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Much of this article has been adapted from a press release at http://hubblesite.org/newscenter/newsdesk/archive/releases/2004/12/text/
This appears to be OK from a copyright point of view, as the press release appears to be in the public domain, but we should a) give credit to the source, b) rewrite in a style suited to an encyclopedia article. -- The Anome 18:27, 22 Feb 2004 (UTC)
Someone added the following content which reads very poorly, and seems POV, but may be possible to work in more coherently. -- zandperl 01:41, 18 Mar 2004 (UTC)
Einstein’s version of the cosmological constant (which I will refer to as Λ) is extremely flawed, however. The Λ dark energy is said by him to form a balance with gravity creating a static or flat universe (model of the universe where there is a set limit to the size of the universe). However, if the universe even slightly expanded somehow, energy is released causing more expansion throwing off the balance. The same is true for contraction. Because of these circumstances Einstein said that his formulation of the Λ was “the biggest blunder” of his life. However, many physicists say it could be the greatest legacy of his life despite these problems. Quintessence is simply another theory on the mechanics of dark matter. There is much less information about this simply because it is a variable to the Λ where the dark energy will push the universe further and further out into the void for infinity. Thus, there may never be a new universe caused by a Big Crunch and then Big Bang in succession. is a hypothetical form of energy which permeates all of space and has negative pressure resulting in an effective "repulsive gravitational force". Dark energy may account for the accelerating universe as well as a significant portion of the mass in the universe. Two proposed forms of dark energy are the cosmological constant and quintessence, where the former is static and the latter is dynamic. Distinguishing between the two requires high precision measurements of the expansion of the universe to see how the speed of the expansion changes over time. Making such measurements is a topic of current research.
[some older stuff and some retorical questions are sent to history pages; questions that might be real are responded to below]
What on earth do you mean with "real" energy? How is the energy contained in the zero-point fluctuations of quantum fields different from "real" energy, in your opinion? Bjoern 15:49, 3 Dec 2004 (UTC)
Besides, you only allowed creation of energy from nothing in gravitation, not in particle physics.
Explaining every unexplained phenomenon (like e.g. dark energy) with another unexplained phenomenon (like e.g. creation of energy from nothing) won't explain much, will it?
Why couldn't the density of matter be smaller than the density of the vacuum energy??? Bjoern 15:49, 3 Dec 2004 (UTC)
Those measurment are not direct measurements of dark energy but (correct me if I'm wrong) only conclusions drawn from an assumption that dark energy causes accelerating expansion, by some so far unknown mechanism.
If you happen to know a physical mechanism of this effect please provide.
So far you proposed cosmological constant which is only a mathematical term
which purpose has been originally to prevent Einstein equation from predicting expansion of the universe.
There is also possible another assumption, namely that expansion (accelerating or otherwise) is an illusion and so what would be the dark energy according to this other assumption if it were true? Jim
Don't you remember that Einstein was wrong the first time about the deflection of light by half and had to correct his ideas after Edington's expedition proved him wrong (or I was mislead by some historian of science)? And that this was when he discoverd the curvature of space after he proposed gravitational time dilation, by which he explained all the Newtonian gravitation?
There are several errors in your derivation. For starters, you might consider that it would apply to *any* acceleration, not just acceleration by gravity. Hence your calculation would show that a body does not gain energy when it is accelerated. Don't you think that that is a somehow weird result?
For a more direct error, you assert that half of the bending of the light comes from time dilation and the other half from the curvature of space. Where on earth did you get that strange idea from? You also mentioned that in some other places, and attributed this to Einstein himself. I would like you to give a reference where he says that (please not a popular science quote, but an actual calculation!)
And even more important is the error which I have explained several times now, but which you still fail to understand: The change in the mass is measured in the system of the *non-accelerated* observer. The change in the speed of light is measured in the system of the *accelerated* object. It simply makes no sense to use the changes of m and c in two different systems of reference in order to calculate the change in the energy of the object!!!
Also I notice that you keep ignoring my actual arguments, namely (1) the geodesic equation implies that something can be accelerated without a force acting on it,
i.e. its kinetic energy can increases without a force acting on it,
i.e. energy is not conserved,
... and (2) the energy of a falling body can actually be measured (i.e. by letting it fall on a spring), and the actual measurement shows that its energy indeed *does* increase. Bjoern 15:12, 6 Dec 2004 (UTC)
What on earth has a change in the speed of light to do with light deflection at the sun? Bjoern 15:12, 6 Dec 2004 (UTC)
The modern view in General Relativity is that light speed indeed does not change in gravitational fields - as measured by free-falling observers. It *does* change for observers who are *not* free-falling -
but we were discussing an object which *is* free-falling, if you did not notice. Bjoern 15:12, 6 Dec 2004 (UTC)
(2) People who are far more knowledgeable in GR than both you and I also disagree with you. Bjoern 15:12, 6 Dec 2004 (UTC)
[Einstein] would tell you that you have some strong misunderstandings about his theory. Have you ever read his paper on the application of Hamilton's principle in GR?
If [Einstein] had nothing better to do he could predict Hubble redshift and explain it before it was discovered. Even Newton could predict it and explain it if he knew as much as any high school student in 20th century (as truly yours) knew. So if Einstein imagined gravitational energy it means only that he didn't have enough interest in gravitation to spend enough time on it to fix his ideas.
But we have our own brains to think and don't need to stick to wrong ideas when we see that they are wrong. BTW, did Einstein explain conservation of energy in GR or he supported your idea that it is not conserved? Could you produce any quotes from Einstein's texts to demonstrate that he thought that energy is not conserved in GR? Jim 09:58, 1 Nov 2004 (UTC)
... apparently you forgot that Newtonian gravitation was only replaced when (1) evidence accumulated that it could not explain and (2) a new theory was proposed which could not only explain this new evidence, but also all the old stuff which Newtonian gravitation already was able to explain. So far, you have neither of those two points. Bjoern 15:12, 6 Dec 2004 (UTC)
You have a rather convoluted view of science, I see. Obviously you would *like* science to be that way (because then you would have a better point for your apparent argument that scientists are simply to close-minded and senile to accept your ideas) - but this simply is not true in general. One central point you are missing is e.g. that usually when a new theory comes along, it *incorporates* the old one - the old one is still right as a limiting case of the new one. So your claim that the new people do not even know "the old crap" is simply nonsense. Best counterexample: Newtonian gravitation was replaced by GR, but nevertheless Newtonian gravitation is still taught and used in most applications - simply because it is a useful approximation to GR. I have pointed out this several times now - you keep ignoring this point. Bjoern 15:12, 6 Dec 2004 (UTC)
The big bang theory didn't manage yet to produce a single prediction that agreed with observations (source: Hawking, 2000, calling for turning BBT into science from pseudoscience, by measuring e.g. deceleration of expansion). Jim
Bjoern: Reasons why we should think the universe is expanding (or, more precisely, why the current cosmological model is correct):
1) Nicely explains the observed redshift relation (as long as your model does not explain it, please don't answer this with "but a static universe could also explain this!")
2) Nicely explains the observed Cosmic Microwave Background Radiation. Not only its existence, but also its homogenity, the scale and gaussianity of the fluctuations observed in it (ever heard the terms "power spectrum" and "acoustic peak"?), and that it changes its temperature with time.
3) Nicely explains the observed abundance of light elements, and that there are less of them if we look at distant galaxies.
4) Nicely explains where the large-scale structure we observe in the universe comes from. (quantitively)
5) Nicely explains why there seems to be an upper limit on the age of stars.
6) Nicely explains why galaxies far away are in general much smaller and less "developed" than the ones we see in our neighbourhood.
More? Bjoern 13:36, 8 Oct 2004 (UTC)
BTW, don't you think that *before* trying to construct an alternative cosmological model, one should first try to find out *why* the *current* cosmological model is accepted by most cosmologists?
Additionally, weren't at least *some* of the things I mentioned here also mentioned in at least some of all the books you've claimed to have read about GR and cosmology? E.g. Peebles (IIRC you said that you have read his book?) mentions several of these arguments, and adds yet another argument about the surface brightness of galaxies. 129.206.21.125 11:51, 9 Oct 2004 (UTC)
So what to do about it? Educate Peebles on gravitation? Do you think it would work before I get my PhD in astrophysics? Jim 20:02, 26 Oct 2004 (UTC)
How can you be soooo sure that there is indeed such an alternative explanation?
Do you *really* think you are brighter, more creative or whatever than several generations of cosmologists, who have not managed to find such an explanation? Bjoern 15:04, 3 Dec 2004 (UTC)
Oh, BTW, you can add as a seventh point the dependence of the surface brightness of galaxies on the redshift. Bjoern 12:04, 11 Oct 2004 (UTC)
A good reason seems to be a fact that the hypothesis of expansion of space violates the principle of conservation of energy. The assumption of conservation of energy explains (through Einsteinian gravitation) only the illusion of expansion of the universe
and its acceleration and there is still a number of other phenomena waiting to be explained, yet it seems easier to explain all those other phenomena than to explain the required by the
Big bang theory the mechanism of creation of energy from nothing every time the light travels through the universe. Creating energy in the light traveling through the universe is needed in Big bang theory at least to compensate for the energy lost to
dynamical friction of photons that otherwise would decrease the real value of speed of expansion to about zero.
Jim 19:35, 31 Oct 2004 (UTC)
All the equations present on this page must be appropriately wikified.... having them in text is unreadable and not acceptable.17:02, 23 Feb 2005 (UTC)~~
I agree. I have moved the new content here. It is not clearly written, too technical and is more a discussion of the cosmological constant, or vacuum fluctuation problem than of dark energy.
[That shows how much you know. The point is that the dark energy is vacuum fluctuation energy of negative pressure.]
The material at the beginning is basically correct, but the two paragraphs at the end get a bit weird. -- Joke137 18:08, 23 Feb 2005 (UTC)
The unwikified text was restored by 68.122.6.198. I have removed it. It may be a copyright violation -- it looks like it was lifted directly from a paper, and it certainly has no place in its current form. -- Joke137 20:34, 23 Feb 2005 (UTC)
[NO IT'S NOT A COPYRIGHT VIOLATION AT ALL. IT'S ORIGINAL MATERIAL by a Ph.D. (UC) physicist. However, I now see how to make the equations properly, but that will take a lot of work. Getting the new ideas out there is more important than having equations Wikified, although that will be done in due course.]
Fine, but the wikipedia is no place for original ideas.
You still did not give me a direct answer to my question. Are you part of the official Wikepedia or are you just an outsider? In the case of "dark energy" everything is speculative at this point. So if one sticks to rigid "no original ideas" not only does that make the Wikepedia boring and irrelevant but there should be no mention of dark energy at all. Clearly not a good position. Now I have already made a preliminary cash contribution to Wikepedia and I could cover the $75,000 but not if the staff of Wikepedia exercises repressive censorship like you have been doing. Capische?
Put them up on arXiv. The article on dark energy is meant to be a reasonably succinct overview of dark energy, not a place to communicate original, technical ideas. I won't rise to the "that shows how much you know" bait, except to say that there is already an article on the cosmological constant which is a more appropriate framework that this for explaining such ideas, rather than the general dark energy overview. By the way, wikipeda allows you to insert equations in TeX format: see the help pages. -- Joke137 20:55, 23 Feb 2005 (UTC)
"In cosmology, dark energy is a hypothetical form of energy which permeates all of space and has negative pressure. According to general relativity, the effect of such a negative pressure is qualitatively similar to having a force acting a large scales that works in opposition to gravity. Invoking such an effect is currently the most popular method for explaining the apparent observations of an accelerating universe as well as accounting for a significant portion of the missing mass in the universe." Wikepedia
The reason that negative pressure, if strong enough, causes a universal repulsive anti-gravity field is as follows. Einstein's field equation is
Guv = -(8piG/c^4)Tuv
Guv is the Einstein curvature tensor here has dimensions of (Area)^-1
Tuv is the stress-energy density tensor here has dimensions of Energy/Volume
The coupling coefficient (8piG/c^4) of the source Tuv to the 4D warped space-time geometry Guv has dimensions (Length/Energy) = (String Tension)^-1
To show the basic idea we consider the Galilean-Newtonian limit of Einstein's field equation where the curvature is weak and the speeds v of matter particles in Tuv obey v/c << 1. If we, further assume that Tuv is an isotropic fluid as is done in the standard cosmological FLRW model
TraceGuv = (8piG/c^4)TraceTuv = -(8piG/c^4)[T00 + T11 + T22 + T33] = (8piG/c^4)T00(1 + 3w)
T00 = energy density, T11 = T22 = T33 = isotropic pressure of the "fluid" medium warping the space-time geometry.
In Chapter 1 of John Peacock's "Cosmological Physics" one finds, in the Galilean-Newtonian limit
TraceGuv ~ c^-2 Laplacian (Grad^2) of the gravitational potential energy V per unit test particle at event P created by the source density Tuv at the same event P.
This is essentially the same as the Poisson equation of Newton's gravity theory with the additional Einstein correction of (1 + 3w) where w = (Pressure/Energy Density) of the source.
See Michael Turner's Op/Ed in Physics Today April 2003 for more details on this.
Ordinary cold matter (real on-mass-shell particles) has w ~ 0, which is precisely the assumed source in Newton's gravity theory!
Real photons, i.e. transverse polarized radiation has w = + 1/3. Therefore, (1 + 3w) = 2 for light. This is indeed the origin of the famous factor of 2 in the gravitational lens effect first found by Sir Arthur Eddington's expedition in 1919 that made Einstein a Super Star. Eddington's measurements were rough but recent measurements with new technology show that Einstein's theory is really correct, that factor of 2 for radiation is really there.
Now here comes the weird quantum stuff. It can be shown from Lorentz invariance of quantum field theory and Einstein's equivalence principle (EEP) that gravity and inertial forces in local non-inertial frames (LNIF) are indistinguishable, that the Heisenberg uncertainty "zero point energy" vacuum fluctuations for all fields obey w = -1. This is done in Peacock's book p. 26 and in Michael Turner's Op/Ed. Look again now at the "Poisson equation"
Grad^2V ~ -(8piG/c^2)T00(1 + 3w)
When w = 0 and the energy density is positive T00 > 0, we have Newtonian gravity with a universal attractive field.
Note the critical threshold w = -1/3 where (1 + 3w) = 0. Any source where -1 < w < -1/3 is called exotic matter because when T00 > 0 it causes a repulsive anti-gravity field. Kip Thorne and his students at Cal Tech showed that exotic matter would enable "traversable wormholes" (AKA "Star Gates') and perhaps permit time travel to the past. Kip debates this with Stephen Hawking and that is another story about the "chronology protection conjecture". Alcubierre showed that this same exotic matter permits faster-than-light weightless/geodesic warp drive without time dilation. The warp is globally faster than light, like in the inflation of the universe, although the "flying saucer" :-) is locally slower than light on a free float timelike geodesic inside its local invariant light cone. What is happening is that the space in front of the ship contracts whilst the space behind the ship expands. The Star Ship in Warp is literally surfing on this Vacuum Tsunami!
Now look at the zero point energy where w = -1. Zero point energy qualifies as "exotic matter"! The problem is that there is too much of it. That leads to the cosmological constant problem that naive quantum field theory predicts ~ 122 Powers of Ten (actual observed dark energy density). This is the greatest catastrophe in physics today. Not only that, but it is easily shown (Peter Milonni's "The Quantum Vacuum" that random incoherent virtual photons inside the vacuum have T00 > 0 with negative pressure causing repulsive anti-gravity exactly like "dark energy" (DE). However, random incoherent virtual electron-positron pair neutral ionized plasma inside the vacuum have T00 < 0 with positive pressure causing attractive gravity exactly like "dark matter" (DM). Wait a minute? Dark matter has w = 0, i.e. CDM. Jack Sarfatti has shown that compact sources of exotic vacuum with T00 < 0 and w = -1 look like w = 0 CDM at a distance in terms of the gravity lensing! Sarfatti also predicts that there are no neutralinos nor any other exotic real on-mass-shell particles that will make dark matter detectors "click with the right stuff" to explain Omega(DM) ~ 0.23. Note that Omega(DE) ~ 0.73 and total Omega ~ 1 consistent with the flat 3D space on large-scale of inflation theory. Sarfatti shows that cohering of the virtual electron-positron zero point false vacuum fluctuations causes inflation and creates the universe in the Big Bang along with Einstein's gravity and dark energy coming out of the phase and amplitude of the Higgs field respectively. Sarfatti has published these ideas in "Developments in Quantum Physics" ed. F. Columbus & V. Krasnoholovets (Nova Scientific Publishers, 2004 ISBN 1-5954-003-9) "Wheeler's World: It From Bit". He also discusses it in popular media in the two books "Destiny Matrix" and "Space-Time and Beyond II" both on Amazon, and in Paramount Pictures Star Trek IV DVD Special Collector's Edition Disk 2 "Time Travel: The Art of the Possible."
Subject: Sakharov, Russian Torsion Field Theory, Cartan's Forms & Metric Engineering W^3
Memorandum For The Record
The complete solution to Sakharov's "Metric Elasticity" 1967 problem for the emergence of gravity from zero point energy is given below. The competing program of Haisch, Puthoff and Rueda does not work as advertised by Eric Davis, Nick Cook, STAIF et-al.
"Einstein-Cartan theory extends general relativity to correctly handle spin angular momentum. There is a qualitative theoretical proof showing that general relativity must be extended to Einstein-Cartan theory when matter with spin is present. Experimental effects are too small to be observed at the present time." Wikepedia
That experimental effects of torsion fields are too small to be detected is controversial. Richard Hammond of the Department of Physics at the University in Fargo, North Dakota, US, then working on a US Navy contract, reported torsion radiation that is forbidden in some versions of torsion theory. Torsion radiation has also been reported by Akimov in Moscow based on a very controversial theory by Gennady Shipov. Akimov and Shipov have been harshly attacked by their Russian colleagues. However, it's much too soon to rush to premature judgment on the reality of torsion fields although the extraordinary claims by Akimov are suspect and cannot be taken on face value.
All the dynamical force fields of physics come from the principle of local gauge invariance. Start with a global symmetry group G of the action S of some dynamical system. Let L be a member of the Lie algebra generating G. The local action density is &S/&V^4. The unitary operator for a symmetry transformation is of the form U(L) = e^iL@/h, where @ is a global phase (constant over space-time region V4). Invariance of the dynamical action under the global symmetry is expressed by &S/&V^4 = U(L)^-1&S/&V^4U(L). The principle of local gauge invariance means allowing the phase @ to be an arbitrary function over space-time. The ordinary partial derivatives ,u need to be replaced by a gauge-covariant partial derivative ;u = ,u - Bu where Bu is the compensating gauge potential that is a new independent dynamical "force" field that restores the dynamically broken global symmetry to the extended action S' that now includes Bu. For example, if G = U(1) and the original source field is the Dirac field of the electron, then Bu -> Au the well-known "4-vector potential" of Maxwell's EM field theory. In terms of Cartan forms, the EM Maxwell field equations are simply F = dA, where d = exterior derivative, d^2 = 0, therefore, dF = 0 contains both Faraday's law of induction and no magnetic monopoles. Taking the Hodge-dual *F of F = "curvature", gives d*F = J which contains both Ampere's law and Gauss's law. The first equation dF = 0 is topological independent of arbitrary metrics. The second equation with the * operation is metric-dependent. The metric is a kind of covariant "aether" combining the Lorentz-Fitzgerald substratum dynamical hidden-variable model for the emergence of the Lorentz group O(1,3) with Einstein's phenomenological geometrodynamics. See also G.E. Volovik's book "The Universe in a Helium Drop" for details on the use of the renormalization group flow to a fixed point for the emergence of O(1,3) from a Galilean relativity substratum where Bohm's quantum potential acts instantly. The gauge force picture with Bu is dual to the geometrodynamic "Force-without-force" picture developed by John Archibald Wheeler. You can switch between them like going back and forth between the Schrodinger and Heisenberg pictures in quantum field theory. When G = U(1)xSU(2)xSU(3) on the parity-violating Dirac lepto-quarks we get the standard model of elementary particles in globally flat space-time without gravity prior to the Higgs-Goldstone spontaneous breaking of symmetry (SBS) for the SU(2) weak sector of the physical vacuum that allegedly should generate all the rest masses m of the lepto-quarks and weak bosons. See for example, "In search of symmetry lost" Frank Wilczek (Nobel Physics Prize 2004), NATURE, 433, 20 Jan. 2005. The model for the origin of rest inertia from friction in the sea of virtual transverse photons suggested by Haisch, Puthoff and Rueda has been rejected by experts as too simple and "not-even-wrong" in Wolfgang Pauli's sense (e.g. Space-Time and Beyond II by Jack Sarfatti, Author House (2002))
Einstein's 1916 General Relativity (GR) comes from locally gauging T4 the translation subgroup of the Poincare symmetry group of Einstein's 1905 Special Relativity (SR). The early version of this theory is in "Wheeler's World: It From Bit?" pp. 41-84, "Developments in Quantum Physics", F. Columbus, V. Krsnoholovets ed., Nova Science Publishers, 2004 ISBN 1-59454-003-9.
The compensating gauge potential Bu from locally gauging T4 is
Bu = (Goldstone Macro-Quantum World Hologram Coherent Phase of the SBS "multi-layered multi-colored" (Wilczek) Higgs Field),u = bu^aPa/h
{Pa} = mom-energy Lie algebra of T4 in tangent space indices a = 0,1,2,3,4
h = Planck's quantum of action
The local gauge transformations on Bu -> local GCT tensor Diff(4) transformations of Einstein's geometrodynamics.
bu^a is the non-trivial nonholonomic piece of the Einstein-Cartan tetrad eu^a, where u indices are in the warped base space of the tangent bundle of Einstein's GR.
eu^a = &u^a + bu^a
&u^a = trivial Kronecker delta holonomic tetrads of 1905 SR where the tangent space is degenerate with the base space. Local gauging of T4 removes the degenerary replacing global inertial frames (GIF) with local frames, both inertial non-rotating timelike Levi-Civita connection geodesic (LIF) and non-inertial off-geodesic (LNIF). Einstein's curved metric guv is only for the LNIF where the local equivalence principle (EEP) is
guv(LNIF) = eu^anab(LIF)eu^b
Note the linear elastic terms ~ bu^a&v^b and the nonlinear quadratic "plastic" (Hagen Kleinert) terms ~ bu^abv^b in the EEP. The latter are the spontaneous self-organizing couplings allowing the Wheeler geons of "Mass without mass" solutions of the non-exotic vacuum equation for the Ricci tensor
Ruv = 0
The Ricci rotation coefficients Au^b^c needed for the Riemann tidal stretch-squeeze curvature and for the dynamics of Dirac spinors on curved space-time are
Au^b^c = eu^aAa^b^c
Where, in 1916 GR without torsion fields, the Aa^b^c are constant global phases conjugate to Sbc the space-space rotation and space-time rotation (rapidity) boost Lie algebra of O(1,3) the local Lorentz group in the tangent vector fiber space. If we locally gauge O(1,3) as Gennady Shipov does and as Kibble and Utiyama did in the 1960's, then Aa^bc are arbitrary functions, the torsion field is then
Tu = eu^aAa^b^cSbc/h
The extended covariant derivative is then
Du = ;u - Tu = ,u - Bu - Tu
we then expect Einstein-Cartan field equations of the same Cartan form as Maxwell theory, ie.
R = DB
DR = D^2B = 0
Bianchi identities for local conservation of both curvature and torsion current densities (the key to practical metric engineering the fabric of space-time using the generalized Bohm-Aharonov-Josephson-Berry effect from the weak link/\ZPF ~ cosine(phase difference) between a real macro-quantum control system and the virtual physical macro-quantum coherent vacuum.
D*B = J
i.e., generalized Einstein field equations with both translational curvature and rotational torsion sources from exotic vacuum virtual (off-mass-shell) dark energy/matter sources as well as real (on-mass-shell) sources like rotating superconductors (e.g. Podkletnov/Ning Li - both highly controversial like Akimov's claims. See Marc Millis NASA BPP and STAIF Exotic Propulsion Proceedings of AIP).
D^2*B = DJ = 0
mutual transfer of source current densities to curvature and torsion current densities with total local conservation.
D = Dudx^u
B = Budx^u
John Archibald Wheeler calls these kinds of dynamics "The boundary of a boundary is zero."
R = DB is a boundary, but D*B is not a boundary.
Thanks to R. Kiehn for explaining Cartan's forms and to Art Wagner for telling me about an interesting paper from Brazil from Arcos and Pereira (gr-qc0501017).
end of removed stuff -- Pjacobi 00:52, 2005 Feb 24 (UTC)