Big rips and little rips

Jul 04, 2011 By Steve Nerlich, Universe Today
The concept of accelerating expansion does get you wondering just how fast the universe can end up expanding by. Theorists think that the rate of expansion might become so extreme as to produce a Big Rip. Or, after fiddling with the math a bit, maybe just a Little Rip? Credit: NASA.

One of a number of seemingly implausible features of dark energy is that its density is assumed to be constant over time. So, even though the universe expands over time, dark energy does not become diluted, unlike the rest of the contents of the universe.

As the universe expands, it seems that more appears out of nowhere to sustain the constant dark energy density of the universe. So, as times goes by, dark energy will become an increasingly dominant proportion of the – remembering that it is already estimated as being 73% of it.

An easy solution to this is to say that dark energy is a feature inherent in the fabric of space-time, so that as the universe expands and the expanse of space-time increases, so dark energy increases and its density remains constant. And this is fine, as long as we then acknowledge that it isn’t really energy – since our otherwise highly reliable three laws of thermodynamics don’t obviously permit energy to behave in such ways.

An easy solution to explain the uniform acceleration of the universe’s expansion is to propose that dark energy has the feature of negative pressure – where negative pressure is a feature inherent in expansion.

Applying this arcane logic to observation, the observed apparent flatness of the universe’s geometry suggests that the ratio of dark energy pressure to dark energy density is approximately 1, or more correctly -1, since we are dealing with a negative pressure. This relationship is known as the equation of state for dark energy.

In speculating about what might happen in the universe’s future, an easy solution is to assume that dark energy is just whatever it is – and that this ratio of pressure to density will be sustained at -1 indefinitely, whatever the heck that means.

But cosmologists are rarely happy to just leave things there and have speculated on what might happen if the equation of state does not stay at -1.

Three scenarios for a future driven by dark energy - its density declines over time, it stays the same or its density increases, tearing the contents of the universe to bits. If you are of the view that dark energy is just a mathematical artifact that grows as the expanse of space-time increases - then the cosmological constant option is for you.

If dark energy density decreased over time, the acceleration rate of universal expansion would decline and potentially cease if the pressure/density ratio reached -1/3. On the other hand, if dark energy density increased and the pressure/density ratio dropped below -1 (that is, towards -2, or -3 etc), then you get phantom energy scenarios. Phantom energy is a dark energy which has its density increasing over time. And let’s pause here to remember that the Phantom (ghost who walks) is a fictional character.

Anyhow, as the universe expands and we allow phantom energy density to increase, it potentially approaches infinite within a finite period of time, causing a Big Rip, as the universe becomes infinite in scale and all bound structures, all the way down to subatomic particles, are torn apart. At a pressure/density ratio of just -1.5, this scenario could unfold over a mere 22 billion years.

Frampton et al propose an alternative Little Rip scenario, where the pressure/density ratio is variable over time so that bound structures are still torn apart but the universe does not become infinite in scale.

This might support a cyclic universe model – since it gets you around problems with entropy. A hypothetical Big Bang – Big Crunch cyclic universe has an entropy problem since free energy is lost as everything becomes gravitationally bound – so that you just end up with one huge black hole at the end of the Crunch.

A Little Rip potentially gives you an entropy reboot, since everything is split apart and so can progress from scratch through the long process of being gravitationally bound all over again – generating new stars and galaxies in the process.

Anyhow, Sunday morning – time for a Big Brunch.

Explore further: Chandra X-ray Observatory finds planet that makes star act deceptively old

More information: Frampton et al. The Little Rip: arxiv.org/pdf/1106.4996v1

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omatumr
1 / 5 (11) Jul 04, 2011
So, even though the universe expands over time, dark energy does not become diluted, unlike the rest of the contents of the universe.


Yes, of course.

The force of expansion is the same force that causes fragmentation of heavy nuclei of

a.) Atoms
b.) Stars and
c.) Galaxies

Neutron Repulsion.

That force is recorded as rest mass in every nucleus with two or more neutrons.

That is the force that powers the Cosmos, the Sun and sustains Life itself.

That is the force that world leaders and politicians cannot control.

With kind regards,
Oliver K. Manuel
Former NASA Principal
Investigator for Apollo
omatumr
1 / 5 (9) Jul 04, 2011
References:

1. "Super-fluidity in the solar interior:
Implications for solar eruptions and climate",
Journal of Fusion Energy 21, 193-198 (2002)

http://arxiv.org/.../0501441

2. "Earth's Heat Source - The Sun",
Energy and Environment 20, 131-144 (2009)

http://arxiv.org/pdf/0905.0704

3. "Neutron Repulsion", The
APEIRON Journal, in press, 19 pages (2011)

http://arxiv.org/...2.1499v1

4. "Is the Universe Expanding?"
The Journal of Cosmology 13, 4187-4190 (2011)

http://journalofc...102.html
Caliban
4.7 / 5 (9) Jul 04, 2011

Yes, of course.

The force of expansion is the same force that causes fragmentation of heavy nuclei of

a.) Atoms
b.) Stars and
c.) Galaxies

Neutron Repulsion.

That force is recorded as rest mass in every nucleus with two or more neutrons.

That is the force that powers the Cosmos, the Sun and sustains Life itself.


Yes. Of course, Oliver.

And your neutron-repulsion acts over billions of lightyears of space-the vast majority of which is hard, interstellar/galactic vacuum with nary an atomic nucleus to be found, much less to repel itself from anything else. And all the while still more space is being created, placing that much more distance between your neutron-repulsive atomic nuclei.

So, unless you are willing to go so far as to say that your neutron-repulsion force is contant AND infinite in range, then you need to go back to the drawing board, because your neutron-repulsion bucket has a hole in it, and it just keeps getting bigger, and bigger, and bigger, and...

George_Rodart
1 / 5 (1) Jul 04, 2011
omatumr
1 / 5 (9) Jul 04, 2011
And your neutron-repulsion acts over billions of light years of space


Can a rapid chemical drive the bullet that kills a deer a mile away?

Could nuclear forces vaporize the entire city of Hiroshima in 1945?

May I suggest that you read the paper?

"Is the Universe Expanding?"
The Journal of Cosmology 13, 4187-4190 (2011)

http://journalofc...102.html

With kind regards,
Oliver K. Manuel

GoldenBear12
5 / 5 (8) Jul 04, 2011
Oliver, I'm an undergraduate in astrophysics and even I can see that the hypothesis offered in this journal entry is far too vague and incomplete to even come close to explaining the expansion of the universe on large scales, not just local scales. Am I just interpreting this wrong or are you seriously suggesting the cause for dark energy and expansion on large scales to be caused by neutron repulsion. I think if we ever find out what drives this expansion, it will have nothing to do with normal baryonic matter and nuclear forces for that matter.
Callippo
1 / 5 (1) Jul 04, 2011
The models extrapolating the speed of universe expansion (and therefore the density of alleged dark energy) to the future or to the past of Universe evolution are still very flexible. In many theories the dark energy density simply wasn't constant in time.

http://www.physor...ion.html

http://www.physor...042.html

http://www.physor...176.html
mrlewish
1 / 5 (2) Jul 05, 2011
"Dark energy" is nothing but virtual information about the rest of the universe that has passed beyond the event horizon due to expansion. Since information can not be made or lost but just rearranged the universe has to make what we call dark matter or energy to compensate.
hush1
1 / 5 (1) Jul 05, 2011
The concept of accelerated expansion is staggering. More than imagination is needed to save or discard laws of conservation.
shams
not rated yet Jul 05, 2011
interesting.dark energy density remains constant throughout.though dark energy itself is still a hypothesis,so according to this paper it is the medium of the space time fabric.Can't we just say the fabric of space and time is expanding? like one of those fishing nets, when thrown spreads out in a conic shape and the individual pockets expands in this case aswell.wonder where the energy might be coming from?From another dimension?
omatumr
1 / 5 (6) Jul 05, 2011
Oliver, I'm an undergraduate in astrophysics and even I can see that the hypothesis offered in this journal entry is far too vague and incomplete to even come close to explaining the expansion of the universe on large scales, not just local scales. Am I just interpreting this wrong or are you seriously suggesting the cause for dark energy and expansion on large scales to be caused by neutron repulsion.


Thanks for the question, Golden.

I am seriously suggesting that the causes of dark energy (explosions of the nuclei of atoms, stars and galaxies) and expansion on large scales are neutron repulsion.

By the way, I personally knew many leading astrophysicists and cosmologists - Willie Fowler, A. G. W. Cameron, Fred Hoyle, Geoffrey and Margaret Burbidge, Hannes Alfven, David Schramm, Don Clayton, etc.

Here is a photo Oliver sitting behind Willie Fowler at the 1976 Gregynog Workshop on Isotopic Anomalies

www.omatumr.com/P...shop.pdf
Decimatus
1.5 / 5 (4) Jul 05, 2011
My coworker and I were throwing around an idea about Dark Energy.

Basically, Dark Energy comes from all the light that has ever been emitted in 14 billion years of the history of the universe. As all this light escapes out beyond the reaches of all normal matter, it drags the rest of the universe with it. Think about the quantity of light this represents as well as however much excess light came from the initial explosion. Now imagine the mass of this light and it's possible magnetic pull on the light following it, perhaps in a giant chain of magnetism and gravity.

Essentially this mass of light, forever beyond the horizon and continually added upon, is what drags our universe apart.

In that scenario, as the size of the universe increases and the light mass added decreases, we eventually end in a big crunch.
lengould100
1 / 5 (4) Jul 05, 2011
I've considered that myself, Decimatus. I believe that the standard response is that "the universe (appears to) fold back on itself so there actually is no place where photons leaving the big bang at C can get beyond baryonic matter leaving the big bang a (e.g.) 1/2C . This sort of argument is used to explain to me the illogical proposition that we can still detect the background radiation photons generated by the big bang, which is also a totally irrational proposition in a simple model of the universe. However, if I accept this sort of argument, apparently solely on faith, I must then ask "So if the background radiation photons emitted in the big bang exist everywhere at uniform density due to the geometry of the universe (presumeably having folded back on their path after travelling specified distances), why is it that starlight from extremely distant galaxies, which was emitted only a few hundred thousand years after the big bang arrives to us in coherent timesequenced packets?
lengould100
not rated yet Jul 05, 2011
The point above being that the big bang stopped making background radiation very shortly after the big bang itself (I think about 400,000 years), so all the photons emitted by it should be some very far distance away from our slower-moving baryonic galaxies.
Decimatus
1 / 5 (3) Jul 05, 2011
Well in terms of background radiation reaching us, I can see how inflation would mess that up. Given that they say the universe expanded to it's present size in a very short time, there was bound to be some light leftover in the exact center of the explosion that did not get inflated as much as the rest and is therefor just now reaching us. If this is the case, I think you would find that this background radiation decreases over time at some predictable rate.

But that is only if inflation and dark energy are even true.

I kind of have a conceptual problem with the big bang, inflation, dark matter, etc.

It seems like a series of contrived circumstances based upon one key observation(redshift) that seems to be self-fulfilling.

Decimatus
1 / 5 (2) Jul 05, 2011
I hope that sometime in the not-too-distant future we have some telescopes that can peer back to the supposed moments of the big bang. I expect when we do, the physicists are going to find more galaxies like ours and will then have to push the age of the universe back even further and tweak all the theories accordingly.

How much stronger will the James Webb be, assuming it ever reaches orbit? Will it be able to see 15 billion years back, 20? At which point do all our standard theories get thrown completely on their head?
lengould100
not rated yet Jul 05, 2011
I think it's an error to hope for getting visible light (or any photon-based) images of anything further back in time before the end of the "ionization period", about 400,000 years after the big bang.

I'm fairly sure the "inflation period" ended only micro-seconds after the big bang itself ?? and shouldn't explain the current universality of the background radiation. No doubt there exists a lot of abstract mathematics beyond my understanding which can logically clear up my confusion, but unfortunately I haven't had it explained to me, and any intuitive solution excapes me.
antialias_physorg
5 / 5 (4) Jul 05, 2011
mass of this light and it's possible magnetic pull on the light following it, perhaps in a giant chain of magnetism and gravity.

Whut? This makes no sense whatsoever.

This sort of argument is used to explain to me the illogical proposition that we can still detect the background radiation photons generated by the big bang,

Consider this: Space expands (which seems pretty well documented). This means that between far enough points the space in between can expand faster than light could travel between them. Such points are effectively beyond our visibility horizon.

Now consider points that currently NEARLY expand away from us at the speed of light. The light that was emitted there at the big bang (or at the 400k year mark to be more precise) would just now be reaching us. This is what we see when we record cosmic background radiation.

The big bang is not an 'explosion that happened far away'. It is an expansion of all space. Every point in it is the 'center'.

lengould100
not rated yet Jul 05, 2011
This article by JR Minkel at Space.Com

http://www.space....fog.html

'Earliest Galaxies Helped Lift Universe's Cosmic Fog' clarifies the parameters somewhat for me. The issue (as far as peering back into the big bang) is not excessive ionization but insufficient ionization, for a period up to perhaps 800 million yrs after the big bang (not the 400 thousand I'd recalled).

antialias_physorg : Thanks, that helps. HOWEVER, I still fail to make a coherent relationship between the universally coherent CMB, apparently emitted 800 million years after the big bang during the re-ionization period, and the neatly time-sequenced light arriving to us from galaxies 12.6 million light-years away (eg. which left them 800 million years after the big bang.
Decimatus
1 / 5 (1) Jul 05, 2011
What I meant was that big new telescopes would look further in the past and show that the universe isn't ~13.8 billion years old, but older, 15, 20, more. That is what I want to see happen because it would undermine the current theories.

Antialias, I am just saying that 10-13 billion lightyears of photons all traveling "out" from the universe could have some of the effects of dragging the universe apart as a dark energy mechanic.

Also, the amount of photons and other such particles that actually came out of the big bang could outweigh all other matter in the universe by who knows how much.

Thus, with possibly multi-universe-weights of photonic matter rushing outward at C, it could be enough to drag the universe apart as a dark energy mechanic.
lengould100
not rated yet Jul 05, 2011
That's interesting Decimatus. You propose that what we term dark energy is simply the gravitational attraction of all the light which has been emitted by all stars in the universe which has travelled beyond the baryonic matter and now exerts a gravitational effect on the baryonic matter behind it. That actually gives a fairly neat explanation for why the expansion is accelerating, since the mass of those photons would be continuously increasing.

I think current equations of gravity provide for the curving of spacetime too much to allow such travelling (so what does happen to that light?). Perhaps current equations of gravity are the problem?
lengould100
not rated yet Jul 05, 2011
The problem with the proposal is that the energy (= mass) of a photon drops with reduced frequency, and the further away from any observer a photon gets the lower its apparent frequency (redshift) so at a limit eventually it would have zero energy therefore zero gravitational effect. Doesn't really handily deal with acceleration of expansion.

Also, without doing the detailed calculation, I suspect that there is insufficient total mass in all photons emitted to implement the effect.
lengould100
not rated yet Jul 05, 2011
But if a photon was emitted from a point near the "surface" of the "universe" immediately after the big bang and re-ionization, directly outward, one can assume it must carry some "energy=mass" beyond the limits of the universe since no baryonic matter can travel outward as fast as a photon. So it must "escape the universe" carrying some energy=mass with it. Then it continues onward for 12 billions of years until it is nearly completely red-shifted to approaching zero energy=mass reference the nearest observer in the universe, the star which emitted it.

So what happened to the energy=mass which it lost? (I'm guessing someone will raise the word Relativity. How sure are you? In what way does it make sense to you?)
lengould100
not rated yet Jul 05, 2011
Here's an interesting question. (To me at least.) By how much would the "force of gravity" need to drop off with separation distance to explain BOTH the accelerating expansion of the universe (dark energy) AND the amount of loss of energy due to redshifting of photons with increasing negative relative velocities?

I'll bet John Moffat could do an answer.
Decimatus
1 / 5 (1) Jul 05, 2011
Good points. In terms of the expansion of the universe, I think we would see a hump. Basically a gigantic volume of photonic mass would be ejected by the initial explosion, perhaps many times more so than all baryonic matter. As time goes on, this photonic mass gets further and further away and also looses energy to the redshift. There should be a point where this becomes critical for the acceleration/decceleration of the expansion.

We may not have reached that point. Right now we calculate that dark energy is ~73% of the universe' mass with normal matter being somewhere near 3-5%? Perhaps that ratio began at something like thousands to one, with the dark energy being 99% and as it gets further away and redshifts the ratio lowers. However, after a certain point, the energy rate that the baryonic matter adds to this mass outweighs the rate of loss that the photonic mass experiences. Hence expansion.

Decimatus
1 / 5 (1) Jul 05, 2011
So, in the beginning, photonic mass = 99% of the universe mass. Hyper inflation exists as it drags the universe outwards at C velocities. Due to time dilation, the relative period(to the present) is measured in the milliseconds. An outside observer(if possible) sees perhaps billions of years go by in this expansion.

At some point, the material closest to the big bang epicenter, yet far enough away from the photonic shockwave, ends inflation. However, due to the shockwave's continuing outward trajectory, the universe continues to be stretched as everything is pulled in the direction of the shockwave.

Our big bang timeline could merely be the point at which we "fell off" the shockwave. Galaxies closer to the shockwave are being pulled away from us. Galaxies further from the shockwave are not being pulled as much as we are and are therefore receding at a relative rate away from us.

Decimatus
1 / 5 (1) Jul 05, 2011
It would be interesting if you could make correlations between the "Great Wall" and perhaps the alignment of the shockwave's direction of movement. It could merely be a vast ripple in a gargantuam cosmic explosion.

I agree that your final question is rather interesting. It seems that this gravitational drop off point would be the most important aspect of the expansion of the universe. However, at current rates, I do not see this happening before we are forever separated from all galaxies in the visible universe apart from our local cluster.

If there ever is a big crunch, it could be trillions of years from now and invlove nothing more than dormant blackholes and neutron stars.
Decimatus
1 / 5 (1) Jul 05, 2011
My secondary thought for the photonic shockwave expansion relies less on gravity and more on the force of the explosion.

Basically you have the same giant mass of photons outrushing from the big bang.

Instead of relying primarily on gravity for expansion, the shockwave would literally push at a pre-existing "membrane" you might say. Essentially the photons hit this wall with enough force to push it outward in all directions. As there is a finite amount of space, and spacetime has a fabric that is connected thoroughly, all space in the universe experiences inflation.

The rate of expansion accelerates as a result of space being less tightly woven the more you stretch it; essentially becoming easier to stretch the further you pull it apart, similar to rubber.

A question might be whether space would have a breaking point or rebound point where it either can no longer stretch, or slows down expansion until it can contract under it's own force.
lengould100
5 / 5 (1) Jul 05, 2011
I really think you should confine your speculations to highly probably data. Nothing I know of indicates either any interstellar medium in which a shockwave may travel, or any 'pre-existing membrane' to push at.
lengould100
not rated yet Jul 05, 2011
I'd also like someone to explain to me why "dark energy"'s supposed repulsive force is a more rational explanation for expansion of the universe than an additional factor on Einstein's equations of gravity which causes gravitational attraction to drop off exponentially with distance, perhaps starting only beyond a large distance.
Decimatus
1 / 5 (1) Jul 05, 2011
The shockwave doesn't require a medium, it is simply the forefront of photons that exploded out of the big bang. On a grand scale they would represent a shockwave. One key point being that it's mass and velocity is inflating space out as it travels.

There should be testable points. Obviously(or most probably) we will never see the shockwave itself as it has likely inflated itself far beyond detection range.

However, there should be certain features left behind that could point to this theory.

Actually, the remnants of this shockwave would not be that different from the remnants of the current theory, it is only the cause that has changed. Replace "dark energy" with the shockwave. Both inflate the universe and can potentially have accelerating expansion.

Decimatus
1 / 5 (1) Jul 05, 2011
I am not sure you could have a second dropoff for gravity given that we have some good observations of vast galactic clusters interacting gravitationally. If the dropoff point is larger than a galactic cluster then I am not sure it would be small enough to allow the expansion.
stanfrax
1 / 5 (2) Jul 05, 2011
this dark matter that's pulling or pushing matter apart could explain the earth expansion theory - the theory goes is that the earth a hundred million years ago was only half the size it is today http://www.google...;cad=rja - they form a kind of eagle carrying its prey - a heart life started ? - the Himalayan dragon - bear ? coincidence
alanborky
not rated yet Jul 05, 2011
No offence, Caliban - I'm not sure I follow Oliver 'Iron Sun' Manuel's line of thought completely, especially that last line about "the force that world leaders and politicians cannot control."

But all that spatial expansion which you suppose to be spiking the guns of his "neutron-repulsive atomic nuclei" ain't doing much of a better job busting up all those endless root and branch like traceries of physical filaments connecting all the galaxies together like they're all part of one gigantic organism.

If it can't stop them forming across supposedly vast empty expanses of endlessly expanding space, then why the hell d'you suppose it'll put a stop to his particular doings?

...not particularly having a go, just wondering how you square the two things, especially since it seems to me when you stop looking at this stuff as so many bits and start trying to Rubik's Cube them together, the more you begin to realise it only works so long as you keep all the contradictory data sets apart.
Caliban
not rated yet Jul 05, 2011
None taken, alanborsky.

I don't have an answer to that.

But applying the same question to Oliver's neutron-repulsion principle, wouldn't we be seeing an even greater expansion/flying apart of all the structures contained in the universe?

If the principle is actually real, then there wouldn't be any fine structure, and not much gross structure, either, in the universe, unless the neutron-repusion force is centered in, and radiates from, the very low-density, hard vacuum vesicles of empty space that are interstitial to the structures in the universe. And hence my question- in these void spaces, where are the atomic nuclei in sufficient numbers to generate that magnitude of repulsive force?
ziphead
not rated yet Jul 06, 2011
ok, I just let one rip.
omatumr, go fetch; let us know if you can sniff out any Cherenkov radiation from the residual nebula.
Also, hope you don't find the neutron odour in it too "repulsive".
iiibogdan
not rated yet Jul 09, 2011
I'm not a physicist (i'm a programmer), so i'm basing this just on the things i've read and watched over the years and my imagination (i hope it's not ignorance)... so this is just a general ideea:

I think the reason why the expansion of the universe (or anything else that happens in our universe) has no effect on the density of dark energy is that the source of dark energy is somewhere in the four dimensional space and everything that happens in our 3D world is trapped in this 3D world.

Let's make a mental exercise:

We go one dimension lower and think of our (3D) world as a 2D plane and we replace gravity with let's say "air currents". In the 2D world there are things that produce "air currents" but we also have an inexplicable background "air current" that doesn't change no matter what happens in the 2D world. That background "air current" is produced by a "fan" that exists in the 3D world and nothing from the 2D world can ever reach it.

Sounds like "evidence" for 4D space :)