The Big Bang versus the 'Big Bounce'

Jul 06, 2012
The Big Bang versus the ‘Big Bounce’
Credit: Thinkstock

Two fundamental concepts in physics, both of which explain the nature of the Universe in many ways, have been difficult to reconcile with each other. European researchers developed a mathematical approach to do so that has the potential to explain what came before the Big Bang.

According to ’s (classical) theory of general relativity, space is a continuum. Regions of space can be subdivided into smaller and smaller volumes without end.

The fundamental idea of quantum mechanics is that physical quantities exist in discrete packets (quanta) rather than in a continuum. Further, these quanta and the physical phenomena related to them exist on an extremely small scale (Planck scale).

So far, the theories of quantum mechanics have failed to ‘quantise’ gravity. Loop quantum gravity (LQG) is an attempt to do so. It represents space as a net of quantised intersecting loops of excited gravitational fields called spin networks. This network viewed over time is called spin foam.

Not only does LQG provide a precise mathematical picture of space and time, it enables mathematical solutions to long-standing problems related to black holes and the . Amazingly, LQG predicts that the Big Bang was actually a ‘Big Bounce’, not a singularity but a continuum, where the collapse of a previous universe spawned the creation of ours.

initiated the ‘Effective field theory for loop quantum gravity’ (EFTFORLQG) project to further develop this exciting candidate theory reconciling classical and quantum descriptions of the Universe.

Scientists focused on the background-independent structure of LQG which requires that the mathematics defining the system of spacetime be independent of any coordinate system or reference frame (background).

They applied both semi-classical approximations (Wentzel-Kramers-Brillouin approximations, WKBs) and effective field theory (sort of approximate gravitational field theory) techniques to analyze a classical geometry of space, study the dynamics of semi-classical states of spin foam and apply the mathematical formulations to astrophysical phenomena such as black holes.

Results produced by the EFTFORLQG project team exceeded expectations. Scientists truly contributed to establishing LQG as a major contender for describing the quantum picture of space and time compatible with general relativity with exciting implications for unravelling some of the major mysteries of the Universe.

Explore further: Step lightly: All-optical transistor triggered by single photon promises advances in quantum applications

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Bewia
2.1 / 5 (7) Jul 06, 2012
How the assumption of space-time spin foam implies the Big Bounce cosmology? I don't see any logic in it...
vacuum-mechanics
1.5 / 5 (10) Jul 06, 2012
Two fundamental concepts in physics, both of which explain the nature of the Universe in many ways, have been difficult to reconcile with each other. European researchers developed a mathematical approach to do so that has the potential to explain what came before the Big Bang.


By the way, it is interesting to note that nowadays we still do not understand the basic foundations of both theories, such as why and how electron could act as both wave and particle (in quantum mechanics), or how and why space-time could be curved (in general relativity). By consider these philosophical ideas (such as one below) parallel to mathematical approach may give the way to reconcile both theories.

http://www.vacuum...mid=4=en
Parsec
4 / 5 (4) Jul 06, 2012
How the assumption of space-time spin foam implies the Big Bounce cosmology? I don't see any logic in it...

Because the theory predicts on extremely fine space scales, gravity is repulsive. Think of a foam that is completely filled with matter. You cannot add more. So when space-time gets extremely compressed, the mathematics predicts that space-time would "bounce".
Parsec
3.7 / 5 (3) Jul 06, 2012
@vacuum-mechanics - wave/particle duality may be difficult to understand and visualize, but it certainly isn't difficult to formulate mathematically. I suspect you are confusing the extreme difficulty of human visualization with a lack of understanding.

In terms of space-time curvature, that is both easy to visualize and easy to understand.

Meanwhile recent discoveries in how to combine the two theories (Quantum mechanics and general relativity) are showing that the so called intractable infinities caused by combining these theories are almost certainly a product of the math used, rather than being real.
Deesky
5 / 5 (2) Jul 06, 2012
the theory predicts on extremely fine space scales, gravity is repulsive. Think of a foam that is completely filled with matter. You cannot add more. So when space-time gets extremely compressed, the mathematics predicts that space-time would "bounce".

The obvious (perhaps too obvious) question is, how is the universe going to achieve such states of compression (which sounds like the Big Crunch idea) when we see the opposite happening as Dark Energy is accelerating the expansion of space-time, leading perhaps to the Big Rip?

Also, how many times could this cycle repeat before the inevitable loss of energy after each iteration would halt the cycle?

I think LQG has a long way to go, even compared with string theory. For example, it cannot even reproduce the predictions made by the current standard model.
Parsec
5 / 5 (1) Jul 06, 2012
the theory predicts on extremely fine space scales, gravity is repulsive. Think of a foam that is completely filled with matter. You cannot add more. So when space-time gets extremely compressed, the mathematics predicts that space-time would "bounce".

The obvious (perhaps too obvious) question is, how is the universe going to achieve such states of compression (which sounds like the Big Crunch idea) when we see the opposite happening as Dark Energy is accelerating the expansion of space-time, leading perhaps to the Big Rip?

Also, how many times could this cycle repeat before the inevitable loss of energy after each iteration would halt the cycle?

I think LQG has a long way to go, even compared with string theory. For example, it cannot even reproduce the predictions made by the current standard model.

It almost certainly can't. And I agree with you about LQG.
JIMBO
3.4 / 5 (5) Jul 07, 2012
PHYSORG is DisOrg ! No links, No authors, just this:'Effective field theory for loop quantum gravity & CORDIS ? WTF is CORDIS ?
A quik scan of the arxiv under gr-qc reveals no such paper.
Suspect this is just filler. When will they stop doing this & allow their readers to follow up on the original research ??!!
antialias_physorg
4.5 / 5 (8) Jul 07, 2012
Also, how many times could this cycle repeat before the inevitable loss of energy after each iteration would halt the cycle?

I'm not sure there would be an inevitable loss of energy. Why would energy conservation be violated?

The bounce is an interesting consequence of LQG, but it doesn't really solve the origin problem
(I'm very careful not to write 'first cause', here)

The obvious (perhaps too obvious) question is, how is the universe going to achieve such states of compression

We really don't know if the universe has already gone through all the phase changes it is going to go through. There's nothing that says that ALL phase changes have to happen early on or at higher temperatures than the current CMB. There may be a phase change in the future that leads to eventual collapse.
sanita
5 / 5 (4) Jul 07, 2012
..WTF is CORDIS? A quik scan of the arxiv under gr-qc reveals no such paper.
It's Community Research and Development Information Service of European union. LQG phenomenologists are concentrated in Europe-Canada with compare to string theory fans. In US is only one university (Penn State), that has a research group doing non-string QG (I mean more than one faculty member).
JIMBO
1 / 5 (1) Jul 07, 2012
Still, WHERE is the arxiv citation in this article ?? THAT fellow is Martin Bojowald, but there are others, non-cited in the CORDIS webpage. WTF, are they ashamed of work done under their auspices ?
nkalanaga
5 / 5 (1) Jul 07, 2012
Not all published papers are in arxiv. It would be nice if they were, but many researchers still go straight to the pay-to-read journals.
baudrunner
1.1 / 5 (7) Jul 08, 2012
Creation of the universe is a continuum of Big Bounces. Creation continues at the periphery, accelerating until an infinite mass front is attained, yielding the gravitational factor that accelerates universal expansion, and because infinite mass is equivalent to infinite density, and infinite density represents infinite potential, yielding the quantum fluctuation that sparks creation once again, we have a series of infinite mass creation fronts - creation cycles of the Great Creation Wave, but the universe never collapses in on itself, it just continues to create outwards, from the nothing that is infinite density. Perhaps the next infinite mass front is what we are interpreting as dark matter - dark because nothing is mathematically represented as infinite density, and infinite density is infinite potential. Those creation cycles are Big Bounces.

Crazy? How less so then LQG, or DE?
antialias_physorg
5 / 5 (8) Jul 09, 2012
Crazy? How less so then LQG, or DE?

Because DE and LQC have solid math behind them that matches with other observed phenomena. Your tripe does not. If you were to go through any math that would fit with your 'theory' then you'd see that it doesn't fit anything we currently observe.

Understand this: Unproven theory are not the same as made up theories. Serious unproven theories (like string theory, Brane theory, super symmetry, or LQG) have the math that fits with past observations. It is only when you make predictions from that math that you can find discrepancies betwen them. And it is exactly at that point where future experiments will separate the good from the bad.

Made up theories that some interent-poster pulled out of his rear are useless, as they neither fit past observation nor make testable predictions. They're just fairy tales.
ewj
1 / 5 (5) Jul 10, 2012
Fairy tales are fictional stories. However, some science fiction writers are on the point and present ideas unthought of by the regular scientific community. i.e. HG Wells and the death ray spitting matians. Hence latter day lasers. In a book 'Absolute relativity theory of everything'. The author presents us with the idea that the universe is made up of 4 spatial dimensions. The primary being the expansion of space (ignores time as a by product of the Euclidian 3D & GFT Spacetime). The opening velocity of this dimension determines whether atoms associate and or dissociate. Currently the constant 300kms enables an atomic Hold On, which means atoms can continue to exist. Should however, this velocity change will cause the entire dissociation of atoms back to energy - and hence initiate a further expansion cycle and new big bang. The universe is nothing more than an on ongoing series of pulses. We just happen to be existing in one of them at this time - lasting some 14 billion year
ewj
1.8 / 5 (6) Jul 10, 2012
Another science fantacist would be Galileo. He predicted that the moon caused the ebb and flow of tides as the water followed the moon around the Earth. He was condemned for heresy and was due to have his head cut of. Fortunately, an influential person in the Vatican managed to commute this sentence to a life imprisonment to his house. Another example would be the man who said molecules exist. He was made fun of and he committed suicide. Another example would be Faraday - he was only a lab technician - and he left us a substantial legacy. Euclid envisaged we exist in 3D and wrote a 'science fiction called The Elements! Still in print today. Science is understanding nature not just writing pages of math formulae. Einstein said himself imagination is far more important than intelligence. Intelligent people can do the donkey work and calculate how many threads you need to put onto a bolt to make it fit the hole. If one completely understands nature then you must be god without a sum
ewj
1 / 5 (5) Jul 10, 2012
We need people with fresh ideas and notions, which are born of their unique sensitivity to nature. As indeed Einstein was. He imagined things which no one else did. Otherwise we are in danger of constantly digging the same bit of ground in the hopeless search of finding a gold nugget. And our cognition limited by formal doctrine. The Vatican being a perfect example which supressed new ideas which Galileo nearly lost his head for. Looking at the little picture of sub atomic construction of course is useful but this does not provide a means to understand the big picture - this persuit may in fact be taking us backwards not forwards as we become more and more possessed with the tiny structure. For example does any data exist which determines if all suns spots are simultaneous? Has anyone thought of that? If they are indeed simultaneous then there is information between them. Which must be occuring at the rate of 300kms. This would prove the existence of the Primary dimension.
antialias_physorg
5 / 5 (4) Jul 10, 2012
HG Wells and the death ray spitting matians. Hence latter day lasers.

I think you have a VASTLY oversimplified idea of what science is and how it works and how little scientists take pointers from fictional literature.

And yes: some people were 'made fun of' for their quirky theories which tured out to be true. But to turn that around and say that every quirky theory therefore has to be true is crazy in the extreme. For every theory that pans out there are literaly thousands that don't - and as long as a quirky theory makes no predictions different from the current best model it's useless.

Science is understanding nature not just writing pages of math formulae

Science is what works. Note the "what works" part. If your science doesn't work and holds no predictive value it's wankery.

antialias_physorg
4.2 / 5 (5) Jul 10, 2012
We need people with fresh ideas and notions,

We have those. They're called scientists. Being a scientist is as much about being innovative as it is about being able to learn what has alread ben discovered and understand complex ideas.
But neither works without the other - and all these "arm-chair-theorists" ever do is jot down a brainfart and then think they have discovered the grand unified theory.

But when you look through history: those that REALLY came up with the groundbreaking changes were never arm-chair theorists. It was solid scientists, with a deep understanding of what was already learned, working hard and dilligently and putting it together in novel ways (E.g. relativity can be deduced from very simple principles with just two additional assumption: c is constant, and the principle of equivalence)
neiorah
5 / 5 (1) Jul 11, 2012
From what I just read, we are getting smaller in the big picture than we were before.
Claudius
2.6 / 5 (5) Jul 12, 2012

But when you look through history: those that REALLY came up with the groundbreaking changes were never arm-chair theorists. It was solid scientists


While I agree with you about arm-chair theorists, it seems to me that those "solid scientists" who come up with truly groundbreaking changes are often ridiculed for their work until later vindicated. From what I have observed, most "solid scientists" seem to lack imagination, work exclusively within the box, and the few that have imagination have an uphill fight to get their work accepted.
casualjoe
not rated yet Jul 12, 2012
The uphill fight is what makes science work, it's harsh scrutiny and it's against anybody who can proove you wrong. For something to be considered remotely real it must satisfy every experiment that anybody in any scientific field can do.

The great discoveries in science have shown us that we are all studying the same thing.
antialias_physorg
5 / 5 (2) Jul 13, 2012
From what I have observed, most "solid scientists" seem to lack imagination,

Then you should probably try to meet one in real life.

EVERY article here on physorg has (at least) one innovative idea behind it that, to date, non one on the planet has had. If you don't call that innovative, then what do you? And EVERY article here is the work of a group of 'solid scientists'.

If you work exclusively within the box then you're an engineer. (Not knocking engineers. They do also a LOT more for humanity than the armchair theorists)

Do revolutionary findings get questioned by other scientists? Yes.
Do they sometimes get fought? Yes.
Do they ever get ridiculed by other scientists? No.

Science is hard. Not every scientists understands what other scientists do immediately. I can't even read some papers in my own specialty straight away because sometimes I'm unfamiliar with the particular subset of math used. It's not surprising that revolutionary ideas take time to take root.
CNA
5 / 5 (1) Jul 13, 2012
This description of a Big Bounce reminds me of the premise of the scifi novel Tau Zero by Poul Anderson back in 1970.
exequus
5 / 5 (1) Jul 23, 2012
This is a public service from a curious non-scientist who has gained rudimentary acquaintance with the basic themes/concepts/theories of physics such as string theory, quantum mechanics, special and general relativity, higgs bosons, the standard model, etc. Buy, borrow or steal Brian Greene's 'The Elegant Universe' and 'The Fabric of the Cosmos' where all of these concepts plus the theories that use them are described and explained in lucid-to-the-max prose that is a pleasure to read. He really writes for the rank beginner but without being condescending or trivial.