So the press conference is over. I did not listen to it, but the gist of it, from the press release, seems to be that they’ve observed several more supernovae to pin down even more accurately what the universe’s expansion rate was at very early times (up to nine or ten billion years ago). Image below from their site:
From the site, we learn (for background):
Astronomers used the supernovae to measure the expansion rate of the universe and determine how the expansion rate is affected by the repulsive push of dark energy, a mysterious energy force that pervades space. Supernovae provide reliable measurements because their intrinsic brightness is well understood. They are therefore reliable distance markers, allowing astronomers to determine how far away they are from Earth.
From the press release (what came before):
Previous Hubble observations of the most distant supernovae known revealed that the early universe was dominated by matter whose gravity was slowing down the universe’s expansion rate, like a ball rolling up a slight incline. The observations also confirmed that the expansion rate of the cosmos began speeding up about five to six billion years ago. That is when astronomers believe that dark energy’s repulsive force overtook gravity’s attractive grip.
The new crop of supernovae tell us about quite a bit earlier…. nine or ten billion years…. From looking at them, they find evidence that Dark Energy was playing a role at that time too, still a repulsive component to the story, which is certainly good to know.
These Hubble observations show for the first time that dark energy has been a present force for most of the universe’s history. A spectral analysis also shows that the supernovae used to measure the universe’s expansion rate today look remarkably similar to those that exploded nine billion years ago and are just now seen by Hubble.
These latest results are based on an analysis of the 24 most distant known supernovae, most of them discovered within the last three years by the Higher-z SN Search Team. The images were taken between 2003 and 2005 with Hubble’s Advanced Camera for Surveys.
This does not yet tell us what Dark Energy is, I should stress. It could well be the repulsive force given by a simple cosmological constant (energy density of the vacuum), or it could still be due to a dynamical field, as in a quintessence model. I suppose that this new data set serves the purpose of ruling out some dynamical models, but I’d imagine that it leaves a wide class of dynamical models as still candidates.
All very interesting and valuable for ongoing research -the nature of Dark Energy is one of the biggest mysteries about our universe, after all- although I must say that I’m not really clear on the wisdom of NASA announcing things in this way. It is not quite “the boy who cried wolf”, since there was a wolf, but it’s a bit of a tame wolf really, and one we knew about already using the same wolf-identifying scenarios (i.e. this is not like the Bullet Cluster Dark Matter annoncement, which I think was indeed worth a bit of media excitement). We have to be careful about these things… what sort of press release would they orchestrate when there is something truly huge to announce?
-cvj
[Update: The detailed report on the research upon which the press conference was based is now out. You can find it here.]
In fact, we were talking to Louise, and asked the specific questions of her already. You jumped in with your business about being able compute blah blah blah with twistors and the like. The specific questions about Louise’s equation were asked already.
Thanks,
-cvj
Clifford
If you ask a specific and careful question, I will do my best to answer it. Otherwise, you may read any of the miles of stuff I have written on this topic on my blog and elsewhere.
Cheers
But c change is inconsistent with physics that we already know, and has no foundation in a coherent theoretical development that you have presented so far. We’d like to understand the foundations, rather than playing with what seems to be a fairly arbitrary formula, that’s all. If you have no foundation as yet, that’s fine, but I hope you agree that this means that there is work to be done. So claiming that all of cosmology is wrong and is a major setback for physics (as you seem to be going around and doing on several blogs) seems a bit premature, don’t you think?
Cheers,
-cvj
I’ve put some of the basic physics under “The Paper” post. I’m not claiming to leap tall buildings in a bound (Should I? Read some claims of the string theorists!) but c change does solve problems of current cosmology.
Kea: –
In carrying out a discussion about physics, continued random claims that you can leap tall buildings in a single bound don’t help your case at all. It just makes you sound rather nutty. You wouldn’t want that now, would you?
How about addressing the physics question? I refer you to my advice above, linked here. If you can’t address it yet, since you’re still working on the answer… that’s ok! You’re not obliged to say anything if you’ve not got an answer yet. Silence on the issue is just fine. And, there’s no need to get aggressive when someone politely asks a question, ok?
Best,
-cvj
Since when did String theorists want a CC anyway?
Clifford
It is not expected that everybody will be convinced that such a cosmology is worth investigating until it is derived from a full unified theory. We might be closer to that than you think. For example, the lepton masses were derived by Brannen in a formulation that is fitting into our picture for M-theory. Do you know why MHV techniques work? Well, we do. I can derive the gluon amplitudes from Machian first principles, for which twistor space is always prior to a Minkowski type interpretation.
Sorry, what estimate? I made no estimate. I don’t put time limits on ideas. You have me mixed up with someone else, I think.
Cheers.
-cvj
Still waiting to hear what the underlying physics is.
-cvj
I hope that my responses helped answer all your questions. GM=tc^3 is the result of 15 years work, during which other solutions were considered. By Clifford’s estimate, we may have just 5 years to go! Since Relativity survived about 100 years, 15-20 years is a very reasonable time to come up with an improvement.
Lab Lem, it turns out that permeability \mu_0 increases as t^{2/3}. Magnetic fields grow at the same rate as the Universe.
Pingback: The Paper - Asymptotia
Hi Clifford,
Thanks for your comment 34 – I’ve a discussion of alleged evidence why G ~ t at http://feynman137.tripod.com
Regarding the detailed advice about the burden of proof you give in comment 38, I’m very appreciative for that.
I do agree with you that when someone gets a complete explanation of everything which is very convincing, they will likely be taken seriously. The problem with this argument is that it’s very hard indeed to get any ideas that are original or that can’t be ruled out almost instantly. So most steps forward can be viewed as steps backward by critics (Copernicus in 1500 AD reinventing Aristarchus’s solar system of 250 BC, as an example).
There’s no guarantee that someone who happens to stumble on a useful idea and build on it, will be super-duper intelligent. Just briefly, Feynman’s Character of Physical Law has some very nice passages. He has a diagram of LeSage’s push gravity mechanism, shows that it accounts for the inverse law, but dismisses it because any gauge boson radiation would slow the planets down and make them spiral into the sun!
This reminds you of the objection Rutherford used against Bohr’s atom in 1916! (Rutherford cruelly wrote that Bohr’s idea is false because an orbiting electron radiates and lose energy, spiralling into the nucleus; that gets rid of Bohr’s theory. Luckily, Bohr ignored Rutherford.)
I keep wondering why Feynman did not associate the radiation with gauge bosons? And why he didn’t suggest the Lorentz length contraction is the effect of moving through gauge boson exchange radiation?
Later I discovered LeSage had been ridiculed because his theory had predicted the “nearly empty atom” too long ahead of X-rays and radioactivity! Once that part of LeSage’s predictions were confirmed, he was then ridiculed by Maxwell and others who claimed that the exchange radiation of gravity would heat up atoms until they were red hot! By the time the Standard Model was built on exchange radiation, these naive objections to LeSage (which would also more easily kill the Standard Model which is entirely based on exchange radiation for forces stronger than gravity) were no longer physics.
Finally, I discovered that LeSage was allegedly a plagarist and had stolen the theory from Newton’s alleged homosexual lover, Nicolas Fatio de Duillier. No wonder Feynman didn’t back it! However, Feynman did say:
‘It always bothers me that, according to the laws as we understand them today, it takes a computing machine an infinite number of logical operations to figure out what goes on in no matter how tiny a region of space, and no matter how tiny a region of time. How can all that be going on in that tiny space? Why should it take an infinite amount of logic to figure out what one tiny piece of spacetime is going to do? So I have often made the hypothesis that ultimately physics will not require a mathematical statement, that in the end the machinery will be revealed, and the laws will turn out to be simple, like the chequer board with all its apparent complexities.’
– R. P. Feynman, Character of Physical Law, November 1964 Cornell Lectures, broadcast and published in 1965 by BBC, pp. 57-8.
Cheers,
Nigel
11 18 06
Clifford, these questions have been posed by myself and Christine Dantas previously. I agree that alternative theories should be explored, but they must be put into the context of known information. So if I come up with a theory of everything, I should be able to explain it in layman’s terms.
BTW what a nice even handed discussion of DE that you have done!
Lab Lem: I think you are referring to the coulomb constant k or /epsilon_0. It is more likely that /mu_0 changes, since changing k would violate conservation of energy and screw up chemistry, as you say. Changing epsilon_0 would affect size of magnetic fields.
Kea, I know how you feel. We are on track to working all this stuff out soon. The consequences will keep physicists busy for decades
Please take some time to learn the history of the subject.
You mean Peirce’s 19th century philosophy? Or maybe Leibniz’ monadology. Or maybe the old Veneziano paper, the amplitudes of which I know how to recover rigorously from first principles?
Kea: – I’ve no idea how many people are involved. I don’t care, since it is not relevant. I wish you all well. I’m sorry you can see no sense in the advice I gave. But it was unsolicited advice, so that’s perfectly fine.
Please take some time to learn the history of the subject. 20 years is a short time for a truly great idea about our universe to come to fruition. There are myriad examples. At 39 years old, and having worked in the field for so long, I’d have imagined you’d know that.
All the Best – I mean that.
-cvj
Clifford
We’re talking about a job for many people. You are quite mistaken if you think I meant that I was intending to do it all myself. And 20 years is not a short time. On the contrary, in this business things can change very, very quickly.
Kea: – 20 years is a very short time in which to achieve what you want to, if it is as significant as you say. To lose patience so soon is sad. I fail to see the relevance of the fact that you are 39 years old.
Best,
-cvj
Louise,
Changing the coloumb interaction would screw up chemistry, which is God’s one true path for constancy and understanding in the portions of the universe where physical conditions allow it to occurr.
Specifically, you would change the relative diameters of positive and negative ions, which in turn would change the co-ordination states of these ions in ionic compounds (e.g. silicates), which would change the equilibrium compositions of early solar system bodies. Such changes are not observed.
Perhaps more important for the locals here, you would change the excitation energy of H and He, making redshift calculations a royal pain in the butt.
As Cliff said, it is geat if you can overturn fundamental physical paradigms, and we’ll all buy you beers in Stockholm if it works. But in order to do that, you need to show that your new world order explains everything that takes the old system for granted as well as, or better than, the old system. There’s a lot of everything out there.
As for the faint young sun, an increasing number of early Earth geologists are getting quite fond of a snowballed Hadean and early Archean planet. The direct evidence for surface water is scarcer that one might suspect.
Clifford
I’m 39 years old. I have spent 20 years talking and working (some of the time) with professional physicists. Until now, I have been mostly polite and silent in the face of discrimination and condescension. Those days are now gone. I say what I think. If someone doesn’t want to listen – too bad for them.
I think you’re missing the point. Please don’t get defensive… I’m actually trying to help.
Cheers,
-cvj
In what way is twistor string theory not mainstream?
Thanks Kea…
Kea, Louise, nc… I very much wish you all a lot of success with what you are trying to do. I confess to not understanding it (probably due to my own failing to invest the time), but I see no reason why you should not go ahead with what you are doing, and if it all comes to fruition and you develop a coherent prodictive framework that explains all we observe and predicts some great new stuff that we can go out and check…. This would be rather wonderful… we’re all looking for something like that in our own ways.
My only advice, which you are free to ignore, is this: – If you want to take a bold step from the mainstream and try a different approach to physics (possibly producing valuable and new results), when you come back with your results, in order to get them taken seriously you need to find ways to describe them in the terms of the mainstream, otherwise nobody will listen to you or take you seriously. I say this not because the mainstream is always right, but because of the fact that when you take a bold step away from everyone else.. the burden is proof is on you… so to start the process, it makes sense to do in on the mainstream’s terms… sometimes the mainstream will ask something that seems high-handed, or impatient, or annoying….. but you should consider those sorts of questions as helpful remarks that can help strengthen what you are doing.. maybe refine it.. if it is worth doing. I give you, Louise, and nc, the example of Jacques’ questions…. Take what he says on board and either answer his objections or refine what you are doing to take them into account. If there is something in what you’re doing.. it is possible. And then what you will be doing will be stronger… and easier to bring to the mainstream the next time you try… This is the way I suggest you proceed to get your work and ideas looked at by the wider physics community. Feel free to ignore me, of course.
-cvj
Yukawa/Mass-t = 1 ….
Shall I continue?
Um, the non-observation of Higgs, proton decay and gravitational waves should also be noted here.
Clifford
Most of physics depends on the Standard Model and GR, for which G and c and hbar are all constant. However, we now know a lot more about the link between the SM and quantum gravity at G –>0 (see eg. Freidel and Baratin). Even better, by studying N=4 YM in the context of twistor Strings using categorical methods we now have a clear picture of how gravitons and rigorous QCD are linked (you might want to start paying attention to all my comments on this matter). I have heard many cosmologists admit that the Lambda paradigm hinges on three things: structure formation, WMAP and supernovae IA. If all of these are better accounted for by Louise’s analysis (and they are – look at the data), then you need to start taking this very, very seriously. Oh, and by the way, we have a method for calculating the particle masses in the SM. A pity that no one else seems interested in helping us calculate them.
Cheers
Kea
nc…. I’m pretty sure you’ll make a fairly terrible mess of a lot of physics that we know to be correct to great accuracy by the above argument. You seem to be suggesting that all of the physics that science has checked in observation and experiment depends only on a single combination of G and c…. This is a remarkable and bold statement, I’d say.
-cvj
Lab Lemming,
There’s a small landscape of possibilities. Regards Louise’s formula, another variable is G which Edward Teller in 1948 claimed can’t vary or the sun’s output would vary massively since it’s sensitive to the compression due to gravity, and recently this has also been claimed of the big bang fusion rate, which shows G to have been within 10% of current values at say 1 minute after BB, to produce observed abundances of light elements.
But all force coupling strengths are likely to vary in the same manner if there is an underlying cause (ie unification). A variation in G is accompanied by the same variation in the strength of the Coulomb (electromagnetic) interaction, which opposes fusion by repelling protons in stars. The two force variations (gravity and electromagnetism) cancel out since both obey inverse square laws: one is compressing matter, the other resisting compression, so doubling both changes nothing. All you can say experimentally is that the ratio of gravity / electromagnetism coupling strengths has been constant to within +/- 10%, from 1 minute after the BB to now. The absolute strength of gravity thus varies without affecting fusion rates in the BB or in stars, so Teller’s argument is wrong.
[snipped out the remainder as it was very long indeed … nc may well provide a link to his longer explanations on his blog (link on his name)…. – cvj.]
Hi All: Not to worry Jacques, I don’t expect anybody to accept all this right away. I still appreciate your expertise and comments.
Lab Lem, thanks for the link. Most measurements indicate that product hc, and the fine-structure value are indeed constant. This would mean that h increases, providing a small link between Relativity and quantum mechanics.
For a given m, E=mc^2 would indeed be bigger in the past, something that has been factored into the predicted ssupernova curve. This does not violate the first law of thermodynamics because total energy of any object E + U = 0.
Going back a few Ga, GM=tc^3 can explain the Faint Young Sun Paradox. As you can see, solar luminosity is no longer an upward curve but a nearly level line. If c had not changed in the precise amounts predicted, we would not be around to talk about it. (For cosmologists, Earth’s history covers redshifts up to 0.3, including the transitional “jerk” period.) Earth sciences can help tell us whether fundamental values are constant.
thank you
Result of Effective Changes in the Cosmos
Have not included the substance of “thought held,” but by generalization, wanted to lead too. I know “math produced” would be preferred. Thanks for your patience.
Plato, feel free to speculate… just don’t fill the comment space with too much in the way of irrelevant material. Feel free to place a link to that sort of thing on your own blog.
-cvj
While still provoking thoughts from “the three ring circus,” I thought I might continue with my speculations and present a possible scenario, if that’s okay Clifford?
Look, Louise, you can call the combination a(t)/t by the name “c(t)” if you want. Giving it that name doesn’t make it “the speed of light.” You can call the combination a_0^3/ G t_0^2 by the name “M”. Giving it that name doesn’t make it “the mass of the Universe.”
And you can say that the metric above “is not spatially flat,” even though it manifestly has vanishing spatial curvature.
The constancy of the speed of light is built into the pseudo-Riemannian geometry of General Relativity. If you’re not going to change that, playing games with the names of various symbols is not going to achieve anything.
[Clifford: I’ve eschewed the use of <sub> and <sup> above. The “preview” javascript supports a fixed subset of HTML markup (including <sub> and <sup>), regardless of what HTML markup you actually allow in comments on your blog. It is extraordinarily frustrating for commenters if the subset allowed by the “preview” is not the same subset as the one allowed by your comment system.]
Dear Louise,
Pardon my ignorance, but I’m a geochemist, and all this physics is a bit over my head. I was wondering, though. If c is variable, does E no longer equal mc^2? I ask because we geologists know that the penetration distance of alpha particles- particularly those from 212Po decay- in geologic materials has not changed by more than a few percent over the past 2-3Ga.
I don’t know enough physics to be able to determine the change in alpha decay constants caused by a change in c, but the geologically determined ratio between lambda238U and lambda 235U is now more precise than the lab values from by nuclear physicists. These decay constants have not changed for the past 3 Ga. The decay constant ratio for 238/235 over this time period is 0.15738 ± 0.00003, so any change in c can’t effect alpha decay by very much. See http://www.earth-time.org/pdf/Schoene_GCA2005.pdf for details of te new decay constants.
The R ~ t^{2/3} expansion is not the observed expansion, which is (since Perlmutter’s observations in 1998), R ~ t. The 2/3rds power law in conventional Friedmann cosmology derived from GR is the effect of long-range gravitational retardation.
Dark energy/acceleration is supposed to be offsetting the gravitational slow-down. However, the alternative to dark energy is that gravitation disappears at long distances.
The long range gravitational coupling strength (if Yang-Mills quantum field theory is the theory of quantum gravity) will fall due to the redshift effect (energy loss) of exchange radiation in an expanding universe.
There is nothing speculative about this: any radiation emitted by distant receding matter should be redshifted or slowed down. Similarly, distant receding matter would receive redshifted/slowed down radiation from matter near us. So the gravitational attraction – mediated by exchange radiation – will be weakened over very large distances due to cosmic expansion. GR contains no dynamics for this.
This predicted Perlmutter’s results (that distant supernovae etc wouldn’t be slowed down as Friedmann’s solution predicts) via Electronics World in Oct 96, two years ahead of Perlmutter’s observations (couldn’t get it published anywhere it would have been noticed when the result came).
What you need to do, Louise, is to concentrate on what we know for certain about energy in the Yang-Mills QFT context. An apple dropped is gaining kinetic energy which comes from the gravitons it is absorbing.
The reason for the gravitational potential energy of m with respect to the surrounding mass of the universe M, is pretty obvious: if the universe could collapse, that energy would be released. In that sense, it is true. The expansion of the universe prevents collapse, but the argument still holds, just as Einstein’s equivalence between mass and energy holds. You might not be able in practice to release all the energy trapped in matter using fission or fusion, but it is still real energy(annihilation using antimatter proves this).
(I wish Louise would consider the causal dynamics of gravity, general relativity, and the standard model more, and also try to find detailed dynamics before promoting ideas about a varying velocity of light. Loudly making an error here would just label this whole area crackpot to others, which would prevent others people from being taken seriously if they wanted to investigate it a little.)
Part of life is taking everything as a compliment. If someone can’t make heads or tails of what you’ve done, they compliment your intelligence. It’s easy to repeat the absurdity that c = 1. (It’s 3 E8 m/sec and decreasing) That common practice prevents one from seeing that c changes. Here c is not even a factor until page 2.
In this interpretation the Universe has “critical” density but is not spatially flat, and therefore has finite mass M. An infinite universe would have infinite mass and would never expand. The first post doesn’t modify much, but shows that R = ct and GM=tc^3 form a solution to the field equation. I am glad you see they produce the Einstein-de Sitter expansion R ~ t^{2/3}.
You might wish to read a bit more.
I feel your pain Jacques… I don’t know why the previewer does that. I have gone in and fixed some of your comment by hand.
Cheers,
-cvj
Oh %$#@!
I “forgot” that <sub> and <sup> work just fine in the so-called “preview”, but get stripped out in the final posted comment. (There seems to be something funky about δ, too.) What’s the point of having a “preview” that doesn’t actually represent what gets posted?
Anyway, I hope you can interpolated the subscripts and superscripts in the above comment.
Umh. I’m sorry. I must not have very good reading comprehension.
In this post, you reproduce two pages of notes which derive the FRW metric
ds2 = – dt2 + a(t)2 δij dxi dxj
for a spatially-flat matter-dominated universe. “r(t)” in those notes is the scale factor (more commonly denoted as “a(t)”). The function “c(t)≡ a(t)/t” is not the speed of light. The speed of light (as can be seen from the Einstein field equations at the top of the page) is 1.
[As a side point, the solution is parametrized in a funny way. A spatially-flat universe is infinite in extent, so I don’t know what you mean by calling “M” the mass of the universe. A more conventional parametrization of the solution is
a(t) = a0 (t/t0)2/3
But whatever… ]
Aside from proffering an idiosyncratic interpretation of some of the symbols therein, it doesn’t look like you’ve done anything to modify standard GR in that post. Ergo, I don’t see how you could thereby modify any of the conclusions of standard GR.
The other page, I can’t make heads or tails of, but it doesn’t seem to contain anything that looks like (some modification of) the Einstein field equations, either.
JD, it has been written down for you. Please read the links before replying.
I don’t understand how you can “reconcile” Special and General Relativity via a mechanism (a time-varying speed of light) that is incompatible with both of them.
In any case, whatever it is that you are doing involves some nonlocal modification of General Relativity. Until you write down what that modified theory is, I don’t think we can have an intelligent discussion of it.
Can I amend my last comment please to include the word “potential” before energy:
gravitational potential energy (mMG/R) = inertial potential energy (mc2)
is implied by Einstein’s GR equivalence principle:
gravitational mass = inertial mass
Hello Clifford and Jacques, and thank you for interesting questions. Clifford, I enjoy our blog posts, which show that you are not ready to swallow everything NASA tells you. If you see Sean, tell him congratulations.
On underlying dynamics: Theory predicts that the value c takes beween 0 and infinity is moderated by gravity. This comes from an attempt to reconcile the local conditions of Special Relativity (which does not include gravity) with GR while modifying them as little as possible.
At a given value of t, photons are orbiting at the same Space/Time distance from the “Big Bang” origin, like satellites at a fixed altitude. As that distance expands, the velocity goes down. Near the Big Bang, c was nearly infinite and has been slowing since.
Publishing papers on this has been limited, so some relevant equations are on the blog. August 30 entry shows how this forms a solution to the field equations of gravitation. September 25 entry uses an imaginary time coordinate to link SR and GR. The latter post is most controversial, so I don’t expect anyone to absorb all this at once.
How would the equation look in a general spacetime? That is hard to say, since c and t are dependent. In Planck units, it becomes even simpler: M/M_p = t/t_p. In a general spacetime it reduces to the equations of GR and SR, with a local value of c.
I respect all your opinions. You are welcome to suggest improvements and things that need clarification.
Sorry, what I should have said is that Einsteins’s equivalence principle, ie
gravitational mass = inertial mass
implies:
gravitational energy (mMG/R) = inertial energy (mc^2)
Which leads to some law like Louise’s. General relativity is only changed slightly because this approach leads to some dynamics: the redshift of “gravitons” exchanged over vast distances by masses receding from one another will weaken gravitation in a way not modelled by GR.
Dear Jacques,
Louise’s equation can be obtained from equating the rest mass energy of matter (mass m) to its gravitational potential energy with respect to mass of the rest of universe (M) located at the average radial distance R:
Energy, E = mc^2 = mMG/R
Rearranging and inserting R = ct immediately gives Louise’s equation of cosmology.
This raises a number of interesting points I’ve written about.
The equivalence dynamics appears to be the exchange of energy by radiation (Yang-Mills type gauge bosons), which are responsible for gravitational force.
All masses radiate Yang-Mills gravitational radiation (gravitons, whatever they are), and normally receive they at a similar rate.
The exchange of gravity causing radiation from masses far removed from us are (1) earlier in the history of the universe (hence of higher density than the universe near us, because density falls with time), and (2) the long-range graviton radiation will either be redshifted or slowed, depending on its nature (either way, the energy it delivers will be affected by the recession of the masses it is emitted by). I’ve gone into this dynamics in depth and obtained several checkable results, but can’t get anything published in mainstream publications.
Until Louise comes back, perhaps I might just point out that the boundary conditions of an observed universe are not arbitrary with the addition of Machian type principles. Hence Louise’s equation does not belong in a ‘general spacetime’.
Maybe a better way to phrase the question is: what replaces General Relativity?
Recall that the basic principle of General Relativity is that of (pseudo)Riemannian geometry: the neighbourhood of any point in spacetime is a local Lorentz frame. But, in your theory, the speed of light varies in time. So we’re not doing General Relativity any more. Moreover, it’s not some simple local modification of GR, since the equation governing the value of c is a global one.
So you must have in mind some nonlocal modification of GR. What is it?
(Note that, among other things, your equation picks out a preferred time coordinate. In an (approximately) FRW cosmology, there is, of course, a preferred time coordinate: the one in which the 3-geometry is (approximately) homogeneous and isotropic. But that, as it were, is an accident of initial conditions. What would your equation look like in a general spacetime?)
Hi,
What is the mechanism giving rise to the varying c? Is it just empirical, or do you have some underlying dynamics in mind?
-cvj
HI Clifford: I enjoy all your posts on this subject.
First independent data: CMB flatness and horizon data are explained by GM=tc^3, without repulsive fields. “Flat” density Omega=1 is the stable density predicted by the math.
The 4.507034% proportion of baryons is predicted. Models also can predict 23.87% dark mass in clusters, 71.62% undiscovered mass.
The lack of low-l and large-scale fluctuations greater than 60 degrees is also predicted. Theory’s predicted spectrum follows WMAP and COBE data precisely.
More independent data about c change is provided by the geological record of Earth’s temperature compared to solar luminosity. This precisely verifies c change up to redshift of 0.3, covering the transitional “jerk” period.
Additional independent data is provided by Lunar Laser Ranging Experiment data of the Moon’s apparent recession compared to geological and paleontological data.
Further indicators are supermassive primordial black holes, which could only form if c were higher in the past.
Thank you very much for replying. It is much easier to follow the prevailing mantra, so we don’t expect this to be accepted right away. It is a big step forward when you go beyond the press release to examine the data. To quote Penrose: “In my opinion, we must be exceedingly cautious about claims of this (repulsive energy) kind–even if seemingly supported by high-quality experimental results. These are frequently analysed from the persepective of some fashionable theory.”
More on name.
I have some thoughts that I explain about the “cross over point” in the LHC which serves to encourage thinking about the physics involved. Of course, I speculate and some could better explain it, but I thought I would give it a jab anyway.
One needed a “supersymmetrical” view of this situation?
Hi Clifford,
Thanks for your reply.
You were probably wondering (from re-reading the last bit of your message) about why they see anything of the effects of Dark Energy during an epoch when it was subdominant to matter? In other words, we might see the repulsion at late times, because of the relative rise fo teh Dark Energy component, but at earlier times, what are we measuring to see its effects?
Yes, that is what puzzles me. I wonder whether it’s more a negative statement that they can make. Like: we don’t see any influence, so the dark-matter density has to be smaller than that of the baryonic stuff.
My understanding is that they are seeing a small be still significant effect of the Dark Energy’s repusltive component, and I’m guessing that they are finding that it is consistent with that which you should expect (although way smaller than the late time effect) from those earlier times.
Ah, yes. That would be good to know whether they still measure a small repulsive component. I find it hard to believe though, it must be incredibly hard. It’s already difficult to find the change in slope around z=1, how would they find an influence at even earlier z? See, what I was looking for was a plot like this
Luminosity/Redshift (PDF)
But extended to z=2. My impression is, the curve (blue one) would just proceed linearly, indicating that there’s no further funny transition, and dark energy stays sub-dominant (when looking backwards). Thus, they can exclude a dominance at earlier times. I am wondering about the statement (from the NASA site) dark energy […] has been present for most of the universe’s history. It’s not that I would disagree, I just don’t see how this can possibly come out of the highest redshift supernovae.
But thanks again, I guess I’ll just wait for a detailed publication.
Best,
B.
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Clifford and Louise
I’m sure Louise can answer all of Clifford’s questions. But Clifford, if you have further questions about the full M-theory context of a varying c cosmology I would be happy to answer them on my blog.
Cheers
Kea
“It’s just doing what w=-1 (or so) would do: waiting for the university to expand so that it grows up in density relative to matter… ”
Yes, the one here is getting denser all the time too.
Not quite sure as the paper does not seem to be available yet. But I would guess they are trying to constrain the so called ‘tracking models’ of dark energy. According to these models, dark energy is a scalar field rolling down the potential in such a way that its w tracks the dominant component of the universe during early times (w=1/3 during radiation domination, w=0 during matter domination) till at some point it slows down and begins to acquire a negative w (which typically happens ~ z=1.
So at times corresponding to z>1 tracking would predict w=0 for dark energy; and I suspect the paper is trying to argue that this is not the case even at z>1. I am not sure how good that would be at ruling out tracking models (even if they make them a little implausible), in that the theory may be tweaked to get dark energy domination a little earlier than z =1, since the supernovae seem to be at less than z
Hmmm Bee… I suspect that you were not asking the basic stuff about standard candles at all. You were probably wondering (from re-reading the last bit of your message) about why they see anything of the effects of Dark Energy during an epoch when it was subdominant to matter? In other words, we might see the repulsion at late times, because of the relative rise fo teh Dark Energy component, but at earlier times, what are we measuring to see its effects?
My understanding is that they are seeing a small be still significant effect of the Dark Energy’s repusltive component, and I’m guessing that they are finding that it is consistent with that which you should expect (although way smaller than the late time effect) from those earlier times. Presumably they are also using the known flatness of the universe (from WMAP, etc), which presumably has not changed, as another tool in their analysis. At this point, I must give up, since I have not seen a graph, seen analysis (which I would not be an expert on anyway… I’d hand it to a colleague I trust), etc…. I’m inferring this from the press release.
Best,
-cvj
Hi Bee,
I’m not sure what you’re asking. Perhaps several things. With regards to what they are measuring, they are using their deduction of the intrinisic luminosity of the Type IA supernovae (deduced from information about relatively nearby ones) to deduce their distance and find deviations from where they should be (given their redshift) according to a standard model of expansion that has no acceleration component. Supernovae as standard candles. This is more of the 1998 result from the two groups that first told us about dark energy from these measurements… now they have more data for much higher redshift (earlier times), and so can probe the nature of dark energy even earlier. A characteristic of dark energy (the w=-1 (or thereabouts) aspect) is the slow variation of its energy density as the universe expands, while a characteristic of matter is that it dilutes with the expansion…. so at these earlier times, the dark energy was subdominant to the matter, and so it is an interesting epoch within which to study what dark energy is doing. What they find is that it is still behaving rather like it does at later times…. so it is not doing some rather unusual type of evolution, switching on its more recent properties at late times…. It’s just doing what w=-1 (or so) would do: waiting for the university to expand so that it grows up in density relative to matter… they are comparable now, and in fact it has taken over…
Louise…. how does your varying speed of light model model explain all the other independent data about the existence of Dark Energy?
Cheers,
-cvj
From the press release: “Pinpointing supernovae in the faraway universe is similiar to watchihg fireflies in your back yard. All fireflies glow with about the same brightness. So, you can judge how the fireflies are distributed in your back yard by noting their comparative faintness and brightness, depending on their distance from you.”
All fireflies do not glow with about the same brightness. This has relevance because redshift and luminosity of supernovae are affected by change in c, making “dark energy” unnecessary.
… SOORY, I always forget the subtlety with the smaller-than in HTML…
The rest was:
Matter has w=0, meaning: if dark energy doesn’t have much influence on these supernovae, then we can conclude it has w smaller than 0. Is that the statement?
What did they actually measure? I mean, how does the luminosity behave with higher redshift? I couldn’t find very much info about that, do you know?
Best,
B.
Hi Clifford,
The observations also confirmed that the expansion rate of the cosmos began speeding up about five to six billion years ago. […] The new crop of supernovae tell us about quite a bit earlier…. nine or ten billion years…. From looking at them, they find evidence that Dark Energy was playing a role at that time too, still a repulsive component to the story
I don’t quite get it: dark energy becomes important around z=1, 5-6 billion years ago. When it was indeed constant with w=-1, it would have been sub-dominant before that. Now they measure supernovae at even earlier times. Isn’t the essence of what they can say: if there was dark energy, it was still sub-dominant at z ~ 2, because we don’t see any influence. I.e. when we go backwards from z=1, density of dark energy should not increase faster than that of matter. Matter has w=0, meaning: if dark energy doesn’t have much influence on these supernovae, then we can conclude it has w