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The Dark Matter Myth Magnetic Fields and Galactic Rotation Curves Introduction The shape of galactic rotation curves (i.e. the galactic rotation velocity as a function of the distance from the galactic center), has led astronomers to the conclusion that galaxies must be surrounded by an invisible massive halo of 'dark matter' which exceeds the visible mass by up to 10 times (see http://ned.ipac.caltech.edu/level5/March01/Battaner/ for a detailed review of the Dark Matter theory and 'observations' ; for a more popular account see http://www.owlnet.rice.edu/~spac250/elio/spac.html). The underlying assumption with this model is that gravity is the only force determining the dynamics of the galaxy. However, practically all rotation curves indicating the existence of dark matter have been obtained by observing the Doppler shift of gas (usually the 21 cm line of hydrogen) rather than of stars. It is generally assumed that the gas provides a tracer for the motion of the stars, but this assumption neglects the fact that ionized atoms are very much affected by electromagnetic forces: it is easy to show that with the generally assumed galactic magnetic field of 10^-6 Gauss, the Lorentz force on a thermal proton is about 10 orders of magnitude stronger than the gravitational force (assuming a galaxy of the mass and size of the Milky Way) and should therefore completely determine the dynamics of the plasma, which in turn should also have an impact on the neutral gas because of recombination. Even a large additional amount of dark matter would therefore not exclusively determine the galactic gas dynamics. Note: It is surprising that the dark matter theory has not been challenged yet on grounds of general scientific implausibility alone: as the mass of the dark matter is usually many times the normal mass of the galaxy, it would be bizarre to assume that the formation of the dark matter halo has been triggered by the normal matter (one might as well assume that the planets are responsible for the formation of the sun). One would have to conclude therefore that, on the contrary, the dark matter has led to the formation of the visible galaxy. This however would mean that all galaxies should show evidence for dark matter, which is clearly not the case. Magnetic Field Lines and Lorentz Force A magnetic field line is an imaginary line along which the Lorentz force FL= q/c*vxB = 0. This condition effectively defines the direction of the magnetic field B. However, the Lorentz force is not only zero if v is parallel to B, but also if v is zero. As velocities are by definition relative, a preferred reference frame defining v and therefore FL uniquely has to be specified. It is obvious that this can only be given by the physical object producing the magnetic field (a circumstance commonly neglected in electrodynamics). For a magnetic field produced dynamically by a plasma current (dynamo), the velocity v in the Lorentz force has therefore to be referred to the average velocity of the plasma ions in the dynamo region (as these constitute the main mass of the current system). Plasma- and Gas Dynamics in the Galactic Magnetic Field The galactic magnetic field can be assumed to be produced by a rotating plasma (dynamo region) in the more central region of the galaxy, i.e. the velocity v in the Lorentz force term has to be referred to the rotational velocity vD of this region (vD itself refers obviously to the center of the galaxy). As vD is not constant throughout the dynamo region, one would in principle have to perform an average over the whole volume, but since the magnetic field strength produced by each sub-region decreases with distance, one can assume as a first order approximation that vD is determined by the dynamo region closest to the point in question. Only charged particles with a velocity v=vD will therefore not experience any Lorentz force, i.e. this is the speed with which the plasma will be dragged along by the magnetic field. Because the condition v=vD is independent of the distance from the dynamo region, the rotation curve of the plasma is consequently constant in the outer regions of the galaxy, as observed (see illustration below). The neutral gas is of course not immediately affected by the magnetic field, but once an atom becomes ionized, it will be imparted the velocity vD by the magnetic field. If the ion recombines it will maintain the tangential speed despite not being trapped anymore by the magnetic field. If this speed exceeds the gravitational escape velocity, the atom will then escape from the galaxy. The ionization rate of the neutral gas varies obviously quite strongly throughout the galaxy, but one can estimate that a neutral atom in interstellar space is ionized after 10^6-10^9 years which is smaller or at least about equal to the dynamical time scale of the galaxy, so that most of the neutral gas should appear to co-rotate with the plasma. Because of the conservation laws of mechanics, the dynamo region must therefore continuously lose energy as well as angular momentum. This circumstance could well explain the slightly increasing rotation curve for some galaxies if one assumes a more extended dynamo region (in a different context, this mechanism could also account for the apparent loss of angular momentum in the process of star formation). On the other hand, rotation curves decreasing with distance could indicate that the (rotating) galactic magnetic field blends into the (near-stationary) intergalactic magnetic field. The plasma dynamics in the magnetic field of galaxies could in this sense explain most of the rotation curves seen as an evidence for dark matter. ![]() Schematic representation of galactic gas rotation: the plasma at the rim of the central dynamo region rotates with velocity vD. Therefore the magnetic field lines outside the dynamo region rotate with the same velocity (v=vD), dragging the plasma with them. Note: the above is a copy of my webpage http://www.physicsmyths.org.uk/darkmatter.htm. |
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1) Cluster gas dynamics that is on scales so huge your magnetic fields cannot explain them since they'd have to be too enormous. 2) Gravitational Lensing. This is totally unaffected by any dynamical models at all. 3) Cluster dispersion velocities. Galaxies in clusters are assumed to be virialized near the center, but are moving around too fast to explain the matter that is visible. Thus, more dark matter. Quote:
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__________________
Everything I need to know I learned through Googling. |
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cyreks comment:
I agree with Thomas here with his opening statement that the dark matter around our galaxy which is ten times greater is unbelievable. As a matter of fact, it is absolutely ludicrous. My post on 'dark matter' here in the BABB is the simplist and the most realistic explanation. The small number of negative hydrogen ions in the outer gaseous perimeter of our galaxy interacting with the inner positive ions of our galaxy, create the apparent mass that does not exist. It would take a very small amount of these seperated charges to enhance the gravitational effect of the spiral structure by a factor of ten because of the enormously greater strength of the electric force as compared to gravity. |
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Fact is that galactic rotation curves constitute the main 'evidence' for it (historically anyway) and that the underlying theory on which this conclusion is reached is simply incomplete in terms of conventional physics (as outlined in my opening post). Quote:
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As long as this time is not much longer than the time scale on which the neutral gas is 'recycled' through large scale transport processes, the ionization should therefore affect the neutral gas dynamics significantly. Quote:
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What I am saying here is that the papers purporting to prove the existence of 'dark matter' through the analysis of galactic rotation curves should not have been accepted in the first place because of the point explained in my opening post. this is not to say that I support the peer review system in its present form. It is too often abused by referees to consolidate their own scientific position and block any critical work. Also, it has become prohibitively expensive, in particular for individuals, to get their work published in print. The internet will soon make the present system redundant anyway, as everybody can publish their own work with a minimal cost and everybody can make up their own mind about the scientific value of an article without being patronized by a self-appointed board of censors |
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Michael Cyrek: "I agree with Thomas here with his opening statement that the dark matter around our galaxy which is ten times greater is unbelievable. As a matter of fact, it is absolutely ludicrous."
Ho! But critics of quantum theory said much the same thing, as did critics of relativity theory. The universe is not constrained to behave in ways you or I, personally, find believable. ------ Nicely detailed post, Thomas. Good to see. |
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Assume you have a magnet with an electron moving in a circle around one of its field lines. Are you saying then that the electron would not move with the magnet if you move the latter ? |
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More than that, in order to really explain it since the magnetic fields decrease as you increase radius, neutral gas on the outskirts of the galaxy will have to be ionized LONGER than neutral gas interior (so that you can get up to the proper orbital velocity speeds). The opposite is actually the case. Quote:
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By the way, the reason they're destroyed is because of the "cascade" effect. When recombination occurs, a likely cascade photon shower is likely to occur which will result in lower energy photons rather than a single high energy UV photon. This means that ionization cannot occur beyond the Stromgren Radius for a given star. It's ridiculously close to the star for everything but the hottest O and B type stars. Quote:
By the way, Thomas, you didn't address any of my critiques. This implies to me that you didn't do your research before coming up with this idea. Best to learn about the subject in great detail before you begin to "prove" it's wrong. |
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http://adsabs.harvard.edu/cgi-bin/np...e5c03c80a07384 |
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) I would have to say that at this time it is the most scientifically valid explanation for the rotation curves of spiral galaxies. Quote:
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What you have to realize is that you must at least try to go through the peer review process if you want to convince the scientific community to look at your results. A significant part of that is referencing other people's research published in the Journals. Did I miss the references on your site? If you have not added them you should because it would go a long way toward demonstrating that you are taking a scientific approach. Good luck! ![]() |
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If an atom is ionized, it is immediately trapped by the magnetic field and moves in a Larmor circle around the local magnetic field line (this happens on a timescale given by the gyro- frequency and is about 100 sec for an ion in a magnetic field of 10^-6 Gauss). If the field line is moving itself, the ion will therefore be dragged along with the field line. This does not depend on the magnetic field strength but only on the effective velocity with which the 'magnet' is rotating. The relevant time here is the time the atom stays neutral, not the time the ion stays ionized (as already mentioned, the neutral atom maintains the velocity of the ion at the moment of recombination; if there is an overall rotation of the magnetic field, the corresponding neutral atoms will therefore have a corresponding velocity component). This time obviously becomes shorter for higher ionizing radiation intensities i.e. in the vicinity of stars. If this time is of the order of a galactic rotation, then one can say that after about one galactic rotation all neutral atoms will (on average) have been briefly ionized once and thus aquired the rotational speed of the magnetic field. The calculation of the time an atom stays neutral in interstellar space can be estimated from the solar UV flux shortward of 911 A, which is about 10^12 ph/cm^2/sec at the earth (1AU distance from the sun). At 1 pc (= 2*10^5 AU) this intensity is reduced to 25 ph/cm^2/sec (assuming no absorption, see below). Multiplying this with a photo-ionization cross section of 10^-17 cm^2 yields an ionization frequency of 2.5*10^-16/sec which corresponds to about 10^8 years. Regards the UV absorption: if you assume a hydrogen density of 0.1 cm^-3 (see http://casa.colorado.edu/Publication...ayaug/283.html ), then, with a photo-ionization cross section of 10^-17 cm^2, you get a mean free path of the UV radiation of 10^18 cm, i.e. about 1 lightyear. Also, a significant fraction of the photoelectrons (about 50% for electrons with an energy of 1 Rydberg (13.6 eV); see my website http://www.plasmafacts.de/recrsect.htm) will recombine into the ground state again, therewith restoring the UV photon. The UV radiation can therefore well penetrate into the interstellar medium. There is the further theoretical possibility of auto-ionization in the course of collisions of neutral atoms, which I have suggested to explain the nightime density of the earth's ionosphere (see my website http://www.plasmaphysics.org.uk/#auto). This would be completely independent of any radiation flux. Also, as already mentioned, other sources like cosmic rays supernova explosions etc. could produce ionization. This shows that my proposed mechanism can well fulfill the required conditions considering the uncertainties in some of the above figures (it is not necessary anyway that all galaxies fulfill the condition; after all, not all galaxies (including our own) show conclusive evidence of 'dark matter'). |
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By the way, the rationale for why spirals in clusters shouldn't exhibit the change is because the idea goes that spirals haven't had time to interact with the dynamics of the cluster yet (only the older E/SOs). As I said, I'm not necessarily in agreement that this is the explanation, but it certainly isn't outside the realm of possibility. Just to reiterate, every galaxy we've so far named has shown evidence of annamolous dynamics indicating SOMETHING isn't right about the way the matter is interacting. They all have dark matter indications, even if they don't extend all the way out to large halo distances. |
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If you take the topic addressed by me in this post for instance, this is solely my own idea and I could not possibly quote anybody else here, and for those interested in other theories of galactic rotation curves, I have indeed given a link where they can find hundreds of references if they want. Most of the proponents of the theories I criticize may probably not appreciate anyway if I quote them. By the way, I had work published in a peer reviewed journal, but the response was zero despite the original and controversial nature of the paper. In contrast, I get at least some sort of response from posting my work on the web. |
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For example, JS has noted a number of different lines of evidence that he (and most researchers) feels supports the dark matter theory. In order to get any general response from the mainstream regarding your idea, you'll probably have to show that it is applicable to several more phenomenon. I think that is one reason why MOND (while not accepted by most) gets responses - including published critiques. Dark Matter proponents look at MOND and recognize that the MOND proponents are trying to explain spiral rotation curves - for high and low surface brightness galaxies and galaxy cluster dynamics among other things. So dark matter supporters have evaluated MOND for themselves. Quote:
I suppose this story probably supports your point more than contradicts it, but I really feel that had I had the same scientific editor as I had for the first paper that was accepted, I probably would have managed to get the second paper accepted. I’m not saying the second scientific editor was not patient and fair with me, but he had a different approach than the scientific editor of the first paper. In fact one major motivation for the second paper was a comment made by the referee of the first paper who said something to the effect of “Well, I still think the result is because of sample selection.” So I figured if I could demonstrate the result again with a much larger sample that could only be a good thing –and that what the second paper was about. |
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http://public.lanl.gov/alp/plasma/Pe...uurDec2000.pdf The concept of a critical ionization velocity (CIV )... If a neutral gas and a magnetized plasma are in relative motion.a rapid ionization of the neutrals take place if the kinetic energy of the neutral relative to the plasma exceeds the ionization potential cV2 of the neutrals.. |
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The main reason why I have not sent any new work to journals anymore for the last 10 years is however my unemployment (lack of proper computing resources mainly), but with the increased possibilities of the internet, I would probably opt for self-publication now anyway. I feel that I can critically review my work myself, so that there should not be any crucial errors in it, and it costs less time and nerves. The downpoint is that at the moment non-peer-reviewed work is still classed as second-rate, but I hope this will soon change as well. |
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