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Closing in on Dark Matter: Another “Tentative” Step

The views expressed are those of the author and are not necessarily those of Scientific American.

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Dark matter around Abell 1689 galaxy cluster

A galaxy cluster with the distribution of dark matter marked by purple overlay. Credit: NASA, ESA, E. Julio (JPL/LAM), P. Natarajan (Yale) and J-P. Kneib (LAM).

When physicists and mathematicians want to get an idea into circulation before going through all the hoo-hah of peer-reviewed publication, they often post a paper on the arXiv server, where anyone who is curious can go and read it. Some arXiv papers turn out to be important, but much evaporates on closer inspection. Judging whether a new arXiv paper is one or the other can be extremely difficult. That is certainly the case with physicist Christoph Weniger’s paper, “A Tentative Gamma-Ray Line from Dark Matter Annihilation at the Fermi Large Area Telescope,” posted on April 12, on dark matter.

Dark matter, invisible and undetectable, makes up more than a quarter of the universe and has been an enigma to physicists and astronomers for more than a century. While physicists can’t look at dark matter directly, they can try to tell-tale trails that dark matter was present. Weniger has produced an analysis of data that—if it holds up—is a major step forward in explaining dark matter, and might provide the first unambiguous evidence of what this mysterious and elusive substance is.

Of course, we’ve heard dramatic claims like this before that didn’t pan out—and it’s certainly possible this one won’t either. We won’t know which way it goes until other scientists digest the analysis and weigh in, which could take months. And even so, it may take years before the findings are confirmed. In the meantime, it’s worth having a look at this latest experimental claim, if only to see how an outsider —a theorist unaffiliated with an experimental collaboration— occasionally tries to make a splash in the big collaboration world of physics.

The outsider, of course, is Weniger. A post-doc at the Max-Planck Institute of Physics, he is not a member of the collaboration that works on the Fermi Large Area Telescope (the collaboration goes by the acronym Fermi-LAT). However, Fermi-LAT makes its data publicly available, which allowed Weniger to use it for his investigation. In fact, his analysis goes over ground that researchers collaborating on the Fermi-LAT project have already trod. When they analyzed their data in previous years, the Fermi-LAT researchers found no strong evidence for dark matter. Weniger, however, wasn’t convinced. He and a few colleagues opted to re-crunch the Fermi-LAT data and in March, posted hints of dark matter that they had spotted. Weniger’s April 12 paper goes a step further, suggesting he’s spotted an even stronger signal at a specific energy.

Weniger’s analysis relies on a theory that predicts that when particles of dark matter meet, they will annihilate one another and create photons. In principal, you should be able to spot these photons in the form of high-energy gamma rays. Since the Large Area Telescope was built to study gamma rays, it’s an ideal instrument for this kind of search.

Weniger analyzed 43 months of data, which yielded strong evidence for a gamma ray source in the outskirts of the galaxy—a region called the galactic halo—which is exactly where theorists would predict you could find dark energy annihilations. Specifically, he’s claimed to spot the candidate gamma rays at 130 billion electron volts. For those of you keen on the statistical details, he’s claiming it with as much as 4.6 sigma certainty—which is to say, a high degree of certainty. For context: In current particle physics, evidence for the Higgs boson would be accepted as a discovery at 5 sigma certainty, so 4.6 is pretty good. That said, when he incorporates the necessary statistics for his targeted search and sample size, his results drop to a 3.5 sigma certainty, barely strong enough for publication.

What makes Weniger think that he got it right while the insiders at Fermi-LAT got it wrong? His is the first to include a full 43 months of data. Previous Fermi-LAT collaboration publications, such as results published in 2010, are limited to just 11 months. In addition, to updating the dataset, Weniger has developed his own algorithms for the dark matter search, which he believes do a better job understanding the region of the galaxy where dark matter is alleged to be. This improves his chances of distinguishing the sought out gamma rays from other galactic events.

But before we pop open the champagne, there are several important caveats. As Weniger himself acknowledges, several more years of data will be needed before it’s clear whether what he thinks he’s seen is real. In addition, because Weniger isn’t a member of the team that gathers data at Fermi-LAT, it’s possible he doesn’t entirely understand how the technology involved in detecting and collecting the data may affect the data. This is something that only collaborators are likely to have studied with enough care to correct for in their analysis. The paper could amount to nothing more than another dark matter dead end.

Things might get interesting if the Journal of Cosmology and Astroparticle Physics, to which Weniger is submitting this paper, opts to publish. That stamp of approval would set Weniger’s work above a great many other arXived efforts. Another development to watch for is a response from the folks on the Fermi collaboration. They know this data better than anyone, and if there’s something to be learned from Weniger’s approach, they’ll want to take it seriously. If nothing else, this is one more in a string of recent examples that shows how we are closing in on dark matter. For now, we watch and wait.

About the Author: Daisy Yuhas is an associate editor at Scientific American Mind. You can follow her on Twitter, @daisyyuhas

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. Dredd 3:50 pm 04/23/2012

    There are also published papers and conference comments one can peruse.

    Link to this
  2. 2. TTLG 4:22 pm 04/23/2012

    Very strange. S.A. posts a non-reviewed paper while ignoring a reviewed paper which provides strong evidence that dark matter does not exist, at least in our neighborhood:

    At the very least, I would think that people here would be interested in reading this.

    Link to this
  3. 3. quarkgluonsoup 5:15 pm 04/23/2012

    Dark Matter doesn’t make up part of the universe because it doesn’t exist. It is an epicycle inserted into physical theories to account for the fact that the universe simple doesn’t behave as theory predicts.

    Link to this
  4. 4. jtdwyer 7:20 pm 04/23/2012

    TTLG – This is certainly very strange, especially since the article can’t seem to settle on whether it is dark matter or dark energy annihilations that have been discovered:
    “Weniger analyzed 43 months of data, which yielded strong evidence for a gamma ray source in the outskirts of the galaxy—a region called the galactic halo—which is exactly where theorists would predict you could find dark energy annihilations.”

    What most troubling though, is the big dark matter news last week is a new research report that failed to find dark matter where it was expected. It concludes that, even if an enormous dark matter halo does envelope the galaxy, it’s most likely that the experiments attempting to detect some kind of dark matter on Earth are not likely to succeed.

    In addition to the article references, the official announcement can be found at the European Southern Observatory’s (ESO) site:
    “Serious Blow to Dark Matter Theories?”, (4-18-12),

    Other news articles reporting on this research last week include Nature (Nature is Scientific American’s parent publication):
    “Survey finds no hint of dark matter near Solar System”, (4-19-12),

    “Has Dark Matter Gone Missing?”, (4-19-12),
    “The Case of the Missing Dark Matter”, (4-18-12),

    Unlike the research report dredged up here, the research report garnering all the news articles has been accepted for publication in the Astrophysical Journal (ApJ) but is currently freely available on an ESO preprint server: Moni-Bidin et al., (2012), “Kinematical and chemical vertical structure of the Galactic thick disk II. A lack of dark matter in the solar neighborhood”,

    BTW, I also recommend another recent research report, accepted for publication last month by the Publications of the Astronomical Society of Australia, Kroupa, (2012), “The dark matter crisis: falsification of the current standard model of cosmology”,

    Also see the video of a 2010 DM Debate including the above author at the University of Bonn:

    Back to the big news of last week, I’ve been very curiously awaiting a report in Scientific American, especially since Nature produced such a very article.
    Very strange indeed!

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  5. 5. jtdwyer 8:30 pm 04/23/2012

    Regarding this article, I’m merely a lay person, but as stated in
    “Indirect detection experiments search for the products of WIMP annihilation. If WIMPs are Majorana particles (the particle and antiparticle are the same) then two WIMPs colliding could annihilate to produce gamma rays or particle-antiparticle pairs. This could produce a significant number of gamma rays, antiprotons or positrons in the galactic halo. The detection of such a signal is not conclusive evidence for dark matter, as the production of gamma rays from other sources are not fully understood.”

    The last sentence references two sources:
    Bertone, et al.,(2005), “Particle dark matter: evidence, candidates and constraints”. Physics Reports 405: 279–390,

    Bertone and Merritt (2005), “Dark Matter Dynamics and Indirect Detection”, Modern Physics Letters A 20 (14): 1021–1036,

    Dark matter annihilations (that may produce gamma rays) are expected only in the case where so far unidentified dark matter particles are Majorana neutrinos.

    I don’t know, but I’d have to wonder why a dwarf spheroidal Milky Way satellite galaxy would be expected to produce more dark matter collisions than the supposedly enormous Milky Way dark matter halo…

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  6. 6. baileydh 8:41 pm 04/23/2012

    The author above writes “In principal, you should be able to spot these photons”. This should be “principle” (noun), meaning idea or philosophy. “Principal” (adjective, usually) means “chief”, as in the “principal Investigator” of a scientific project.

    Yesterday another article, by a different SciAm article, made similar mistakes. Could I suggest that all of them consult a dictionary if unsure which to use?

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  7. 7. trafficproducts 10:55 pm 04/23/2012

    In the universe, this needs a lot of large objects in the study of human input problem

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  8. 8. jtdwyer 1:05 am 04/24/2012

    trafficproducts: great – more junk.

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  9. 9. sjn 4:20 am 04/24/2012

    “Dark matter, invisible and undetectable, makes up more than a quarter of the universe and has been an enigma to physicists and astronomers for more than a century”

    dark matter has been an enigma for over a century???? – that would put it prior even to the establishment of the concept of an expanding universe – let alone one where the details of the expansion are dictated by dark matter/energy. Please explain? What evidence / discussion of dark matter goes back more than a century??

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  10. 10. jtdwyer 5:42 am 04/24/2012

    sjn – Good point! While Jan Oort and Fritz Zwicky each postulated the existence of some missing mass to account for their anomalous observations of stellar and galactic cluster velocities, respectively, in the early 1930s, those reports were effectively disregarded for 40 years.

    It was the precise observations of surveyed galactic disc rotation velocities by Vera Rubin and her many collaborators, primarily in the 1970s that established the apparent requirement for dark matter among most physicists. In a seminal report: Rubin et al., (1980), “Rotational properties of 21 SC galaxies with a large range of luminosities and radii, from NGC 4605 /R = 4kpc/ to UGC 2885 /R = 122 kpc”,…238..471R
    section VIII. Discussions and Conclusions states:
    “Most galaxies exhibit rising rotation velocities at the last measured velocity; only for the largest are the rotation curves flat. Thus the smallest Sc’s (i.e., lowest luminosity) exhibit the same lack of a Keplerian velocity decrease at large R [radial distances] as do the high luminosity spirals. This form for the rotation curves implies that the mass is not centrally condensed, but that significant mass is located at large R [radial distances]. The integral mass is increasing at least as fast as R. The mass is not converging to a limiting mass at the edge of the optical image. The conclusion is inescapable that non-luminous matter exists beyond the optical galaxy.”

    The fundamental problem with that conclusion is that it presupposes that disk objects orbit the central mass of the galactic bulge and should comply with Kepler’s laws of planetary motion, exhibiting rotational velocities that diminish as a function of radial distance.

    Newton explained in his Principia that Kepler’s equations were specifically suited to the Solar system, where the Sun contains 99.86% of total system mass. Keplerian rotation curve charts are the product of his third law, considering each orbital as it were independently orbiting a central mass, each representing a 2-body gravitational problem consisting of a dominating mass and a trivial one. Each relatively independent orbital’s rotation velocity diminishes as a function of its radial distance from the dominatingly massive ‘central object’, thus producing the characteristic Keplerian rotation curve. This condition does not represent that of discrete massive objects within the discs of spiral galaxies, which cannot be adequately evaluated as an independent two-body problem. The expectation that the rotational velocities of discrete masses within the self-gravitating discs of spiral galaxies would fit Keplerian rotation curves was and is simply invalid.

    In other words, spiral galaxies are not planetary systems and the ‘laws’ of planetary motion are not universal laws. It has never been formally established that the laws of planetary motion or Keplerian rotational curves should apply to spiral galaxies. The analyses that established the requirement for galactic dark matter were invalid.

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  11. 11. 6:39 am 04/24/2012

    To jtdwyer

    Any idea regarding the % of mass at the center of milky way galaxy of the total mass of galaxy (Milky way)? Scientist believe that massive black holes are occupying central positions in galaxies?

    Can it be generalized that Kepler’s laws are applicable to the gravitational mass systems where dominant mass of system is centralized?

    One thing I can;t understand why planets revolve around the center of Solar system and other recently discovered exo planet systems in elliptical orbits and not in circular orbits which appears to be a more natural arrangement. To say that it is as per Kepler’s Law does not reveals the innate physical process

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  12. 12. jtdwyer 9:02 am 04/24/2012

    I’ll answer as best I can. There have been several studies of supermassive black hole mass in relation to the mass of their galactic bulge (see – generally 0.2% or less), but I haven’t found any that attempt to establish galactic bulge mass in relation to total galaxy mass. Since the M-sigma relation is so low, any relation to total galactic mass would be a tiny fraction. In recent years it’s been discovered that some even large spiral galaxies don’t have a significant galactic bulge. At any rate, galaxy and bulge mass is estimated from their luminosity in the visible light spectrum, which is often obscured by dust clouds. While luminosity is an excellent proxy for the mass of main-sequence stars since there is a direct causal relationship, not all galactic mass produces nuclear fusion or luminosity. It’s certainly safe to say that the spatial distribution of spiral galaxy mass is proportionately vastly greater than the Solar system.

    I’m no physicist, but again, Newton proved that Kepler’s equations were accurate only for planets whose mass was a negligible percentage of total system mass. Many people with some education in physics seem to relay on pragmatic methods of approximation that determine gravitational force in n-body systems based on total system mass represented by the center of collective mass, but as I understand this violates Newton’s stipulation that gravitation is a force between two point masses and his shell theorem that only spherically symmetrical distributions of mass can be represented as a point-mass (except when their separation distance effectively renders each to be a point).

    As an information analyst, it seems that Kepler’s first law specifying that the orbit of every planet is an ellipse is simply a product of empirical observation and, as you say, does not explain why elliptical orbits occur. As I understand, the actual causes of orbital eccentricity include perturbations from other objects and possibly object mass differentials and certainly their proximities. However, as far as I can determine, the actual causes are not clearly described.

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  13. 13. 11:10 am 04/24/2012

    “At any rate, galaxy and bulge mass is estimated from their luminosity in the visible light spectrum, which is often obscured by dust clouds. While luminosity is an excellent proxy for the mass of main-sequence stars since there is a direct causal relationship, not all galactic mass produces nuclear fusion or luminosity.”

    galaxy and bulge mass is estimated from luminosity in the VISIBLE SPECTRUM. What about mass emanating from other part of the spectrum viz gamma ray, micro wave, infra red ? And what about mass of black holes which shall be a significant porion? unless this mass is not taken into account, how the real picture of mass shall emerge.

    “As I understand, the actual causes of orbital eccentricity include perturbations from other objects and possibly object mass differentials and certain”

    Perturbations from other objects? in a multi planetary system, does it mean perturbation to a planet from is peer members? In a SINGLE planetary system, should the orbit be PERFECT circular?

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  14. 14. brodix 1:47 pm 04/24/2012

    Gravity is associated with the existence of mass, but what if it’s a function of energy condensing into mass and creating a vacuum? This might explain why there is a halo of excess radiation around galaxies, but not dark energy. As well as why fusion seems to routinely produce bubbles of impurities:
    So the flat rotational curve would be due to a constant creation of mass proportional to the vacuum formed by its collapse out of energy.
    We know how mass converts to energy, but how much do we know about energy converting to mass?

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  15. 15. jtdwyer 2:42 pm 04/24/2012

    vinodsehgal1957 – regarding mass estimation from the visible light spectrum, IMO the most critical shortcoming of this method of mass estimation is likely that visible light is often obscured by opaque dust clouds, especially in the discs of spiral galaxies.

    Regarding elliptical orbits being caused by perturbances from other masses, while I can’t fully evaluate this question I think that in a perfect two-body system with one dominant mass the orbit would be circular. In addition, however, imperfect orbits are also caused by factors such as deviations from spherically symmetrical distributions of mass. When flying over a planet or moon at close proximity, for example, variations in the effects of gravitation caused by either mountains or underground masses subject a spacecraft to changing flight characteristics. In the Solar system, perturbances from other planets also affect the orbit of our singular relatively massive moon around the Earth. General relativity better predicts the proximal, precessional orbit of Mercury around the Sun than Newtonian gravitation, although I suspect its mechanical cause include the Sun’s deviation from a spherically symmetrical mass distribution at such proximity. Remember that even a non-spherically symmetrical distribution of mass such as a spiral galaxy resolves to a valid point-mass at sufficient distance…

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  16. 16. graycat 3:18 pm 04/24/2012

    to jtdwyer and all,
    You said “. It has never been formally established that the laws of planetary motion or Keplerian rotational curves should apply to spiral galaxies.”
    The laws of universal gravitation, having been well established, and well utilized [look at the success of deep space probes, etc.]could very easily be applied to multi-body problem such as a galaxy. I’m sure this has been done many times using super computers to do the job; starting with a few dozen bodies, then a few hundred, and finally billions, as in a real galaxy. I have not read anywhere that any unexpected phenomena emerge as the number of bodies and duration of the experiment gets larger. I’m sure somebody has done this using Einstienian physics as well, though i cannot reference it. The only solution is that there is extensive invisible mass beyond the visible galaxy.
    In my opinion this mass in not some exotic mystery substance [however popular the notion may be] but simply billions of planet sized objects. Since they are cold, they are invisible at any wave-length. The ambient light is too dim to illuminate them. Occultations of distant stars wouldn’t detect them because their apparent diameter would be much less than the usual distant star, and the huge distances involved would render partial occultations undetectable.
    I would like to see some scientists do a “spectral analysis of body-size distribution versus total mass at that size” within a sample galaxy. It is well understood that the total mass of smaller things usually exceeds the total mass of larger things. There is a continuum which I would call a “mass / size spectrum”. In biology the total mass of insect size animals on the Earth, or in the oceans, far exceeds the total mass of small birds and mammals for example, which far exceeds the total mass of elephants and whales. Spread over a large number of size ranges this would graph as a skewed bell curve, with, perhaps, bacteria being the most massive cohort, and virus sized critters tapering to zero at one end and blue whales at the other.
    I suspect this size distribution is also true for celestial objects. Mass of gas molecules in the perceptible universe exceeds total mass of dust which exceeds total mass of comets and asteroids which exceeds total mass of planets which exceeds total mass of stars. If one assumes this is true, one can fill in the blanks in the curve by extrapolating and interpolating from known masses. For example the total mass of stars in some given volume of space should be estimable. The amount of gas and dust should also be reasonable estimable with the new current technology. This is the first graph to construct. Then we do the same thing for each given galaxial radius. Start with the central bulge, then concentric rings out from the center. Now you’re consructing a 3-D graph: X is object size, Y is total mass of objects of that size, Z is distance from the galaxy center. There will be holes in the graph, which could be visually interpolatable.
    I would bet this would, or will some day, reveal that the outer reaches of galaxies are neither gas’n'dust, which, in any appreciable amount, would have enough surface to be detectable, nor stars, which we know already. It must be objects with a large mass to surface area ratio, ie: PLANETS. Since planets are in the middle of size to mass bell curve they would amount to the greatest amount of mass in the universe, and are essentially invisibe, and therefore account for the “missing mass” of galaxies. In fact they may be distributed throughout intergalactic space. I don’t know because I haven’t seen an analysis of gravity distribution there.

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  17. 17. jtdwyer 4:36 pm 04/24/2012

    graycat: Please note that I stipulated that Kepler’s ‘laws’ of Planetary Motion have not formally been shown to apply to spiral galaxies. That does NOT in any way imply that Newton’s laws of motion and universal gravitation do not apply to spiral galaxies.

    In recent years there has been successful research into describing the rotational characteristics of spiral galaxies using Newtonian dynamics without depending on enormous amounts of undetected matter to provide compensatory mass. They, in turn, reference preceding research into mass distribution dynamics, primarily by Kenneth Nicholson, using a concentric ring disc partitioning analyses method somewhat like you suggest, except partition mass is derived directly from it observed dynamics. Please see:

    Feng & Gallo, (2011), “Modeling the Newtonian dynamics for rotation curve analysis of thin-disk galaxies”,

    Jalocha et al, (2011), “Vertical gradients of azimuthal velocity in a global thin disk model of spiral galaxies NGC 2403, NGC 4559, NGC 4302 and NGC 5775.”, doi:10.1111/j.1365-2966.2010.17906.x,

    Also, I’m aware of one similar effort using general relativity:

    Carrick & Cooperstock, (2010), “General relativistic dynamics applied to the rotation curves of galaxies”,

    Link to this
  18. 18. Wayne Williamson 7:12 pm 04/24/2012

    I think the statement…

    “Weniger’s analysis relies on a theory that predicts that when particles of dark matter meet, they will annihilate one another and create photons.”

    pretty much says it all…think about it, that +75 percent of the mass of the universe reacts as mater/antimater….what would be the chance that even a star could exist….

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  19. 19. Wayne Williamson 7:18 pm 04/24/2012

    graycat…I think you’re on the right track…

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  20. 20. Postman1 11:34 pm 04/24/2012

    Jt- As usual, your comments are more informative than the article. Thanks and keep up the good work.

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  21. 21. jtdwyer 1:04 pm 04/25/2012

    graycat – I failed to mention that the missing galactic mass estimated by most astronomers is 6-10 times that of observed ordinary matter. While gas, dust, brown dwarfs, planets and perhaps black holes contribute very significant amounts of low luminosity mass to galactic totals, its unlikely that the total non-luminous ordinary matter could be up to 10 times more massive than the total luminous galactic matter. I suspect it is the application of improper approximation methods and the fundamentally invalid expectation that Keplerian rotation curves should apply to spiral galaxies’ vast planar distributions of masses that result in the perception that additional mass is necessary to produce observed rotational characteristics.

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  22. 22. Donzzz 1:40 pm 04/25/2012

    Scientists invented dark matter to account for the additional mass needed to keep the galaxies from flying apart. Rather then additional matter that cannot be seen or even shown to exist, this article advocates that a body’s mass varys with it energy level relative to absolute space, its “space energy level”. A body’s space energy level rises as its mass increases – this is what we perceive as the dark matter. There is not additional unseen dark matter – it is only that matter becomes more massive as its energy level relative to absolute space increases. This is just high school physics – as a force is exerted on an accelerating body, the body requires more and more force to keep it accelerating at the same rate.

    Cyclotron Mass – “When a force is exerted on a proton in a cyclotron it accelerates to a higher velocity relative to other matter. (This is a vector value, it has motion and direction as represented in Newton’s F=MA relationship). At the same time the force also elevates the proton to a higher energy level relative to space itself. This is a scalar energy, relative to space itself, it has no direction nor motion. A body always has these two forms of energy.

    This higher energy level relative to space (space energy level) is perceived as an increase in the (inertial) mass of the proton. The more force that is exerted on the particle, the more massive it becomes. At low velocities, this mass increase is modest. A particle moving at one-fifth the speed of light, for example, gains only two percent over its original “rest” mass. But at higher velocities that are easily attained in large cyclotrons, the inertial mass increase can become very large.” This holds true whether the protons are whirling around in a cyclotron or traveling as part of a star in a spiral galaxy.

    Since the velocity of stars are much higher in the outer reaches of the spiral arms of a galaxy (according to the findings of astronomer Dr. Vera C. Rubin) their protons will be at a higher space energy level and their inertial mass will therefore be greater. This phenomena not only effects the inertial mass of the proton but it also effects the strength of the proton’s gravitational force according to Issac Newton’s Law of Gravitation. As the inertial mass of the proton (nucleon) increases, the gravitational force of the nucleons will also increase.

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  23. 23. HubertB 3:52 pm 04/25/2012

    If Kepler’s equations do not apply at a galactic level and if dark matter does not exist, the only thing left is relativity. The closest distance between two stars becomes a curved line, thus a spiral. The entire galaxy starts trying to spin as one unit.
    Read section 4 of the theory of relativity. That could be a possible answer.

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  24. 24. jtdwyer 9:31 pm 04/25/2012

    HubertB – Kepler’s description of planetary motions applies to each planet and the Sun as an independent two-body problem. This condition does not correctly apply to objects within the disks of spiral galaxies.

    Please see my references in comment #17, which describe how classical and relativistic gravitation and dynamics, respectively, can be properly applied to spiral galaxies without modifications or compensatory mass. It’s critical that the disk be represented as a self-gravitating entity.

    Of course in reality, discrete objects of mass within the vast planar disks of spiral galaxies locally interact to form ad hoc objects of mass that collectively rotate around their dynamic collective center of mass. A singular disc model is an adequate simplification that can collectively represent all the disc objects an aggregation for approximation of dynamical effects.

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  25. 25. jtdwyer 9:44 pm 04/25/2012

    HubertB – Discrete objects near the periphery of a galactic disk are not just interacting gravitationally with a distant center of collective mass, they is also interacting gravitationally with many much nearer objects of mass in their galactic neighborhood, in opposition to the centrifugal force of rotation. Rapidly rotating stars located at the periphery of spiral galaxy disks are not expelled from the galaxy because the are more strongly bound to millions and even billions of relatively proximal masses throughout the disk.

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  26. 26. jtdwyer 9:46 pm 04/25/2012

    Correction – the preceding comment was intended as a response to Donzzz’s comment #22.

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  27. 27. eurotimbr 2:51 pm 04/26/2012

    “Weniger analyzed 43 months of data, which yielded strong evidence for a gamma ray source in the outskirts of the galaxy—a region called the galactic halo—which is exactly where theorists would predict you could find dark energy annihilations.”

    I think that should be “dark matter annihilations”.

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  28. 28. 2:03 am 04/27/2012

    To jtdwyer

    Ref; Post at 15

    My query at post 14 was how light from visible part of spectrum only, and that too obscured by dust, shall reflect the correct mass? What about the light from other part of the spectrum viz X-ray, gamma ray, ultra violet, infra red, radio, micro and so on. And then what about the mass of MASSIVE BLACK HOLES? Correct mass of any galaxy shall be reflected when mass of all Physical entities, whose combined gravitation force contributes to the stellar velocity, is taken into account

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  29. 29. jtdwyer 8:18 pm 04/27/2012

    As I mentionedd in comment #4, a more recent peer reviewed research report received a great deal of publicity this week:
    Moni-Bidin et al., (2012), “Kinematical and chemical vertical structure of the Galactic thick disk II. A lack of dark matter in the solar neighborhood”,

    Also, it has been pointed out to me that there had been some earlier independent, published research that agreed with the above findings. Please see: Jalocha et al., (2011), “Transverse gradients of azimuthal velocity in a global disc model of the Milky Way Galaxy”, Monthly Notices of the Royal Astronomical Society 407, 1689-1700 (2010),

    Lo and behold, yet another peer reviewed research report released this week found not evidence for dark matter in the structure composed of satellite galaxies and spherical clusters of stars orbiting the Milky Way. Please see “Vast Structure of Satellite Galaxies Discovered: Do the Milky Way’s Companions Spell Trouble for Dark Matter?”,

    Please see: Pawlowski et al., (2012), “The VPOS: a vast polar structure of satellite galaxies, globular clusters and streams around the Milky Way”, Monthly Notices of the Royal Astronomical Society, (2012) (in press),

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  30. 30. So-Crates 1:53 pm 04/28/2012

    My understanding of cosmology is from docos and science journals, so I consider myself a layman on the subject. Maths is hard. That said, space falls towards matter creating gravity wells. Wouldn’t that falling space create a pushing force, unnoticeable on the small scale of solar systems, but noticeable on the large scale of galaxies? I would go as far as to saying Gravity might not exist. We observe falling space and misinterpret it as Gravity. Yer, I re-read this and no, I’m not off my rocker.

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  31. 31. jtdwyer 6:13 am 04/29/2012

    So-Crates – If I loosely interpret what you might be saying, your ideas may to some extent align with mine. One comment: I don’t agree that space falls towards matter but I think some variable physical property of space (kinetic energy) causes objects to accelerate towards aggregations of (potential energy) mass. I think that this directional vacuum energy of space is contracted by the localized potential energy of mass. In the absence of mass (intergalactic space), the vacuum energy must disperse, expanding spacetime.

    If I’m not crazy (I’m sure I’m not!), I also don’t think these ideas conflict with either Newton or Einstein, although I’m not familiar enough with either to express them in terms that are fully compliant with either theory. That doesn’t stop me from trying (many would say too often). Rather than interjecting that discussion here also, I suggest that you refer to my last attempt, beginning with comment #27 posted to article

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  32. 32. stargazzn 2:38 pm 05/3/2012

    I’ll post this as a question. What percentage of matter in the Universe is in the form of plasma? What conditions are required for plasma to be visible? Is it possible that plasma accounts for some 99% of matter in the Universe?

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