Much Ado About Nothing by Peter Jackson

Peter,

Thanks again for your reply, which was to some extent helpful in identifying the source of confusion. However, I must point out that you've not addressed the specific reference to the image caption referring to "Visible 'Dark Matter'. Galaxy Cluster CL 0024+17." As demonstrated by the NASA & Wikipedia references, this is definitely a misinterpretation.

Your last response stated:

"Just to give you a flavour, a Sept AGN paper abstract is here, discussing the high density jets of re-ionized matter. And one thing I forgot the Milky Way certainly DOES 'still have' and AGN. (iro Sagattarius A) Not (back) up to any great speed yet, so the 14 hypervelocity stars it has spat out recently are still in one piece, but there's also plenty of ions and gas."

The Milky Way certainly does NOT exhibit the relativistic jets characteristic of an AGN. As I understand, the enormous gamma-ray emitting polar bubbles of plasma are thought to be the remnants of past galaxy nucleus activity. Please see the NASA press release, NASA'S Fermi Telescope Discovers Giant Structure In Our Galaxy.

Your Claude-André Faucher-Giguère, Eliot Quataert reference abstract makes no mention of dark matter. I could not find a free version of that paper, however, I think much more to the point, an FQXi essay entry attributes the observed rotational velocity of spiral galaxies to those very same AGN outflows producing spiral arms moving to the galaxy periphery. This proposal also does not require dark matter to explain the observed rotational characteristics of spiral galaxies. Please see A New Model Without Dark Matter for the Rotation of Spiral Galaxies: The Connections Among Shape, Kinematics and Evolution by Mario Everaldo de Souza.

Still trying to understand the source of confusion regarding visible dark matter, I could not find any accessable Claude-André Faucher-Giguère papers in arXiv, but I did find some with contributor Eliot Quataert. Specifically, I found a very curious report, On the Structure of Hot Gas in Halos: Implications for the Lx-Tx Relation & Missing Baryons. As the title implies this model evaluation of, as I understand, hot gases in the intraclustr medium of galaxy clusters is also applied to the composition of galaxy dark matter halos. It also suggests that galaxies were formed from primordial dark matter.

What I think may be occurring is that researchers studying the characteristics of hot gaseous intracluster media (ICM) (perhaps produced by AGN outflows) are applying their results to supposedly galactic dark matter halos thought to have been accreted from the hot gas/presumptive dark matter ICM, depleted of baryonic gases.

I can understand how confusing this is from the varying perspective of those studying hot gases in the ICM and the presumedly colocated galaxy cluster dark matter, and those that specified the presence of dark matter to explain the non-Keplerian rotational characteristics of spiral galaxies.

Keep in mind that the visible ICM matter is thought to be twice as massive as the visible galactic matter of all galaxies within a galaxy cluster. It's difficult to understand how the more massive visible ICM could have been ejected from the relativistic jets of less massive AGN.

Moreover, galactic dark matter halos are thought to be about 10x the visible mass of spiral galaxies - this mass seeming to be necessary. It's also very difficult to believe that AGNs produce much more massive dark matter galactic halos.

At any rate, I have yet to see any reference to "visible 'dark matter'" in galactic halos. I don't think there's any support for this interpretation in any of the literature.

I hope this helps, Jim

Dear Peter,

Thanks for your valuable support.

In my opinion, at this stage of the contest we should not get bogged down in minor points of differences in our viewpoints. We should pickup about 40 to 50 essays that are broadly to our liking, generally represent our viewpoints in different styles and are novel contributions in our opinion. We should rate them 'high' to see them in the list of finalists.

I definitely want to see your essay in the list of finalists!

Best of Luck

G S Sandhu

Peter,

Thanks very much for your consideration. I must say, though that the image caption "Visible 'dark matter'" certainly does not even clearly convey your assertion that it represents (as stated in the Figure 1 caption) "... a diffuse plasma medium of ions, CO and molecular gas." Neither interpretation is correct, as the 'visible' 'clouds' actually illustrates a gravity map inferred by the researchers. No plasma medium has been detected within any inferred galactic dark matter halo - no 'clouds' or anything else is visible there.

Sorry to be so obstinate - I do see value in your emphasis on the importance of plasma media in the universe. I'm just compelled to clarify points of confusion.

Best wishes - you're doing very well in the competition!

James

Thanks. The 'map' is overlaid on the image on the left, also showing REAL X ray results. The caption is, correctly, on the visible band HST image. That was precisely my point; That 'dark matter' need NOT be some mysterious unknown substance. The Ostriker quote gives the 'Concordance' view which I vary from. That fact, or that it's a different modification to yours, cannot make it 'incorrect.'

Your following comment "No plasma medium has been detected within any inferred galactic dark matter halo - no 'clouds' or anything else is visible there." is indeed incorrect.

Firstly you have two propositions; 1. "No plasma medium has been detected", which is quite wrong. 'detection' covers all forms of detection not just the limited visible wavelengths. It is detected everywhere, and generally at increasing densities nearer matter. Its normally considered as 'electron density'. Gravitation is only one indicator of a number used. In fact I disagree with gravitational mass estimation level from lensing as it ignores the kinetic diffraction well known from optics etc. (and kSZ).

2.; "no 'clouds' or anything else is visible there." Agreed, plasma scattering is not detectable in the optical range, but is otherwise. CO and molecular gas can only come from bound ions (from pair production). Wherever we find gas being formed we find the ions that form it (less in long established undisturbed gas clouds). Also check the sums; the gravitational effects can and do include the gas itself (or the plasma density is even greater!)

I'm sorry if my thesis appears to disagrees with yours, but that does not make mine wrong. I make mine very clear in the text, there are no ghost-like dark characters, just Eddie and the electrons, and Penny and the protons, who might just couple one day!

I've now read Evaraldo's essay as you suggested, and commented. It's original and I can see why you like it, as it offers your idea support. But beware of being unscientific. I suggest the best science is about 'falsifying' a model, so zeroing in and honestly analysing the conflicting, not supporting evidence. Evaraldo's does seem to conflict with much evidence, i.e. he has ring galaxies expanding not accreting! (just look at the 'spokes of the Cartwheel galaxy) so it should be an interesting process.

You'll have seen from my papers (I hope) that I do however agree with his note ref formation from Quasars. Do comment on those.

Best wishes.

Peter,

"The 'map' is overlaid on the image on the left..."

This is incorrect - the gravity map overlay I've repeated referred to is included only in the image on the right. The process using weak gravitational lensing to generate the gravity map used to produce the artificial dark matter 'cloud' overlay image is clearly and undeniably explained in the NASA announcement: Hubble Finds Ghostly Ring of Dark Matter. Both the overlaid and unmodified images are included in that document.

If you will refer to the above NASA document I'll be happy to discuss any issues you might have.

James,

You're right. If we considered 'visible' as only the optical em range the right hand image is also not strictly 'visible', same as as the left one. However, in astronomy we're almost never dealing with the optical range (which is a tiny part of observation), so 'visible' is shorthand for visible 'at' 'in' or 'by'...' i.e. it's synonymous with 'detectable'. It is a very anthropocentric view to think the 'visibly' range is more important than any other. Astronomy is by it's very nature NOT anthropocentric! The ring shown was 'detectable' by the standard lensing based mass estimation techniques that have been used for decades. The technique is not that complex, based largely on radius of curvature. Remember, our eyes use lensing, so even our visible image of the universe depends on it! Present astronomy is equivalent to 'bionic eyes', including taking lensed images and inferring both original image and lens characteristics.

The matter is indeed then rendered 'visible', and that sense it is better than just 'optical range' detection, but, I agree it is also open to as much or even more misinterpretation as other observation (certainly including optical!

I also agree that estimation of galaxy and cluster mass from lensing is faulty. It has always been to high, and I consider 'caustics' and 'gravity wells' are used too liberally as 'patches' to cover the cracks. The 'Curved space-time' basis is in any case still unexplained (however many claim it is!).

But consider this carefully; It is not just lensing that tells up of the IGM, and whether from 'space-time curved by gravity' or from simple diffraction by the (mainly) free electrons found, (with protons, positrons, CO and basic bound molecular gas) the lensing exists. (Look carefully at the optical image and you can see the many curved 'smears' around the centre which they used).

Now we know plasma DOES refract light, and very effectively, but has a refractive index very close to 1. That's why it normally isn't detectable optically. That does not mean it is not visible by other means (including first hand by Voyager 2, and other closer probes including Cluster).

Now I say the plasma etc. we find out there moves and diffracts just like plasma anywhere else, so acts like a giant lens, and propose that the fact that lensing can be quantitatively explained in this way, along with unexplained effects such as kSZ, Faraday Rotation, ellipticity, aberration, Chirality etc, is no accident. Nothing we have found contradicts this hypothesis, only current interpretation does so.

You have a different view, which I agree should be studied considered equally with all others, as the de Souza proposal. So I should then ask questions, such as do you agree there is diffuse plasma CO and molecular gas out there, and why that might not be expected to behave with the plasma we find locally. The question is one I have asked proponents of the mainstream interpretation, with, as yet, no credible answer.

I hope that fully answers your points.

Best wishes

Peter

Peter,

Thanks for you consideration and understanding. However, I object to the use of the term 'visible' in regard to the dark matter illustrated in your Fig. 1 image of galaxy cluster Cl 0024+17. That image has effectively been 'photoshopped' by NASA to illustrate the presence of dark matter that has been inferred through a complex series of analyses including the statistical analysis of minute optical distortions imparted to thousands of background galaxies - a very complex process subject to error. Again, the process is described in Hubble Finds Ghostly Ring of Dark Matter. As you say, I don't think the optical effects produced by the ICM is adequately considered in galaxy cluster weak gravitational lensing analyses used to infer dark matter.

No, this is not an issue of semantics, the term 'inferred' is applied to describe how the presence of dark matter is hypothetically determined. The term 'visible' indicates that an object can be seen through the direct detection of photons, usually but not necessarily those within the visible spectrum. Many objects, including the intracluster medium (ICM) of galaxy clusters, are visible using X-ray telescopes, for example. The 'clouds' illustrating the inferred presence of dark matter in the referenced NASA document do not represent any photons. NASA also did not intend those 'clouds' to illustrate the presence of any enormous clouds of plasma encircling the galaxy cluster. As such, I insist that your Fig. 1 image caption is misleading, as the statement: "The 'clouds' represent a diffuse plasma medium..." is completely false.

In the case of galaxy clusters, I agree with you that identified weak gravitational lensing results from the combined effects of ICM diffusion and the gravitational curvature of spacetime distorted by the combined mass of the cluster's galaxies and the more massive ICM.

Where your conception differs from both my essay and Mario Everaldo de Souza's A New Model Without Dark Matter for the Rotation of Spiral Galaxies: The Connections Among Shape, Kinematics and Evolution is that you seem accept the analyses that compensatory mass provided by some form of undetected matter is necessary to account for identified gravitational effects. My essay and de Souza's (along with several galactic models referenced in my essay that also do not require dark matter to account for observed spiral galaxy rotation) are complementary: I argue that galactic dark matter is erroneously inferred, while de Souza's model explains spiral galaxy evolution without dark matter.

Regarding "So I should then ask questions, such as do you agree there is diffuse plasma CO and molecular gas out there, and why that might not be expected to behave with the plasma we find locally:"

The presence of massive, hot plasma comprising the ICM of galaxy clusters is confirmed by detection of x-ray emissions. I don't think there is any compelling evidence that enormous massive halos of plasma envelope galaxies, contributing to their discrete rotational characteristics. I think that only proper representations of ordinary galactic mass and its gravitational effects is necessary to account for galactic rotational characteristics.

At this point in our discussion I cannot expect you to acknowledge the inappropriateness of your "Visible 'dark matter'" caption. I also understand that I'm being intractable in my arguing this point, but I assure you there is nothing personal intended.

Best wishes, Jim

I am thinking to the detection idea, or collapse in quantum mechanics, reading your Act 1-Scene 1.

I am thinking on the double slit experiment: the screen is a quantum macroscopic object; so is the photon that make interference, or the multiple screen not-correlated electron (and proton) to make quantum effect? Is it possible to distinguish the two effects?

In general a measure is a collapse of a quantum function using a macroscopic object, this is the reason of my problem.

I think that the Act 1-Scene 2 is very interesting: what happen in a half transparent(index n)-half vacuum tube in movement with velocity v, with two mirror that reflect a photon? What is the law n(v) in the rest system, and in the movement system? What happen for a neutrino in the same system? If there exist an hypothetical transparent observer (like very intelligent jellyfish), then the light velocity is the maximum velocity in the medium (for example glycerol)? The neutrino is more quick!

I must make some calculus, but your article give me some suggestions.

Amusing event: the same post has been write before (for error) in the Matthew Peter Jackson blog!

The netiquette require the erasing of this post.

Saluti

Domenico

Peter,

Thinking more about the additional effects contributing to galaxy cluster lensing, as you mentioned, I recalled seeing the Nature News article back in June, Galaxy clusters caught in motion, clearly describing the recent identification of the kSZ effect. That had been my first exposure to either the tSZ of kSZ effect.

Interestingly, I commented back then, speculating that the SZ effects should apply not only to CMB photons but all others as well, likely contributing to weak lensing effects produced by galaxy clusters that are now attributed only to gravitational effects. I further speculated that the result may be the overestimation of the total galaxy cluster mass necessary to produce the identified weak lensing effects. This then would at a minimum result in the overestimation of dark matter present within galaxy clusters.

My assertion is that the hypothesized enormous amounts of galactic dark matter have been misconceived, and that huge galactic DM halos do not actually exist.

That would not necessarily preclude the existence of dark matter to explain observed galaxy cluster lensing, or its inference (however that's accomplished) as the structural backbone of the 'cosmic web'.

I strongly suspect that, at large scales, no enormous dark matter halos envelop galaxies. I'm also beginning to suspect that, at very large scales, much of the effects attributed to dark matter in and among galaxy clusters may be the product of ICM and amorphous plasmas, as I think you suggest.

Best wishes on your work (although I suggest you focus on galaxy clusters & above :-) Jim

Peter,

I recognize that you are well prepared to defend your view. I have read about it over and over:

"I think this has proved too difficult dynamic visualisation of most readers, so introducing theoretical speculative neutrino's would just confuse more. We need to assimilate the concept that there is BOTH real and APPARENT speed, so apparent superluminal speed is allowed with no violation of c."

I don't think that I have having a problem visualizing it. But there remains something that I have asked in past and feel uncertain about of your answer:

Does relativity's length contraction consist only of remote appearances due to effects which occur upon the photons, doing the reporting, during their travels including their arrivals? In other words, does the original object suffer length contraction as a real local physical effect before the reporting photons begin their travels and undergo their own changes? Is length contraction only a remote visual effect?

Time and talk may have blurred my memory about your position. But, I do find myself reading your messages and today at least am uncertain about your answer. Thank you.

James

Peter,

Ok, I think what I have been missing in my question is that I am not asking about special relativity. I am interested in what happens in the real world. If there is a long straight closed tube with a vacuum inside it, and, that tube is lying stationary on the surface of the Earth, and, an object inside that tube is moving through it at very high speed relative to the tube and Earth, will that object experience length contraction as a real physical effect due to its velocity relative to the tube and Earth? What happens to photons afterwards is not a point of confusion. I picture the object as a thin rod with its length parallel to the tube.

James

dear Peter

this is just to say that I enjoyed reading your essay

as you expected (your post on the blog for my own essay) I found in it some intriguing physical intuitions and a little theatre, all combined in enjoyable reading material

best wishes for the competition

Giovanni

Peter,

Ok I am clear about your view. Thank you.

James