Talk:Dark energy

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Maybe...

This is just a minor thought, but perhaps our spacetime existence lies along more than three or four dimensions, and Dark Matter and particularly Dark Energy are forms of energy (as matter is, if memory serves, comprised of pure energy plus chargeless filler) which lie between phase, far enough inside our plain to effect, but not perceive.

Writing this, however, I realize that if something can have an effect on our spacetime, should it not be perceivable?

Perhaps, then, it gives off EM waves far behind or beyond the currently perceivable spectrum.

However, since the little I've had the attention span and concentration to read has suggested that DM and DE are mere theories, or hypotheses, I state the obvious in saying that my words depend solely on the existence of DM/DE.

Maybe I don't know enough to say anything, though.

CerberusYBlue (talk) 12:25, 18 November 2007 (UTC)

You have a good point. I thought however that perhaps, with the growing acceptance of a multiverse. It is the universes around us overwhelming the gravity of our universe, stretching us. This raises another question as to what lies between the verses and what separates them. More questions would be if that is the reason that gravity is the weakest of all, because it is spread across multiple universes. So many questions and not enough answers.--

Universes other than our own would (essentially by definition) have no possible effect on our own in the absence of obscure but arguably possible quantum-tunneling or other effects. However, the possibility that we exist in more than 4 dimensions has been brought up on numerous occasions. String theory (in particular M-theory) postulates the existance of 10 or 11 total dimensions, 6 or 7 of which are so small that they are completely invisible to all modern equipment, but that are required for strings to look like particles/waves the way experiments have shown them to be. String theory has a few ways to attempt to explain dark energy (in particular the heirarchy problem), but none are in any way proven, and none invoke quantum gravity.

Certain theories postulate the existance of larger dimensions using constructs known as "branes" (as in "membranes"). In this theory, ends of strings are confined to move only on the brain they are in (for simplicity, imagine a 2-brane as a plane or huge sheet of paper that the string ends must stay on), although the string as a whole vibrates in the whole space (bulk). If this is the case, we could be living in just one 3-brain in a higher dimensional universe. However, these extra dimensions cannot be more than about 1 mm long because gravity is the one force NOT confined to the brane, and it has been shown to operate 3-dimensionally over distances as short as about 1 mm.

These theories all have a major problem of why some dimensions are curled up into extremely tiny circles whereas the 4 larger dimensions are enormous. One possible idea of solving this heirarchy problem is that the extra dimensions are actually arbitrarily large (perhaps as large as the 4 we're familiar with), but curved so extremely that gravity only significantly affects us from a very tiny fraction of the extra dimensions, as if they were very small. This still has a heirarchy problem of curvature, however.

All of these theories are based on string theory, all are completely unverified (and in some cases perhaps unverifiable for a very long time), and none seem particularly outstanding or likely. Unfortunately, as far as I know, none of these theories seem likely to explain dark energy, either. By the way, matter is not quite, as you say, "comprised of pure energy plus chargeless filler," but is in fact entirely equivalent to energy (no filler required). You can discuss the energy of your pencil as 900 Terrajoules if you like, or the mass of your jogging as a few femtograms. However, mass differs from energy in practacle situations, so generally they are not treated as identicle. Dark energy is also in one sense like the opposite of gravity, so it is unlikely to be a result of the same force.Eebster the Great (talk) 00:03, 2 April 2008 (UTC)

cleanup-section

I added {{cleanup-section}} to the article because I think the section needs to be written with citations, without bold, with wikilinks (if applicable) and without the signature (not sure why that is there). Also this section appears to be too technical for a general audience (it doesn't seem to fit with the rest of the article). -- Tsuite ^T/C 10:53, 17 September 2007 (UTC)

Rewrite

I decided to take a stab at reorganizing this page, rewriting much of it and adding content, per User:Pjacobi's suggestion below. I think a lot of work probably still needs to be done, but it will ultimately result in a better article. I have taken a first stab, drawing on material in the articles quintessence (physics), cosmological constant and accelerating universe, all of which I edited extensively over the past weeks. I think these articles, along with ultimate fate of the universe and Equation of State (Cosmology) should be retained, but should perhaps be more technical, with this sort of an umbrella page for this set of ideas. Please let me know what you think. P.S. Incidentally, if someone wants to move the old talk to an archive page, please go ahead. I don't know how, so I just nuked it. P.P.S. I added some, hopefully simple, equations in the cosmological constant section. Do you think the argument is comprehensible to the reader with little specialized knowedge? --Joke137 00:55, 4 Mar 2005 (UTC)

I think you did a very good job with rewriting this article. There are a few places where I thought your presentation was ambiguous or imprecise, and I may try and do something about that, but overall a remarkably good effort. Dragons flight 01:27, Mar 4, 2005 (UTC)

Thanks a lot. It is something I had been thinking about doing for a while. I've tried to touch it up a little bit, and will probably come back to it again in a few days once it has had some time to settle in my mind. Please edit away where you've found ambiguities. --03:07, 4 Mar 2005 (UTC)

I redirected the accelerating universe page to this one, since it now contains a more complete discussion of SN Ia etc. --Joke137 15:50, 10 Mar 2005 (UTC)

I've worked as a science news reporter and editor (I can give URLs to those who would like samples of my work) and I think this page really needs simplification for regular readers, we non-physicists and non-scientists. I've generally avoided contributing to pages in the hard sciences on Wikipedia since if I know one thing, it's that I'm not a scientist. I can't check the facts on things like this. However, I can double-check the language, and this page is definitely written in "scientistese," which is to say words and sentence structures that are very distancing for non-scientists, words like "qualitatively," and "homogeneously" and, god help me, "parameterized" (seriously, what the hell?). I'd like to do some cleanup, but I don't want to step on toes (as much as Wikipedia policy encourages "being bold," I've never seen it help an article). Does anyone seriously object? --Boradis 04:18, 2 April 2007 (UTC)

I've taken a look at the article, and it seems to have already been simplified as much as it can be without becoming completely inaccurate. The lead paragraph gives as good a layman's summary as we're likely to get, and the remainder of the article tries to explain things in layman's terms until it gets into the details of the cosmological constant and quintessence options (which have to be at least a little bit technical, or else they're useless). What specific sections and paragraphs do you consider too confusing? --Christopher Thomas 04:45, 2 April 2007 (UTC)

Pretty much all of them, honestly. For starters, any sentence that includes words that aren't used in common, everyday English, needs to be reworded so folks can understand it without digging out a dictionary. I gave examples above, and I don't think changing the phrasing into something lay people can understand will bring innacuracies. No one uses words like "qualitatively" in everyday speech, and the effect it has on lay readers is to say "This is hard, this isn't written for you, you shouldn't be reading this." Here's how I would lightly tweak the lead paragraph with a few simple changes:

---

In physical cosmology, dark energy is a hypothetical form of energy that permeates all of space and has strong negative pressure -- unlike gravity, it pushes rather than pulls.[1] According to the Theory of Relativity, the effect of such a negative pressure is essentially a force acting in opposition to gravity at very large scales, the distances between galaxies for example. Assuming the existence of such an effect is currently the most popularly accepted method among scientists for explaining recent observations that the universe appears to be expanding at an accelerating rate, as well as accounting for a significant portion of the missing mass in the universe.

---

--Boradis 06:04, 2 April 2007 (UTC)

To explain: Cosmologists and scientists in general have their own terminology for things. But to a person who's expertise is in, say, cabinetry, "large scales" probably means the distance from their home to the next state over, or something similar. So it needs to be explained. "Invoking" is a term I've heard only used by physicists and wizards in games of D&D (sorry, but it's true!). It means, in this case, "to assume the existence of," and since the idea here is to communicate with non-scientists, that's the way it should be phrased. This isn't dumbing it down, it's de-jargonizing it, since all the concepts are still present.--Boradis 06:04, 2 April 2007 (UTC)

Rewrite specifics

Coming from Wikiproject Physics, I haven't looked over the entire article, but I think this discussion needs to be much more specific. Saying "it seems to have already been simplified as much as it can be" or "Pretty much all of (the sections)" need to be changed is not nearly as useful as specific suggestions. I tried revising the intro. Hope that helps. Gnixon 14:29, 9 April 2007 (UTC)

Since I haven't seen any support for my suggestions I haven't taken any action. But this is a valid question, so here's my answer. I didn't actually mean "pretty much all of the (sections and paragraphs)", I was trying to soften what I said. So to be precise, I meant all of them. In every section I see examples of writing containing unneeded precision, and loads of unexplained jargon and technical terminology. Put another way, every section contains buried ledes, pleonasms and logorrhoea. If you didn't understand that last sentence without following the links, then you get my point. --Boradis 20:20, 10 April 2007 (UTC) (Fixed my own wikilink --Boradis 20:20, 12 April 2007 (UTC))

Point well-taken. I'll be borrowing your pleonasms/logorrhea example from time to time.  :) How about if you either pointed us to the worst paragraphs with suggestions or went through yourself and just let others redo your edits if they damage precision? Be bold! As for your suggestions on the intro, it's changed since you wrote that, becoming more accurate and, I hope, more readable. How does it look now? (Edit: now I see your comments below.) Gnixon 21:26, 10 April 2007 (UTC)

Then I am afraid you're going to be disappointed. Any explanation beyond "it's something that makes space expand" will require jargon, because this is a technical topic. --Christopher Thomas 20:27, 10 April 2007 (UTC)

It does not require jargon in order to explain what is known and how it is known to a general audience. In fact, jargon blocks the reader from understanding, it sabotages the purpose of an encyclopedia. See above for my suggestion of a rewritten lead paragraph to this article. The current version contains just as much jargon, and here's some translations of terms that are stumbling blocks to the intended audience of Wikipedia:

• Hubble expansion -> expansion of the universe
• Invoking -> assuming the existence of
• lambda-CDM model -> simplest known model of the universe --Boradis 21:14, 10 April 2007 (UTC)

I agree that those translations would work just as well, at least in the intro. Remember that wikifying plays a useful role here, and can go either direction. I think people in any field tend to use a lot of jargon without thinking about whether it's necessary or appropriate. On the other hand, sometimes it is necessary in order to avoid that logorrhea you mentioned. One advantage of Wikipedia is that there's plenty of room for highly technical articles in addition to general ones---the trick is finding the right balance, both within the articles and in terms of what articles exist. Gnixon 21:26, 10 April 2007 (UTC)

I disagree that these translations work. The last point is roughly equivalent to replacing "pistons" with "engine parts" when describing a motor. I object to dumbing down the article if it loses important information in the process. At most, give parenthetical definitions for terms you think may be confusing. --Christopher Thomas 21:30, 10 April 2007 (UTC)

Then I suggest you read the lambda-CDM model article which is where I took that description from. And since that description is specific and unique (there can only be one "simplest" of anything), it is not equivalent to confusing pistons and carburetors. --Boradis 20:26, 12 April 2007 (UTC)

I made an edit before hearing your objections, sorry. At least when we're talking about the intro, I think it's very important to stay accessible, and these translations seem fine for that purpose. They're wikilinked and we can certainly explain things more technically in the body of the article. I'm generally against parenthetical phrases, which tend to ruin flow. Gnixon 21:36, 10 April 2007 (UTC)

Confusion

I was hoping we could work to get rid of the "confusing" tag. Boradis, were you the one who added it? Can you give us a laundry list of problems to discuss? Gnixon 21:50, 10 April 2007 (UTC)

Stay focused on article

Please remember that this page is only for discussing the article, not for discussing dark energy itself. When comments are made here that do not pertain directly to the article, I suggest editors respond simply with "This page is only for discussing the article," and avoid provoking further discussion that clutters the page. Gnixon 13:50, 9 April 2007 (UTC)

Shibli

The text below is written by User: Murad.Shibli. While a Wikipedian cannot publish his or her own work on Wikipedia (at least not until it has attained some level of acceptance in the academic community), I think there is nothing wrong with posting the text on the talk page. This could help us to keep track of this theory and readd parts once his work is peer-reviewed and published. Sijo Ripa 12:04, 17 May 2007 (UTC)

Dark Energy, Its Nature and its Governing Law

New results proposed by Dr. Murad Shibli at the German Jordanian University will be published this summer at the IEEE International Conference On Recent advances in Space Technologies and will be held in Turkey on June 14-16 2007. His Paper is entitled as "The Foundation of the Theory of Dark Energy: Einstein's Cosmological Constant, Universe Mass-Energy Densities, Expansion of the Universe, a New Formulation of Newtonian Kepler's Laws and the Ultimate Fate of the Universe". Dr. Shibli's paper presents a basis of the theory of universe dark energy, a solution of Einstein's cosmological constant problem, physical interpretation of universe dark energy and Einstein's cosmological constant Lambda (=0.29447x10^-52m^-2), values of universe dark energy density (=1.2622x10^-26kg/m^3=6.8023GeV), universe critical density (=1.8069x10^-26kg/m^3=9.7378GeV), universe matter density (=0.54207x10^-26kg/m^3=2.9213GeV), and universe radiation density (=2.7103x10^-26kg/m^3 = 1.4558MeV). The interpretation in his paper is based on geometric modeling of space-time as a perfect four-dimensional continuum cosmic fluid and the momentum generated by the time. In such a modeling, time is considered to have a mechanical nature so that the momentum associated with it is equal to the negative of the universe total energy. It is found that dark energy is a property of the space-time itself. Moreover, based on the fluidic nature of dark energy, the fourth law of thermodynamics is proposed, a new formulation and physical interpretation of Kepler's Three Laws are presented. Furthermore, based on the fact that what we are observing is just the history of our universe, on the Big Bang Theory, Einstein's General Relativity, Hubble Parameter, the estimated age of the universe, cosmic inflation theory and on NASA's observation of supernova 1a, then a second-order (parabolic) parametric model is obtained in Dr. Shibli's proposed paper to describe the accelerated expansion of the universe. This model shows that the universe is approaching the universe cosmic horizon line and will pass through a critical point that will influence significantly its fate. Considering the breaking symmetry model and the variational principle of mechanics, then the universe will witness an infinitesimally stationary state and a symmetry breaking. As result of that, a very massive impulse (Big Impulse of magnitude 10^33 x the linear momentum of the universe) will occur soon and, correspondingly, the universe will collapse. Finally, simulation results are demonstrated to verify the proposed models. see www.icrepq.com or [1] for full sccript.

Presure and Expansion

If a negative pressure can contribute to do negative gravitation, then gravitation it self produces a kind of negative pressure because when massive objects fall down have negative pressure, then that negative pressure can produce negative gravitation, and all the process can produce dilatations and contractions of the universe in whole.Pérez 20:28, 20 August 2007 (UTC)

I'm Confused

The article says the universe is expanding, if it is expanding there is each time more and more space. It also says that "a volume of space has some intrinsic, fundamental energy." More space logically means more "intrinsic, fundemantal energy" so either energy can be created out of nowhere or space is not expandng?

Also how can you say that this energy is dense? D = M/V D= g/cm² or something like that. The energy weights? --201.252.49.55 22:00, 19 May 2007 (UTC)

To answer the conservation of energy question: as the space expands the energy required to form the space is balanced by the negative gravitational energy -- see cosmic inflation.--Michael C. Price ^talk 22:17, 22 July 2007 (UTC)

I'm confused about how dark energy expands the universe.

Dark energy is a slow, low energy form of cosmic inflation.--Michael C. Price ^talk 22:17, 22 July 2007 (UTC)

Energy is not necessarily conserved in general relativity unless you have an asymptotically flat metric. In fact, one cannot even define the total energy of the universe, let alone state that it's conserved. Dan Gluck 20:13, 27 June 2007 (UTC)

A common myth. Conserved total energy-momentum can be precisely defined via the Landau-Lifshitz pseudotensor for any metric.--Michael C. Price ^talk 21:26, 22 July 2007 (UTC)

I'm Also Confused

In a search for scientific information on hyperforce, I was redirected to this page. I'm not a scientist, but I do recall scientific articles from roughly 20 years ago referring to a phenomenon where elements with greater nucleon concentration, such as iron, fall in a gravitational field slightly more slowly than those with lower nucleon concentration. The redirect to this entry on dark energy, and the contents listed here, provide no details of this at all. Can someone either detail this part of the topic here, if it is truly related to dark matter, or create a separate entry in wikipedia for hyperforce? Matt Battison 13:00, 11 July 2007

Never heard of it. I suspect "hyperforce" is not WP:NOTABLE, unless it's related to the fifth force, which apparently interacted with hypercharge. Perhaps the redirect should go there. (My undergrad advisor was Fischbach.) Gnixon 18:27, 11 July 2007 (UTC)

If anyone thought he had observed such a phenomenon, it must have turned out to be experimental error or error in data interpretation. Such a differential effect of gravity on nucleons would be a violation of the equivalence principle (the foundation of general relativity) and as such would garner a great deal of press coverage unless it was quickly discounted as a mistake. JRSpriggs 03:41, 12 July 2007 (UTC)

The Fischbach et al PRL came out exactly 20 years ago. That must be what Battison is thinking of. It generated a lot of attention as an interpretation of the Eotvos experiments, but didn't hold up. The equivalence principle is tested now to something like a part in 10^13 by the Eotvos technique. They're still refining the experiment, and others are planning or doing related experiments where two masses in free fall are monitored for deviations from constant distance. See here.

Gnixon 07:22, 12 July 2007 (UTC)

I'm Triple Confused

It has been quoted above that …

“In physical cosmology, dark energy is a hypothetical form of energy that permeates all of space and tends to increase the rate of expansion of the universe. [1] Assuming the existence of dark energy is the most popular way to explain recent observations that the universe appears to be expanding at an accelerating rate. In the standard model of cosmology, dark energy currently accounts for almost three-quarters of the total mass-energy of the universe. “

What I pose is the following …

“Assuming that this “black energy” “Atlas” with broad shoulders adheres to the same principles of mutual attraction, i.e. the formulae that describe the relationship between distance, mass and gravitational force of attraction. However if the reason the “Black Energy” is black is not because of 180 degree out of phase energy cancellation but because it is in fact non existent … then what is it that is “pulling apart” or acting like anti-gravitational forces at work? Could it be the source of all theoretical anti-gravitational concepts, i.e. the force field of Equilibrium … that which maintains the systemic symmetry between gravity  equilibrium in our dynamic systemic symmetrical universe?”

Since I don’t get to this site very often, if someone has a clarification to unconfused my map of cosmic reality will you please email me at LJohnCarson@msn.com. I would deeply appreciate that. 63.16.46.108 (talk)Lawrence Carson63.16.46.108 (talk) 25 November 2007

I get what you are saying but think about it like this. Whatever is pushing the universe apart can be seen as hands. Being held by the hands is Play-Doh. Pull apart the play-doh and it gets thinner. Think of the thinning as all the different forces in the universe weakening, like the bond of the play-doh. Eventually probably hundreds of billions even trillions of years, the most basic properties fall apart, and all the atoms can't bond together. Then weakening further to the point where protons, neutrons, and electrons can't be held together. Then they break up. Then perhaps (all guesses) dark energy cannot stay together and breaks apart. Then once everything is down to the fundamental singularity, with dark energy gone, gravity and all the other properties, slowly, painstakingly slow, start to work again. The singularities come together and everything, after trillions maybe quadrillions of years by this point, comes together in the Big Crunch. Just my views on it. Hope they help.

You're email bounced, you have a long road ahead, start here http://arxiv.org/abs/gr-qc/0605083v1 —Preceding unsigned comment added by Omeganumber (talk • contribs) 01:59, 1 March 2008 (UTC)

Removed paragraph

I have removed a paragraph stating that the FLRW metric with a cosmological constant has solutions with discontinuities and stating that as a problem of the cosmological constant idea. The reference paper has no citings at all, and anyway having singularities in general relativity is something extremely generic. Dan Gluck 20:16, 27 June 2007 (UTC)

Wikipedia is an encyclopedia, not a place to advertise your research. The issue raised in the paragraph below is neither widely acknowledged in the scientific community, nor is it particularly enlightening for laymen. SwordSmurf (talk) 11:56, 25 February 2008 (UTC)

Another problem arises with inclusion of the cosmic constant in the standard model, which is appearance of solutions with regions of discontinuities (see classification of discontinuities for three examples) at low matter density. These predictions have been recently confirmed using all publicly available, supernovae type Ia data. The discontinuity also affects the past sign of the vacuum energy, changing from the current negative pressure to attractive, as one looks back towards the early universe. This finding should be considered a shortcoming of the standard model, but only when a term for vacuum energy is included.

B-class? I give it an F.

According to the Friedmann-Lemaître-Robertson-Walker metric, which is an application of General Relativity to cosmology, the pressure within a substance contributes to its gravitational attraction for other things just as its mass density does. Negative pressure causes a gravitational repulsion.

I'm curious how you can call this an "application" of GR, when in fact it blatantly violates the equivalence principle, without which there is no GR. Pressure is not mass. Pressure is not density. Pressure is not gravity. Gravitational repulsion is physically impossible because mass can only be positive and real. To say that something other than mass can warp space-time is a contradiction of GR, not an application of it. --76.217.89.63 02:40, 7 August 2007 (UTC)

Pressure is part of the stress-energy tensor that is at the core of general relativity. You should keep in mind that pressure is dimensionally the same as energy density, and hence represents another form of mass-energy. Dragons flight 09:35, 7 August 2007 (UTC)

Alternative Ideas

   section  revision

If g.w. observatories with up to 10^-21 sensitivity don’t detect gravity waves, might this then be interpreted as indicating that C_R pseudo-Riemannian spacetime continuum (i.e. manifold’s) stiffness is not INsignificant; rather than the assumption that g.w.s propagate long distance, and that it just requires a more sensitive detector? Statistically g.w. observatories seems to have a large enough volume and sample size for inclusion of compact objects in NS and BH binary systems in tight orbits at least, even if not catching any coalescing events. However even for binary coalescence of BHs, might generated {g.w.} decay very rapidly? So resistance to deformation (normal stress: extension and compression, and even any shear stress) might not be insignificant. Might such stiffness (resistance to deformation/distortion) be considered as like inertia of C_R manifold? That is, {g.w.} have non-localized energy, but such energy is associated with deformation of manifold. Hence such {g.w.} energy might be considered as trying to overcome resistance to deformation (i.e. stiffness) of C_R manifold. Hence such inertia of manifold (resistance to deformation) would seem to represent a contribution to stress energy momentum tensor and it’s matrix representation; thus contributing not insignificantly to overall curvature? So if long range g.w.s are not detected, then might g.w. observatories actually be exploring a qualitative assessment (not limits) as to stiffness of C_R manifold? Thus might C_R manifold be quite robust to perturbation? Any such robustness would seem consistent with such manifold not breaking up (i.e. so no ‘foam’?) for near to, and at C_p Planck scale; hence also consistent with no quantization of manifold C_R? Also then less likely to have leakage of g.w.s propagating out of a manifold into another dimension i.e. brane? Also wouldn’t any such significant stiffness of C_R manifold be less consistent with deformations associated with superstrings? Also if the concept of inertia of manifold is descriptive, then any entertained recent new acceleration (i.e. resulting then in a strain or elasticity of manifold) of such C_R manifold would seem less likely. Might energy associated with resistance to deformation of manifold represent a significant portion of energy required to approach flatness? That is, one significant contribution to dark energy is right before us, in the form of energy of manifold C_R; such stiffness of C_R manifold contributing to stress energy momentum tensor, and hence to curvature. How would one further explore such latter conjecture, other than any qualitative finding of no long range g.w. propagation? Perhaps one could consider all alternative possibilities of sources of energy sufficient for approach to flatness. Then to the extent that they can be found to be less probable and/or no supportive evidence, then the last standing definitive contributing source of such energy (i.e. energy of C_R manifold) might have to be in part (or in full) accepted. So have g.w. observatories already made a GREAT DISCOVERY - that is, the inertia of C_R manifold? So C_R manifold seems to have significant stiffness, and hence contributes a significant amount of energy to T_uv, and thus contributes significantly to curvature. SRM.[2]Zanardm (talk) 07:25, 22 November 2007 (UTC)

I think nobody responded to this because it's idle speculation, with no basis in current accepted science. Nobody expects to find relic GWs with current sensitivities. This sort of thing does not belong in an article. --131.215.123.98 (talk) 03:58, 29 November 2007 (UTC)

Explain why gravity waves can propagate through the Universe unimpeded.

What's the answer? Or is it a 50/50 call, whether they can or cannot propagate long distance? And if g.w.s don't propagate long distance, then what would be expected from our exquisitely sensitive (~10^-21)[3] interferometry observatories, surveying a large statistically adequate volume for g.w. sources?Zanardm (talk) 01:00, 30 November 2007 (UTC)

This is not an issue that can be decided on a Wikipedia talk page. In order to add something to wikipedia, you need to be able to cite your sources, and they need to be verifiable sources that are notable -- not original research. Your additions meet none of those criteria.

If you find notable, verifiable sources, you can add material relating to them. If you can't, you can discuss your ideas further on pages other than the article. --131.215.123.98 (talk) 04:46, 30 November 2007 (UTC)

I don't understand

Why do they call it dark energy? Is it "dark" like shaded, or is it evil in nature? Also, I do not understand this topic in it's full capacity. I can't help but hope I'm not a complete moron. So, out of my self esteems' attempt of self preservation, I must assume that the article is not written in such a way an individual without a PhD could decipher it. Either that, or I must accept the fact that I'm an idiot. Anything we can do about this (besides saying I'm stupid)? 68.143.88.2 (talk) 20:45, 26 November 2007 (UTC)

I'm not an expert by any means, so take my answer with a mountain of salt. But I think it's called 'dark' energy because it is hypothetical - we can't see it, or measure it. It's like a 'fudge factor'. It's existence is simply assumed in order to "explain recent observations that the universe appears to be expanding at an accelerating rate." Dlabtot (talk) 17:55, 17 January 2008 (UTC)

The term 'dark energy' was coined by Michael Turner I believe, so you probably should ask him. I think hes still at University of Chicago. now this is just told to me off hand but its called dark energy in analogy to dark matter, both unknown components of the universe. of course dark matter term makes sense, (you can't see it, no radiation). if Zwicky called dark matter -> 'black matter' instead, then we might all be calling it black energy instead of dark energy. --Blckavnger (talk) 07:41, 30 January 2008 (UTC)

If you merely "believe" that Michael Turner coined the term and cannot give a basis for that belief, should it be stated as fact in the article? The term is used in the paper cited in footnote 10 (http://arxiv.org/abs/astro-ph/9808133) as if already in general use, so that cannot be the basis for the assignment to Turner. The term is misleading, in my nonexpert opinion, because saying, "We are trying to determine the nature of dark energy," implies a different sort of research project than saying, "We are trying to find the reason for the accelerating expansion of the universe." —Preceding unsigned comment added by Simplizissimus (talk • contribs) 03:13, 10 February 2008 (UTC)

It's called 'dark' because it is completely decoupled from electromagnetism, i.e. it doesn't interact with photons at all and hence we can infer it's presence from observations (supernovae) but cannot actually 'see' it at all Dazza79 (talk) 01:13, 22 February 2008 (UTC)

Summary

I'm going to link to this, because it's relevant to the article: http://xkcd.com/171/ —Preceding unsigned comment added by 76.180.120.161 (talk) 20:05, 4 December 2007 (UTC)

Comments

The recent fate of this article really gives a clear picture of why I don't edit Wikipedia much any more: reversion to mediocrity. (For a picture of what the article looked like in the not too distant past, see [4].) In any case, some comments:

• The proliferation of section headings is really, really bad style. There is absolutely no reason a one sentence section should be in any article. (Another example of bad style is the pointless (i) and (ii) in the introduction. Why introduce a numbering scheme if you don't go ahead and use those numbers for something?)
• The "current research" section contains one section, about a table top test of dark energy. What about the myriad CMB surveys, large scale structure surveys, measurements of the equation of state from the baryon acoustic peak, Supernova Legacy Survey, the Joint Dark Energy Mission, etc...?
• The superconductivity section is totally fringe stuff, but presented along with the rest of the evidence.
• The section about LHC provides absolutely no detail. I'm not even sure how Krauss thinks we can learn about dark energy from LHC, and I know a lot about dark energy.
• The Christianity section. Whiskey tango foxtrot?

Well, anyways, I don't know if my comments are doing any good – in fact, I suspect this is distinctly unhelpful – but I still find Wikipedia useful for a lot of stuff, and it pains me when the quality of an article degrades this much. It certainly wasn't perfect back when I was actively working on it, but it was at least reliable and improving. –Joke (talk) 17:39, 6 January 2008 (UTC)

First, this is not an essay; the article needs to be organized with usability in mind. Being a user as well as editor of Wikipedia, having a detailed outline structure helps tremendously in finding information. Second, I did not put the (i) and (ii) in; that was there before. Third, please go ahead and add to the current research section; what is there currently is just a start. Fourth, we can create an "alleged evidence" section where we can put the superconductivity section, but I would like to see others opinion on this evidence. Fifth, I would also like to know why the LHC is expected to yield results, but that doesn't neglect that this idea is sourced to a respectable source. Finally, the Christian section makes this article more complete.--JEF (talk) 23:59, 6 January 2008 (UTC)

Yeah, I'm going to have to go ahead and say that Jorfer shouldn't be editing this article as he doesn't seem to understand the basics of Wikipedia editing style. I'm going to revert wholesale. ScienceApologist (talk) 18:18, 13 January 2008 (UTC)

I understand that Wikipedia:Layout states that single sentence sections should be minimized, but WP:IAR applies since the article is better for it.--JEF (talk) 19:39, 13 January 2008 (UTC)

IAR only works if everyone agrees with you. ScienceApologist (talk) 00:57, 14 January 2008 (UTC)

Fringe science

These removed sections just so happens this some of the best sourced information in the article. Beside the Christian section they are sourced to peer-reviewed journals a peer-reviewd journal. ScienceApologist may argue undue weight, but there is so much confusion as to what Dark Energy and how it fits into are current view of the universe that it is difficult to assess correct weighting. Information removed from article as fringe science:

Superconductivity

In 2006, Martin Tajmar at the Austrian Research Center facility in Seibersdorf along with his colleagues discovered that once a spinning ring of niobium became cold enough to superconduct, accelerometers on the device suddenly picked up a signal. The controversial experiment seems to defy Einstein’s equivalence principle, a principle saying that the location in space-time of the laboratory should not affect the results. The experiment also suggests that energy isn’t conserved in a superconductor. Clavios de Matos, who works at the European Space Agency in Paris stated, “We did the sums and found out that energy wasn’t conserved but perhaps that was just because we were missing dark energy”.

Current research

Table top test

Originally a test for dark energy without a reason given for why it would work, Christian Beck of Queen Mary, University of London and Michael Mackey of McGill University created an experiment which measures the varying current induced by quantum fluctuation in a Josephson junction. It was based on the idea that if dark energy and quantum fluctuations are related then the current should die beyond a certain frequency. They later came up with the theory as to how exactly dark energy would cause the cutoff basing it on quantum mechanics, which dictates that photons are “popping in and out of existence” in the vacuum of space. They proposed that when the frequency of the photon goes below a certain level they interact gravitationally which contributes to dark energy. Specifically they expect that if the “virtual photons” reach a frequency of below 2 terahertz the current will taper off.

Religious ideas

Christianity

Christians associate dark energy with God driven design in the universe. Two creationist websites use Stanford University and MIT work that they say indicates that if dark energy is a cosmological constant, the traditional idea for what dark energy is, the chances of our universe existing as we know it are virtually non-existent. --JEF (talk) 20:07, 13 January 2008 (UTC)

New Scientist is not a reliable source. Period. Christianity does not belong in this article. Period. ScienceApologist (talk) 00:57, 14 January 2008 (UTC)

thanks ScienceApologist for the vigilance. Jorfer, if you don't understand why your argument 'with God driven design' doesn't belong in a science article, then you should reread some physical science book (Hewitt, Conceptual Physics) to see what qualifies as scientific hypothesis/theory. It doesn't mean that your assesment is wrong; it just doesn't belong in the science realm. --Blckavnger (talk) 07:49, 30 January 2008 (UTC)

Organization of article

--JEF (talk) 18:02, 14 January 2008 (UTC)

I attempted to format the page in what I felt was a more user friendly manner by sectioning, but User:ScienceApologist feels that what I did was not appopriate style to use, and he also disagreed with the inclusion of the material in the above section of the talk page into the article. He also wiped away other information from the journal Nature with his wholesale reversion.--JEF (talk) 18:02, 14 January 2008 (UTC)

Unless the fringe theories are demonstrated to be notable, I don't see a point in putting them on this page. In a situation for which there are notable and competing theories, there needs to be a benchmark for inclusion, and that's not merely being published, no matter where. Someguy1221 (talk) 04:18, 15 January 2008 (UTC)

It is notable. It is the only unconventional research going on in this area as far as I am aware. People are willing to fund this research, so they must think it is worthwhile. The table top group presented the theory at a conference on unsolved problems for the standard model of cosmology held at Imperial College London which may make their research notable enough for this article. They were respected enough to be invited. The superconductivity group evidence is in a peer-reviewed journal, so if anyone has a problem with the research then they are free to try and repeat the research for a null result.--JEF (talk) 17:08, 17 January 2008 (UTC)

Publishing in a journal does not make something notable, as this is not "coverage in secondary sources". Until anyone bothers to review, report, or repeat the research, there is no evidence of notability. Further, the existence of only primary sources (self-published research papers) creates an inherent POV issue, namely that we only have these researcher's own word to go on that this isn't complete bullshit. Nature does review the work, yes, and Nature does endeavor to see that the research was performed properly, but does not promise the validity of the researcher's conclusions (New Scientist doesn't do squat). Someguy1221 (talk) 21:21, 17 January 2008 (UTC)

So you would say the superconductivity experiment is notable enough for the Martin Tajmar article but not this one? Fair enough. I will put a see also link then.--JEF (talk) 23:02, 17 January 2008 (UTC)

I see only self-published studies for just about everything on his page. I would say I don't care what you put on his page, but I see nothing to suggest he deserves the slightest mention on this page. Someguy1221 (talk) 23:09, 17 January 2008 (UTC)

If it is true, than it is most definitely notable as it would suggest Dark Energy is creating a violation in Einstein's equivalence principal.--JEF (talk) 23:13, 17 January 2008 (UTC)

And as I said, the problem with that is he and his colleagues are the only ones saying it's true. It violates undue weight to present such claims when they contradict existing and notable theories. Someguy1221 (talk) 23:18, 17 January 2008 (UTC)

Martin Tajmar is not notable enough for this encyclopedia. I AfD'ed the article. ScienceApologist (talk) 23:20, 17 January 2008 (UTC)

I tryed to give a more detailed outline, because as a student doing research on the subject, I found it annoying trying to find and use the information on this page. For example the percentages for the composition of the universe are on the bottom of the evidence section. I just used the pie chart because it was quicker than searching for the actual written material; there is no reason that should be on the bottom of evidence. That is an important detail that it should be easily visible. Also, for the implication of the Universe, the last paragraph could at least be seperated into two paragraphs as the Big Rip and Big Crunch are totally divergent ideas that should not be grouped together in the same paragraph. I want to see what Someguy thinks about a more detailed outline.--JEF (talk) 23:46, 17 January 2008 (UTC)

While the pie chart is a very informative image, it is probably even more informative to the uninformed after being introduced to the concept, and so below the introduction would be best. I'm confused as the ordering of the first three sections, however. The first section (negative pressure) seems entirely out of place, as far as I can tell, and could probably be worked into the "nature of" section in a more encyclopedic tone (and sources to boot). Maybe it could be argued it follows from the introduction, but it still seems silly to explain one specific aspect seperate from the others. The other odd ascpet of the arrangement is the placing of "evidence" before "nature of" (to provide proof of its existence before explaining what it is). Though dark energy is an odd thing, and I can personally attest that physicists often introduce the evidence for dark matter before suggesting what it is; so maybe this isn't so odd after all. But I don't see a justification for bifurcating the description. Someguy1221 (talk) 06:51, 18 January 2008 (UTC)

im not sure the original intent; but it seems to be that they are trying to seperate the description of the nature of dark energy (the cause of acceleration) with the popular explanations of dark energy (here titled the 'nature of dark energy'). As stated in the section, the nature of dark energy is quite speculative. this is opposed to the nature of dark matter which is a little better understood where we have frameworks like SUSY that predict particles that would behave as the (cold) dark matter observed. other than vacuum fluctuations in the form of a cosmological constant, i think the cosmology community didnt have much in the beginning to explain the nature of dark energy. of course vacuum fluctuations (as we know it) cant be the cosmological constant.

also it seems that first section was meant to clarify confusion for non-specialist on the use of the term "pressure" in cosmology/GR. if thats so, then it should definately be kept the first section IMHO, but maybe rewritten a bit.--Blckavnger (talk) 08:09, 30 January 2008 (UTC)

(1) An article published in Nature should be an excellent V RS, and cited, the only question being how much WP:WEIGHT, which should be determined by grownups cosmology-literate editors. (2) Citation of the creationist websites in New Scientist may make them notable in an article about themselves, but not here. (3) The questions posed about formatting and the pie chart aren't clear to me. --Jim Butler^(talk) 07:18, 19 January 2008 (UTC)

Just to make it clear the creationists websites are not part of the New Scientist articles (the creationist websites both picked up on the same research by a respectable source, however). The question on formatting is on the heading, organization, and paragraphing. Are you satisfied with the current state? I am not. The pie chart is fine. I was stating that it was easier to use the pie chart from this page then to actually find the seemingly randomly place of composition of the universe in the text (showing the lack of organization here).--JEF (talk) 15:41, 19 January 2008 (UTC)

Pie Chart Incorrect

The pie chart legend gives 25% for Dark Matter, but this is not the proportion represented in the chart (or am I missing something?) DavidCh0 (talk) 13:29, 23 January 2008 (UTC)

I get that feeling too. From the look of it, it appears the shaded part for Helium and Free Hydrogen is too small. Somebody at NASA seems to have blown it.--JEF (talk) 16:17, 23 January 2008 (UTC)

Re new gravity model

Looks like this might be worth reading and mentioning in article:

"In a paper in the August 3 online edition of the Institute of Physics' peer-reviewed Journal of Cosmology and Astroparticle Physics, they put forth the idea that scientists were forced to propose the existence of dark energy and dark matter because they were, and still are, working with incorrect gravitational theory.

The group suggests an alternative theory of gravity in which dark energy and dark matter are effects – illusions, in a sense – created by the curvature of spacetime (the bending of space and time caused by extremely massive objects, like galaxies). Their theory does not require the existence of dark energy and dark matter.

“Our proposal implies that the 'correct' theory of gravity may be one based solely on directly observed astronomical data,” said lead author Salvatore Capozziello, a theoretical physicist at the University of Naples, to PhysOrg.com."

Dark Energy and Dark Matter – The Results of Flawed Physics? By Laura Mgrdichian, Copyright 2006 PhysOrg.com Discussion of J. Cosmol. Astropart. Phys. 08 (2006) 001.
http://www.physorg.com/news77190620.html —Preceding unsigned comment added by Writtenonsand (talk • contribs) 21:41, 31 January 2008 (UTC)

-- Writtenonsand (talk) 21:33, 31 January 2008 (UTC)

Already obliquely mentioned in the article. There are a lot of ideas like this floating around. ScienceApologist (talk) 21:35, 31 January 2008 (UTC)

(A) Is it?, and (B) Would there be any point in discussing them in more detail somewhere?

(And obviously, this idea apparently comes from a reputable source, not NutJob@Mom'sBasement.) -- Writtenonsand (talk) 21:45, 31 January 2008 (UTC)

The more prominent idea is a form of modified gravity known as the DGP model. ScienceApologist (talk) 14:41, 1 February 2008 (UTC)

i dont believe there should be any detailed mention just as there shouldnt be too much detailed information of any modified gravities in the dark matter article. While in the dark matter case its more justified, modified gravities have yet to provide satisfactory evidence as a possible explanation of dark energy. i think any detailed explanation of alternative gravity theories should be simply linked from this article to another specific article (such as DGP article). modified gravities will always be explored, but i think its safe to say that the general consesus of a negative pressure (w<-1/3) added to the CDM and "baryonic" matter is the best current (or the best simple solution ((Occam's Razor)) fits all the observational data (Sne IA, CMB, LSS, BAO, weak lensing, etc etc). although i dont think any cosmologist would dare say that dark energy is even closely understood; i do believe that the consesus is dark energy solution is currently better than any alternative gravitation theories. unlike dark matter though, dark energy seems to highly debated for a long time--Blckavnger (talk) 16:29, 6 February 2008 (UTC)

Modifying gravity to account for dark matter is not quite as mainstream as modifying gravity to account for dark energy, I'd say. They're both "out there", but MOND, for example, has been attacked from multiple angles while DGP has received some, but less flack. ScienceApologist (talk) 04:23, 9 February 2008 (UTC)

Dark energy is not an evidence, it's needed to keep alive the Standard model

It's just unfair to claim the existence of Dark energy without strongly stressing that we do not observe it. Simply, as we blindly trust in Standard Model, we must adjust the numbers adding that dark energy. But a much simpler way is that the standard Model is flawed. I think an article on dark energy should start from this dogmatic need. The current dogma needs the dark energy but we have NO OBSERVATION about it. Please consider rewriting the whole article —Preceding unsigned comment added by 83.103.38.68 (talk) 16:58, 27 February 2008 (UTC)

It is inappropriate to suggest a rewrite of the entire article without even signing your name. Besids, saying that dark energy hasn't been observed is untrue; the OBSERVED acceleration of the universe's expansion is almost undeniable, and it is upon this that dark energy is essentially defined. Keep in mind that various different explanations of dark energy are indeed speculative and unconfirmed, but the fact that some sort of repulsive force, negative pressure, cosmological constant, dark energy, whatever you want to call it, MUST exist for current observations to make any sense. There is no dogma in science, only experimental data and theories to explain it. Dogma would be if we found this expansion and still denied dark energy in the face of the evidence.Eebster the Great (talk) 00:24, 2 April 2008 (UTC)

naive absense of criticism

There is very little in this article to warn the reader that this hypothesis may be utterly wrong. All that is needed to explain Perlmutter's results is a bit of grey extinction between us and the supernova — a bit of ionized hydrogen, perhaps, or free electrons, something which, amazingly, Permutter never accounted for. (He only considered molecular hydrogen, which, conveniently, isn't grey.) Extraordinary claims require extraordinary evidence, as the saying goes, and if we're faced with a choice between revoking much of known physics and entertaining the possibility that there might be a bit of plasma in intergalactic space, then it is only responsible to say that this may all have a perfectly mundane explanation. — kwami (talk) 20:56, 30 March 2008 (UTC)

The optical depth due to scattering by free electrons in the IGM is miniscule. On average, only two out of every thousand photons leaving a source at the distance of these supernovae will encounter a free electron's Thomson cross section. The average residuals for the flux decrement with a magnitude difference of averaged at 0.5 (seen here) is approximately 50%. In other words, one out of every two photons would have to be scattered for this explanation to work. ScienceApologist (talk) 21:20, 30 March 2008 (UTC)

What about ionized hydrogen?

"A mean grey extinction of 0.25 mag would be required to explain the measured MLCS distances without a cosmological constant."

"Grey intergalactic extinction could dim the SNe without either telltale reddening or dispersion, if all lines of sight to a given redshift had a similar column density of absorbing [or scattering] material. The component of the intergalactic medium with such uniform coverage corresponds to the gas clouds producing Lyman-α forest absorption at low redshifts. […] these clouds reside in hard radiation environments hostile to the survival of dust grains." [A nice ionizing environment!] (Filippenko & Riess 1998:11–12) — kwami (talk) 21:31, 30 March 2008 (UTC)

In my calculation above, I used ionized hydrogen at an IGM density of 1 per cubic meter. Even with 0.25 mag extinction instead of a 0.5 mag extinction, it would still require 1 out of every 4 photons to be scattered. There just isn't enough atoms in the intergalactic medium. ScienceApologist (talk) 21:39, 30 March 2008 (UTC)

Thanks. — kwami (talk)

You'd also need to explain the flatness measurements of WMAP and other structure probes, which aren't affected by grey extinction. Dragons flight (talk) 21:53, 30 March 2008 (UTC)

Yes, but the flatness problem doesn't imply that the expansion is accelerating, and so isn't as revolutionary. — kwami (talk) 22:05, 30 March 2008 (UTC)

In some sense, Kwamikagami is right. Cosmic subtraction (as dubbed by Rocky Kolb) is the only independent evidence of omega_lambda from the CMB. Well, not the only one: you might get a handle on it by getting a good measure of the distance to the surface of last scattering, or taking into account some SZ polarization. But, on the whole, it's the assumption (measurement?) of flat WITH the omega_m=0.3 measurement that demands omega_l=0.7. ScienceApologist (talk) 15:24, 31 March 2008 (UTC)

Misleadingly factual style

Dark energy is hypothetical at best, conjectural at fairest, and downright fictional at worst. Could someone please reword the article so that the impression is not so strongly given that this article deals with a real, observable phenomena of the universe, rather than the product of human imagination which might at some point in the future be considered physical. Thank you, A. Realist 85.194.245.82 (talk) 21:09, 4 April 2008 (UTC)

It says right in the first sentence that it is hypothetical. That seems pretty clear to me. Dlabtot (talk) 03:08, 6 April 2008 (UTC)

There is no dark energy. It is an illusion caused by either, or both, a slowing rate of expansion, or an accelerating rate of collapse. See "ACCELERATING UNIVERSE", discussion page.78.149.211.167 (talk) 19:20, 14 April 2008 (UTC)

Suggestion

I can't even find my earlier comments even in the archived talk. This is indicative of a sick article in the sense of the health of the wiki process (i.e. people trying to "forge" the discussion). I would suggest that everybody who is a professional physicist or has other similar credentials identify themselves as such either here or on their home pages. Obviously I would be in favor of protecting this article from anonymous/IP edits. Lycurgus (talk) 11:36, 13 April 2008 (UTC)

Alternative to Dark Energy

I want to contribute a possible scenario that does not require dark energy. It goes as follows: Just before the Big Bang, spacetime is infinitely curved, with close to infinite spin and gravity. After symmetry is broken, spacetime uncurves according to inflation theory and general relativity. Rapid expansion causes immense torque which brings spin to a near halt. The gradual uncurving of spacetime reduces gravity, acting like a cosmological constant. The uncurving should be noticeable as a slight lateral movement of galactic clusters. Eventually, spacetime should become ‘straightened out’ leaving no gravity, and galaxies should fall away – like pearls from a broken string. I posit, however, that spacetime will not ‘snap’ into a straight line and remain that way, but flip from ‘positive’ to ‘negative’ curvature, thus reversing expansion, as a result of spacetime’s elastic rebound of spin and torque, with reversion of direction – towards the next ultimate ‘reset.’ --Robert van der Hoff (talk) 02:03, 17 April 2008 (UTC)

Has your possible scenario ever been published in a reliable source? We don't include original ideas in articles. Someguy1221 (talk) 02:41, 17 April 2008 (UTC)

No, it hasn't, but I don't expect inclusion in the article, but only hope for some response. I apologize if I'm in the wrong place for that.--Robert van der Hoff (talk) 09:31, 17 April 2008 (UTC)

You can ask at the science reference desk. Someguy1221 (talk) 18:07, 17 April 2008 (UTC)

Thank you--Robert van der Hoff (talk) 23:42, 17 April 2008 (UTC)

Modification Proposals

This is my proposal about how to improve the "negative pressure" paragraph - I have a degree in Physics, with specialization in General Relativity, but I am new to Wikipedia so I am open to constructive criticism, including the ones related to Wikipedia rules and guidelines. Cosmos72 (talk) 21:42, 16 June 2008 (UTC)

---

In order to explain the observed acceleration in the expansion rate of the universe, dark energy would need to have a strong negative pressure.

According to General Relativity, the pressure within a substance contributes to its gravitational attraction for other things just as its mass density does. This happens because the phisical quantity that causes matter to generate gravitational effects is the Stress-energy tensor, which contains both the energy (or matter) density of a substance and its pressure and viscosity.

In the Friedmann-Lemaître-Robertson-Walker metric, it can be shown that a constant negative pressure in all the universe causes an acceleration in universe expansion if the universe is already expanding, or a deceleration in universe contraction if the universe is already contracting.

This last effect is sometimes described as "gravitational repulsion", which is probably confusing if not misleading. Infact a negative pressure does not influence the gravitational interaction between masses - which remains attractive - but "only" alters the overall evolution of the universe at the cosmological scale, typically resulting in the accelerating expansion of the universe despite the attraction among the masses present in the universe. Cosmos72 (talk) 21:42, 16 June 2008 (UTC)

---

Since I received no feedback, I have tentatively replaced the old "negative pressure" paragraph with my proposal. I also moved it inside the "Nature of Dark Energy" section, as it seemed a more appropriate place - negative pressure is a strangeness of Dark Energy, but I do not consider it so important to be at the very beginning of the article. Cosmos72 (talk) 12:47, 25 June 2008 (UTC)

Pls explain - article seems to contradict itself

Obviously I'm nor understanding things correctly, but it seems to me:

1) (+'ve) pressure causes things to expand. If dark energy has a negative pressure, shouldn't that cause universe to contract?!?! Or to slow the expansion until it stops and then contracts.

2) If dark energy is a constant per unit volume of space, then as universe expands the volume of space increases, so amount of dark energy increases. That energy has to come from somewhere.

I don't think there would be much conversion of mass->energy going on at the outer limits of the universe...

So at the edges of the universe surely further expansion (and creation of dark energy) will have to detract from kinetic energy, ie the speed of expansion will slow, or and/or temperature/pressure will drop even more than one would expect due to Boyles law, with the extra energy lost being converted to this dark energy.

So that seems to contradict what this article is saying... ie that dark energy causes accelerated expansion.

I mean, this dark energy concept means it costs more energy to create space. Theres not just the energy in the gravitational and other fields, now theres more dark energy we have to supply in order to create space. So if it costs more energy to create space, then I don't see how this is going to cause accelerated expansion... surely its going to slow expansion...

The only convoluted reasoning I can come to in which dark energy could cause accelerated expansion is:

3) If the universe is expanding in its internal areas, like the way the surface of a balloon expands while its being blown up, then some of the dark energy for the new space could come from kinetic energy, and some could be from mass->energy conversion. So this could be causing some expansion of the universe. But surely it would be a gradually decreasing rate of expansion, as time goes on there is going to be less and mass available to be converted to dark energy.

4) Energy and mass are equivalent so the dark energy will still exert gravitational force, so its not like gravity is being weakened as mass is converted to dark energy. So there wont be any decrease in gravity, so that can't explain any acceleration of the expansion.

5) Unless gravity sort of prevents or works against the conversion of mass->dark energy/space, ie in earlier universe, mass was more evenly spread out, so mass of universe wasnt concentrated in such high-density areas like stars/galaxies, so maybe there was more conversion of mass->dark energy/space.

6) Then, as mass in the universe became concentrated in clouds/planets/stars/black holes/galaxies, ie areas with higher density, the rate of mass->dark energy conversion slowed in those regions.

7) Except for things like in a supernova, where the mass of the star is suddenly blasted over large area and density suddenly decreases, maybe rate of conversion of mass->dark energy/space will increase those areas.

8) And in general, now the universe has evolved to a point where most matter has condensed into stars which are burning their mass off by radiating energy away into space, the density of these galaxies is decreasing. So maybe that is causing rate of conversion of mass->dark energy to increase. Which creates space which lowers density which increases rate more.

9) So that would mean the universe has gone through early period of expansion, then galaxies start to coagulate and rate of expansion/dark energy conversion slows, then suns form and light up and start radiating mass away so rate of conversion of mass->dark energy can increase again.

Is any of that nonsense sort of in the right direction or have I completely misunderstood? IbleSnover (talk) 01:28, 6 July 2008 (UTC)