# Cyclic Universe - Fixed in Size but Divided into 8 Sections

1. Oct 9, 2011

### Buckeye

What is wrong with assuming a fixed size universe, dividing it into 8 octants, and allowing the various octants to expand and contract against each other? In such a situation, could our octant be currently expanding and due to the pressure of our expansion cause one or more adjacent octants to contract and still maintain the fixed volume of the total universe?

2. Oct 9, 2011

### Vorde

Nothing is 'wrong' with that assumption. However there is absolutely no experimental basis for it, nor it there any way to get experimental evidence (assuming the size of one of your 'octants' is greater than the size of the observable universe), so thinking about it serves little use.

And out of curiosity, why 8?

EDIT: It is not objects which are expanding, but space itself, and I am doubtful that space reacts in the compression-expansion way that objects do.

3. Oct 9, 2011

### Buckeye

The cyclic universe model is an old one that is denounced mainly due to our beliefs about entropy. In 2007, a new effort was started to refresh it (see Wiki).

An octant frame allows each section to expand or contract due to pressure. Pressure in such as model requires that space is never void, and that matter forms space instead of filling it to some level of density. You might be able to use dark matter, dark energy together with observable matter and observable energy to form that space. In this model, space and matter could be combined.

From Wikipedia:
A cyclic model is any of several cosmological models in which the universe follows infinite, self-sustaining cycles. For example, the oscillating universe theory briefly considered by Albert Einstein in 1930 theorized a universe following an eternal series of oscillations, each beginning with a big bang and ending with a big crunch; in the interim, the universe would expand for a period of time before the gravitational attraction of matter causes it to collapse back in and undergo a bounce.

4. Oct 9, 2011

### marcus

In the x-y plane, the x and y axes divide the plane into 4 quadrants.

In the 3D space with x-y-z axes, you get the 3D space divided into 8 sectors.
You might call them octants.

The kind of expansion this picture suggests would not agree with Hubble law. The rate that a distance is expanding would not be proportional to its length.
But as you point out, the idea has no motivation. It is needlessly complicated. No reason has been proposed why distances in any one sector should expand.

5. Oct 9, 2011

### Vorde

Ah, I misunderstood your model to be a different one I had read about recently that involved separate universes expanding and contracting into each other.

EDIT: To Marcus, but if you're splitting the universe into 8 sectors based off the origin in a coordinate system, for that coordinate system to have physical meaning doesn't that imply that you are choosing a 'center of the universe' as the point (0,0,0), and by doing that you rule out a spherical universe (it would have no center), and by asserting the universe is of a fixed volume doesn't that imply there IS an 'outside' wall of the universe? Which doesn't make sense.

6. Oct 9, 2011

### marcus

Vorde, I don't know what Buckeye has or had in mind. I just wanted to offer one possible construction that has 8 sectors. That might be what he is talking about. Or on the other hand what you read about might be the right picture (I'm not clear about that though.)

AFAICS your logical objections to this 8 sector picture are reasonable enough. To me it is so drastically in conflict with observation that I cannot take it seriously. But if you take it seriously you will quickly find many things wrong I suppose (as you seem to be in course of doing.)

Last edited: Oct 9, 2011
7. Oct 9, 2011

### Vorde

Ah, guess I jumped the gun there.

The model I'm talking about I think I read in a Scientific American a couple months ago, I'll have to find it to be sure though, I don't remember much about it at all.

8. Oct 9, 2011

### George Jones

Staff Emeritus
After deleting some posts, I have closed this thread. Promotion of personal theory and non-mainstream view violate Physics Forums rules.