil". If real, this relegates our current model to the scrap-heap as it could mean the universe is longer in one direction than another i.e the universe is not isotropic. Pretty soon, the Planck satellite may be able to confirm whether this is the case or not.

Exciting, isn't it!
Regards, Rob.