The universe can be a very sticky place, but just how sticky is a matter of debate.
That is because for decades cosmologists have had trouble reconciling the classic notion of viscosity based on the laws of thermodynamics with Einstein's general theory of relativity. However, a team from Vanderbilt University has come up with a fundamentally new mathematical formulation of the problem that appears to bridge this long-standing gap.
The new math has some significant implications for the ultimate fate of the universe. It tends to favor one of the more radical scenarios that cosmologists have come up with known as the "Big Rip." It may also shed new light on the basic nature of dark energy.
The new approach was developed by Assistant Professor of Mathematics Marcelo Disconzi in collaboration with physics professors Thomas Kephart and Robert Scherrer and is described in a paper published earlier this year in the journal Physical Review D.
"Marcelo has come up with a simpler and more elegant formulation that is mathematically sound and obeys all the applicable physical laws," said Scherrer.
The type of viscosity that has cosmological relevance is different from the familiar "ketchup" form of viscosity, which is called shear viscosity and is a measure of a fluid's resistance to flowing through small openings like the neck of a ketchup bottle. Instead, cosmological viscosity is a form of bulk viscosity, which is the measure of a fluid's resistance to expansion or contraction. The reason we don't often deal with bulk viscosity in everyday life is because most liquids we encounter cannot be compressed or expanded very much.
Disconzi began by tackling the problem of relativistic fluids. Astronomical objects that produce this phenomenon include supernovae (exploding stars) and neutron stars (stars that have been crushed down to the size of 20-30 km in diameter).
Scientists have had considerable success modeling what happens when ideal fluids - those with no viscosity - are boosted to near-light speeds. But almost all fluids are viscous in nature and, despite decades of effort, no one has managed to come up with a generally accepted way to handle viscous fluids traveling at relativistic velocities. In the past, the models formulated to predict what happens when these more realistic fluids are accelerated to a fraction of the speed of light have been plagued with inconsistencies: the most glaring of which has been predicting certain conditions where these fluids could travel faster than the speed of light.
"This is disastrously wrong," said Disconzi, "since it is well-proven experimentally that nothing can travel faster than the speed of light."
These problems inspired the mathematician to re-formulate the equations of relativistic fluid dynamics in a way that does not exhibit the flaw of allowing faster-than-light speeds. He based his approach on one that was advanced in the 1950s by French mathematician André Lichnerowicz.
Next, Disconzi teamed up with Kephart and Scherrer to apply his equations to broader cosmological theory. This produced a number of interesting results, including some potential new insights into the mysterious nature of dark energy.
In the 1990s, the physics community was shocked when astronomical measurements showed that the universe is expanding at an ever-accelerating rate. To explain this unpredicted acceleration, they were forced to hypothesize the existence of an unknown form of repulsive energy that is spread throughout the universe. Because they knew so little about it, they labeled it "dark energy."
Most dark energy theories to date have not taken cosmic viscosity into account, despite the fact that it has a repulsive effect strikingly similar to that of dark energy. "It is possible, but not very likely, that viscosity could account for all the acceleration that has been attributed to dark energy," said Disconzi. "It is more likely that a significant fraction of the acceleration could be due to this more prosaic cause. As a result, viscosity may act as an important constraint on the properties of dark energy."
Another interesting result involves the ultimate fate of the universe. Since the discovery of the universe's run-away expansion, cosmologists have come up with a number of dramatic scenarios of what it could mean for the future.
One scenario, dubbed the "Big Freeze," predicts that after 100 trillion years or so the universe will have grown so vast that the supplies of gas will become too thin for stars to form. As a result, existing stars will gradually burn out, leaving only black holes which, in turn, slowly evaporate away as space itself gets colder and colder.
An even more radical scenario is the "Big Rip." It is predicated on a type of "phantom" dark energy that gets stronger over time. In this case, the expansion rate of the universe becomes so great that in 22 billion years or so material objects begin to fall apart and individual atoms disassemble themselves into unbound elementary particles and radiation.
The key value involved in this scenario is the ratio between dark energy's pressure and density, what is called its equation of state parameter. If this value drops below -1 then the universe will eventually be pulled apart. Cosmologists have called this the "phantom barrier." In previous models with viscosity the universe could not evolve beyond this limit.
In the Desconzi-Kephart-Scherrer formulation, however, this barrier does not exist. Instead, it provides a natural way for the equation of state parameter to fall below -1.
"In previous models with viscosity the Big Rip was not possible," said Scherrer. "In this new model, viscosity actually drives the universe toward this extreme end state."
According to the scientists, the results of their pen-and-paper analyses of this new formulation for relativistic viscosity are quite promising but a much deeper analysis must be carried out to determine its viability. The only way to do this is to use powerful computers to analyze the complex equations numerically. In this fashion the scientists can make predictions that can be compared with experiment and observation.
Explore further:
The mysterious dark energy that speeds the universe's rate of expansion
Reg Mundy
This is the sort of logic by establishment "scientists" that sticks in my craw. How can a negative result ever be a proof? If they had found something which moved faster than light (how about quantum entanglement as a candidate?) then the result would be that things could move faster than light. But not finding something by experiment is inconclusive, it merely means that nothing has been found YET, and that PROBABLY the theory is true, but it does not prove it.
What, atoms falling apart? Expanding? Of course, this couldn't possibly be the explanation for what we call "gravity", now could it?
24volts
cantdrive85
"We have to learn again that science without contact with experiments is an enterprise which is likely to go completely astray into imaginary conjecture." Hannes Alfvén
As above...
"Today's scientists have substituted mathematics for experiments, and they wander off through equation after equation, and eventually build a structure which has no relation to reality." Nikola Tesla
Again, as above...Pathetic the state of space science is these days, absolutely pathetic.
thingumbobesquire
someone11235813
Steve 200mph Cruiz
It's theoretical physics, that means it could be wrong, all this article said was, "we think this looks promising", hardly shoving anything down your throat.
Why not get a freaking imagination?
Steve 200mph Cruiz
The comment section of anonymous internet board is not an accurate source of information. You can look up college lectures online on youthube and well maintained articles on Wikipedia are perfectly fine, just remember to reread them later as they aren't perfectly accurate sometimes.
cantdrive85
Bloodyorphan
vlaaing peerd
Gravity isn't what is keeping atoms together. But like gravity can crush atoms (or however you want to interpret what happens with atoms in a Black Hole) the expansion from DE can be so strong even the nuclear + EM force will eventually be not powerful enough to keep molecules and eventually atoms together.
At least, that's as far as my layman interpretation goes.
syrix
What comes around goes around.. ;)
viko_mx
This mental illness in modern world is highly contagious. Philosophy does not need facts, only vanity.
There is something masochistic in such conceptions of the world that promote hedonism and in society robbing the meaning of human life.
Andragogue
I would remind the reader that gases are fluids too and we have a lots of empirical experience with gas viscosities. Relativistic gas viscosity still being a special case, of course.
All in all, something else to worry about... the Big Rip. Only 22 billion years or so to go. :-(
Nice tie-in with Dark Energy properties. Thanks for the article!
Steve 200mph Cruiz
Philosophy is not science.
Valuable philosophies follow the scientific method themselves, like the Socratic method, but I've never studied any of that stuff in a meaningful capacity.
How is this masochistic to our sense of ourselves in the first place? I love people, the gleam of curiosity in a babies eyes is one of the most beautiful things in the world to me, and its a really special thing to watch us all get older and grow as people. Even watching teenagers get in trouble brings a smile to me in private even if I have to yell at them.
If anything we are sadists because we like to talk down to you, but it's not our fault that you don't have a passing high school education in science. If you want smart people to be nice to you, quit making stuff up. We are never going to listen to you over people with actual qualifications.
NoTennisNow
TheGhostofOtto1923
Because their personal god is very familiar to them, having been created in their own image.
And he wouldn't have produced anything that they would find in any way unpalatable or unfathomable now would he?
Otherwise what good would he be?
SkyPanther
cantdrive85
Moving electric charges is gobbledygook? Well you had better call your local power company and have them shut your gobbledygook down, because who wants to pay good money for gobbledygook!
Captain Stumpy
no - grand canyon formation by plasma discharge is, though... (as JeanTate pointed out above with other stuff as well!)
here are more:
your insistence that moon craters are formed by plasma despite observations of strikes...
Saturns storm formation!
what about your comments regarding the internet! pseudoscience posted on any gov't server is supported by the gov't, right? LOL
your comments re: Shoemaker-Levy striking Jupiter are nonsense ...
then there is the star/galaxy/etc formations all from birkland currents ...
lets not forget your outright blatant lies about astrophysicists and their education, all readily researched... as well as your continued insistence that your eu engineers and trolls (like yourself) know more about our sun than helioseismologists or astrophysicists...that is the biggest gobbledygoop of them all!
RealityCheck
Why do you (and Ren82 etc) keep injecting your religious/political/personal 'takes' into the science articles/discussions whose perspectives and implications should be argued based on observations, interpretations and meanings which have some reality-probability to actually be correct as to what is and what is happening around us and in the wider universe? It would help you and humanity and science/knowledge advancement/improvement if you stuck to strictly objective factors when putting your views across on the items presented in a science forum. If you want to discuss religious themes and supernatural entities then you should go to an appropriate religio-politico forum. What you keep doing here with that stuff is not only counter-productive to your 'cause' or whatever, it is also creating loss of credible observations on the science which you might otherwise have which might touch upon some real science aspect that might lead to good discussion/insight. :)
cantdrive85
http://www.cosmol...hkin.pdf
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Jul 02, 2015antialias_physorg
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Protoplasmix
http://forum.nasa...313.1100
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Jul 02, 2015Captain Stumpy
python logic? really?
your entire argument to JeanTate is hand waving PYTHON logic?
you might as well have just posted the following link:
https://www.youtu...MhU_4m-g
NoTennisNow
Reg Mundy
How do you know that? A perfect vacuum is IMPOSSIBLE to create, so maybe the speed of light in it is infinite or zero, or anywhere inbetween.
Seeker2
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Jul 03, 2015viko_mx
I appreciate highly the science based on facts. Unfortunately here the articles in the sections cosmology and biology are not imbued with the spirit of truth. To call them science is your right of course, but every other partisipant in this forum also have the right for him personal opinion.
cantdrive85
You think I'm funny, like a clown? I amuse you? I make you laugh?
www.youtube.com/w...NtUCshxY
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Jul 03, 2015NoTennisNow
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Jul 04, 2015HeloMenelo
Well said Captain and the rest of the reputable scientists !
cantdrive85
Yet, here we are discussing the metaphysical "Big Rip", Phys.org would have about four articles in the whole of the 'Astronomy & Space' section if the unfettered stupidity of your comment was followed. You obviously are devoid of any sense, common or otherwise.
cantdrive85
I take pride in my 1.4 out of 5 rank average, I know I'm doing something right.
"Thinking is the hardest work there is, which is probably the reason why so few engage in it."
Henry Ford
Your comment above regarding Cap'n Stupid only goes to prove my point in your inability to think and your extreme ignorance. Cap'n Stupid is so far from a "reputable scientist" the notion reflects a comedy of infantile stupidity, in the grandest meaning of the term.
Semmster
HeloMenelo
Of course monkeys can't understand ratings, 1.4 out of 5 being very low btw... so meaning your'e doing something wrong not right ;) (the average joe however does understand it ;)
It's been noted that you take pride in the dumb comments you deliver over the years, no need to mention it.. ;) we know :D
Again Captain, Mytwocts, JeanTate, Antialias, Excellent comments from you.
nevermark
I think that is a fantastic question.
Two seemingly unstoppable forces in opposition. Any experiments or models that can shed light on what happens in that situation should lead to deep insights, assuming the Big Rip is a likely scenario.
My uneducated guess would be that this would result in a profound matter/energy phase transition in the universe. Perhaps the result of Dark Energy being needed to create new quarks to maintain color charge balance would bring an abrupt halt to expansion. Whatever happened would be interesting.
antialias_physorg
That is what the Big Rip is.
In order if particles (like protons and neutrons in a nucleus, or even the quarks within them) to hold together they have to be connnected by a force. The mediation of these forces works by the exchange of force carriers (photons for the electromagnetic force, gluons between quarks for the strong nuclear force, W/Z bosons for the weak force, gravitons for gravity (possibly) ).
These force carriers are also subject to the comsic speed limit. If the expansion speed exceeds that of light within the volume where such a force carrier wants to do its work then two particles connected by them cannot feel the the mutual forces anymore (the force carriers never reach the other particle) - and then stuff flies apart.
It'd be like every particle sitting within its very own private event horizon (without the gravity).
Reg Mundy
So you can prove that what I stated is untrue? Perhaps YOU should do some research before shouting YOUR mouth off....
Quote your sources, and if they are conclusive I will apologise to you.....fat chance!
Reg Mundy
Suppose I postulate that the speed of light is always not quite "c" depending on what medium it is travelling thru'. So, in almost perfect vacuum, it is 99.999999999999etc. percent c. Interesting then that depending on medium, light would always experience refraction as it progresses between different densities of matter, e.g from extremely tenuous in intergalactic space thru' merely tenuous as it passes huge clumps of matter. As the refractive index change is extremely small, there would be miniscule refraction differential between wavelengths, almost achromatic..... So, do we need gravitic lensing? No, we don't, and that knocks away a support for the existence of the force we call gravity which is merely a manifestation of the effects of matter expansion (we brings us back to the relevance of this discussion to the article, and the dis-assembly of atoms over time..).
Over to you...
RealityCheck
Re 'vacuum', light propagation and diffraction/dispersal etc. Consider in context...
1) The QM 'vacuum' model has a full gamut/spectrum of 'virtual' transient particles/features 'fizz' in and out quickly everywhere; hence all light frequencies would be 'on average' 'dispersed/attenuated equally over long deep space travel distances.
2) The 'lensing' galaxies gravity well 'gradient' has vast radial reach, so every EM frequency would be accommodated along a radial segment, where 'angle' of incident' spread of light is 'converged' at the 'focus' (our observer position 'here') so ALL EM frequencies coincide because if incident light is of all frequencies over a vast radial gradient 'front', then they would be refracted accordingly and the outermost diffractions 'angles' would be merged with the innermost diffractions 'angles' to give 'single' but 'mixed EM' image from differing 'lines of flight from source' as if 'all from one path'.
Gotta go! Bye. :)
IronhorseA
Sounds like the period of inflation after the big bang.
antialias_physorg
Well, according to the model there weren't any particles around at the time inflation started.
Stevepidge
Johnpaily
TimLong2001
(cont'd)
TimLong2001