Dark matter what is it?

[Brother No. 1]

Comrades if 1% of the universe is particals or 99% of the universe what is the other 1% or 99%. Well I think it is the mistrious Dark Matter and through my reserch I found out that dark matter is one of the rare particals that became real at the time the universe was created during the big bang and also I found out that thousands if not millions or billions flow through us each second but the reason we can see them or feel them is that they rarely or dont interact with matter. So comrades give me your answers about this good or bad and did you know it before

[GPDP]

Dark Matter is a doozy, but more and more scientists are convinced that it is the real deal.

Even more mysterious, however, is Dark Energy. Did you know that the objects at the farthest reaches of the universe are the ones moving away from us the fastest? There's got to be some unknown and unseen force causing such rapid acceleration of the expansion of the universe, and only Dark Energy explains it so far.

[Brother No. 1]

it is still a mystery and new we only dicovered it in maybe 2000 or 1999

[ÑóẊîöʼn]

Comrades if 1% of the universe is particals or 99% of the universe what is the other 1% or 99%.

Photons (electromagnetic radiation) or various forms of energy. But the line is blurred at the quantum scale because under certain circumstances particles can behave like waves and vice versa.


Well I think it is the mistrious Dark Matter and through my reserch I found out that dark matter is one of the rare particals that became real at the time the universe was created during the big bang and also I found out that thousands if not millions or billions flow through us each second but the reason we can see them or feel them is that they rarely or dont interact with matter.

Those are called neutrinos, and are a product of proton-chain fusion reactions that take place in the Sun. Maybe dark matter was created after the Big Bang, when stars began to shine? Physicists and cosmologists are working on the answer. I don't know.


So comrades give me your answers about this good or bad and did you know it before

What are you reading?

[Brother No. 1]

I will check it on wikipedia again

[Brother No. 1]

sorry comrade

[mikelepore]

No one knows what it is. They only know that the rate of rotation of the galaxy, and the constancy of the rate of rotation between the center and the edge, can't be accounted for solely by the presence of a lot of mass at the center, such as the supermassive black hole. The observed motion indicates a distribution of a lot of mass far from the center. The hundred-billion-plus stars isn't enough to account for the mass.

[Rosa Lichtenstein]

It's the modern day equivalent of the epicycles that medieval astonomers used to add to the motion of the planets when observation failed to match theory.

So, as Mike pointed out, the observed rate of rotation of the galaxies fails to match theoretical predictions. Solution: invent 'dark matter'. [A bit like angels were the 'dark forces' that pushed the crystalline spheres.]

We'll probably need a modern day equivalent of Copernicus to rid us of this odd 'substance', but I can safely predict now that he or she will be as well-received as Copernicus and his followers were! House arrest and martyrdom, maybe not -- but ostracism definitely.

[ÑóẊîöʼn]

I don't get the hostility to dark matter. Why is it so offensive to come up with such an explanation, based on what we actually know about the laws of physics? How is that any worse than say, proposing a special modification to existing physical laws?

The facts are decided by reality, not by whether or not they offend one's philosophical quirks.

[Rosa Lichtenstein]

Noxion, I am not hostile, just skeptical. If it pans out, fine. But, in the history of science, most things do not pan out.

And I agree that facts are decisive, but at present we do not have any facts at all about 'dark matter', just loads of theory.

And it is not a question of my 'philosophical quirks', any more than it is of yours

[mikelepore]

Either there is some invisible mass, or else Kepler's third law, which relates how orbiting particles far from the center have different speeds than particles nearer the center, must be wrong. Once a proposed physical law has passed so many practical tests, people hesitate to drop it.

Apparently, the reason why they assume it has to be some uncataloged form of matter, and not the ordinary stuff, that is, why it can't be just a distribution of neutrons, is that the kind of matter we already know about causes a lot of light absorption. The answer has to be consistent with interstellar space being so transparent.

My own speculation, I wonder if it will later be discovered that dark matter consists of a type of mesons. I will explain why I said that. Every time an object moves through "empty" space it must be passing through all that invisible matter, with no apparent friction. That could mean that it's a form of matter which doesn't obey Pauli's exclusion principle, so that more than one object can occupy the same space at the same time, that is, bosons. Right now the bosons that we are the most accustomed to are the massless kind, that is, photons, but we also know about some bosons that have mass, and these are the mesons.

[Rosa Lichtenstein]

Mike, this is exactly the sort of reasoning used 700 years ago to justify yet another epicylce: either Ptolemy's model is wrong or we need another epicycle.

There are other explanations for this; for example:

http://en.wikipedia.org/wiki/Modified_Newtonian_dynamics

http://www.astro.umd.edu/~ssm/mond/

http://www.astro.umd.edu/~ssm/mond/blunder.html

http://www.universetoday.com/2008/04/08/a-case-of-mond-over-dark-matter/

Alternatives are often rejected out of hand by traditonalists in science; why they do this is not too clear since the history of science shows that these alternatives often win out:


"...[I]n the historical progression from Aristotelian to Cartesian to Newtonian to contemporary mechanical theories, the evidence available at the time each earlier theory was accepted offered equally strong support to each of the (then-unimagined) later alternatives. The same pattern would seem to obtain in the historical progression from elemental to early corpuscularian chemistry to Stahl's phlogiston theory to Lavoisier's oxygen chemistry to Daltonian atomic and contemporary physical chemistry; from various versions of preformationism to epigenetic theories of embryology; from the caloric theory of heat to later and ultimately contemporary thermodynamic theories; from effluvial theories of electricity and magnetism to theories of the electromagnetic ether and contemporary electromagnetism; from humoral imbalance to miasmatic to contagion and ultimately germ theories of disease; from 18th Century corpuscular theories of light to 19th Century wave theories to contemporary quantum mechanical conception; from Hippocrates's pangenesis to Darwin's blending theory of inheritance (and his own 'gemmule' version of pangenesis) to Wiesmann's germ-plasm theory and Mendelian and contemporary molecular genetics; from Cuvier's theory of functionally integrated and necessarily static biological species or Lamarck's autogenesis to Darwinian evolutionary theory; and so on in a seemingly endless array of theories, the evidence for which ultimately turned out to support one or more unimagined competitors just as well. Thus, the history of scientific enquiry offers a straightforward inductive rationale for thinking that there are alternatives to our best theories equally well-confirmed by the evidence, even when we are unable to conceive of them at the time." [Stanford (2001), p.9.]

Stanford, P. (2001), 'Refusing The Devil's Bargain: What Kind Of Underdetermination Should We Take Seriously?', in Barrett and Alexander (2001), pp.1-12.

Barrett, J., and Alexander, J. (2001), (eds.), PSA 2000, Part 1, Supplement to Philosophy of Science 68, 3 (University of Chicago Press).

[PSA = Philosophy of Science Association; the PSA volumes comprise papers submitted to its biennial meeting.]

[ÑóẊîöʼn]

How would MOND be tested?

[Rosa Lichtenstein]

I've no idea -- but then, I'm not a scientist. All I am saying is that there are always alternatives, and this rather desperate invention of an unknown form of matter to fix a glitch in celestial mechanics is not the only way to proceed.

[Coggeh]

It's the modern day equivalent of the epicycles that medieval astonomers used to add to the motion of the planets when observation failed to match theory.

So, as Mike pointed out, the observed rate of rotation of the galaxies fails to match theoretical predictions. Solution: invent 'dark matter'. [A bit like angels were the 'dark forces' that pushed the crystalline spheres.]

We'll probably need a modern day equivalent of Copernicus to rid us of this odd 'substance', but I can safely predict now that he or she will be as well-received as Copernicus and his followers were! House arrest and martyrdom, maybe not -- but ostracism definitely.

Thats like saying the observed understanding of how humans came here failed to match our current understanding .Solution :Invent evolution.

But do ya know what , thats exactly what happened . This is how sceince works , if this unknown force is proved right then it will rewrite our understanding of physics and thus we will understand a whole lot more about the universe .

[Rosa Provokateur]

I'm not much for science but this Dark Matter stuff has cought my interest, I read an article on it in Scientific American. Could any of you guys explain to me (in "english" lol) what it is

[revolution inaction]

its matter that doesn't glow, it can mean be any thing from dust and rocks to undiscovered particles.
Dark matter is though to exist because galaxies appear to be much more massive than the visible matter can account for. Some of it is certainly normal matter that we can't see and some of it is neutrinos (http://en.wikipedia.org/wiki/Neutrinos), but its not known how much, so other particles have been suggested to explain the missing mass.

[Rosa Lichtenstein]

Coggy:


Thats like saying the observed understanding of how humans came here failed to match our current understanding .Solution :Invent evolution.

But do ya know what , thats exactly what happened . This is how sceince works , if this unknown force is proved right then it will rewrite our understanding of physics and thus we will understand a whole lot more about the universe .

It's also how science stalls. There are plenty of examples of this over and above the 'extra epicycles' fiasco. For example, the discovery of Neptune, and then the non-discovery of the planet Vulcan (no, not the on from Startrek):


"The arguments which terminate in an hypothesis's positing the existence of some trans-Uranic object, the planet Neptune, and the structurally identical arguments which forced Leverrier to urge the existence of an intra-Mercurial planet, the planet 'Vulcan', to explain the precessional aberrations of our 'innermost' solar system neighbour are formally one and the same. They run: (1) Newtonian mechanics is true; (2) Newtonian mechanics requires planet P to move in exactly this manner, x, y, z, …; (3) but P does not move à la x, y, z; (4) so either (a) there exists some as-yet-unobserved object, o, or (b) Newtonian mechanics is false. (5) 4b) contradicts 1) so 4a) is true -- there exists some as-yet-undetected body which will put everything right again between observation and theory. The variable 'o' took the value 'Neptune' in the former case; it took the value 'Vulcan' in the latter case. And these insertions constituted the zenith and the nadir of classical celestial mechanics, for Neptune does exist, whereas Vulcan does not." [Hanson (1970), p.257.]

Hanson, N. (1962), 'Leverrier: The Zenith And Nadir Of Newtonian Mechanics', Isis 53, pp.359-78; reprinted in Hanson (1971), pp.103-26.

--------, (1971), What I Do Not Believe, And Other Essays (Reidel).

[GPDP]

Wasn't there an observed collision of two galaxies a couple of years ago that lent further credence to the existence of dark matter? I'll see if I can find the article...

[ÑóẊîöʼn]

Astronomers are sure enough about it's existance to map it: LINK (http://www.space.com/news/cosmic_shear_000512.html)

[Rosa Lichtenstein]

Noxion, well, 800 years ago scientists also mapped the celestial spheres; and 200 years ago they measured Caloric and Phlogiston. 120 years ago they constructed models for the luminiferous ether.

No doubt in 200 years a future version of yours truly will remind scientists that they used to believe in 'dark matter'...

[mikelepore]

Could any of you guys explain to me (in "english" lol) what it is

Let's see if this serves as a plain english explanation. All matter attracts other matter with gravitational force. But matter doesn't respond to the gravity that it generates itself. Matter responds to the gravitational field that some other piece of matter has generated. Object A moves due to the grav field produced by object B, but it doesn't feel the gravity that it generates itself. Similarly, Object B moves due to the grav field produced by object A, but doesn't feel the gravity that it generates itself. Now, if you can picture that, go on to the next sentence. When people look through the telescope at how the hundred-billion-plus stars in the galaxy are moving around, they can see the stars moving as if they are responding to the gravitational force that "something else" is producing. This "something else" isn't seen. We see its effects, but we can't see the cause. It's something that is distributed around and between all of the stars, which we earlier thought was empty space. So, to use the the title of a TV documentary, "96 percent of our universe is missing."

[Rosa Lichtenstein]

Mike, you must know that there are alternative explanations for such phenomena that do not require belief in this mysterious form of 'matter', conveniently invented to fill a gap in currently 'orthodox' theory (just like the extra epicylces dreamt up in the later stages of Ptolemaic astronony).

It's an odd sort of materialism that accepts a theory that tells us that 90% of the universe is missing!

[WhitemageofDOOM]

It's the modern day equivalent of the epicycles that medieval astonomers used to add to the motion of the planets when observation failed to match theory.

So, as Mike pointed out, the observed rate of rotation of the galaxies fails to match theoretical predictions. Solution: invent 'dark matter'. [A bit like angels were the 'dark forces' that pushed the crystalline spheres.]

We'll probably need a modern day equivalent of Copernicus to rid us of this odd 'substance', but I can safely predict now that he or she will be as well-received as Copernicus and his followers were! House arrest and martyrdom, maybe not -- but ostracism definitely.

The problem is two fold.
1) The equations work for everything else, somehow we would need to change the equations while not changing the equations.
2) We have observed the effect of dark matter via gravitational lensing. Invisible gravity sources clearly exist.
3) The amount of gravity noticed is many many many times higher than the amount of observable matter.

Is it so hard to believe that your senses don't grant you the ability to perceive the entirety of the universe? Would you disbelieve in light if you couldn't see?



It's an odd sort of materialism that accepts a theory that tells us that 90% of the universe is missing!

That's a philosophical justification, that just because the universe is materialistic we must somehow be able to perceive it all directly. Lots of things you believe in that science claims must exist but you can't see, all of them like dark matter only observable through there effects on what we can perceive. We have always been working with an incomplete puzzle, only now do we realize how incomplete it really is.

[Rosa Lichtenstein]

White Image:


1) The equations work for everything else, somehow we would need to change the equations while not changing the equations.
2) We have observed the effect of dark matter via gravitational lensing. Invisible gravity sources clearly exist.
3) The amount of gravity noticed is many many many times higher than the amount of observable matter.

1) and 2) are exactly how a Ptolemaist would have defended his/her ideas 700 years ago. 3) I have already dealt with.

Recall, I am not saying that Dark Matter does not exist, just reminding you all not to jump on yet another 'scientific' band wagon.


Is it so hard to believe that your senses don't grant you the ability to perceive the entirety of the universe? Would you disbelieve in light if you couldn't see?

This has nothing to do with anything I have said, so I do not know why you asked this.


That's a philosophical justification, that just because the universe is materialistic we must somehow be able to perceive it all directly. Lots of things you believe in that science claims must exist but you can't see, all of them like dark matter only observable through there effects on what we can perceive.

As indeed were the celestial spheres.

[Rosa Provokateur]

its matter that doesn't glow, it can mean be any thing from dust and rocks to undiscovered particles.
Dark matter is though to exist because galaxies appear to be much more massive than the visible matter can account for. Some of it is certainly normal matter that we can't see and some of it is neutrinos (http://en.wikipedia.org/wiki/Neutrinos), but its not known how much, so other particles have been suggested to explain the missing mass.

Very interesting. What about Dark Energy?

[ÑóẊîöʼn]

Very interesting. What about Dark Energy?

Dark energy is a hypothetical form of energy that permeates all of space and is responsible for increasing the rate of expansion of the universe. It is reckoned to account for 74% of the total mass-energy of the universe in the standard model of cosmology (http://en.wikipedia.org/wiki/Lambda-CDM_model). There is speculation that dark energy might be a fifth physical force in the universe (after gravity, electromagnetism, the strong force and the weak force) called "quintessence".

[Rosa Lichtenstein]

It is appropriate that it is named after the mythical fifth element of ancient Greek Philosophy, and no doubt it will go the same way: into the trash can of history.

[ÑóẊîöʼn]

It is appropriate that it is named after the mythical fifth element of ancient Greek Philosophy, and no doubt it will go the same way: into the trash can of history.

Well, we'll see about that, won't we?

[Rosa Lichtenstein]

Noxion:


Well, we'll see about that, won't we?

In view of the fact that very nearly every scientific theory from the past was later rejected, my observation stands a high probablity of being correct; its opposite, a low probability.

[Rosa Lichtenstein]

To that end, you might like to read this paper, entitled 'Why Most Published Research Findings are False':

http://medicine.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pmed.0020124&ct=1

[benhur]

It is appropriate that it is named after the mythical fifth element of ancient Greek Philosophy, and no doubt it will go the same way: into the trash can of history.

Gosh, that sounds so much like something Mr. Spock would say.:crying:

[mikelepore]

Mike, you must know that there are alternative explanations for such phenomena that do not require belief in this mysterious form of 'matter', conveniently invented to fill a gap in currently 'orthodox' theory (just like the extra epicylces dreamt up in the later stages of Ptolemaic astronony).

I think everyone who looks into it knows that they're comparing one tentative model to another tentative model. Claims about a unique truth have become rare.

But they always want to throw away the least amount of earlier principles which they consider already tested and reliable. We will see the greatest resistance to reopening the case for momentum and Kepler's laws.


It's an odd sort of materialism that accepts a theory that tells us that 90% of the universe is missing!

I suppose they were already prepared to imagine undetectable matter among us, because it was so long ago that neutrinos were imagined to make nuclear equations balance. No one complained about imagining neutrinos because if they exist they are also so lightweight. But now when they claim that the supposed undetectable matter is the majority, it feels more drastic. In both cases they chose to give a name to something invisible so that a piece of old theory can be preserved. Save the belief in conservation of energy by imagining neutrinos; save the belief in conservation of momentum by imagining dark matter.

There were many occasions when people predicted that unseen things had to be out there. Perturbation of Saturn is what told them where to look for Uranus, and then perturbation of Uranus is what told them where to look for Neptune. There was a time when people couldn't detect some of the elements of the periodic table, but theory left a bunch of blank squares in the table which the new elements later fit into.

[ÑóẊîöʼn]

Wasn't there an observed collision of two galaxies a couple of years ago that lent further credence to the existence of dark matter? I'll see if I can find the article...

I think this might be it: Observations of the Bullet Nebula are in line with the dark matter hypothesis but not with MOND (http://www.damninteresting.com/?p=652).

[Rosa Lichtenstein]

BenHur:


Gosh, that sounds so much like something Mr. Spock would say.

Sounds like your Dilithium crystals need replacing.

[Rosa Lichtenstein]

Mike:


But they always want to throw away the least amount of earlier principles which they consider already tested and reliable. We will see the greatest resistance to reopening the case for momentum and Kepler's laws.

Which is exactly the sort of reasoning that meant that Ptolemy's system went unchallenged for 1000 years or more.


There were many occasions when people predicted that unseen things had to be out there. Perturbation of Saturn is what told them where to look for Uranus, and then perturbation of Uranus is what told them where to look for Neptune. There was a time when people couldn't detect some of the elements of the periodic table, but theory left a bunch of blank squares in the table which the new elements later fit into.

Which is why I posted this earlier:


It's also how science stalls. There are plenty of examples of this over and above the 'extra epicycles' fiasco. For example, the discovery of Neptune, and then the non-discovery of the planet Vulcan (no, not the on from Startrek):


"The arguments which terminate in an hypothesis's positing the existence of some trans-Uranic object, the planet Neptune, and the structurally identical arguments which forced Leverrier to urge the existence of an intra-Mercurial planet, the planet 'Vulcan', to explain the precessional aberrations of our 'innermost' solar system neighbour are formally one and the same. They run: (1) Newtonian mechanics is true; (2) Newtonian mechanics requires planet P to move in exactly this manner, x, y, z, …; (3) but P does not move à la x, y, z; (4) so either (a) there exists some as-yet-unobserved object, o, or (b) Newtonian mechanics is false. (5) 4b) contradicts 1) so 4a) is true -- there exists some as-yet-undetected body which will put everything right again between observation and theory. The variable 'o' took the value 'Neptune' in the former case; it took the value 'Vulcan' in the latter case. And these insertions constituted the zenith and the nadir of classical celestial mechanics, for Neptune does exist, whereas Vulcan does not." [Hanson (1970), p.257.]

Hanson, N. (1962), 'Leverrier: The Zenith And Nadir Of Newtonian Mechanics', Isis 53, pp.359-78; reprinted in Hanson (1971), pp.103-26.

--------, (1971), What I Do Not Believe, And Other Essays (Reidel).

[mikelepore]

Rosa, when Ptolemy handled the retrograde motion of Mars by adding circles on top of circles, he made it more complex, assuming more arbitrary entities in Ockham's sense. Then when Galileo saw moons orbiting Jupiter, even more so, and I guess they might have tried to save Ptolemy one more time, by adding circles on top of circles on top of circles, but oh, what a mess. To be simple, not to be correct, was the gift of Copernicus. Do we really have an analogous situation here? In the behavior of the galaxy, do you see one model as having more arbitrary entities than another? I can't tell which one that might be. The choice seems to be ad hoc no matter which way we turn.

[Rosa Lichtenstein]

Mike:


To be simple, not to be correct, was the gift of Copernicus. Do we really have an analogous situation here? In the behavior of the galaxy, do you see one model as having more arbitrary entities than another? I can't tell which one that might be. The choice seems to be ad hoc no matter which way we turn.

Not really. Copernicus had to add a few epicycles of his own, and he had to complicate the Medieval the universe to make his model work.

This was because his theory predicted that stellar parallax should be observable from earth as it moved around the Sun. But, it wasn't, so he introduced a major copmplication, that the universe was far bigger than anyone had imagined.

[Stellar paralllax was not in fact observed until 1834 and the work of Bessell.]

Anyway, who says nature should run according to our notions of 'simplicity'?

And this is quite apart from the fact that it has proven to be impossible to define 'simplicity'.

For example, which is the 'simpler' of these two formulae?

(1) θ = Ae^-kt

(2) θ = At^2 + Bt + C

(2) is algebraically 'simpler', but (1) is 'simpler' if we judge simplicity on the basis of the number of terms used.

Finally, Einstein's system has undone all Copernicus's good work:

On this, Robert Mills had this comment to make:


"Another way of stating the principle of equivalence, a way that better reflects its name, is to say that all reference frames, including accelerated reference frames, are equivalent, that the laws of Physics take the same form in any reference frame…. And it is also correct to say that the Copernican view (with the sun at the centre) and the Ptolemaic view (with the earth at the centre) are equally valid and equally consistent!" [Mills (1994), pp.182-83.]

It is worth recalling that the late Professor Mills was co-inventor of Yang-Mills Theory in Gauge Quantum Mechanics, and was thus no scientific novice.

http://en.wikipedia.org/wiki/Yang-Mills_theory

http://en.wikipedia.org/wiki/Robert_Mills_(physicist)

And this is what Fred Hoyle had to say:


"Instead of adding further support to the heliocentric picture of the planetary motions the Einstein theory goes in the opposite direction, giving increased respectability to the geocentric picture. The relation of the two pictures is reduced to a mere coordinate transformation and it is the main tenet of the Einstein theory that any two ways of looking at the world which are related to each other by a coordinate transformation are entirely equivalent from a physical point of view....

"Today we cannot say that the Copernican theory is 'right' and the Ptolemaic theory 'wrong' in any meaningful physical sense...." [Hoyle (1973), pp.78-79.]

"We now know that the difference between a heliocentric theory and a geocentric theory is one of relative motion only, and that such a difference has no physical significance. But such an understanding had to await Einstein's theory of gravitation in order to be fully clarified." [Hoyle (1975), p.416.]

http://en.wikipedia.org/wiki/Fred_Hoyle

Similarly, Max Born commented:


"Thus from Einstein's point of view Ptolemy and Copernicus are equally right. What point of view is chosen is a matter of expediency. For the mechanics of the planetary system the view of Copernicus is certainly the more convenient. But it is meaningless to call the gravitational fields that occur when a different system of reference is chosen 'fictitious' in contrast with the 'real' fields produced by near masses: it is just as meaningless as the question of the 'real' length of a rod...in the special theory of relativity. A gravitational field is neither 'real' nor 'fictitious' in itself. It has no meaning at all independent of the choice of coordinates, just as in the case of the length of a rod." [Born (1965), p.345. I owe this reference to Rosser (1967).]

Born, for those who might not know, was a Nobel prize winner in Physics.

http://en.wikipedia.org/wiki/Max_Born

Born, M. (1965), Einstein's Theory Of Relativity (Dover, 2nd ed.).

Hoyle, F. (1973), Nicolaus Copernicus. An Essay On His Life And Work (Heinemann).

--------, (1975), Astronomy And Cosmology. A Modern Course (W H Freeman).

Mills, R. (1994), Space, Time And Quanta (W H Freeman).

Rosser, W. (1967), Introductory Relativity (Plenum Press).

The universe is not a 'simple' place.

[piet11111]

i do not know what i like more about Rosa its either that she can be incredibly cynical or that she knows startrek :wub:

[Rosa Lichtenstein]

Why "cynical"?

[mikelepore]

"Today we cannot say that the Copernican theory is 'right' and the Ptolemaic theory 'wrong' in any meaningful physical sense...." [Hoyle (1973), pp.78-79.]

"We now know that the difference between a heliocentric theory and a geocentric theory is one of relative motion only, and that such a difference has no physical significance. But such an understanding had to await Einstein's theory of gravitation in order to be fully clarified." [Hoyle (1975), p.416.]

Hoyle didn't say that quite right. We could define the earth as the origin of our axes for any application, but then we'll have an noticably accelerated reference frame, which causes several fictititious forces to appear. Things go flying off for no apparent reason, for example, the coriolis force. By defining the sun as a center of creation we're a lot closer to having an intertial reference frame. It's reasonable to treat any point as the center of the universe as long as it has a nearly constant velocity. A rotating frame shouldn't be selected.

[Rosa Lichtenstein]

Maybe so, but you get the idea.

[Rosa Provokateur]

Dark energy is a hypothetical form of energy that permeates all of space and is responsible for increasing the rate of expansion of the universe. It is reckoned to account for 74% of the total mass-energy of the universe in the standard model of cosmology (http://en.wikipedia.org/wiki/Lambda-CDM_model). There is speculation that dark energy might be a fifth physical force in the universe (after gravity, electromagnetism, the strong force and the weak force) called "quintessence".
I heard something about either Dark Matter or Dark Energy being somehow responsible for the Big Bang, you guys know anything about that?

[ÑóẊîöʼn]

I heard something about either Dark Matter or Dark Energy being somehow responsible for the Big Bang, you guys know anything about that?

I can't see it being possible, since dark matter and dark energy were presumably formed out of the big bang along with all other forms of matter and energy. Since as far as we know spacetime also arose at the instant of the big bang, there would have no time or place for any kind of mass-energy to exist in, no more than you or I could stand north of the North Pole.