Mystery of Dark Energy: Unravelling the GR Expansion of Universe

In summary: Dark Energy is a misnomer, it is only an extra gravitational force that has been misinterpreted as a 'pushing apart' of the universe.In summary, the conversation discusses the expansion of the Universe and how it is predicted by Einstein's theory of General Relativity. The concept of dark energy, a supposed mystical force of repulsion between matter, is brought up and it is explained that it is a result of a constant that Einstein added to his equation. However, there are differing opinions on whether this is the correct explanation for dark energy. Some suggest that it could be a result of strings joined together, while others argue that it is simply an extra gravitational force. There is also discussion about the
  • #71
Nereid said:
You know turbo-1, I had to go get myself a nice glass of one of my favourite Australian cab-savs before I could answer your post; I mean, is this the same turbo-1 who wrote all those other posts?

Shall I wave my hands, invoke gorgons, angels, and the spirits of long-since enjoyed chardonnays? "Hey, I've got a really cool idea, seems kinda plausible, and (nudge, nudge, wink, wink) will rid the world of corns and carbuncles to boot, oh and explains AIDS too. What? Consistency with observations? Don't be silly! Of course I haven't done any calculations yet! But just feel the plausibility! What? Explain, with equations, how ZPE-matter interactions account for the observed CMBR? That's got nothing to do with it! I'm only talking about what poor deluded astronomers call 'gravitational lensing', and only that to do with distant galaxy clusters! What? If these ZPE-matter interactions could explain 'cluster lensing', then there'd be humongous early universe effects too? even affecting the CMBR?? Hmm, maybe ... but feel the plausibility!"

If you "see it [mass-ZPE-interaction] to be [...] an elegant solution to a couple of GR's biggest problems[color]" then show us how! With equations! If not, why shouldn't we move these speculations off to TD? :rolleyes:
Plays well with others.. C .. I am a bad influence.
 
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  • #72
Nereid said:
What? Explain, with equations, how ZPE-matter interactions account for the observed CMBR? That's got nothing to do with it! I'm only talking about what poor deluded astronomers call 'gravitational lensing', and only that to do with distant galaxy clusters! What? If these ZPE-matter interactions could explain 'cluster lensing', then there'd be humongous early universe effects too? even affecting the CMBR?? Hmm, maybe ... but feel the plausibility!"

If you "see it [mass-ZPE-interaction] to be [...] an elegant solution to a couple of GR's biggest problems[color]" then show us how! With equations! If not, why shouldn't we move these speculations off to TD? :rolleyes:
You are quite correct. They are thought-experiments only. I have linked to some relevant papers (with math) that illustrate some of the concepts I'm struggling to explain, but unfortunately, I don't have the math skills to explain how to "connect the dots" in a way that will satisfy you. Nor will logical argument suffice - not rigorous enough. I'm stuck. Maybe if I try to explain myself in a strictly GR language (which I don't speak that well:rolleyes: )...

By the way, you misstated me just a bit. If you read that post, you will see that I said that the effects of space-time distortions on matter and light would likely be easiest to see and measure in places where there is a LOT of matter (clusters) or where matter distribution is non-uniform (spiral galaxies). I didn't say that is those are the only places or the only times we might see a measurable effect, just that those might be productive places to look first. Gravity is a very weak force, and it stands to reason that anomalous gravitational effects (ones not yet predictable by GR) would most easily be seen where there are dense concentrations of matter and/or strong gradients the distribution of matter.

Cluster lensing is a strong effect that has been well-modeled in one study (at least in terms of describing the extent and density of the "missing mass"),
http://antwrp.gsfc.nasa.gov/apod/ap030814.html
so that's a more productive place to look, as opposed to studying shear effects caused by individual galaxies, which are small. Also, since the galactic rotation curves of a LOT of spirals have already been measured, and the density ratios of the central bulges and arms have already been calculated, the concept of distorted (densified or aligned...) space-time fields interacting with matter could be tested and subjected to falsification very quickly. It may be that ad-hoc MOND is a description of inertia/mass variation across a gradient in a space-time field. I hope someone with good math skills will try modeling it.

I have avoided any reference to quantum fields in this post. I have used only the term space-time. I do this because GR folks will readily agree that matter curves (distorts) space-time and that curved space-time determines the paths of entities traveling through it. A bigger logical step is considering that since curved space-time mediates gravity, variations in the structure or "curvature" (in the GR sense) of space-time itself might result in variable gravity for the objects embedded in it.

Might an object have more gravitiational mass and/or inertia in a densely-curved space-time field than it would have in a space-time field that is more relaxed? It is a very basic question, and because it bears on a fundamental concept in GR, it will engender strong reactions. Intuitively, most people will reject it out of hand, but I think that's a mistake. Most people (including a VERY smart guy who knew a little something about GR) would reject quantum physics out of hand, too, because so much of it is counter-intuitive and seemingly illogical, but we know now that quantum physics is quite valuable and predictive.

If more strongly curved space-time results in more gravitational mass/inertial mass for matter embedded in it, we could explain why clusters act far more massive than we expect (excess lensing, given the visible matter there) and could at the same time explain how the clusters manage to hold together, even though the member galaxies have high relative motions and seemingly have insufficient mass to remain bound. We could also explain how the rotational curves of spiral galaxies flatten out as we look farther out from the very dense central bulges. Stars farther and farther from the massive central bulge exist in less-distorted space-time fields and have therefor have less inertial/gravitational mass. (I'm not going to even contemplate breaking that mass equivalence lest Nereid hunt me down like a dog. :rolleyes:) I called this idea elegant before, and I still believe it to be so. It provides a resolution to some seemingly intractable problems without having to invoke additional entities beyond sensible baryonic matter and the space-time field in which it exists.

The folks working on quantum gravity may one day come up with a robust dynamical model that can describe how mass distorts space-time, and how distorted space-time affects mass. Judging from the papers I've found, that is likely to be many years away, at best. We may be at a point where observational astronomers can model and measure the effects of variable gravity in a space-time gradient, and express it in a GR framework long before the theorists can explain why it works. It won't be a TOE, but there might never be anyway, despite the best efforts of the theoreticians.
 
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