Balloon model for the expanding universe...

[randomname12345]

Whenever I've tried to graspe the concept of the expanding universe, I've made my way to the balloon model. Three dimensions are shrunken down to 2 on the surface of a sphere, and the sphere is inflated. In this manner every point on the surface is moving away from all the other points.

 

I have a few questions about this.

 

1) In the model, patches on the surface will grow in size. Does this mean a 1m x 1m x 1m box will grow in size? How can this be measured, as a 1m ruler will also grow.

 

2) Does space have any property of elasticity?

 

3) Does it take energy to inflate the universe as it does to inflate the balloon?

 

 

Thanks a lot, I look forward to discussing this.

 

-s

[Aki]

1) no, only the space between the galaxies that are expanding.

for a better explanation, go to http://www.sciam.com/article.cfm?chanID=sa006&articleID=0009F0CA-C523-1213-852383414B7F0147&pageNumber=5&catID=2

go down to "Is Brooklyn Expanding?"

 

2) not sure

 

3) yes, and that energy is called the dark energy

[Bo]

1) yes and no: as you said; your 1 m^3 box will look the same to you, since your meter is also grown. however, since the speed of light is finite, we can look into the past of the universe, and see that certain things have 'grown' (most notably: the redshift of distant galaxies)

 

2) depending on what you mean by elasticity... If space is deformed, and you remove the source of this deformation, it becomes flat again.

 

3)yes, to give an accelerated expansion you always need some force. Think of it as 'reversed gravity'; normal matter causes the universe to collapse (or not; depending on the curvature); while dark energy causes the universe to collapse

 

 

bo

[DivineNathicana]

while dark energy causes the universe to collapse

 

Bo, don't you mean expand?

[Bo]

whoops :friday:

you're of course absolutely right!

 

Bo

[Tormod]

*phew* We are saved by the bell. :friday:

[C1ay]

Whenever I've tried to graspe the concept of the expanding universe, I've made my way to the balloon model. Three dimensions are shrunken down to 2 on the surface of a sphere, and the sphere is inflated. In this manner every point on the surface is moving away from all the other points.

 

I have a few questions about this.

 

1) In the model, patches on the surface will grow in size. Does this mean a 1m x 1m x 1m box will grow in size? How can this be measured, as a 1m ruler will also grow.

 

2) Does space have any property of elasticity?

 

3) Does it take energy to inflate the universe as it does to inflate the balloon?

 

 

Thanks a lot, I look forward to discussing this.

 

-s

 

I do not believe your box grows. It is simply moving away from the origin of the big bang like everything else. It is a particle on the surface of the balloon such that it is not expanding as the balloon is, the balloon is merely carrying it.

 

I believe space itself is just that, space, a void of everything. Space itself is not expanding, only the matter within that space is moving apart through space which offers no resistance to that movement. If space did have elasticity it would impart a resistance to the movement of mass as an external force. This would result in an eventual contraction of everything expelled by the big bang leading to the big crunch model.

 

IMO, the balloon model is a derivative of the big bang theory. As such, the energy driving it would be that from the initial explosion that expelled mass in all directions. According to Newton's Law of Inertia, all of that mass will continue in motion until acted on by an external force. This makes the model somewhat unlike the balloon in that a balloon has resistance to expansion, mass traveling through space, unacted on by external forces, does not. That said, I don't believe there is a continuing energy input that drives the expansion.

[Aki]

It is simply moving away from the origin of the big bang like everything else.

 

There is nothing such as the origin of the big bang. The big bang happened everywhere, there is no centre or a point where it happened. The big bang is just an expansion of space at a very very fast rate.

[BlameTheEx]

1) Here is a real question. Aki says no, and Bo yes and no!

 

I say that its worth thinking about. The normal view is that Bo's box will not expand, but I have always been fascinated by the possibility that he may be right.

 

If so then the ONLY effect of the universe's expansion is the red shift. It is the same size as ever because we can only measure it with an expanding meter stick. If there was a Big Bang it occurred in a universe that was in effect as big as it is now.

 

The red shift could then be equally thought of as a property of space with no relationship to expansion! It could just as easily be due to some other process such as a speeding up of time or a gravitational effect.

 

Does Bo's box expand? I don't think there are any observations that prove the case ether way. It is a question for cosmology, and as yet the evidence is highly inconclusive.

 

If there was to be proof it would come from measuring the apparent size of distant galaxies. The problem is that such galaxies come from an earlier time in the universe's evolution. They are not directly comparable to modern galaxies. I dare say that soon we will have sufficient evidence to say one way or the other with conviction. Proof is only a few years away, but right now the jury is out.

[C1ay]

There is nothing such as the origin of the big bang. The big bang happened everywhere, there is no centre or a point where it happened. The big bang is just an expansion of space at a very very fast rate.

 

Are you stating that as fact? IMO, if everything is moving away from each other, then there is some point at the center of that expansion.

[lindagarrette]

Are you stating that as fact? IMO, if everything is moving away from each other, then there is some point at the center of that expansion.

Before the BB, there was nothing to be a center of. Space has no "center" and no "boundary" but there is nothing outside it. Our ability to visualize this is limited.

[C1ay]

Before the BB, there was nothing to be a center of. Space has no "center" and no "boundary" but there is nothing outside it. Our ability to visualize this is limited.

 

That depends on your viewpoint. IMO, space is the void that matter and energy occupy and it is infinite without a center or a boundary. If there was a big bang though, it expelled matter and energy in all directions and that portion of space that is now occupied by the matter and energy expelled from that event does have a center.

 

I do not believe space itself was created by the big bang, I believe it is infinite and it has always existed. I accept that it is possible that the matter and energy that are what we call the universe, may have collapsed into a singularity that resulted in the big bang. I am finding that I am accepting that less and less now because of the discoveries of old clusters and galaxies that should not have existed when the local universe was young. They suggest the local universe is much older than we think, or our local universe contains old material that was not expelled by the big bang, material that already existed in space around the singularity that contained the matter and energy for the big bang. This would also explain known clusters that are thought to be older than our universe.

[lindagarrette]

That depends on your viewpoint. IMO, space is the void that matter and energy occupy and it is infinite without a center or a boundary. If there was a big bang though, it expelled matter and energy in all directions and that portion of space that is now occupied by the matter and energy expelled from that event does have a center.

 

I do not believe space itself was created by the big bang,

The generally accepted scientific model of the BB is that space and time were created at that instant. If you have evidence that would indicate otherwise, then you should present it to the scientific community and perhaps be eligible for a nobel prize.

[C1ay]

The generally accepted scientific model of the BB is that space and time were created at that instant. If you have evidence that would indicate otherwise, then you should present it to the scientific community and perhaps be eligible for a nobel prize.

 

Perhaps one day our observations of the observable universe will reveal conclusively that matter exists within our universe that is older than our universe. Until then it is only speculation.

[Aki]

Are you stating that as fact? IMO, if everything is moving away from each other, then there is some point at the center of that expansion.

 

Because the cosmic background radiation left from the Big Bang is uniform and constant in every direction it is coming from in space, that shows that there is no center for the expansion. If there was a center of expansion, the cosmic background radiation would only be coming towards the Earth in one direction, and not in every direction.

[Aki]

I do not believe space itself was created by the big bang, I believe it is infinite and it has always existed. I accept that it is possible that the matter and energy that are what we call the universe, may have collapsed into a singularity that resulted in the big bang.

 

I agree with you. I don't believe that our universe was created at the big bang. Our universe before the big bang was already infinite in size. The big bang was only an expansion of our universe, and only happened because the Higgs field dropped from its non-zero value.

[Qfwfq]

The various cosmological models are so far quite conjectural. There isn't much evidence either way, for space-time existing or not before tha BB. While some could concievably be found for previous existence, I don't see how in principle any observation could rule it out.

 

IMO, even if the bubble model is correct, single objects are not expanding, only the overall manifold is. The cosmic background radiation does have an anisotropy that the bubble model would vave to account for too.

 

Space has no "center" and no "boundary" but there is nothing outside it. Our ability to visualize this is limited.

No it isn't, a boundless and homogenous but finite space of n dimensions with uniform positive curvature is the hypersurface of a hypersphere in n + 1 dimensions. In the case of 2 dimensions it's the ordinary spherical surface. Visualizing 4-D objects only takes a bit of practice.

 

IMO, if everything is moving away from each other, then there is some point at the center of that expansion.

This isn't consequential. In the steady state model, the universe would be infinite with matter spread all through it, no centre of mass, but expanding. In the bubble model there would be no c. m. in space, to have one you need to embed space in a 4-D manifold which can even be space-time, but to say that there is a centre doesn't really have physical meaning, as the centre isn't in space.