# Eternal Universe

1. Apr 24, 2006

Hi everyone,

I am just looking for opinions here! I want to know what all you peoples think about the universe we are a part of, is it Eternal or does it have a start and also an END?

Just curious.....

2. Apr 24, 2006

### Garth

Hi Shadowmonk710 and welcome to these Forums!

Under the GR paradigm the universe definitely had a global singularity in the past, the Big Bang, which was a singularity for time as well as space.

However as that singularity is approached (in time reversal) there will come a point where QM effects become dominant.

There is no Quantum Gravity theory to date, although Loop Quantum Gravity is a promising candidate, and so we do not know what actually happens when $t \rightarrow 0$ as an alternative to the singularity. However it seems that there may be a 'bounce' from an earlier universe, i.e. an overwhelming repulsion that reverses a previous contraction or 'Big Crunch'.

One unknown is whether this universe will contract again and 'crunch', if it does not it seems peculiar that a previous cycle of oscillating universes should end in such a way and just peter out into an infinite 'nothingness'.

However, as the overall density of the present universe seems to be just above the critical density, the prediction of GR is that our universe may well crunch in about 1011 years time.

Other scenarios are presented by the Ekpyrotic Universe M-brane theory,

or the Quasi-steady state cosmology model, which has been criticised, see Ned Wright's page: Errors in the Steady State and Quasi-SS Models.

or the http://en.wikipedia.org/wiki/Self_creation_cosmology [Broken] for example.

In the pure GR theory the universe has a once-for-all beginning at the Big Bang but in all these other theories, or in the Jordan frame of SCC, the greater universe is eternal.

I hope this helps...

Garth

Last edited by a moderator: May 2, 2017
3. Apr 24, 2006

### BornLogician79

Gravity unification closely related to EMS.

An idea I've developed pertaining to this question relates to a law of physics. If energy is neither created or destroyed, than how is universe created or destroyed? May it just evolve as does any life form? Are areas shaped or reformed in remote areas, expanding and contracting? Most occurences in nature do both!
I do however believe there is no such thing as nothing at all. Everything has a state or has properties regardless of if you cannot see a particular entity.
Very good question to ponder!
At least we are in a quiet part of the universe!

4. Apr 24, 2006

### EL

In what way does "it" seem so? Or are you simply just speculating?
I thought the "oscillating universe" had big troubles with for example creating the element abundances we observe.

The mainstream opinion is that a significant part of the total energy density is made up by a cosmological constant (or something similar with w~-1), and hence predicts an ever expanding universe.

Last edited: Apr 24, 2006
5. Apr 24, 2006

### SpaceTiger

Staff Emeritus
Measurements aren't pointing to a super-critical density at the moment. Even if they were, the generic $\Lambda$CDM model still predicts CC dominance at late times. It's hard to say anything about the far future of the universe because there could be hidden energy components that are too weak to measure now. Also, since we don't know the dark energy equation of state, we can't say how it will behave down the line. These uncertainties would remain regardless of whether the density were critical or barely supercritical.

6. Apr 24, 2006

### aguy2

Science, bye-in-large is saying "finite".

Philosophy and
Religion, bye-in-large are saying "eternal".

I would say it is presently finite, but it can be made to be eternal, if we and our descendents can combine competence with commitment and "make it so".
aguy2

7. Apr 24, 2006

### sunblock

Consider that when I look at a star at night the Earth is rotating but I can still see the star continuously. That means that the star is radiating an energy wave of a very wide range of frequencies in all directions. It also means that all stars in all galaxys are doing the same. The energy wave even can be detected by Hubble from galaxys billions of light years away. That light passed all the matter and galaxys between there and here and still got here and the majority continued on it's journey past Earth. Collective, over 13.5 billion years, that is a lot of energy that just went that-a-way, not counting the loss in the future billions of years. If there was a big bang in the past is if possible that the next collapse will not cause another one because of the down-grade of energy content occuring. (I don't think anyone has detected a return of this energy, just a bounce of the amount that ran into matter along the way and got reflected in another direction, etc.)

In addition to that, it appears that the only thing that generally occurs in our universe is that one galaxy runs into another and makes a larger galaxy. As time goes by we should wind up with some pretty large galaxies. These will probably just become "collector" galaxies, collecting all the other galaxies until there is only one. With one very huge galaxy (with maybe a few little ones avoiding the process), the concentration of stars rotating around the center (like the eye of a hurricane) may reach a critical mass of some type and explode back into a large cloud of matter to start the process all over again. Maybe this is what the big bang actually is. If so then there has probably been billions or even trillions of big bangs.

Sunblock

8. Apr 25, 2006

### Garth

Yes thank you EL & SpaceTiger, perhaps I should have emphasised the may in:
We do not know what DE will do in the future and the observed density in the mainstream model is so close to the critical density that it is still too close to call, I was just playing devil's advocate anyway!

There always has been an entropy problem with the oscillating universe, which cannot be resolved until a QG theory actually describes what was going on at the BB singularity.

My
was only reflecting the speculation from string theory such as discussed in the "Beyond the Standard Model" Forum Latent QG and the Quantum Nature of the Big Bang.

Garth

9. Apr 25, 2006

### SpaceTiger

Staff Emeritus
My point was that it doesn't matter, for this purpose, whether the universe is critical or barely supercritical. Either way, the far future is beyond our current abilities to predict. Yes, the universe could recollapse, but at this point we can't determine one way or the other from the data.

10. Apr 25, 2006

### hurk4

Eternal , or start and end?

I suppose that here the term Universe is meant in its mos general sense (including multivers etc).
- Only when there are possibilities to go from high to low entropy then it will never die and will not have met the nescessity to be created.
- Intuitively I feel that in this Universe there must be processes which will convey from high entropy/ (low specialness) to low entropy (high specialness). Only this stems with the impossibility of nothingness and rules out "a God of the gaps".
So far we only see the entropy in our observable universe increasing and my arguments do not stand on firm physical grounds, but I find it better to accept an autonomous ever (changing) existing reality then helping myself with ununderstandable notions like begin and end and trying to devellop physical models for these which will never be the (never understandable) autonomous reality.

11. Jan 29, 2010

### Tregg Smith

It ain't easy to think outside the box! It could be this physical universe is like a bubble-one of gazillions-in which case it has a physical beginning but maybe for practical purposes it doesn't matter because it will come to an end due to expansion and the death of all. Then you jump to- flobt- higher dimensional universes-from which this one could owe it's beginning. The question arises because of our lack of ability to understand-our conditioned concepts-the box.

12. Jan 31, 2010

### celebrei

"There always has been an entropy problem with the oscillating universe, which cannot be resolved until a QG theory actually describes what was going on at the BB singularity."

- the bb singularity, and what about Hawkings imaginary time then? doesn't it remove the singularity problem?

13. Jan 31, 2010

### marcus

This thread was resurrected from 2006, four years ago.

It asks about Eternal universe models. In fact there are several eternal universe models that are currently being studied---the research area is called "quantum cosmology".

One way to find out about current work is to scan the titles and read some of the abstracts summarizing recent technical papers.
http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=dk+quantum+cosmology+and+date%3E2005&FORMAT=WWW&SEQUENCE=citecount%28d%29 [Broken]
Some research papers listed here may have portions (of the firstpage introduction and lastpage conclusions section) which are accessible and non-technical. Others do not. Almost everything listed here is free for download--just click on "abstract" to see a summary and if you like the summary click on PDF.

Another way would be to go for a semi-popular book compiled for non-specialists like this:
http://www.springer.com/astronomy/general+relativity/book/978-3-540-71422-4 [Broken]
Beyond the Big Bang: Competing Scenarios for an Eternal Universe.
Advance draft copies have already been reviewed. The book gathers chapters by experts who are proponents of the different schemes that are currently being considered. It is intended for general audience.

Some of the ideas that used to be considered interesting, say back in the 1980s and 1990s are not pretty much neglected by researchers. There are plenty of models where the U. is eternal. And where the classical singularity (arising when vintage 1915 General Rel is used) is resolved. But the models currently under active study may not be those which come to mind if you learned about the subject from books written a few years back.

Last edited by a moderator: May 4, 2017
14. Feb 7, 2010

### rhody

You may find this interesting, recorded Feb 2008: by http://en.wikipedia.org/wiki/Burt_Ovrut" [Broken]" yesterday. Click the Daily Galaxy link in this link and then scroll to watch the TED video. For some reason I tried to find it on the real TED site and could not. Their display is much better.

The meat of the presentation happens here:

6:00 begin​
8:15 Big Bang discussion​
9:00 - 10:00 Endless Universe discussion​

From the article:
In essence Orvut suggests we live in an endless Universe... separated by brane collision events...

I don't think the serious mainstream physics community takes it too seriously. But you may enjoy the video.

Rhody...

Last edited by a moderator: May 4, 2017