'Big Bounce' theory may be testable?

[river-wind]

http://www.newscientist.com/article/mg20026861.500-did-our-cosmos-exist-before-the-big-bang.html?DCMP=OTC-rss&nsref=cosmology

New Scientist reports on a possible new idea for testing the viability of pre-big-bang theories via measuring the universal cosmic background radiation's clumpiness - more specifically, looking for a signature polarization. The upshot is that this theory doesn't require a QM-busting singularity prior to the big bang, instead suggesting that the universe cycles between expansion and contraction, never quite reaching the point of being a singularity.

[quantum_wave]

That is a great article. The cyclical cosmology implied by LQC is a step forward but as the article explains it doesn't answer some questions that immediately come up. Never-the-less it breaks the taboo of talking about "before and beyond" Big Bang Theory.

There has always been a fundamental realization with cyclical models. It is thought that eventually enough energy will be lost that the next cycle will not occur. The loss of energy with each cycle occurs because the crunch cycle and its bounce occur before 100% of the energy of the previous expanding phase has been recalled back into the crunch.

If that deficiency of energy occurs during a collapse then the universe will end in the big crunch that doesn't "bounce" as it has with each previous cycle.

If the energy runs out during expansion, then the universe will end in a Big Rip (http://www.google.com/search?hl=en&q=big+rip&aq=f&oq=) or what is called the heat death of the universe.

You really end up with the same options that Big Bang Theory and General Relativity give us only the "end" is put off for a number of cycles.

Still, LQC is a significant step in the right direction.

[river-wind]

Would such thermodynamic-style loss of energy assume botha begining, end, and also that such a cycle follows thermodynamic rules?

What if the bounce is perfectly elastic, not based on energetic work, but based on, say gravity? Gravity doesn't cause loss to heat in doing it's work. (does it? I'm not a physicist).

[quantum_wave]

Would such thermodynamic-style loss of energy assume botha begining, end, and also that such a cycle follows thermodynamic rules?It does not assume a beginning. The cyclical model assumes that the cycles have always been recurring and will always continue to occur. The loss of energy is the problem with the model. If the model is correct there would not have been a beginning and there would be no end to the cycles.

Lets break the problem down. If the cycles had been recurring forever, then time would be infinite backward and even if the cycles stop, time would continue as the defeated remnant of the model suffers one of its two fates, i.e endless expansion or a final big crunch.

The rules that apply have to be sound physics. The bounce has a great basis in LQC; that being a finite limit to energy density. If there is a maximum energy density that is possible, and the collapse of the universe has increasing momentum during the collapse, then the energy of the collapse cannot be absorbed at the instant that the maximum density is reached. The energy of the collapse is said to be expended in a rapid re-inflation of the volume of the crunch.

What if the bounce is perfectly elastic, not based on energetic work, but based on, say gravity? Gravity doesn't cause loss to heat in doing it's work. (does it? I'm not a physicist).The collapse is caused by gravity and the bounce overcomes gravity. The forces involved on that scale are almost unimaginable.

But the bounce does not have to even be perfectly elastic.

What if there are two expanding arenas and they expand until they intersect with each other. The intersection would interrupt the expansion and in that area of convergence where the two expanding arenas merge, a gravitational collapse could result in a big crunch that encompassed portions of the galactic material from each of the expanding arenas.

What if there are more than two such expanding arenas? Say there were a potentially infinite number of them in an infinite expanse of space. Then the cycles would never run out of energy and the crunch/bang cycles would always incorporate different galactic remnants. Each crunch would include energy from a different set of energy sources for each crunch/bang.

[TruthSeeker]

Purple elephants fly....

Sorry, I just thought this would be a relevant point in the discussion.... :p

[quantum_wave]

:o

Lol, you do have a way of cutting through the bull sh!t.

However, I'm not sure your theory is quite as relevant as the "bounce" theory :).

[Asguard]

quantum_wave

actually it WOULD be compleatly elastic, posably the only thing that is.

Energy and matter cant be created or destroyed, they can only be changed from one state to another. There for as the whole of reality colaps it must have EXACTLY the same total of mass and energy as when it exploded. There for if its cyclic then there must be no net loss

[quantum_wave]

You do have some firm ground to take that stand on. Some cyclical models predict that all of the energy can be recalled.

But ...

It wouldn't be likely that all of the energy of the last expansion cycle would be recaptured before the next bounce occurred.

For example the electromagnetic radiation that was emitted in the early stage of the previous expansion. It would have to be recaptured by the gravitational effect before the next bounce in order to participate in the bounce and the next expansion. If the photons don't have enough mass (some say they have No mass), then what mechanism is there to bring back that radiation?

[Asguard]

how?
where would it go?

Lets pretend there is something outside the universe, nothing INSIDE can interact with whats outside so where is the energy going to go?

this will be a bad model but pretend that matter and energy is all matter for a min. I have a ballon that is compleatly impermidable, no leaks so nothing inside can get out. This is the universe. I blow it up half way and thats ALL the stuff in the universe. Now i freze it and it shrinks, i heat it and it gets bigger but no matter what i do there is still the same amount of "stuff" in it.

Now yes in the ballon case what im doing is adding energy but in the universe we know thats not possable. There for if your model is correct NOTHING CAN BE GAINED OR LOST across the cycle. It must all remain

[merkababozo]

I'm all in favour of a 'wavicle' universe, one of multi-dimensional trans-geometry / phase differentials - problem being; it simply requires the formation of singularities, totally crucial for self regenerating 720 degree dualities provided by exo/endo event horizon relativiso-geometric energy transit

[quantum_wave]

I'm all in favour of a 'wavicle' universe, one of multi-dimensional trans-geometry / phase differentials - problem being; it simply requires the formation of singularities, totally crucial for self regenerating 720 degree dualities provided by exo/endo event horizon relativiso-geometric energy transitYes, clearly :). But read the lead article again. The model claims to be able to avoid the singularities all together as river-wind points out.

how?
where would it go?

Lets pretend there is something outside the universe, nothing INSIDE can interact with whats outside so where is the energy going to go?

this will be a bad model but pretend that matter and energy is all matter for a min. I have a ballon that is compleatly impermidable, no leaks so nothing inside can get out. This is the universe. I blow it up half way and thats ALL the stuff in the universe. Now i freze it and it shrinks, i heat it and it gets bigger but no matter what i do there is still the same amount of "stuff" in it.

Now yes in the ballon case what im doing is adding energy but in the universe we know thats not possable. There for if your model is correct NOTHING CAN BE GAINED OR LOST across the cycle. It must all remainYes, you are correct. My only answer from the perspective of the LQC model is that the space itself is not being retracted as the collapse cycle occurs. The space occupied by the expansion cycle at the full energy of the previous cycle, though finite in size, established itself by the EM radiation foot print. The EM occupying that foot print at the furthest reaches of the footprint is expanding the foot print at the speed of light. The EM that is expanding the foot print has no rest mass.

If the gravitational collapse pulls on the expanding EM forever I don’t see how it gets back into the crunch before the next bounce.

The system is still closed and therefore complies with your parameters. But if what I am saying about the expanding footprint is true then the next bounce occurs while the footprint is still expanding. The un-retrieved EM radiation increases with each cycle. Eventually the energy invested in that un-retrieved zone draws down the retrieved energy to the point that each consecutive bounce has less expansion momentum. That is a formula for eventual failure of the cyclical event IMNO.

[merkababozo]

Yes, clearly :). But read the lead article again. The model claims to be able to avoid the singularities all together as river-wind points out.


Read the article a few weeks back, but it does not go into any great depth (only a pop science job) ..... in order for an event recursion to arise, surely energy is required to converge beneath an auto-dynamically generated event horizon? - thus a duality exists, one creating the other, each swapping identities via the EH. In addition, greatest condensation (singularity) occurs simultanously with moment of maximum trans-dimensional dissapation. Therefore the beginning and end are merely 'one point' in the overall relativiso-geometric self perpetuating process.

[TruthSeeker]

:o

Lol, you do have a way of cutting through the bull sh!t.

However, I'm not sure your theory is quite as relevant as the "bounce" theory :).
Not that I disagree with the bounce hypothesis... I've envisioned it when I was 12 years old. But if we cannot test the hypothesis in an objective manner, it's like talking about flying purple elephants. It may be nice... but not necessarily testable....

[kaneda]

Once again the big bang idea survives by ignoring the forces of gravity. The shrinking universe nears 5x10^93 tons per cubic meter before suddenly rebounding.

How insultingly stupid can you get? Why didn't they say Tinkerbelle sprinkled it with pixie dust, causing it to rebound? That is more believable.

[OilIsMastery]

Purple elephants fly....

Sorry, I just thought this would be a relevant point in the discussion.... :p
Mathematical physics at it's finest. And these people criticize religion.

[river-wind]

kaneda - please enlighten me as to why it is so unbelievable.

[kaneda]

river-wind. Let's say it is true that gravity ceases to function at such a density. The universe starts to rebound and at say 10^90 tons per cubic meter, gravity starts functioning again, so the universe starts collapsing again. It will rebound and collapse endlessly, going from maybe the size of a molecule to the size of a house forever.

[quantum_wave]

Maybe, but LQC is looking at a universe that was rewinding back toward the big bang and then bounced instead of reaching a singularity. The whole idea of the simulation was to visit the idea that our observable universe emerged from the collapse of a previous universe. This simulation marks progress with the math that addresses quantization in the Planck regime.

The first simulation got part of it right but it didn't work because as they watched the expansion after the bounce it started to collapse again. This is just what Kaneda mentioned. But that was not the end of the effort. They admitted they had a huge problem and went back to work. They changed the idea from "quanta of area" to the idea that the quanta involved tiny volumes of space.

The new result agreed with GR when "expansion was well advanced, while still eliminating the singularity at the big bang".

They admit that there is more work to do with the math, i.e. developing it completely from LQG instead of borrowing form EFEs, but their current emphasis is the proposed testing to be achieved by a more detailed analysis of the CMB. They also don't all agree on the volume of the universe just before and after the big bang. Was it the size of a proton as the current simulations predict or does the universe occupy more space at maximum density? They are working on that.

At the same time Copeland is looking at superinflation, a period of accelerated expansion before the onset of inflation. That might mean there is no need for the exponential inflation during the first picoseconds after the bang, thus eliminating the inflaton particle and the horizon problem.

Whether you agree that they are on to a transition from a previous universe to our expanding universe or not, that is the direction they are going with LQC. If you have enough understanding of their papers to say they are wrong then you should produce something substantial that they have overlooked.

[river-wind]

kaneda: Why do you think that gravity ceases to function as you approach Planck length?

[kaneda]

river-wind. That is on page 2 of the article. I think the idea is that as density reaches close to infinity, the laws of physics, and so gravity itself breaks down. The idea here is to avoid the singularity (which would probably be ultimately stable), but does not explain how the first big bang happened since most believe that was a singularity.

I think the inside of a black hole is elementary particles, as in a sphere of electrons, quarks, etc. It is possible that at a set density, even these break down to energy. As such, energy has no gravitational force and at that point, the universe would rebound, as pure energy in another big bang.

[river-wind]

So the question is: "If there was no singularity, then how does gravity within the singularity work?"

[LogicTech]

A singularity is just a mathematical construct. Any we find in our physical theories just reflects the fact that our current models are inadequate for describing what goes on under those conditions. That's why we are working on a Theory of Everything, to eliminate those nasty singularities in our equations.

[TruthSeeker]

Here's a thought.....


If you compress an accordion, there's a limit to the smallest size the accordion can be compressed to. So what if there's a limit for matter too, to such an extent that gravity could not make it any more compact?

In the same though, why is gravity always thought of as an internal force pushing everything from within? Why can't gravity be a force outside the universe, pulling the universe? And why can't dark energy follow the same principle?

[quantum_wave]

Here's a thought.....


If you compress an accordion, there's a limit to the smallest size the accordion can be compressed to. So what if there's a limit for matter too, to such an extent that gravity could not make it any more compact?

In the same though, why is gravity always thought of as an internal force pushing everything from within? Why can't gravity be a force outside the universe, pulling the universe? And why can't dark energy follow the same principle?Your thought made me think ... I think your Purple elephants flying idea (http://www.sciforums.com/showpost.php?p=2117730&postcount=5) was better. The accordion analogy ... OK, maybe it is better than the elephants thing, but then you go on to say gravity is thought of as an internal force pushing out. I always thought of gravity as a pull force. Not only that, but if you reference General Relativity, gravity is caused by mass bending spacetime so it is neither a push or a pull; it is more of a "fall in the well".

However, that leaves your last thought, "Why can't gravity be a force outside the universe, pulling the universe?" No, it won't fly. Stick with the purple elephants flying :).

[kaneda]

LogicTech. A singularity was the original idea. A naked black hole without the annoying properties of a black hole which would stop it expanding. Infinity is a mathematical construct too and just as impossible.

[kaneda]

Truth Seeker. The biggest black hole found so far is a mere 18 billion solar masses and that probably has elementary particles inside it. There is no way of even guessing at what point an electron, quark or something far smaller breaks down completely into energy.

Gravity is a pulling force and not a pushing force which I think is what you meant. Gravity comes from massive and dense objects. The more massive or dense something is, the more the gravitational pull. As the force of gravity travels at just light speed, it must be a "local force" to work and be detected.

Dark energy is an anti-gravity force, something that not much more than a decade ago was said to be impossible.

[TruthSeeker]

Kaneda, how do you know gavity is a pulling force?