The Naked Scientists

The Naked Scientists Forum

Author Topic: Is the Universe a hollow ball with its point of creation at its centre?  (Read 6022 times)

Offline woolyhead

  • Jr. Member
  • **
  • Posts: 39
    • View Profile
We're told that the big bang occured at a point and the energy thus released expanded equally in all directions away from the point of release. This should mean that the universe is a hollow ball and the point of its creation lies at the centre. Is this picture of the universe's shape correct
« Last Edit: 14/10/2013 23:03:40 by chris »


 

Offline Bill S

  • Neilep Level Member
  • ******
  • Posts: 1826
  • Thanked: 12 times
    • View Profile
Re: centre of the universe
« Reply #1 on: 14/10/2013 19:32:33 »
Hi Woolyhead; welcome. 

Why would the Universe be hollow?  Have you been set on the wrong track by the balloon analogy?

My own (non-expert) feeling is that the expanding fruit pudding analogy gives a better intuitive picture.

Of course, there is always Donald Hamilton’s theory in which the centre of the Universe is relatively massless, while the boundary is an area of high mass and high energy.  I believe Hamilton is widely regarded as something of a crackpot, though, so it might be good to give that one a miss, unless you like way-out ideas.

 

Offline woolyhead

  • Jr. Member
  • **
  • Posts: 39
    • View Profile
Re: centre of the universe
« Reply #2 on: 14/10/2013 20:23:42 »
Hi and thank you Bill. Now, why would the universe, which began at a single point and expanded IN ALL DIRECTIONS be hollow? Why wouldn't it? For it to be otherwise would require some of the energy to turn round while expanding outwards and go back towards where it came from, wouldn't it? To just call the baloon analogy "the wrong path" doesn't explain anything. How and why is it wrong? If you tell me that astronomy tells us that some parts of the universe are coming towards us I could understand it, but they're not are they? Your expanding pudding analogy assumes that you already understand how it got to have a filled-in form like a pudding has in the first place. That, if you prefer, is what I'm asking.
« Last Edit: 14/10/2013 20:30:57 by woolyhead »
 

Offline Bill S

  • Neilep Level Member
  • ******
  • Posts: 1826
  • Thanked: 12 times
    • View Profile
Re: centre of the universe
« Reply #3 on: 14/10/2013 20:59:00 »
When I was trying to work my way through this (which in a way, I'm still doing) I wrote quite a lot of notes.  With advancing years the memory isn't what it was. :(  I should explain that I tend to write my notes as though I am explaining things to another person.   Anyway, here's a small chunk that may, or may not, serve as a basis for further discussion.

Excluding the possibility of a pre-existing “somewhere” we can say that it makes no sense to talk of the Big Bang as having happened at a particular place.  Never-the-less, it may be difficult for the non-scientist readily to shake off the idea that there must be some place in the Universe where it all started.  The usual response to this in popular science books is simply to state that the Big Bang “happened everywhere”.  Perhaps this is an area in which the balloon analogy can help.  Imagine an un-inflated balloon on which you mark a small dot.  As you inflate the balloon, the dot grows.  Now, ask yourself where, within that enlarged patch, you might find your original mark.  Obviously, the answer must be “everywhere”.  The same can be said of the Big Bang.  At the instant of “creation” it encompassed the entire Universe, and as the Universe has expanded it has not left behind some original Big Bang site.  Having said, and perhaps accepted, all this; if we return to the balloon analogy, there must always be a feeling that because the mark expanded evenly in every direction from the centre, that must be its spreading centre.  I suspect that it is this feeling, rather than an inability to accept that the Big Bang happened everywhere, that is the lay-person’s chief difficulty.  Obviously your original dot has expanded, but has it spread across the balloon?  The answer has to be “no”, because the material of the balloon has expanded, carrying your mark with it.  It is tempting to think that your spot was made in the centre of the extended mark, but such is not strictly the case.

 

Offline Supercryptid

  • Hero Member
  • *****
  • Posts: 606
    • View Profile
    • http://www.angelfire.com/sc2/Trunko
Re: centre of the universe
« Reply #4 on: 14/10/2013 21:10:15 »
If the Universe has a center, it's not in three-dimensional space. The balloon analogy can be misleading if it is not explained adequately. It's not that the galaxies and stars are supposed to be inside of the balloon, but are rather imbedded within the skin of the balloon. Strictly speaking, this is only an analogy since humans can't visualize four-dimensional space. The balloon analogy better represents a universe with two spatial dimensions, and these represent the surface of the balloon (where all of the matter and energy of that universe reside). The fact that the balloon as a whole has three spatial dimensions is beyond the visualization of any two-dimensional beings that may dwell in that universe. Likewise, if our universe is a hypersphere and we are imbedded within a three-dimensional "skin" on it, we cannot perceive its true shape.

The balloon analogy is also deceptive because it assumes that our universe is closed with positive curvature. It could potentially be completely flat or even have negative curvature. Our best measurements point to a flat universe, but the fact that our measurements can only be so precise lend weight to the idea that it could still have positive or negative curvature that is too subtle to detect. If this was the case, we could still live in a hypersphere-type universe which has a diameter much larger than the visible universe. At the moment, this is an unresolved question.
« Last Edit: 14/10/2013 21:12:53 by Supercryptid »
 

Offline Bill S

  • Neilep Level Member
  • ******
  • Posts: 1826
  • Thanked: 12 times
    • View Profile
Re: centre of the universe
« Reply #5 on: 14/10/2013 21:14:16 »
Quote
To just call the baloon analogy "the wrong path" doesn't explain anything. How and why is it wrong?

I was not knocking the balloon analogy, as such, just wondering if that was where the root of the hollow Universe lay.

I think the reality is that any analogy is going to break down somewhere; it is, after all, only an analogy.  I could be entirely wrong here, but I think that describing the BB as an explosion comes with its own pitfall.  Perhaps it would be better to think of it as an expanding entity in which the energy is not uni-directional; centre to outer boundary, but outward from every point, in every direction.  This would bring about expansion without having any part of the Universe moving towards any other.

I'm not adding that to my notes until I see if some expert shoots it down in flames.
 

Offline CliffordK

  • Neilep Level Member
  • ******
  • Posts: 6321
  • Thanked: 3 times
  • Site Moderator
    • View Profile
Re: centre of the universe
« Reply #6 on: 14/10/2013 22:29:49 »
I would think of "the big bang" more as a hand grenade analogy.  What is a bang other than an explosion afterall?

Different shrapnel particles would undoubtedly travel at different speeds, but most will be accelerated away from the center at a high speed.  And, thus, one would expect to find rarefied matter near the center where the explosion initially occurred. 

If you consider the gas inside an inflating balloon, then you could have a space filling model.  However, I would wonder what type of violent explosion could lead to a inflating balloon type of model.

I suppose when one blows up a hand grenade, one is greatly interested in the shrapnel from the fragmentation of the shell.  However, looking at the gas cloud created by the explosive chemicals, one may get an entirely different view.  It may be more space-filling than one would otherwise expect, with the particles near the center moving very little, and those near the edge moving much more.  In the "big bang", one may not have a shell like the grenade, but rather initial compaction from gravity.  Is Hydrogen the only element formed?  Or does the metalicity vary depending on what was before the big bang, and where one is in the structure?
 

Offline woolyhead

  • Jr. Member
  • **
  • Posts: 39
    • View Profile
As you say, the analogies with other things are also not close enough to the big band situation. The expansion was smooth, so all the energy went outwards, not in other various directions, ie across other energies.
A normal explosive leaves gas and particles hanging about near the centre of the explosion but the big bang energy couldn't have done this. For example gamma rays do not stand still. Nor does a pressure wave in the air. The big bang energy had to move away from what I persist in calling the centre of the explosion. My reason for doing so is that at one plank instant after the process began the energy did have a definable centre. It had expanded sufficently to reveal its centre. It was no longer a point. Your analogy with a dot is misleading on this account.
I suspect that the talk of extra dimensions is just a red herring, a smokescreen to hide the fact that you don't know the answer. Let me put it another way: if we could witness creation and leaving aside the obvious for now, how would it look to us? Of course we can't appreciate more than 3 plus time with our senses, so how would this so called multi dimensional moment just after the creation look to us?
« Last Edit: 15/10/2013 12:50:24 by woolyhead »
 

Offline Bill S

  • Neilep Level Member
  • ******
  • Posts: 1826
  • Thanked: 12 times
    • View Profile
Quote from: Woolyhead
The big bang energy had to move away from what I persist in calling the centre of the explosion

This is fine as long as you define the “centre of the explosion” as being everywhere in the Universe.

Dog walks are great for thinking; as long as you don’t meet too many other dogs.  This evening’s walk led me to think of an alternative balloon analogy.

Think of inflating a hot-air balloon.  Hot air is introduced, heating the air already in the balloon.  The balloon inflates, not by virtue of some explosion at the centre, but because molecules of air, throughout the balloon are expanding.  OK, this is not a good analogy because hot air is being introduced from outside – and we all know how unhelpful hot air can be :) – so think of a sealed balloon in which the air is heated spontaneously throughout the balloon.  Directional energy is not from the centre outward; rather it is from every point, towards every other point, but the net result is the expansion of the balloon.

A physical example of this kind of movement in the Universe today is the CMB radiation which you will observe as moving towards you, wherever you are in the Universe.   
 

Offline Bill S

  • Neilep Level Member
  • ******
  • Posts: 1826
  • Thanked: 12 times
    • View Profile
Quote from: Woolyhead
For example gamma rays do not stand still.

Why would they need to stand still. EM radiation must always have been in motion in the Universe.  For example, what was once light moving through the Universe at c, is now microwave radiation, still moving through the Universe at c. 
 

Offline woolyhead

  • Jr. Member
  • **
  • Posts: 39
    • View Profile
Quote from: Woolyhead
The big bang energy had to move away from what I persist in calling the centre of the explosion

This is fine as long as you define the “centre of the explosion” as being everywhere in the Universe.

Dog walks are great for thinking; as long as you don’t meet too many other dogs.  This evening’s walk led me to think of an alternative balloon analogy.

Think of inflating a hot-air balloon.  Hot air is introduced, heating the air already in the balloon.  The balloon inflates, not by virtue of some explosion at the centre, but because molecules of air, throughout the balloon are expanding.  OK, this is not a good analogy because hot air is being introduced from outside – and we all know how unhelpful hot air can be :) – so think of a sealed balloon in which the air is heated spontaneously throughout the balloon.  Directional energy is not from the centre outward; rather it is from every point, towards every other point, but the net result is the expansion of the balloon.

A physical example of this kind of movement in the Universe today is the CMB radiation which you will observe as moving towards you, wherever you are in the Universe.   
From what I've said, Bill, my centre is a point and not everywhere. If you expand a point indefinately you still have just a point. Could you please explain how this point got to be everywhere. By saying the centre is everywhere you seem to be going against logic. Is there something tangible wrong with imagining the big bang? Can't my mental processes cope with it? Can anybody's? Why should I imagine it as having further dimensions beyond 3 plus time? I don't want to appear rude but what's been said so far sounds very much as if you both would like to change the subject because you can't snow me with high falutin concepts and red herrings which aren't really necessary. OK, if I'm wrong, please explain why are extra dimensions necessary? Why does an expanded, zero-dimensiona point go everywhere?
 

Offline woolyhead

  • Jr. Member
  • **
  • Posts: 39
    • View Profile
Quote from: Woolyhead
For example gamma rays do not stand still.

Why would they need to stand still. EM radiation must always have been in motion in the Universe.  For example, what was once light moving through the Universe at c, is now microwave radiation, still moving through the Universe at c.
What I was saying is that when energy expands from a point in all directions equally, if, during the expansion time the source is shut off, this means that behind the last piece of radiation there will be a hollow ball with no more radiation inside. In other words a hollow universe. To answer your question: I pointed out that only if some of the radiation changed direction and reversed its course (which involves slowing down), the hollow ball could conceivably get filled in. But as you said, this couldn't happen with radiation in space. Ergo the universe has a centre and is hollow.
« Last Edit: 16/10/2013 19:38:25 by woolyhead »
 

Offline Bill S

  • Neilep Level Member
  • ******
  • Posts: 1826
  • Thanked: 12 times
    • View Profile
Woolyhead, this is not a criticism, just a suggestion.  It might help if you were to better identify the poster/comment to which you are responding at any given point.

For example, I don't recall having introduced any extra dimensions, so I shall not try to answer that bit.  If the "high falutin concepts" are mine, please be more specific about which ones you mean, and I'll try to be more "lowfalutin", if I can figure out what that means.

Quote
if, during the expansion time the source is shut off

Two questions come to mind here.

1.  What do you see as the source of the expansion?

2.  How sure are you that it shut off?
 

Offline Bill S

  • Neilep Level Member
  • ******
  • Posts: 1826
  • Thanked: 12 times
    • View Profile
Quote from: Woolyhead
We're told that the big bang occured at a point and the energy thus released expanded equally in all directions away from the point of release.

To return to your OP, you seem to have answered your own question.  You say the energy "expanded", rather than exploded.
My understanding of the BB theory is that it involves an expanding Universe, rather than an exploding Universe.

BTW, do you accept that all observers would see the CMB radiation coming towards them, where ever they were in the Universe?
 

Offline Skyli

  • Full Member
  • ***
  • Posts: 54
    • View Profile
Wasn't the "Big Bang" actually a two-stage affair? First an explosion and then, about 380,000 years later, the decoupling and expansion.

Up until the decoupling there would have been no radiation, just photons bouncing off densely packed hydrogen. I thought that, before the decoupling/expansion, the universe had already expanded to some degree.

Going back to the balloon, it's as if one partially blew up a balloon (the Big Bang) and then heated it so the air inside expanded.

If this is the case then there would be no central "point" to the universe, only a central region.
 

Offline woolyhead

  • Jr. Member
  • **
  • Posts: 39
    • View Profile
Quote from: Woolyhead
We're told that the big bang occured at a point and the energy thus released expanded equally in all directions away from the point of release.

To return to your OP, you seem to have answered your own question.  You say the energy "expanded", rather than exploded.
My understanding of the BB theory is that it involves an expanding Universe, rather than an exploding Universe.
Sorry, Bill. I'll be more careful. I understand that the creation of the universe occurred in two phases: the sudden and short lived release of a vast amount of energy (big bang) and its expansion through not being stopped (after Newton's first law). This was followed 380,000 years later by the inflation (after Guth). At some time as the energy density fell, the radiation changed state into sub atomic particles including photons. But by then the big bang was well finished and no further radiation had been sent out. Since the original "batch" of radiation had moved a long way away in all directions by then, there would have been a vast void with nothing inside. Hence the universe could be hollow.

BTW, do you accept that all observers would see the CMB radiation coming towards them, where ever they were in the Universe?
Yes I accept that the "hollow universe" idea permits this. How does that affect the truth of the hollowness? CMB from the other side of the hollow ball would still do so.
« Last Edit: 17/10/2013 18:57:44 by woolyhead »
 

Offline woolyhead

  • Jr. Member
  • **
  • Posts: 39
    • View Profile
Wasn't the "Big Bang" actually a two-stage affair? First an explosion and then, about 380,000 years later, the decoupling and expansion.

Up until the decoupling there would have been no radiation, just photons bouncing off densely packed hydrogen. I thought that, before the decoupling/expansion, the universe had already expanded to some degree.

Going back to the balloon, it's as if one partially blew up a balloon (the Big Bang) and then heated it so the air inside expanded.

If this is the case then there would be no central "point" to the universe, only a central region.
Well, blowing up a balloon puts gas molecules inside and these prevent the balloon from being hollow. I suppose that photons bouncing off hydrogen must scatter them so that some of them would tend to return to the centre of the original big bang. This would count as preventing the universe from being hollow: I must accept the logic of it. Nice try. Thank you for the idea. However, by the time the photons were first formed the universe had undergone inflation at greater than the speed of light. The photons were formed after the inflation event so they could not have gone back sufficiently far to fill in the hollow universe with photons. The universe is hollow. It has a centre. Any extra  dimensions are not necessary to describe it thus far.
« Last Edit: 17/10/2013 20:43:17 by woolyhead »
 

Offline Bill S

  • Neilep Level Member
  • ******
  • Posts: 1826
  • Thanked: 12 times
    • View Profile
Quote from: Skyli
Wasn't the "Big Bang" actually a two-stage affair? First an explosion and then, about 380,000 years later, the decoupling and expansion.

I was not aware that the decoupling event (380,000 yrs) had any influence on the expansion rate of the Universe.  My understanding (which could well be wrong) is that the only significant variation in the expansion rate of the early Universe was the period of inflation which happened during the first fraction of a second.  After this the Universe continued expanding, but much more slowly.  At some stage the expansion began to accelerate, but as far as I am aware this had nothing to do with the decoupling event.  All that event did was make it possible for radiation to pass freely through the Universe; which it has been doing ever since.  It is the light first released at decoupling that is now observed as the CMB radiation.
 

Offline Bill S

  • Neilep Level Member
  • ******
  • Posts: 1826
  • Thanked: 12 times
    • View Profile
Quote from: Woolyhead
Well, blowing up a balloon puts gas molecules inside and these prevent the balloon from being hollow

I think we have to be careful with this idea as it involves introducing something from outside, which would almost certainly not have been the case with the Universe.  Everything would have been inside already.  Another balloon analogy – this time with the whole balloon representing the Universe – would be to inflate the balloon, then take it deep into the ocean.  The water pressure would cause the balloon to become progressively smaller.  At sufficient depth the balloon would become very small.  The point at which you release the balloon is the BB.  From there the balloon would expand rapidly.  There is no explosion, the skin of the balloon moves outward only because the gas inside is expanding in every direction.
 

Offline woolyhead

  • Jr. Member
  • **
  • Posts: 39
    • View Profile
Quote from: Woolyhead
We're told that the big bang occured at a point and the energy thus released expanded equally in all directions away from the point of release.

To return to your OP, you seem to have answered your own question.  You say the energy "expanded", rather than exploded.
My understanding of the BB theory is that it involves an expanding Universe, rather than an exploding Universe.

BTW, do you accept that all observers would see the CMB radiation coming towards them, where ever they were in the Universe?
Yes, Bill. The energy first exploded then expanded then inflated.
 

Offline Skyli

  • Full Member
  • ***
  • Posts: 54
    • View Profile
I think the point is that the CMB did not appear until the decoupling event, by which time it had expanded (and you're right, before the decoupling event). Therefore all the CMB can tell us, at best, is the shape of the universe at the decoupling event - some 380,000 years after the BB proper. So, if the BB was a point "explosion" of Existence it will be lost within that part of todays universe occupying the volume that the universe had back then.

I don't know about a "ball", considering all the lumps in the mix, but a centre seems on the cards, even if we can never find it.
 

Offline Bill S

  • Neilep Level Member
  • ******
  • Posts: 1826
  • Thanked: 12 times
    • View Profile
Quote from: Skyli
a centre seems on the cards, even if we can never find it.

Intuitively, yes.  I’m not going to get into multidimensional issues here.  I’m never really at ease outside the 3+1 dimensions of spacetime; but I suspect that a physicist or cosmologist would point to the 2D surface of a sphere, which has no centre, and say that it was analogous to the 3 dimensional “surface” of a hypersphere.  He/she would then liken this to the Universe. 

However, I’m not going to say that in case it is either wrong or highfalutin. :)
 

Offline woolyhead

  • Jr. Member
  • **
  • Posts: 39
    • View Profile
Quote from: Skyli
a centre seems on the cards, even if we can never find it.

Intuitively, yes.  I’m not going to get into multidimensional issues here.  I’m never really at ease outside the 3+1 dimensions of spacetime; but I suspect that a physicist or cosmologist would point to the 2D surface of a sphere, which has no centre, and say that it was analogous to the 3 dimensional “surface” of a hypersphere.  He/she would then liken this to the Universe. 

However, I’m not going to say that in case it is either wrong or highfalutin. :)

A sphere does have a centre, Bill. If asked where the centre of the sphere's surface is I'd have to agree that it's outside the 2-D scenario. But if I knew that this surface had come from this centre as the spherical balloon was blown up (or if I speculated on it), I'd know where the centre was. I'd say it's outside our 2D universe but it exists. I could draw a geometric diagram to show where it is. But I agree that I'd be employing 3D in a 2D universe. I wouldn't say the centre was everywhere.
You asked me what I thought was the source of the universe's expansion. Answer: inertia. Newton's first law. Am I sure the creative energy splurge shut off? Answer: Yes. Hoyles continous creation theory was proved wrong. The creation did shut off. But I can see something else you may have been referring to. It's this: What are the relative timescales for creation, expansion 1, inflation, expansion 2. You might have a point there. I don't know.
« Last Edit: 18/10/2013 18:57:20 by woolyhead »
 

Offline Skyli

  • Full Member
  • ***
  • Posts: 54
    • View Profile
As luck would have it I found this in my news today:

http://www.space.com/23072-cosmic-microwave-background-light-inflation.html

Things are a bit clearer. It seems that, a fraction of a second after the Big Bang, all the space that exists was compressed around the point of explosion. Every "particle" of this compressed space then started expanding - apparently before all the "Laws of Physics" had been set. I guess, if space was not evenly distributed even in the super-compressed state, this would explain the scattered CMB, but the CMB is an image of the initial effects of the Big Bang, not at the end of the Expansion. I've learned something, and I can only think in 3+1 Dimensions!

As for the energy required to drive the Expansion I have an idea about space being organic, but that was another thread. While I don't doubt that Creation/the Big Bang has stopped, there is ever more space. Where is it coming from?

It still seems perfectly logical to think of a centre of the universe (although the "ball" would be a lumpy sphere at best) but the CMB is not going to guide one there. In fact, depending on how unevenly space was distributed in its compressed state, the "centre" of the universe could physically be anywhere within the universe - even within the "boundary".
 

The Naked Scientists Forum


 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums