Split Thread Michael Mozina's thread on Dark Matter, Inflation and Cosmology

schrodingasdawg said:

The pressure terms in the EM stress tensor are positive, not negative, so they cannot account for an acceleration of universal expansion.

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I think I'm going to have to tackle your posts a few ideas at a time, starting with this one. What makes you think that "dark energy" even interacts with the "gravitational field" directly rather than say "indirectly"?

EM fields can certainly cause the acceleration of material objects, certainly it can accelerate plasma "universally" even inside our own solar system.

Suppose in our thought experiment that you and I happen to become a couple of observers, floating on the photosphere, watching protons and flying ions take off from the surface, and accelerate away toward the heliosphere. It's evidently a "universal acceleration" process because we can observe them flying off the surface. We notice too that the acceleration is continuous for our field of vision and the continue to accelerate as they leave the surface.

According to your statements, the EM field cannot be responsible for this universal acceleration, but that is exactly what *IS* causing that acceleration.

Dancing David said:

You and your silly math.

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No, it's you and your silly assumptions...

The pressure terms in the EM stress tensor are positive, not negative, so they cannot account for an acceleration of universal expansion.

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By that logic our rail gun can't be powered by an EM field.

ben m said:

You are completely ignoring the posts where we show that the observed "cosmic acceleration" cannot be either EM or baryonic.

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No, I'm ignoring it because you're making a host of 'assumptions' when you make that claim, none of which can be verified.

Your priorities are backwards.

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Not at all. IMO it is your priorities that are completely "backwards". Rather than *trying* to come up with an empirical solution (by changing initial conditions for instance), you're absolutely, positively intent on *not trying* to find an empirical solution to your acceleration problem and avoid the one known force of nature that 'might' give you an empirical answer.

Let's talk turkey here and set some real initial conditions for your "creation event". Did the object have mass prior to the "bang"? If so, was it "charged"?

Michael Mozina said:

Suppose in our thought experiment that you and I happen to become a couple of observers, floating on the photosphere, watching protons and flying ions take off from the surface, and accelerate away toward the heliosphere.

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Not uniform at all. They're all moving parallel to each other; there's a preferred vector direction. The only observer who thinks they're "all moving away" is one at the center of the Sun. An observer at the surface thinks that the wind is blowing straight up.

Not accelerating. A solar flare/solar wind/etc. leaves the surface of the Sun (where the fields and/or temperature gradients are strong) and then cruises. It's going basically the same speed at Pluto as it is at Earth. (You imagine it is accelerating only because you imagine that the Sun has a static charge which "repels" it. You are wrong.)

Michael Mozina said:

I think I'm going to have to tackle your posts a few ideas at a time, starting with this one. What makes you think that "dark energy" even interacts with the "gravitational field" directly rather than say "indirectly"?

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The only dark "energy" model I'm familiar with is the cosmological constant ("lamba") model. The cosmological constant term is a term in the Einstein Field Equations, which are the equations governing gravitation in GR. Other dark energy models, I'd presume, contain some sort of field that contributes to the stress-energy tensor, which is the source of gravitation in GR. Either way, the constant/field interacts directly with gravity in GR.

Michael Mozina said:

EM fields can certainly cause the acceleration of material objects,

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This may be where some confusion is arising. The word "acceleration" is being used with two different meanings. When an object is accelerated, its velocity with respect to some reference frame is being changed. This is a simple mechanics concept. When someone says that "universal expansion is accelerating", they're not referring to this mechanics concept. They're stating that the rate at which the universe is expanding is increasing. In both cases, the rate of change of a rate of change is being referred to, which is why the word "acceleration" is used in both cases.

EM fields can certainly change the velocity of charged particles with respect to an inertial observer, but they cannot increase the rate of expansion of the universe.

ben m said:

Not uniform at all. They're all moving parallel to each other; there's a preferred vector direction. The only observer who thinks they're "all moving away" is one at the center of the Sun. An observer at the surface thinks that the wind is blowing straight up.

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Fine, we'll change our initial observation point if you prefer.

Not accelerating.

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Yes, accelerating. It's a "continuous full sphere" process, not just a single flare event!

A solar flare/solar wind/etc. leaves the surface of the Sun (where the fields and/or temperature gradients are strong) and then cruises.

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Some particles perhaps, but solar wind "ACCELERATION" is a full sphere, continuous process. It's not something you will or can explain with only flares. Even those are "EM" acceleration events.

schrodingasdawg said:

The only dark "energy" model I'm familiar with is the cosmological constant ("lamba") model.

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It's probably the only place it's used, so that's understandable, but you're going to have to "think outside the box" a bit if we're going to entertain other "options".

Start with solar wind acceleration. It's a form of constant acceleration of "plasma", sometimes including heavy ions. Is that "dark energy" doing that constant acceleration of mass?

Michael Mozina said:

Start with solar wind acceleration. It's a form of constant acceleration of "plasma", sometimes including heavy ions. Is that "dark energy" doing that constant acceleration of mass?

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I'm very confused regarding your train of thought.

Dark energy models are meant to give a theoretical explanation for the observed increase in the rate at which the universe is expanding. They have nothing to do with mechanical acceleration.

I also am not sure what this "solar wind acceleration" is nor where it's coming from.

schrodingasdawg said:

I'm very confused regarding your train of thought.

Dark energy models are meant to give a theoretical explanation for the observed increase in the rate at which the universe is expanding. They have nothing to do with mechanical acceleration.

I also am not sure what this "solar wind acceleration" is nor where it's coming from.

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With your background in GR, you might find these papers helpful to explain my position:

http://arxiv.org/abs/astro-ph/0601171
http://arxiv.org/abs/0911.3536

I've simply looked to nature to find a working "real" physical example of a constant mass acceleration process. It's an example of a working physical process where you might try plugging in a test particle into those GR formulas. When you do you'll notice that the expansion process is continuous, and for awhile at least, acceleration occurs as well. We don't need to resort to new forms of energy to explain a constant expansion, and a continuous acceleration of mass/plasma. The EM field does that 24/7, 365 days a year.

Michael Mozina said:

Yes, accelerating. It's a "continuous full sphere" process, not just a single flare event!

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Your "continuous sphere process" hypothesis is not supported by the data. You are making it up. All of our deep space plasma probes (Pioneer, Voyager) show that the solar wind cruises through the Solar System at a more or less constant velocity. It is not speeding up uniformly on the way to Pluto. Look at the damn data.

I repeat my request: please cite an EM field configuration (not a vague analogy, not a terella photo---a vector field I can plug into Maxwell's Equations) that you think could be causing the Universe to accelerate.

ben m said:

Your "continuous sphere process" hypothesis is not supported by the data. You are making it up.

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Ya, it's called a "thought experiment" ben. I "made up" that part about floating on the photosphere and being in the core of the sun too. It's an analogy ben.

All of our deep space plasma probes (Pioneer, Voyager) show that the solar wind cruises through the Solar System at a more or less constant velocity.

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No, even that is a very oversimplified statement too as you well know. Solar storms change solar wind densities and velocities all the time. The polar regions tend to experience a higher velocity of solar wind than the equator. It's not "constant velocity" by any stretch of the imagination.

It is not speeding up uniformly on the way to Pluto.

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Is is for purposes of my "analogy", or it's at least accelerating for some "short distance within our view from the photosphere".

Look at the damn data.

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Look at it as an "analogy" ben.

I repeat my request: please cite an EM field configuration (not a vague analogy, not a terella photo---a vector field I can plug into Maxwell's Equations) that you think could be causing the Universe to accelerate.

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I don't need a vague analogy to demonstrated full sphere acceleration from a sphere in a vacuum. Birkeland did that in a real lab with real "empirical physical things", not "dark energy".

Ben the sun is a complicated environment. I was simply blowing s-dawg's claim away about the EM field not being able to sustain a constant acceleration. Even if the solar wind isn't accelerating ben, it's still pulling away from a gravity well and defying "gravity". If we created two test particles leaving different places on the solar surface, as they travel towards the heliosphere, the distance between them will increase over time. *IF* we assume a constant acceleration for some distance, then even a particle in front of us is moving faster than we are and it's moving away from us due to it's greater velocity. Even the particles behind us on the same path from the photosphere will be traveling slower than we are in a continuous acceleration scenario. Yes ben, it's a "make believe" scenario in terms of constant acceleration. On the other hand the sun *DOES* experience constant acceleration of charged particles as that continuous flow of mass demonstrates. It doesn't matter how it gets to "terminal velocity", from the standpoint of the observer in the core of the sun (no I've never actually gone there. ) there is constant flow of mass from a central point, and it's due to the influence of the EM field that your said could not generate that process.

Michael Mozina said:

I was simply blowing s-dawg's claim away about the EM field not being able to sustain a constant acceleration.

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You might do well to pay attention to what people are actually saying, especially when they take the time to point out potential ambiguities and to clarify them. It's understandable that other people on this board would be frustrated with this habit of yours.

It seems from the papers you posted that your position is that the apparent recession of galaxies is due to actual movement through space as opposed to metric expansion, the expansion being the standard explanation. It would have saved time for you to have actually stated this.

I have to go now, so I'll leave my post at this.

schrodingasdawg said:

It seems from the papers you posted that your position is that the apparent recession of galaxies is due to actual movement through space as opposed to metric expansion, the expansion being the standard explanation. It would have saved time for you to have actually stated this.

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I would be mildly cautious of this. Exactly how you translate the metric expansion into 'plain English' is somewhat contentious. I'd certainly not criticise someone for claiming that recession of galaxies is due to movement through space.

http://arxiv.org/pdf/0808.1081v1 and http://arxiv.org/abs/0809.4573v1 go into some of this, and there's more at http://en.wikipedia.org/wiki/Metric_expansion_of_space

Fortunately, while the interpretation is open to some discussion, the mathematics of it and the predictions of observable quantities from GR are not - it's all quite solid.

edd said:

I would be mildly cautious of this. Exactly how you translate the metric expansion into 'plain English' is somewhat contentious. I'd certainly not criticise someone for claiming that recession of galaxies is due to movement through space.

(links)

Fortunately, while the interpretation is open to some discussion, the mathematics of it and the predictions of observable quantities from GR are not - it's all quite solid.

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Thanks for the warning. I suppose I didn't really put as much thought into this as I should have. The expanding space v. movement thing is certainly beyond my knowledge to comment on, so I should probably step down here. But I'll definitely take a look at those papers.

What is "dark energy", really?

Well, everybody (including Mozina) seems to at least accept that the accelerating expansion interpretation of cosmological data is reasonably acceptable (source papers: Riess, et al., 1998, Perlmutter, et al., 1999 and the several thousand references thereto). Generally speaking, the words "dark energy" are nothing more than a place-holder for whatever it is that causes the accelerating expansion. This may be an unfortunate choice of words, for if the cause is found to be, for instance, a cosmological constant, then it is not "energy" at all, at least in classical general relativity, but rather simply an artifact of the geometry of space. Of course, given a quantum theory of general relativity one might reconsider the cosmological constant as a true force.

Now, given that we accept an accelerating expansion, what can we hold responsible for this? If we are constrained to stick tightly only to the physics we know well, then we can start with the realization that there are only 4 known "forces": gravity, electromagnetism, and the strong & weak nuclear forces. If it's not one of these 4 forces that causes the accelerating expansion of the universe, then I think it is safe to say that "physics as we know it" is not responsible, and "new physics" must be derived to explain the observations.

Classical Maxwellian electromagnetism can be ruled out at once by the simple observation that the expansion treats charged particles (i.e., plasma) and neutral material in identical fashion. I don't know how to get classical electromagnetic fields to couple to neutral matter with the same strength as they couple to electrically charged matter, and I am unaware of anyone else professing an ability to describe this. However, there are polarization states in quantum electrodynamics that do not couple to electric charge, but only via gravity. These electromagnetic states are under investigation by some groups as a plausible physical basis for "dark energy" and the accelerated expansion of the universe (i.e., Novello, et al., 2004; Jimenez & Maroto, 2009a; Jimenez & Maroto, 2009b and Labun & Rafleski, 2008).

The data are most consistent with a cosmological constant in Einstein's equations being the root source of the accelerating expansion and therefore the physical basis of dark energy (i.e., Wood-Vasey, et al., 2007 and Davis, et al., 2007 and the numerous references thereto). A classical electromagnetic field cannot effectively mimic a cosmological constant since it couples strongly only to electric charges and not to neutral matter. Furthermore, a "cosmological constant" is so named because it is in fact constant in its effect throughout the entire universe. It's hard to imagine any realistic classical electromagnetic field owning up to such a stringent constraint.

There are hordes of papers on all aspects of dark energy, but a few good general treatments of the topic (or so it appears to me) are Basilakos, 2010; Clarkson, 2009; Urban & Zhitinsly, 2009; Sami, 2009a; Sami, 2009b. And see Freiman, Turner & Huterer, 2008 for an extensive review of the topic of dark energy, the most extensive recent review that I am aware of.

So it is my position that the lack of strong coupling between classical electromagnetic fields and neutral matter, along with the requirement that the accelerating effect be constant (at least within observational constraints) throughout the universe, leads to a confident ruling out of classical electromagnetic fields as the physical basis for dark energy.

Moving Through Space

edd said:

I'd certainly not criticise someone for claiming that recession of galaxies is due to movement through space.

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But we still cannot violate special relativity in the rest frame of the distant galaxy. So the interpretation of "moving through space" is really only a convenience for the distant observer, is it not?

edd said:

We're broadly in agreement RC, but this isn't entirely accurate. Dark energy is a specific class of potential causes of acceleration - it's basically any negative pressure component of the energy density.

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I stand corrected.

Tim Thompson said:

But we still cannot violate special relativity in the rest frame of the distant galaxy. So the interpretation of "moving through space" is really only a convenience for the distant observer, is it not?

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Yes and no, but anyway my point really is that it's not a useful line of argument to take - it's not clear to me if it makes an observable difference which way you think about it, and there are enough easily attacked arguments in play in this thread without it

schrodingasdawg said:

You might do well to pay attention to what people are actually saying, especially when they take the time to point out potential ambiguities and to clarify them. It's understandable that other people on this board would be frustrated with this habit of yours.

It seems from the papers you posted that your position is that the apparent recession of galaxies is due to actual movement through space as opposed to metric expansion, the expansion being the standard explanation. It would have saved time for you to have actually stated this.

I have to go now, so I'll leave my post at this.

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It is not you, it is MM. His theory is incoherent in many ways. You pointed out an inconsistancy, so then he will squirm.

Dancing David said:

It is not you, it is MM. His theory is incoherent in many ways. You pointed out an inconsistancy, so then he will squirm.

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He has a theory?

schrodingasdawg said:

It seems from the papers you posted that your position is that the apparent recession of galaxies is due to actual movement through space as opposed to metric expansion, the expansion being the standard explanation. It would have saved time for you to have actually stated this.

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My apologies. I guess I just assumed you knew like everyone else.

For those that may be interested:
Here is an interesting blog entry of the process that one astronomer went through before they were convinced that the evidence was strong enough for dark energy:
What it took to get me to believe... in Dark Energy

If his response to the 1998 Type 1a supernovae data is typical then it is likely that the existence of dark energy took many years so be acceptd in general.

Michael Mozina said:

schrodingasdawg said:

It seems from the papers you posted that your position is that the apparent recession of galaxies is due to actual movement through space as opposed to metric expansion, the expansion being the standard explanation. It would have saved time for you to have actually stated this.

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My apologies. I guess I just assumed you knew like everyone else.

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I thought that were problems with treating the apparent recession of galaxies as due to actual movement through space.
The ones that I can think of are:

• That means that the Earth (or a point close to the Earth) is the center of the universe. That is a bit of a medieval concept. There is no evidence that the Earth, Solar System, Milky Way or even Local Group are special places.
• Run time backwards. At some point in the past all ~100 billion galaxies in the universe are within a small volume. That looks like a black hole to me. No known explosion could extract the galaxies from the singularity and even if one could then they could not pass outside of the event horizon. So we must still be in that black hole. Where are all the effects that we can expect from this?
• Where does the CMB come from?

Reality Check said:

For those that may be interested:
Here is an interesting blog entry of the process that one astronomer went through before they were convinced that the evidence was strong enough for dark energy:
What it took to get me to believe... in Dark Energy

If his response to the 1998 Type 1a supernovae data is typical then it is likely that the existence of dark energy took many years so be acceptd in general.

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Thanks.

I wish I could live an additional 300 years just to see how cosmology and science in general has advanced... what has become science 'fact' and what ends up getting tossed into the hypothesis garbage bin.

Put me on that cryonic freezer list, thank you very much.

Question for the physicists:

If the acceleration of cosmic expansion in not a form of energy but instead,

"if the cause is found to be, for instance, a cosmological constant, then it is not "energy" at all, at least in classical general relativity, but rather simply an artifact of the geometry of space."__Tim Thompson

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would that not violate the law of conservation of energy since the overall energy of the universe would be increasing?

Cosmological Conservation of Energy

Perpetual Student said:

... would that not violate the law of conservation of energy ...

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This time I will quote a passage from the book Cosmology: The Science of the Universe by Edward Harrison, Cambridge University Press 2000 (2nd edition):

The energy in an expanding universe decreases (not increases) because of the loss of energy to redshifting photons. I think the key to the lack of universal conservation of energy is really the difficulty in defining "energy" for the universe as a whole. We usually associate energy with time (as in, for instance, the energy form of Heisenberg's uncertainty principle, delta-E*delta-T ~ h). But time is not Newtonian, so there is no one "time" that can be assigned to the universe.

Now, Macleod, 2005 disagrees with this notion and restores cosmological conservation of energy by projecting cosmological observations onto flat space-time and applying the rules of special relativity. I don't personally know enough to say if Macleod is right. So at least it is evidently controversial whether or not the conservation of energy principle is globally valid for the universe taken as a whole (no local experiment will violate the conservation of energy principle even in Harrison's case).

And in passing I see Maxson, 2009 who seems to argue that the expansion of the universe is a consequence of conservation of energy, though I have not read the paper, just the abstract.

Conservation of energy comes from the laws of physics not being explicitly time dependent. More specifically, if the Lagrangian of a system doesn't explicitly depend on time, then energy is conserved. If cosmological laws are explicitly time-dependent (that is to say, if given the laws of cosmology in some form, replacing t with t+dt would produce a change in the action) then energy wouldn't necessarily be conserved.

I don't know the Lagrangian or action for GR off the top of my head, but I'd imagine metrics can be constructed that cause the Lagrangian to be explicitly time-dependent.

edd said:

I'd certainly not criticise someone for claiming that recession of galaxies is due to movement through space.

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Likewise an "acceleration through space" is simply a different way of describing the same accelerating expansion process.

Tim Thompson said:

Classical Maxwellian electromagnetism can be ruled out at once by the simple observation that the expansion treats charged particles (i.e., plasma) and neutral material in identical fashion. I don't know how to get classical electromagnetic fields to couple to neutral matter with the same strength as they couple to electrically charged matter, and I am unaware of anyone else professing an ability to describe this.

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You've heard of the term "dusty plasma" haven't you? How much of a given galaxy is in the form of a "neutral" material in your opinion that isn't otherwise generating a magnetic field like a neutron star or "black hole"? (Please refrain from trying to claim that "dark matter" is "neutral")

Energy conservation in GR is in this FAQ:
http://math.ucr.edu/home/baez/physics/Relativity/GR/energy_gr.html

Michael Mozina said:

You've heard of the term "dusty plasma" haven't you? How much of a given galaxy is in the form of a "neutral" material in your opinion that isn't otherwise generating a magnetic field like a neutron star or "black hole"? (Please refrain from trying to claim that "dark matter" is "neutral")

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The answer is irrelevant to mainstream cosmology. The only long-range, well-organized force on plasma, gas, dust, planets, stars, and black holes (and dark matter) is gravity. Electromagnetism, like the strong and weak force, adds lots of interesting short-range details. Gravity exerts exactly the same acceleration on charged objects and uncharged objects, magnetized objects and unmagnetized objects, etc. Electromagnetism does not. That's why the solar corona manages to accelerate electrons and protons (high q/m) but not, e.g., Mercury and Venus (low q/m).

In other words, I don't learn that DM is neutral by studying, e.g., its orbits around the galaxy or its attraction to large-scale structures. That's all gravitational physics which works just the same way on (hypothetical) charged dark matter as on (hypothetical) neutral dark matter. I learn that DM is neutral by looking for the short-range interactions characteristic of charged particles---shock acceleration, photon emission, photon absorbtion, bound states---and finding them absent.

You, meanwhile, are the one with a theory under which things with wildly different charge-to-mass ratios (protons with q/m = 10^5 C/g, dust with q/m = 10^-10 C/g, stars with 10^-34 C/g) are all meant to wind up feeling the same acceleration in an electromagnetic field. As you'd have had to account for if you ever used an electromagnetic field equation ...

ben m said:

The answer is irrelevant to mainstream cosmology. The only long-range, well-organized force on plasma, gas, dust, planets, stars, and black holes (and dark matter) is gravity. Electromagnetism, like the strong and weak force, adds lots of interesting short-range details. Gravity exerts exactly the same acceleration on charged objects and uncharged objects, magnetized objects and unmagnetized objects, etc. Electromagnetism does not. That's why the solar corona manages to accelerate electrons and protons (high q/m) but not, e.g., Mercury and Venus (low q/m).

In other words, I don't learn that DM is neutral by studying, e.g., its orbits around the galaxy or its attraction to large-scale structures. That's all gravitational physics which works just the same way on (hypothetical) charged dark matter as on (hypothetical) neutral dark matter. I learn that DM is neutral by looking for the short-range interactions characteristic of charged particles---shock acceleration, photon emission, photon absorbtion, bound states---and finding them absent.

You, meanwhile, are the one with a theory under which things with wildly different charge-to-mass ratios (protons with q/m = 10^5 C/g, dust with q/m = 10^-10 C/g, stars with 10^-34 C/g) are all meant to wind up feeling the same acceleration in an electromagnetic field. As you'd have had to account for if you ever used an electromagnetic field equation ...

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This thread has fallen down to page 2 ... we can't have that!

Question for long-time posters (and lurkers): can you recall any examples of MM making a *quantitative* case (argument, point, narrative)?

As in a *consistent* quantitative point, with numbers which correspond to observed (or estimated) values of physical quantities (as defined in standard physics textbooks)^?

And what about maths ... any examples of the application of any math (even arithmetic!) - in a consistent, coherent way - to an event, observation, phenomenon, etc in physics or astronomy?

^ not just quoting one (e.g. "million mile an hour solar wind")

DeiRenDopa said:

This thread has fallen down to page 2 ... we can't have that!

Question for long-time posters (and lurkers): can you recall any examples of MM making a *quantitative* case (argument, point, narrative)?

As in a *consistent* quantitative point, with numbers which correspond to observed (or estimated) values of physical quantities (as defined in standard physics textbooks)^?

And what about maths ... any examples of the application of any math (even arithmetic!) - in a consistent, coherent way - to an event, observation, phenomenon, etc in physics or astronomy?

^ not just quoting one (e.g. "million mile an hour solar wind")

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I don't remember any such examples... other than him telling us how many orders of magnitude stronger the EM force is than gravity.

DeiRenDopa said:

This thread has fallen down to page 2 ... we can't have that!

Question for long-time posters (and lurkers): can you recall any examples of MM making a *quantitative* case (argument, point, narrative)?

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In tens of thousands of postings in discussions scattered all around the Internet, nope, never.

As in a *consistent* quantitative point, with numbers which correspond to observed (or estimated) values of physical quantities (as defined in standard physics textbooks)^?

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Nope.

And what about maths ... any examples of the application of any math (even arithmetic!) - in a consistent, coherent way - to an event, observation, phenomenon, etc in physics or astronomy?

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Nope.

^ not just quoting one (e.g. "million mile an hour solar wind")

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Hasn't happened. I've read literally thousands of his posts and can't recall a single time when he demonstrated even the most rudimentary math skills, not pertinent to any of the discussions anyway. Seems he has never ventured into quantitative-land and expressed any of his crackpot notions in actual numbers of any sort. And when asked to support his wacky conjectures quantitatively, he bitches and moans about how he did that once a long time ago so he should never have to do it again. Something like, "I won't bark math on command," if I recall. And I predict his response to these posts will be to badmouth us for insulting him, when pointing out that no quantitative support has ever been provided is not an insult, it's a fact. And it's highly germane to the discussion. I also predict more complaints reflecting his general disdain for math.

DeiRenDopa said:

Question for long-time posters (and lurkers): can you recall any examples of MM making a *quantitative* case (argument, point, narrative)?

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No. But in fairness to MM, the main thrust of his point is not to put forth a new explanation, but a skeptical view of the "quantitative only" (?) explanation of dark matter. So, what would he model exactly?

Where MM falls short is not providing a quantitative *refutation* of the existing model. That is, stating quantitatively where the current model fails.

Dark energy is not classical electromagnetism

Michael Mozina said:

You've heard of the term "dusty plasma" haven't you?

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I have. Dust accounts for about 1% of the mass of the interstellar medium (ISM) in the Milky Way, and the total mass of the ISM is about 10% of the stellar mass, which therefore constitutes about 90% of the baryonic mass of the Galaxy. Furthermore, elliptical galaxies don't have any dust at all.

Michael Mozina said:

How much of a given galaxy is in the form of a "neutral" material in your opinion that isn't otherwise generating a magnetic field like a neutron star or "black hole"?

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The ISM is, by mass, approximately 85% neutral (Galaxies in the Universe by Sparke & Gallagher, Cambridge University Press, 2007 (2nd edition), table 2.4 page 101). The neutral matter is strongly concentrated in the plane of the Galaxy, so the vast bulk of the gaseous material by volume is ionized.

Michael Mozina said:

(Please refrain from trying to claim that "dark matter" is "neutral")

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Why should I refrain from doing the incredibly obvious? If "dark matter" were electrically charged it would be "bright matter" and we would see it easily.

Now, consider the quote from me that Mozina was responding to:

Tim Thompson said:

Classical Maxwellian electromagnetism can be ruled out at once by the simple observation that the expansion treats charged particles (i.e., plasma) and neutral material in identical fashion. I don't know how to get classical electromagnetic fields to couple to neutral matter with the same strength as they couple to electrically charged matter, and I am unaware of anyone else professing an ability to describe this.

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90% of the baryonic mass of a spiral galaxy is stars. While stars are electrical neutral for all practical purposes, we expect a star of solar mass to carry a net electrical charge of about +77 Coulombs because lighter electrons are more easily expelled from the sun. So the sun builds a net charge until it is in equilibrium (Neslusan, 2001)

So, let us consider F = ma = QE where m is mass, a is acceleration, Q is electric charge and E is electric field. We know the mass of the sun, 1.9891x10³⁰ kg. We also know that any systematic cosmological electric field as large as 1 v/m would make itself obvious (induced electric fields in the solar wind are milli-Volts per meter), so I will use that as an upper limit on any cosmological electric field. So the acceleration is just QE/m which is 77/1.9891x10³⁰ = 3.87x10^-29 m/sec². Not much of an acceleration. Let's give it 14 billion years (4.4x10¹⁷ sec) and see what happens. 3.87x10^-29 m/sec² x 4.4x10¹⁷ sec = 1.7x10^-11 m/sec. That's far short of the thousands of kilometers per second that are typical cosmological redshift equivalent relative velocities.

So, let us ask what kind of field strength is required to accelerate a star like the sun to a speed of 1000 km/sec, given 4.4x10¹⁷ sec to pull it off. That's v = at or v/t = a or 10⁶ m/sec / 4.4x10¹⁷ sec = 2.27x10^-12 m/sec². OK, now E = ma/Q or E = (1.9891x10³⁰ kg x 2.27x10^-12 m/sec²) / 77 C = 5.86x10¹⁶ V/m. I think we can all agree that a cosmological electric field on the order of 10¹⁶ Volts per meter would be rather more than simply "obvious".

Something has to push the stars of a galaxy up to a few thousand km/sec recession velocity, at least. The numbers we see above certainly appear to me to rule out classical electromagnetic fields as the physical basis for dark energy.

MM has been repeated presented with, and repeatedly ignored, the "sun's charge to mass ratio is different than proton's" argument.

I think his mistake is in thinking that the Sun is ionized, so it's all charged, so that's what counts. MM, is that right? This view forgets that protons have the opposite charge from electrons; in the presence of any electromagnetic field, either E or B, they feel forces in the opposite directions. If the Sun's protons are feeling a 10^20N force to the left, then its electrons are feeling a 10^20 N force to the right for a net force of zero. (Except, as Tim points out, for the force on the slight excess charge (under 100C) which has been again repeatedly cited and ignored.)

The vectory-ness of the EM forces is one of the many things MM would have discovered if he had been curious about how an EM-forces-causing-dark-accelerations model would actually work.

Pythonic said:

DeiRenDopa said:

Question for long-time posters (and lurkers): can you recall any examples of MM making a *quantitative* case (argument, point, narrative)?

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No. But in fairness to MM, the main thrust of his point is not to put forth a new explanation, but a skeptical view of the "quantitative only" (?) explanation of dark matter. So, what would he model exactly?

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Indeed.

Perhaps I was too terse.

By writing "case (argument, point, narrative)", my intended meaning was not only any new (against-the-mainstream, alternative, fringe, ...) case (etc), but also any consistent, quantitative critique of any theory/model/hypothesis/idea (whether as well-established as QED, or as far out as Thornhill's Electric Star idea, or anything in between).

Where MM falls short is not providing a quantitative *refutation* of the existing model. That is, stating quantitatively where the current model fails.

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Yep ... but I think it's important to always include the second part ("*consistent*") ... it's incredibly easy to "stat[e] quantitatively where the current model fails"^; whether any such statements have a consistent basis is a whole different kettle of sardines ...

^ e.g. estimated primordial abundance of ⁷Li

Pythonic said:

No. But in fairness to MM, the main thrust of his point is not to put forth a new explanation, but a skeptical view of the "quantitative only" (?) explanation of dark matter. So, what would he model exactly?

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Indeed.

Where MM falls short is not providing a quantitative *refutation* of the existing model. That is, stating quantitatively where the current model fails.

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If we quantitatively come up with a number of say how many invisible elves can fit on the head of a pin, how does one refute that number "quantitatively"?

Dark energy doesn't move a single atom in an empirical experiment, so how do we know how much of it is required to move/accelerate a whole universe? How do I refute the number they come up with?