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Thread: Ring of galaxies darting away from us much faster than predicted

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    Ring of galaxies darting away from us much faster than predicted

    Sorry but this is another $100 question but an important one.

    - What is the relation between galaxy speed and GR being wrong?
    https://phys.org/news/2017-03-einstein.html

    - Does that officially move GR out of the mainstream, making place for ATM theories?
    Last edited by philippeb8; 2017-Mar-16 at 02:59 PM.

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    No, this doesn't officially move GR out of the mainstream. It is certainly interesting and may end up contributing to furthering our understanding of gravity, but no, GR has not been "proved" wrong by this new finding. Before getting too excited we should wait for this study to be well verified, at least.

    There is a truly huge mass of evidence supporting GR. To date there has never been a well verified experiment or observation that has contradicted GR. Is GR complete? Almost certainly no, as far as we can tell. But, GR is very unlikely to ever be shown to be just completely wrong. Like GR improved and extended beyond Newtonian physics, but did not make it obsolete or show it to be completely wrong. Whatever comes after GR is likely to add to the regime-space that can be explained and modeled, but it will also have to explain and model everything that GR already does at least as well as GR does. And GR explains and models a lot of things very well indeed.

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    Quote Originally Posted by Darrell View Post
    There is a truly huge mass of evidence supporting GR. To date there has never been a well verified experiment or observation that has contradicted GR.
    Not all ATM experiments have been done yet. PM me for more details, if not then let's put a blind eye and wait a few years.

    Is GR complete? Almost certainly no, as far as we can tell. But, GR is very unlikely to ever be shown to be just completely wrong. Like GR improved and extended beyond Newtonian physics, but did not make it obsolete or show it to be completely wrong. Whatever comes after GR is likely to add to the regime-space that can be explained and modeled, but it will also have to explain and model everything that GR already does at least as well as GR does. And GR explains and models a lot of things very well indeed.
    I agree. GR is certainly not 100% false but probably isn't 100% right either.

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    Quote Originally Posted by philippeb8 View Post
    Not all ATM experiments have been done yet.
    I think the acronym ATM is superfluous in that sentence. Yeah I agree, all experiments have definitely not been done. They never will be. Lots of well supported hypotheses and theories were ATM at one time. The problem with ATM isn't that the idea is literally ATM, it's that so many proponents of ATM ideas don't seem to understand the rigorous science that needs to take place for any new idea to become well verified enough to become mainstream, which takes time.

    There are a couple of reasons, at least why it takes time and lots of science. 1) Because of how easy it is to fool ourselves we've learned to be cautious and that the process has to be followed if we want useful results. Exciting new fundamental discoveries that instantly result in rewriting well established science and enable immediate, amazing new technology happen so rarely that it's pretty fair to say, "only happens in the movies.

    2) New hypotheses and theories have to explain and model things at least as well as the ones they purport to replace, and that is often a lot of ground to cover.

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    Quote Originally Posted by Darrell View Post
    I think the acronym ATM is superfluous in that sentence. Yeah I agree, all experiments have definitely not been done. They never will be. Lots of well supported hypotheses and theories were ATM at one time. The problem with ATM isn't that the idea is literally ATM, it's that so many proponents of ATM ideas don't seem to understand the rigorous science that needs to take place for any new idea to become well verified enough to become mainstream, which takes time.

    There are a couple of reasons, at least why it takes time and lots of science. 1) Because of how easy it is to fool ourselves we've learned to be cautious and that the process has to be followed if we want useful results. Exciting new fundamental discoveries that instantly result in rewriting well established science and enable immediate, amazing new technology happen so rarely that it's pretty fair to say, "only happens in the movies.
    This sounds like a "giving up" approach.

    2) New hypotheses and theories have to explain and model things at least as well as the ones they purport to replace, and that is often a lot of ground to cover.
    Like I said: I cannot talk about ATM stuff and we're drifting away from the original question so PM me to discuss this further, I will not waste your time.

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    No, it really isn't. It is a way to move forward with warranted confidence approach.

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    Quote Originally Posted by Darrell View Post
    No, it really isn't. It is a way to move forward with warranted confidence approach.
    You chose not to PM me either so that's subjectivity.

    Anyway I'm still interested to know:
    - What is the relation between galaxy speed and GR being wrong?

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    Quote Originally Posted by philippeb8 View Post
    Anyway I'm still interested to know:
    - What is the relation between galaxy speed and GR being wrong?
    If we assume that the galaxies were once satellites or neighbours of our galaxy and Andromeda and if we assume that a single simple sequence of events was responsible for imparting their velocity to them, and if we make some assumptions about how the DM halos interacted, then the connection is that they don't have a model for how a dynamical event could have generated the distribution of galaxies they see. Lots more work needed.

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    Quote Originally Posted by Shaula View Post
    If we assume that the galaxies were once satellites or neighbours of our galaxy and Andromeda and if we assume that a single simple sequence of events was responsible for imparting their velocity to them, and if we make some assumptions about how the DM halos interacted, then the connection is that they don't have a model for how a dynamical event could have generated the distribution of galaxies they see. Lots more work needed.
    Ok thanks again Shaula; I'm guessing they tried with an advanced simulator as well, given the complexity.

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    Quote Originally Posted by philippeb8 View Post
    Ok thanks again Shaula; I'm guessing they tried with an advanced simulator as well, given the complexity.
    I am not so sure they did to be honest - I think that is why more work is required. Looking at the paper (https://arxiv.org/pdf/1506.07569.pdf) their approach is a particle model with some twists. They don't cover baryonic interactions or take into account interactions with other galaxies in the local group, among a number of other simplifying assumptions. They do cover the possible sensitivity of their results to these factors but it is hard to get a feel for that based on the numbers they give. Many body gravitational systems are notoriously sensitive to initial conditions and interaction history. I am certainly not saying it is a bad piece of work - it is very interesting. But (as usual) the magazine article on it oversells it.

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    Quote Originally Posted by philippeb8 View Post
    You chose not to PM me either so that's subjectivity.
    No, I won't be PMing you. Absolutely nothing personal, just too few hours in a day to following up on everything, even if it seems interesting. One has to edit.

    Quote Originally Posted by philippeb8 View Post
    Anyway I'm still interested to know:
    - What is the relation between galaxy speed and GR being wrong?

    The researchers' model for how the satellite galaxies in question came to have the motion and location observed today requires that gravity works differently than GR describes / models. The satellite galaxies are moving faster than would be predicted using GR to model the gravitational interactions, and granting all of their starting assumptions, the other parts of their model, are accurate.

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    Quote Originally Posted by Darrell View Post
    No, I won't be PMing you. Absolutely nothing personal, just too few hours in a day to following up on everything, even if it seems interesting. One has to edit.
    Your choice. I won't be spamming either because I rationalise my efforts so no worry.

    The researchers' model for how the satellite galaxies in question came to have the motion and location observed today requires that gravity works differently than GR describes / models. The satellite galaxies are moving faster than would be predicted using GR to model the gravitational interactions, and granting all of their starting assumptions, the other parts of their model, are accurate.
    Ok so rotating galaxies in a cluster was found to be abnormal since the 1950's I think but this time dark matter is interacting as well because of their proximity.


    Thank you both!
    philippeb8
    Last edited by philippeb8; 2017-Mar-16 at 07:24 PM.

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    Quote Originally Posted by philippeb8 View Post
    What is the relation between galaxy speed and GR being wrong?
    https://phys.org/news/2017-03-einstein.html
    This is the paper Dynamical history of the Local Group in ΛCDM – II. Including external perturbers in 3D
    The title hints at an issue. The Local Group is not that affected by the expansion of the universe (Λ) because it is bound gravitationally, e.g. Hubble's law is not well matched until we look at galaxies outside of the Local Group (ETA: actually outside of the Virgo Cluster). However the abstract is mostly about dark matter.
    Then we read the paper and see ΛCDM being used in their previous 2D model, e.g. "The expansion rate of the Universe is quantified by the Hubble parameter..." and in this 3D model. Thus their results are dubious. They have explanations of their results from convectional astronomy, e.g. galaxy flyby. They only mention MOND which is known not to work except for galaxy rotation curves and is not modified GR!

    In summary: That paper may be dubious and the authors are speculating about modifications to GR.

    ETA: Anisotropic Distribution of High Velocity Galaxies in the Local Group by the same authors has the galaxy flyby explanation:
    We recently showed that several Local Group (LG) galaxies have much higher radial velocities (RVs) than in a 3D dynamical model of it based on Λ CDM, the standard cosmological paradigm (MNRAS, stx151). 5 out of these 6 galaxies are located very close to a plane with root mean square thickness of only 88.2 kpc despite a radial extent of almost 1 Mpc. This plane also passes within 140 kpc of both the Milky Way (MW) and M31 and just 6 kpc from their mid-point. The orientation of the plane is such that the MW-M31 line is only 20 ∘ from lying within it.
    We develop a basic model in which a past MW-M31 flyby encounter forms tidal dwarf galaxies that later settle into the recently discovered planes of satellites around the MW and M31. The MW-M31 orbital plane required by this scenario is oriented similarly to that of the LG dwarfs with anomalously high RVs. The fast relative motion of the MW and M31 at one time would lead to LG dwarfs being flung out via gravitational slingshot encounters. These encounters would likely be most efficient for objects flung out close to the MW-M31 orbital plane. This suggests a possible dynamical reason for our findings, which are otherwise difficult to explain as a chance alignment of isotropically distributed galaxies (probability < 0.01).
    GR has passed the tests of general relativity. The only significant test left is a direct observation of an event horizon to confirm that black holes exist.
    The modified versions of GR used to explain dark matter have not passed the tests of general relativity and some are invalid in themselves, e.g. TeVes predicts stars with a lifetime of < 1 second.
    Last edited by Reality Check; 2017-Mar-17 at 12:19 AM.

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    Quote Originally Posted by Shaula View Post
    They do cover the possible sensitivity of their results to these factors but it is hard to get a feel for that based on the numbers they give. Many body gravitational systems are notoriously sensitive to initial conditions and interaction history.
    Quote Originally Posted by The Paper
    We constrain their masses using distance and radial velocity (RV) measurements of 32 LG galaxies. To do this, we follow the trajectories of many simulated particles starting on a pure Hubble flow at redshift 9....
    Yeah, I just started reading this, and I don't even get what they're saying here. They can't possibly start some well chosen configuration of bodies at z=9 and reproduce a near exact version of what we see today, can they? I could see running the current galaxies' motions backward, but it's a long way to z=9! Seems like the current distance and velocity measurements would be so imprecise, as you say, Shaula, sensitivity to initial conditions would probably yield nonsense results long before that.
    Everyone is entitled to his own opinion, but not his own facts.

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    Quote Originally Posted by Cougar View Post
    Yeah, I just started reading this, and I don't even get what they're saying here. They can't possibly start some well chosen configuration of bodies at z=9 and reproduce a near exact version of what we see today, can they? I could see running the current galaxies' motions backward, but it's a long way to z=9! Seems like the current distance and velocity measurements would be so imprecise, as you say, Shaula, sensitivity to initial conditions would probably yield nonsense results long before that.
    I think they basically Monte Carloed it and looked for statistical measures of similarity between the velocity distributions over the cluster - but you are absolutely right. 13 billion years is a lot of time for things to diverge over!

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    Quote Originally Posted by Cougar View Post
    Yeah, I just started reading this, and I don't even get what they're saying here. They can't possibly start some well chosen configuration of bodies at z=9 and reproduce a near exact version of what we see today, can they? I could see running the current galaxies' motions backward, but it's a long way to z=9! Seems like the current distance and velocity measurements would be so imprecise, as you say, Shaula, sensitivity to initial conditions would probably yield nonsense results long before that.
    Yep I felt the same when I started reading it -it's a bit of a fantasy.

    On the other hand, here is an article about a possible past encounter between the MW and M31, which uses the distribution of satellite galaxies as evidence:

    https://darkmattercrisis.wordpress.c...dromeda-flyby/

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    This is interesting stuff - by coincidence we had a talk at our local astronomy society from Indranil Banik just a few weeks ago (and one from Dr Hongsheng Zhao a few years ago).

    Admittedly Indranil's talk was aimed more at us amateur astronomers, so left out a lot of the more complex maths, but he covered a number of other pieces of evidence as well as the local dwarf galaxy motions, all of which contributed to a case for there being more to gravity than our current understanding. Dr Zhao's talk a few years ago didn't really convince me at the time that there was real evidence for any modified gravity theories, but the latest information has at least got me thinking that they may have a case.

    At the very least, there are some interesting new observations which need to be explained...

    (NOTE : I've seen a bit of media hype already about "overturning Einstein", but that's very far from what they're proposing. Most of Newton and Einstein's theories will still be valid, but it's almost inevitable that there are additional "wrinkles" to be added to improve the models.)
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    Quote Originally Posted by philippeb8 View Post
    - What is the relation between galaxy speed and GR being wrong?
    https://phys.org/news/2017-03-einstein.html
    That article said:

    "...researchers... found a gigantic ring of galaxies darting away from us much faster than predicted. This 10 million light year-wide ring made up of small galaxies is expanding rapidly like a mini Big Bang."

    I searched for reference to this is the arxiv paper and found nothing! What gives?
    Everyone is entitled to his own opinion, but not his own facts.

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    We are once again seeing a case of caveat lector, that is, let the reader beware. It appears that certain writers are running wild with interpretation of raw data that have large uncertainties.

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    I am failing to understand what is in question here. Are the claims that 1-the current model of Gravity is wrong. 2- the current model of GR is wrong. Or 3 claiming that a new Big Bang has started?

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    Quote Originally Posted by bruno View Post
    I am failing to understand what is in question here. Are the claims that 1-the current model of Gravity is wrong. 2- the current model of GR is wrong. Or 3 claiming that a new Big Bang has started?
    The issue is that a science journalist used language to make a relatively uninteresting observation sound like everything we know is wrong... and there are people yearning to witness a major upheaval in science who want to run with it. Gravity and GR are still great models, and no new big bang has started ... and it is very misleading to describe these little galaxies as "darting away", but the journalist went to the thesaurus and found the most animated way to describe the situation possible.

    Concerning the story itself, it is nice that observations confirm that little galaxies created by a tidal interaction of two larger galaxies are, after the event, moving away from the larger galaxy in what might be described as a ring.
    Forming opinions as we speak

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    Quote Originally Posted by antoniseb View Post
    Concerning the story itself, it is nice that observations confirm that little galaxies created by a tidal interaction of two larger galaxies are, after the event, moving away from the larger galaxy in what might be described as a ring.
    It may be "nice", but it's also "interesting", and maybe even "unexpected"...

    I'm not convinced that any of the MOND or modified gravity theories are correct, but this is another piece of evidence which lends some support to them. As such it needs to be investigated and understood, rather than brushed off.
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    What would be evidence supporting the already invalid MOND or the flawed modified GR theories would be running the model in the paper using those theories and finding a match to the observations.

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    Quote Originally Posted by Hornblower View Post
    We are once again seeing a case of caveat lector, that is, let the reader beware. It appears that certain writers are running wild with interpretation of raw data that have large uncertainties.
    Thank you for the very good summary of a chronic problem.

    Regards, John M.

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    But we use GR as the main stream. Maybe that is why we cannot prove or understand gravity. Because it is not a cause or even a stand alone force, it is an effect of something much larger we don't yet understand. Stepping away from all that, I suspect Dark matter/energy could be the driving force we call gravity. As if all the matter we can detect with current technology is submerged in a dense and massive ocean that is crushing in on every space occupied by solid matter as we know it. What if GR is completely wrong, and Gravity is Dark energy/matter's weight displaced inside the cosmic cell or membrane our known universe was injected and submerged into , by the big bang. The big bang is just the inside of a black hole. The black hole is just the piercing of a cell wall by enormous displacement of membrane dark energy/matter causing a tear into a neighboring cell. Makes sense to me. Course it means life and universes are infinite. I can handle that, can you? Who knows.

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    GR and the tests that it has passed is our "proof" of gravity (nothing is actually proved in science - think about Newton's law of gravitation). We have understood gravity to a greater and greater extent for at least 400 years (Newton onwards).

    Dark matter and dark energy cannot be the driving force of gravity. The Earth has gravity and it is not made of either. We measure gravity between objects not made of dark matter or dark energy. Dark energy has a negative pressure (pushes, not pulls). The density of dark matter is much, much less than that needs to produce the gravity that we measure locally, e.g. between planets in the Solar System. We need both dark and visible matter to explain observations such as galaxy rotation curves.

    The universe is not inside a black hole. A fundamental property of a black hole is that it has a singularity in the future of all particles. The Big Bang singularity is in the past.

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    I don't think scientific fact can progress by holding onto past theories that have past tests designed to verify themselves, without plugging in new variables . And GR does nothing to explain the structure of our universe (like this additional motion of a galaxy cluster). The cosmic web structure. Nothing to explain the expansion. I somehow see more flaws in GR and any notion that claims Earth is acting on itself. Just because it has mass it attracts other mass (as we understand mass), but how many experiments have been conducted on various Dark Matter/Energy mass, and how it interacts with new particles like the higgs bosen. How might the equations change if we learn that the higgs bosen IS interacting with Dark Energy/Mass, changing its properties to zero mass where needed for matter (as we know it ) to exist? And its WAY too early to rule out that the big bang is not the inside of a black hole. We have no evidence what so ever to make that claim. In fact, it was during Hawkings admittance he had been mistaken about the lost information in black holes (now suggesting the data is stored in the event horizon), that he noted: a black holes' singularity greatly resembles the singularity at the point where our universe expanded. I cannot close my minds eye to glaring visual evidence such as that. We can see it now. I wonder why so many are so resistant to glaring visual confirmation, such as the hubble deep deep field. Look at it. It has structure, as if some foam or water with currents is pushing everything into vessels like a cardio system, or as if everything is being pushed in between some huge invisible bubbles of structure. So any excess motion of galaxies, that does not fit existing gravity theories is absolutely , very important, and needs to be investigated before continuing with the old. It could all be Very wrong, gravity could actually be compression. The earth is not the center of the universe.

    https://phys.org/news/2014-07-myster...c-rethink.html I love the last paragraph of this article. Its quite objective. If previous beliefs or theories can't explain it, we must, for the sake of good science, let go of what we think we know, and start experimenting with new evidence, even if it means everything we painstakingly learned in the past happens to be wrong. Perhaps Dark matter is forming pancake shaped bubble around massive galaxies. Pushed verticly by the expelsion of energy by the black hole in the galaxy in the center? And the dwarf galaxies have no choice but to take the space vacated to them by the massive galaxy's interaction with the Dark Matter that engulfs them? Their longest path of least resistance . Seems possible and would certainly be visually logical. If we could see Dark Matter, and could prove how particles interact with it (such as the Higgs Bosen). So much we don't know, we , as a species should stop clinging to old theories in defiance of clear visual evidence of something that does not fit our models. I personally trust my eyes much more than some established and excepted theory that is proving inconclusive and often not at all applicable. I get excited when findings like this stump the die hard yesteryear theorists. This looks to me like a game changer. Gravity is obviously influenced by something we don't yet understand.
    Last edited by DanielAShinerock; 2017-Apr-05 at 06:24 AM.

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    Quote Originally Posted by DanielAShinerock View Post
    ...It has structure, as if some foam or water with currents is pushing everything into vessels like a cardio system, or as if everything is being pushed in between some huge invisible bubbles of structure...
    Or as if two fluids are mixing. Simulations like the Millennium Simulation quite easily reproduce the same filamentary structure we see using simple models of matter, dark matter and gravity. After all - do you look at foam on the sea surface and say "Look at that foam - there must be invisible bubbles of structure pushing the water away into those patterns"?

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    Quote Originally Posted by DanielAShinerock View Post
    I don't think scientific fact can progress by holding onto past theories that have past tests designed to verify themselves, without plugging in new variables .
    DanielAShinerock,

    First welcome to CQ.

    Second, if you have not done so already, you should review our rules - there is a link in my signature below. You might also wish to review the stickies at the top of Q&A.

    Several of our rules cover non-mainstream or Against The Mainstream (ATM) ideas - we are very strick about such things. We do not encourage wild speculation, nor advocating ATM ideas outside of a special sub-forum for that. You are violating those rules.

    You may ask questions about non-mainstream ideas in Q&A, but you will get only mainstream answers. And you may not give non-mainstreams answers to other people's questions. And just because you find some article on the Internet, does not necessarily make it mainstream.

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    Quote Originally Posted by DanielAShinerock View Post
    I don't think scientific fact can progress by holding onto past theories that have past tests designed to verify themselves, without plugging in new variables . ...
    That is not what scientific progress is , DanielAShinerock.
    Scientific progress is throwing away past theories when new evidence shows that they are totally wrong. We no longer treat the Sun as orbiting the Earth because the evidence showed that the Earth orbits the Sun.
    Scientific progress is using new evidence to create a replacement theory that also matches old evidence. Thus GR replaced Newtonian gravitation because GR matches new evidence, e.g. the perihelion precession of Mercury.

    GR is not used in "additional motion of a galaxy cluster" or "cosmic web structure". The 1933 evidence for dark matter was that applying the classical virial theorem to the galaxies in the Coma cluster gave a mass 400 times that observed. The computer simulations that calculate the large scale structure of the universe use Newtonian gravitation because this is the regime of low velocities and weak gravitational fields.

    GR does explain the observed expansion of the universe.

    Imagined "flaws" in GR and irrelevant musings are not the topic of the thread. The 2014 article Mysterious dance of dwarfs may force a cosmic rethink is not the topic of the thread.

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