Centre of the Universe

[g__day (Matthew)]

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 (Matthew)]

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/mowg...ottle_001.jpeg

[Karls48 (Karl)]

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 (Malcolm)]

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

[g__day (Matthew)]

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 (Rob)]

Originally Posted by g__day

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.

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.