13 Comments

1. 1. jtdwyer 06:27 PM 4/23/11

   I find the interactions among galaxies to be especially interesting in considering the proposed galactic halos or spherical shells supposedly necessary to prevent the peripheral stars of spiral galaxies from flying out into space.
   
   This is an especially useful image because it seems clear that the portions of each galaxy that appear to be nearest are actually the closest to one another, since they have or are interacting.
   
   This article reports that the Hubble operators state:
   "The blossom part of the rose is a large spiral galaxy named UGC 1810. The ring shape of the galaxy's outer arm suggests to scientists that the "stem" galaxy, UGC 1813, rapidly dived through UGC 1810 at one time..."
   
   Conversely, I suggest that the curvature of the nearest portion of the 'stem', UGC 1813, has been distorted by the gravitational presence of the outer portion of the 'rose', UGC 1810. In this case, the 'stem' is only now approaching the 'rose', whose outermost spiral arm is also being distorted towards the 'stem'.
   
   Nowhere in this gravitational interaction among galaxies do I find any indication of gravitational interactions among any possible peripheral dark matter, either among dark matter or visible matter. Dark matter, if it exists, must interact gravitationally. If it existed, dark matter would represent by far most of the mass of these two galaxies. Surely an enormous amount of dark matter would have more extensively distorted the visible mass shown - especially if the 'stem' had already passed through the 'rose'. Dark matter, by any other name...

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2. 2. jtdwyer 02:45 AM 4/24/11

   I'll explain further my interpretation of the interaction of the two galaxies according to the perspective shown. The right spiral arm of the 'stem' is being curved and dispersed by the clockwise motion of the more massive outermost spiral arm of the 'rose'. Correspondingly, the outermost spiral arm of the 'rose' is being extended away from its own distant galactic center by the nearer mass of the stem galaxy.
   
   The curvature and dispersal of the right spiral arm of the 'stem' is clearly the product of its interaction with the proximal rotating mass of the rose galaxy. This indicates that the 'stem' galaxy is still moving towards the 'rose' galaxy and should be confirmable by analysis of its stellar redshifts. Moreover, this direct interaction of proximal visible masses would not be possible if these galaxies were enveloped by enormous dark matter halos, since the initial gravitational interactions would be among the two halos, then the peripheral visible mass would have most likely gravitationally interacted with the dark matter.

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3. 3. rock johny in reply to jtdwyer 05:25 PM 4/25/11

   Dark Energy is where most of the mass is; possibly both galaxies already inhabit the same globular mass of DE & DM so there is not so much of a collision except for the baryonic mass? Or another scenario that might be in agreement with the first is that the interaction already occurred and that is what accounts for the exaggerated elongation of the Stem Galaxy. I can imagine that it was more circular like most galaxies when further away so the larger blob of DM/DE already won the battle as far as who overpowered and deformed who the most.

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4. 4. jtdwyer 07:39 PM 4/25/11

   To further clarify a a few issues, the 'stem' galaxy is seen edge-on from our vantage point: is also generally considered to be a spiral galaxy.
   
   As I understand, the proposed dark matter is required to interact gravitationally with visible baryonic matter in order to provide each galaxy with sufficient gravitational force (each somehow directed to its own galactic center) - to produce the observed 'flat' rotation curve and to prevent peripheral stars from being expelled from the galaxy by the centrifugal forces produced by 'excessive' peripheral rotational velocity. If/when both galaxies were contained within a single shell or halo of dark matter prior to the completion of the two galaxies' merger, I don't see how either galaxy would be prevented from flying apart.
   
   As I understand, cosmologists currently envision that about 73% of the universe's total mass-energy is in the form of dark energy, considering mass and energy to be equivalent but separate manifestations of energy. I don't think that dark energy can considered to exhibit mass effects - dark energy is not understood except as a proxy force to explain the perceived acceleration of universal expansion. I don't think it is seem to have any role in (galactic) gravitational interactions.
   
   As you suggest, if the 'stem' galaxy already passed through the 'rose' galaxy, even as high velocity, what force opened the gap between the outermost spiral arm and it neighbors - allowing the 'stem' to pass through without even more extensive distortion of the 'rose' galaxy spiral arms and complete dispersal of their component stars and gases?

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5. 5. bucketofsquid 03:50 PM 4/26/11

   The latest test to try to find "dark matter" found nothing at all. Why not admit that just as when scaling down to subatomic levels, scaling up to galactic or higher levels requires different formulas. Then you can set about figuring those formulas out instead of trying to disguise the "our math is bad" situation. If "dark matter" or "dark energy" are real then you had best be changing the current formulas that work now because they don't include "dark matter" or "dark energy".
   
   I'm curious as to how the "dark" enthusiasts plan to change the theory of gravity, speed of light and all of the rest of basic physics to get the same results as current formulas but with the 73% mass increase that the Earth must thus have. I have yet to see anything where the darkinistas have even mentioned this. I really enjoy the "dark mass/energy doesn't interact with us but it interacts with us".

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6. 6. Wayne Williamson in reply to bucketofsquid 07:17 PM 4/26/11

   well put...

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7. 7. Wayne Williamson in reply to Wayne Williamson 07:20 PM 4/26/11

   James(jtdwyer)...you to...

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8. 8. Chris Miller in reply to bucketofsquid 07:45 AM 4/27/11

   There are (very reputable) scientists already investigating your suggestion. Search for 'Modified Newtonian Dynamics' (or just MoND) for lots more info. Current observations don't appear to support this idea, however.

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9. 9. pariver56 in reply to jtdwyer 05:12 PM 4/28/11

   You have said something really important, I don't recall the date, but I've read an abstract from the Monthly Notices of the Royal Astronomical Society, and the paper stated that instead of dark matter, gravitational interaction at galactic scale could be explained with an extended Newton's Law.

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10. 10. jtdwyer in reply to pariver56 09:50 PM 4/28/11

    Thanks - I agree, but I do not think that any modification to Newton's inverse square law of universal gravitation is necessary to explain galactic scale gravitational interactions - only to the methods of its application, particularly in the representation of masses.
    
    I'm not familiar with the paper you refer to, but I suspect the extension to Newton's law you mention is the variable effects for larger scale configurations of mass hypothesized as an alternative to dark matter. I do think that such variable effects can analytically better represent the effects of larger scale configurations of mass, but only because they counteract the error introduced by invalidly representing disperse masses as a singular point mass. I do not think that modification to Newtonian dynamics nor dark matter are necessary to correctly describe the effects of gravitation for large scale masses.
    
    The requirement for galactic dark matter originally arose from the erroneous expectation that the 'laws' of Planetary Motion empirically described by Kepler from observations of the few sparse planets orbiting the dominating Sun, which contains 99.86% of total Solar system mass. Newton in fact, in his Principia, proved that Kepler's equations were only accurate for orbitals with relatively negligible mass.
    
    There was never any basis for the invalid expectation that the rotational velocity of many billions self-gravitating stars should diminish as a function of their distance from the axis of rotation. Without exception, galaxies composed of billions of highly distributed massive objects are not planetary systems.
    
    This general assessment is more completely and technically explained by independent research in "Rotating thin-disk galaxies through the eyes of Newton", Feng & Gallo, (2010),
    http://www.arxiv.org/abs/1007.3778
    
    A similar approach using the unmodified gravitational equations of general relativity is described in: "General relativistic dynamics applied to the rotation curves of galaxies", Carrick & Cooperstock, (2010),
    http://www.arxiv.org/abs/1101.3224

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11. 11. rock johny in reply to jtdwyer 06:28 AM 5/2/11

    I didn't mean they had already passed through each other but that the Stem Galaxy had already been deformed as it has been closing in on the Rose G. It'd be pulled at and stretched out as it has gotten closer and that it's lost the battle since it's mass is so much less.
    
    I am confused about the way they map DM/DE; depictions show it globularly enveloping massive areas of the known universe but then it's seen as individually surrounding galaxies. Which is it?

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12. 12. jtdwyer in reply to rock johny 10:53 AM 5/2/11

    Dark energy is not related to dark matter except in cosmologists' so called 'standard model' of the development of the big bang universe.
    
    You're referring to dark matter, which was originally established to explain the rotational velocity and cohesiveness of (especially spiral) galaxies. It had earlier been mentioned to explain an ignored report of excessive velocities in a galaxy cluster. Cosmologists later applied it to the development of galaxies.
    
    The fundamental problem is that dark matter is only inferred to compensate for physicists estimations of gravitational effects, which, for very complex large scale aggregations of matter such as galaxies and clusters of galaxies, nearly always (but not always) fall short of the gravitational effects observed.
    
    So they use dark matter kind of like the butcher used to use his finger on the scale to make the answer more convenient. It is simply a 'fudge factor' that requires an imaginary form of invisible matter that cannot interact with energy or matter except gravitationally. Many millions of dollars have been spent in the past few decades looking for some particle that meets those specifications, but none have been confirmed.
    
    Dark energy is something completely unknown - a new 'fudge factor' to explain how the expansion of the universe could possibly be accelerating. Just like the Sun's energy is reduced as it radially disperses throughout space, or the brightness of a flashlight is diminished the further away it is, the expansion of the universe should decelerate as it expands. Any acceleration of expansion would require some new application of additional energy.
    
    In the late 1990s, astronomers very precisely determined a discrepancy between estimated distances derived from the luminosity of type Ia supernovae and the estimated distances to their host galaxies in which they reside derived from stand cosmological models. From that discrepancy they concluded that the expansion of the universe must have begun to accelerate about 5 billion years ago. Personally, I think they're simply looking at their data the wrong way, but I won't go into that here & now.
    
    So, the >40 year mystery of dark matter and the >10 year mystery of dark energy seem to make cosmologists very happy, because those two 'fudge factors' just happen to make all their calculations come out just the way they'd like... Otherwise, the two are completely unrelated.

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13. 13. kenkoskinen 01:32 AM 5/4/11

    Arp 273 is a thing of beauty. It's interesting that to some extent (and I mean this largely tongue-in-cheek) that such photos act a little like Rorschach or ink blot tests. People do see different things and physics within them.
    
    I favor the given scientific interpretation which has precedent-al support from the study of other galactic mergers in various stages. Without dark matter acting as a cosmic glue (whatever it is, it gravitates) the two galaxies would have been far more distorted. Of course my last statement is meant to be taken ideally since without dark matter there wouldn't be any galaxies.
    
    One hint/key of the stem galaxy having had made a pass-through is the unusual distortion of the rose blossom galaxy (UGC 1813). It is obviously so, as compared to other spiral galaxies. However, notice it still holds essentially a spiral shape. Yes, I think it's a good indication that dark matter holds galaxies together. It's important to note that dark matter may not be isolated to galactic peripheries and may to some extent also be present in the interiors of galaxies. During mergers dark matter may even be exchanged and moved about within, between and around both galaxies.
    
    Oh yes, modified Newtonian (MOND) & modified Einstein-ian gravitation hasn't been very successful in galactic modeling. These models intent to do away with the need for dark matter by changing the math in these high mass areas i.e. galaxies. However, these kind of theories do best within spiral galaxies but fall short in ellipticals and in larger structures like galactic clusters.
    
    The hunt for dark matter (that was mentioned) hasn't yet been found via experiments intended to detect WIMPs or weakly interacting massive particles but the search continues. I'm not discouraged by these failures. Keep in mind we still haven't detected even the so-called graviton believed to carry the force of gravity. Dark matter may turn out to be something we have yet to envision and might require new physics. It's an exciting time to be alive and interested in physics/cosmology!
    
    

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