Cosmological evolution of dark matter is similar to that of visible matter

Jul 22, 2011
Visualization of DM distribution 800 milions years after the Big Bang. (Credit: The Marenostrum Numerical Cosmology Project)

High-resolution computer simulations prepared by a team of scientists from the Faculty of Physics, University of Warsaw (FUW), the Lebedev Physical Institute of the Russian Academy of Sciences and the Institute for Astrophysics in Potsdam made it possible to trace the evolution of large clouds of dark and normal matter that fill the Universe. The results confirm earlier assumptions regarding the basic features of dark matter, especially its distribution on cosmological scales.

For several decades, astronomers have been struggling to explain the motion of stars in galaxies and of galaxies in galaxy clusters. Measurements show that a typical galaxy must contain 10 to 50 times more invisible matter than normal one, and galaxy clusters must contain even up to 100 to 500 times more of the former. “It turns out that normal matter, which makes up our everyday world, is but a slight addition to . There is at least six times more of the latter in the Universe – and nobody knows what it is. Discovering its nature is a thrilling experience,” says Prof. Marek Demiański from the Faculty of Physics, University of Warsaw (FUW).

Nowadays it is assumed that dark matter consists of exotic particles, not yet known to science, which barely, if at all, interact with electromagnetic radiation and other elementary particles known today. Scientists can observe dark matter only indirectly, by investigating the impact of its gravity on the motion of normal matter. Given the significant amount of dark matter, it must have played a fundamental role in the formation of and their clusters.

Scientists are, therefore, interested in the way in which dark matter is distributed across the Universe and in which the structures made up of it evolved over time. In order to answer these questions, one would need to observe galaxy clusters, the light of which travelled to Earth ten or more billion years. Yet such distant object are difficult to detect. As a result, the amount of observational data is insufficient to allow for a statistical analysis.

prove useful in research into dark matter. They make it possible to observe the process of clustering of dark matter on large scales and its impact on the distribution of normal matter. By comparing the results obtained in this way with observational data, it is possible to assess the extent to which the scientists’ assumptions regarding the properties of dark matter coincide with the reality.

In the early periods after the Big Bang both dark and normal matter were more or less equally distributed. In contrast to normal one, dark matter does not interact with electromagnetic radiation, which filled the Universe shortly after the Big Bang and thus could succumb more quickly to the impact of its own gravity. Slight distortions in the distribution of dark matter began to contract gravitationally, attracting dark matter, and in later periods also normal one. The simulations by Polish, German and Russian group of scientists mirror the process.

During the simulations the scientists analyzed the behaviour of about a billion point objects distributed in a cube with side length of several hundred million light years. As time went on, the original cube was expanded along with the “ballooning” Universe. About a billion points were evenly distributed in the cube – the limitation on their number being the computing power of today’s computers. Each point in the simulation had a mass of hundred million times the mass of the Sun. Characteristics of dark matter were assigned to most of the points. Subsequently, the scientists analyzed the way in which the distribution of the points was changing over time under the influence of gravity.

One of the most important conclusions emerging from the performed simulations is the confirmation of the self-similarity of the process of evolution of the structure of dark and normal matter on large cosmic scales. Which means that if we examine a cube four billion years after the Big Bang and later compare it with a ten-billion-year-old cube, then, after matching the dimensions of both cubes, it turns out that the structures inside them made up of dark and normal matter look virtually the same.

“This similarity between the processes of evolution of both types of matter makes it possible to recreate the distribution of dark matter on the basis of the distribution of normal matter. Our simulations have confirmed this effect and we can now say with greater certainty that we are able to gain insight into the invisible world of dark matter by observing the motion of ,” concludes Prof. Demiański.

The results of the computer simulations of the distribution of dark and normal matter were published in the “Monthly Notices of the Royal Astronomical Society” journal and presented on the international conference “JENAM 2011 European Week of Astronomy and Space Science” on July 4-8 in Saint Petersburg, Russia.

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dogbert
2.4 / 5 (24) Jul 22, 2011
High-resolution computer simulations ...
...The results confirm ...


Computer simulations do what you program them to do. They don't confirm anything.

You can simulate Hogwart's, but your simulation will remain an exercise in programming. It will not make fantasy real.

Neither can a simulation make fantasy particles real.
rawa1
1.4 / 5 (10) Jul 22, 2011
Neither can a simulation make fantasy particles real.
I do agree fully with this stance.

Anyway, the clustering of dark matter seems to support my high-level model of Steady state Universe evolution, in which galaxies are evaporating and condensing into/from clouds of dark matter like giant fluctuations of random gas.
dogbert
2.3 / 5 (18) Jul 22, 2011
rawa1,

Interesting, but until we can actually find a dark matter particle and study its properties, everything we construct with dark matter is only in the realm of fantasy.
StandingBear
1.8 / 5 (5) Jul 22, 2011
computer simulations can be, after being run, correlated with observational data to check for fit. In this way a limited amount of data can find itself useful. In statistics, small amounts of data is often used this way, as in in traffic studies with which as an engineer I am familiar. All theoretical and other more proven assumptions go into the model which will incorporate probably the Fermi-Dirac or Reynolds equations for fluid flow in multidimensional hyperspherical coordinate space/time/alternate dimension sets in higher order partial differential tensor calculus. Reliability of existing data fit will be a progressive function of the size of the observational data point set as per standard tests for statistical practice.
Callippo
1 / 5 (6) Jul 22, 2011
Interesting, but until we can actually find a dark matter particle and study its properties, everything we construct with dark matter is only in the realm of fantasy.

IMO it's formed with particles, which are known notoriously: photons, (anti)neutrinos, positrons, atom nuclei stripped of most of electrons, etc.
mrlewish
4.7 / 5 (6) Jul 22, 2011
Wouldn't it be interesting if there were intelligences made out of dark matter wondering how to interact with the other 20% of the universe. Wonder what their their theories say about "their dark matter problem"?
Jaeherys
3.3 / 5 (4) Jul 22, 2011
Computer simulations do what you program them to do. They don't confirm anything.

You can simulate Hogwart's, but your simulation will remain an exercise in programming. It will not make fantasy real.

Neither can a simulation make fantasy particles real.


So when we simulate fluid movements around a plane or car, rendevous of celestial bodies, or all those fancy physics we see in today's games and movies, what is the difference?

Both are simulating what we think is happening and giving us data that we could not, in a single lifetime, calculate by hand. So invalidating one simulation, which is based on what we think to be the most correct representation of how we think things work, solely on the fact you don't think dark matter exists, invalidates them all.

I think you just ruined every engineers life, or not...
dogbert
2.8 / 5 (13) Jul 22, 2011
The difference in simulating fluid movements around a plane or car is that fluids are real, cars and planes are real and we understand their properties. For real objects and real dynamics which we already understand to some extent, simulations can be helpful.

Dark matter is something which has never been observed and may not exist. Its properties are unknown. When you simulate it, you simulate whatever you what it to be. You are not simulating anything based on observable fact.

That is the difference.
Pyle
3.8 / 5 (8) Jul 22, 2011
Dark matter is something which has never been observed and may not exist. Its properties are unknown. When you simulate it, you simulate whatever you what it to be. You are not simulating anything based on observable fact.
While I mostly agree with this statement I feel the need to qualify it. We have never observed dark matter directly. However, our observations point to something missing from our understanding of galactic structures.

The dominant hypothesis, supported by oodles and oodles of observations, is that there is dark matter holding the galaxies and galaxy clusters together. Further, that there are filaments of dark matter throughout the universe.

Yes, the simulations were programmed with a guess at how DM behaves. It shouldn't be a surprise that they behave as we hypothesized, since it was coded that way. "That sweater is green. By the way, the color green is what that sweater is. Now, you tell me what color the sweater is. Green you say? See I was right!"
FrankHerbert
2.1 / 5 (10) Jul 23, 2011
Dark matter is real, we just don't know the exact nature of it. Do you deny the existence of neutrinos dogbert? Do you deny they are dark matter?

Neutrinos are hard enough to detect and they interact through the weak force in addition to gravity.

We know there must be particles that interact only gravitationally because we can see their aggregate influence on galactic scales.

Gravity is extremely weak. Being able to detect large amounts of dark matter at galactic scales while not being able to discern them at a particulate level is totally reasonable. No one is saying "this particular dark matter particle/theory is definitely correct!" All they are saying is "there must be some sort of matter that interacts only gravitationally because we are able to detect its gravity on large scales."

But I'm sure this is some socialist liberal [insert random dog whistle nonsense]... Yeah, that makes sense.
frajo
3.3 / 5 (4) Jul 23, 2011
The dominant hypothesis, supported by oodles and oodles of observations, is that there is dark matter holding the galaxies and galaxy clusters together. Further, that there are filaments of dark matter throughout the universe.

Dominant hypotheses regularly are based on the current paradigm.

In the 19th century the dominant hypothesis to explain Mercury's perihelion precession was Urbain Le Verrier's Vulcan hypothesis. It was founded on the then current paradigm of the universal validity of Newton's laws.

We all know the rest of the story. Some of us might even know Kuhn's view of the importance of paradigm shifts.
lightandmatter
4 / 5 (3) Jul 23, 2011
Is a 'dark matter' black hole any different from a 'visible matter' black hole??
dogbert
1.7 / 5 (10) Jul 23, 2011
FrankHerbert,
But I'm sure this is some socialist liberal [insert random dog whistle nonsense].


No, Franky. You just have to make useless attacks on people for no other reason than to be a useless troll, don't you?

We do, in fact, see that on stellar/galactic scales, we cannot predict the movements of objects with our models of gravity.

We can try to determine why our models do not predict those movements, try to correct our models to reflect the observations, create new models based on the observation which do correspond to the observations or insert a correcting factor (kludge) into our models.

Dark matter is that correcting factor. Our models still don't predict the movements of stellar objects. Our kludged models don't either since we have to add our kludge material after we determine how much we need and where we need it.

A kludge is OK, I suppose, until you can resolve the problem. But when you begin to believe in your own fantasy, how do you discover the reality?
DavidMcC
5 / 5 (2) Jul 23, 2011
"In the early periods after the Big Bang both dark and normal matter were more or less equally distributed."

Is that an observation or an assumption? (I suspect the latter, based on the assumption that dark matter is one of the unobserved kinds of particles, wimps or machos.)
DavidMcC
not rated yet Jul 23, 2011
Is a 'dark matter' black hole any different from a 'visible matter' black hole??

Presumably, only in terms of the source of the matter that originally formed the black hole.
The only thing we know for sure about either is that they are gravitational anomalies - the only difference being that BHs appear to be concentrated dark matter, which could form from anything that's massive enough to collapse under its own gravity (usually massive baryonic bodies called stars dying, but there is no reason to suppose that that is the only way they can form).
Pyle
4.6 / 5 (10) Jul 23, 2011
Dark matter is that correcting factor. Our models still don't predict the movements of stellar objects. Our kludged models don't either since we have to add our kludge material after we determine how much we need and where we need it.
Actually, our kludged models are corroborated by other observations, i.e. lensing. Could there be other explanations? Sure, but our kludge is different than Ptolemic epicycles in that it is used to explain one observation and is supported by a seemingly independent one.

I dislike dark matter, and dark energy for that matter. That doesn't mean I don't recognize its current legitimate status as the leading contender in explaining our observations.

Doggie, care to share your beliefs regarding dark matter? In my experience you lean more towards useless trolldom. Not that your above points aren't reasonable ones. You rarely do anything besides criticize work I am fairly certain you don't fully understand. (You kettle, me pot.)
dogbert
1.7 / 5 (10) Jul 23, 2011
Pyle,

... care to share your beliefs regarding dark matter?


I have. It is a kludge.

Actually, our kludged models are corroborated by other observations, i.e. lensing.


No, you can't corroborate something with more of the same. We use dark matter to explain gravitational anomalies at stellar scales -- movement of stars, galaxies, lensing, etc. To say that lensing validates the kludge which was initially created to address the movement of stars about a galaxy is plainly circular reasoning.

FrankHerbert
1.9 / 5 (9) Jul 23, 2011
Dogbert, what you don't understand is the modified theories of gravity ARE the kludge. Gravity is right, it's our understanding of matter that is wrong.
dogbert
1.5 / 5 (8) Jul 23, 2011
FrankHerbert,

We don't even know what gravity is. We only have models and those models do not describe what we observe.

Dark matter is a kludge. That does not mean it does not exist. It means it is just a kludge unless/until we actually find some, determine its properties and actually show that it exists and that it composes most of the matter in the universe.

Until/unless we do discover dark matter, we should admit that we just don't know.

Posturing a knowledge you don't have is not logical or scientific.
jamesrm
5 / 5 (1) Jul 23, 2011
"Is a 'dark matter' black hole any different from a 'visible matter' black hole??"

As the models for Dark Matter say it is it own antiparticle you cant get a black hole made of it as when two Dark Matter particle collide they annihilate each other
dogbert
1 / 5 (3) Jul 23, 2011
jamesrm,

Perhaps you could have a kugelblitz?

TabulaMentis
1.8 / 5 (5) Jul 24, 2011
@Pyle:

Follow those neutrinos and you will find DM.

Too bad you do not believe in Dark Energy. You may want to read the following 7/15/2011 Physicsworld.com article titled
"Dark energy spotted in the cosmic microwave background."

http://physicswor...ws/46572
FrankHerbert
1.6 / 5 (7) Jul 24, 2011
Dogbert, please give me an argument for dark matter being more a kludge than MOND or whatever it is you support. I say we don't understand the nature of dark matter, and that's not good enough for you, but you can wave my argument away as "We don't even know what gravity is."

So what it comes down to is both of our arguments are shit (particularly yours because mine is just mirroring it), but I'm in line with scientific community.

We only have models [for gravity] and those models do not describe what we observe.


Our models are extremely accurate except for the largest scales, which is where the effects of dark matter would manifest themselves. Why do you feel the need to apply a kludge to gravity in order to explain galaxies? Why would gravity just decide to change it's behavior at large scales?

Dark matter fits the current evidence better than any other model. MOND (and anything you evangelize) fails in comparison.
dogbert
1.9 / 5 (8) Jul 24, 2011
FrankHerbert,
Dogbert, please give me an argument for dark matter being more a kludge than MOND or whatever it is you support.

I can't give you an argument I don't have. I have only pointed out that dark matter is a kludge and should be treated as such.
Dark matter is real, we just don't know the exact nature of it.

That is the problem. Stating that a kludge is real. It is OK to say that we hypothesize dark matter to normalize our models of gravity. It is not OK to say that this fantasy substance is real until/unless we actually observe a particle of it and identify it and its properties.

Science should not inhabit a fantasy world. It should proceed from observation. We have not observed a single particle of dark matter -- a substance which is hypothesized to compose far more of the universe than normal matter.

Find it, observe it, test its properties and then say it is real.
Pete1983
4 / 5 (3) Jul 25, 2011
"Is a 'dark matter' black hole any different from a 'visible matter' black hole??"

As the models for Dark Matter say it is it own antiparticle you cant get a black hole made of it as when two Dark Matter particle collide they annihilate each other


Although in the above process the energy would still all reside within the blackhole. My understanding is that all energy falling into the black hole can only get back out through hawking radiation. So the "type" of energy falling into the black hole is irrelevant, it all gets crushed into oblivion anyway.

Interestingly I guess this could represent a way dark matter converts to normal photons, and one would assume that this occurs at much greater rates in this fashion that in would through random dark matter collisions universe wide.
/end speculation with gigantic assumptions...
FrankHerbert
1.4 / 5 (8) Jul 25, 2011
Dogbert, neutrinos are dark matter and account for part of the missing mass required to make sense of galaxies. They are difficult to detect because they interact only through the weak and gravitational forces. Symmetry and observation suggest there are more undiscovered particles with even more limited interactions.
frajo
4 / 5 (5) Jul 25, 2011
Dogbert, neutrinos are dark matter and account for part of the missing mass required to make sense of galaxies.

I don't think so.
Because it's contradicting the section "Hot dark matter" in Wikipedia's "Dark Matter" article:
"travels too quickly to be bound by an individual galaxy or a galaxy cluster's gravity" and
"hot dark matter is not enough to explain how galaxies form and stay the way they are (e.g. rotation curves)".
Deesky
5 / 5 (4) Jul 25, 2011
Dogbert, neutrinos are dark matter and account for part of the missing mass required to make sense of galaxies.

Neutrinos are generally not classed as DM.

Cosmic neutrinos have a maximum space density. Irregular dwarf galaxies have a very high DM concentration, which means that neutrinos cannot be the DM candidate in these type of systems.

If you assume that neutrinos are the DM in our (big) galaxy, then there is a need for a second type of DM for low mass galaxies. which is getting untidy.

Also, it's difficult for neutrino baryon models to form galaxies early enough and these models tend to predict galaxy clustering properties which are very different from those that we actually observe.
FrankHerbert
2.1 / 5 (7) Jul 25, 2011
Well I stand corrected. My point wasn't that neutrinos are the missing matter, but a small part of it. I didn't realize neutrinos weren't that conducive to creating the shapes of galaxies we see across the universe.

However, I do not believe I'm being overly semantic by calling neutrinos dark matter. They don't interact with electromagnetic radiation and therefore are "dark".
Pyle
3.7 / 5 (6) Jul 25, 2011
Y'all are muddying the drinking hole.

Doggie. In general you are a negative SOB on this site, but in this case your point is valid. DM hasn't been directly observed, we just have an enormous amount of evidence supporting our "guess". Regarding the lensing vs. galactic rotation, these two are both gravitational effects, but you can't conflate the two. That they both agree with the DM model gives it more weight.

On to modified gravity. FH, MOND has mostly just been a tweak with a plug to make gravity formulas work. However, it isn't the only modified gravity work. Moffat's MOG is a parameterless model that seems to fit everything that has been thrown at it. The problem is nobody is really working on it, the math is terribly difficult and it provides no "Why?. So not much utility in it.

Calling DM a "kludge" is probably not inaccurate, but it paints the leading candidate in an unnecessarily negative light. Just call it our best guess if you must.
Callippo
1 / 5 (3) Jul 25, 2011
"travels too quickly to be bound by an individual galaxy or a galaxy cluster's gravity"
The speed of neutrinos which are in thermal equilibrium with CMBR isn't larger, than escape velocity from Sun, for example. I presume, not only our galaxy, but even our solar system is full of cold (anti)neutrinos. IMO they're constituting 20-30 weight percent of dark matter, thus safely balancing all "missing antimatter".
Aristoteles
not rated yet Jul 25, 2011
Without the 'God particle', however, that whole edifice falls apart because the Standard Model fails to answer one fundamental question: why do most elementary particles have mass? Similar situation exist in contemporary cosmology with the so called "DARK Matter". Why not "coloured" ???
We cannt see all matter because our "matterialistic visionery device exist ( works ) only in 3 spatial dimension...
Pyle
3.6 / 5 (5) Jul 25, 2011
DM black hole?...

DM ... own antiparticle ... annihilate each other...

Although in the above process the energy would still all reside within the blackhole.

Interestingly I guess this could represent a way dark matter converts to normal photons,
Problem is that photons are massless so the DM causing the BH would annihilate to massless photons, so no more BH. But this is all assuming that the DM particles we haven't directly observed yet behave the way we guess they do.

Regarding the direct observation of DE in the CMB that @TM cited. I wonder where this sits with respect to the concentric triangleness of Penrose, et al and bouncing branes...
In any event, doggie, you can toss the CMB into your pile of observations that support the DM model. (We know, still gravity, whatever.)
TomSullivan
1 / 5 (2) Jul 25, 2011
Rip Theory made this prediction four years ago! Dark Matter and Visible Matter are both matter! At their root their formation and characteristics are the same/similar, it is only their size, frequency and likelyhood to bond that make them different.
TimESimmons
1 / 5 (1) Jul 30, 2011
Here's an alternative theory - Its anti-gravity matter
http://www.presto...ndex.htm