Dark matter is alive and well, thankyouverymuch

By Phil Plait | March 1, 2011 12:30 pm

I get email press releases from various sources, and a recent one had the subject line "Prediction of Modified Gravity Theory Confirmed". I couldn’t help it; I literally snorted a bit. Modified Newtonian Dynamics (or MOND) — basically, theoretically tweaking the strength of gravity on large scales — is an attempt to circumvent the need to use dark matter to explain some things going on in the Universe, and in my opinion is interesting but unnecessary.

Why?

Well, as those of you who follow me on Twitter know, I just spent 20 out of the past 24 hours traveling from Florida back home to Boulder (next trip I’ll just ride my bike to save time) so I’m pretty exhausted. But happily, my fellow Hive Overmind Discover Magazine blogger Sean Carroll — who’s a real life cosmologist and stuff — takes this issue head-on and shows why the so-called MOND idea really doesn’t work.

Sean goes into lots of detail, but really, for an observer like me, it boils down to two words: "Bullet Cluster" (scroll down to #4 on that page). Until they can explain this, there’s no reason to even worry about MOND. That cluster is the 364 kilogram gorilla in the room, since dark matter explains it simply and easily — Sean covers it in his bullet (haha) list, so go to his post, and find out why so few astronomers seriously doubt the existence of dark matter.


Related posts:

- Found: 90% of the distant Universe
- Fermi may have spotted dark matter
- A tiny step toward dark matter

Comments (73)

  1. Sean’s write up on this stuff is the best most straight forward debunking of MOND I have read. It is a must read.

  2. Alex

    Just wondering, what’s your take on the so-called Train Wreck Cluster result? I’ve heard claims of dodgy systematics (weak lensing is obviously incredibly tricky so this is hardly surprising) but does it not temper your confidence in the Bullet Cluster as final proof (TM) just a little?

  3. Jason Dick

    While I think the Bullet Cluster is a particularly visceral demonstration of dark matter, I actually prefer the CMB as evidence, because in principle, MACHOs might still explain the Bullet Cluster (for the uninitiated, MACHOs, or MAssive Compact Halo Objects, are basically just normal matter that isn’t luminous, such as planets that are too dim to see). But with the CMB, observations demonstrate that basically no compact objects could have formed before the CMB was emitted, and yet we still see a strong dark matter signature.

    This, to me, really is the strongest evidence, because it is a rather definitive demonstration that dark matter exists, and is some form of as yet unknown particle. Of course, it has the problem that it is much harder to explain.

  4. Ryan Brown

    io9 had a good writeup about this the other day. Basically they said that MOND appeared to have predicted a particular scenario with a bit more accuracy than Dark Matter theory did. Interesting, but hardly proof in either direction.

  5. So I clicked on one of your “related posts” links. Any follow up on the Fermi gamma ray signatures?

  6. Ray

    If we assume dark matter exists, where is the detector? Shouldn’t be that hard to cobble together a box that detects darkness. Right?

  7. Amos Zeeberg (Discover Web Editor)

    I know I’m not seeing a mention of “Discovery Magazine” in this post. Couldn’t be.

  8. You better send an e-mail to the Skeptics Guide podcast then, because they seem to be waffling back and forth between dark matter and MOND. ^^

  9. réalta fuar

    There’s nothing worth snorting about in the line “Prediction of Modified Gravity Theory Confirmed”. MOND HAS made predictions that have been confirmed, as pretty much everyone realizes (including Sean C. is his excellent write-up on this). That doesn’t mean that MOND is either necessary or correct (it almost certainly isn’t, as Sean pointed out). Not to understand the difference here illustrates a fundamental misunderstanding of what science is about. MOND is a serious theory, put forth by very serious people, and can’t be trivially dismissed.

  10. Thanks for posting that! I knew it was WAY out of mainstream, but was looking for just such an explanation.

  11. Jeff R.

    Proof of dark matter in large clusters does not falsify MOND, neither does MOND’s ability to explain rotation curves better than Dark Matter falsify Dark Matter.

    Astronomers (and everyone else) have a bad habit of feeding dichotomies that are not necessarily mutually exclusive.

  12. Dave

    Disappointed by this entry, Phil. I usually enjoy your blog. “I literally snorted… no reason to even worry about MOND… few astronomers seriously doubt the existence of dark matter.”

    Of course MOND isn’t perfect, nor is it a replacement for dark matter theory. But dark matter theory has its own problems (such as: dark matter has effects, but otherwise doesn’t seem to exist. Reminds me of caloric, a little…).

    Just because something is the dominant paradigm doesn’t mean it’s right. I’m not saying MOND is right, mind you. Probably it is not. Someday, somebody who doesn’t snort at other people’s ideas will find the truth.

  13. Nicolas

    I would have liked to have read Mr. Carroll’s argument more if he wasn’t so obviously frustrated about the issue. It had a really angry undertone, which I think is typical sometimes of Sceptic arrogance. I would be much more apt to read this, and many other important issues if there wasn’t such an obvious fallacy in letting emotions run wild within a sober, inquisitive mind.

    Get a hold of yourselves. It looks bad on all of Science when you proceed with these public humiliations and other such medieval triviality, wasn’t Jerry Springer enough? We need more decency in our criticisms lest we behold the truth of our proximity of belief.

    To be frank- I want more people to become scientists, to think critically about EVERYTHING. But when you offer such bitter contempt to a different view, you immediately create a distance between me and your subject. And I don’t think I’m the only one who feels that way.

    I demand that you respect and honour your opponent, especially when they desire the same thing: truth.

  14. Daniel J. Andrews

    Every time I see the name Sean Carroll, I think you’re referring to one of my top 5 favourite biology authors , and wonder what neat connection you’ve made between astronomy and biology. Still I suppose Discover Sean Carrol has some good points too even if he isn’t a biologist. ;)

  15. Amos, I have no idea what you’re talking about. Retcon achieved.

    As for the others who think I am dismissing MOND, I’m not. As I said in the post, it’s interesting, but right now dark matter is a far better explanation for what we see, and the Bullet Cluster is extremely strong evidence that DM exists, weakening the need for MOND in the first place. MOND can make lots of predictions which are correct, but until they are of the scale of things like the Bullet Cluster, it’s not much more than an interesting idea.

  16. Gahariet

    Can we have a bit of credit for Professor McGaugh for trying to disprove MOND, getting results that didn’t back her original idea and still publishing them rather than losing them down the back of the sofa.

    Personally though I’m still not convinced on either. Dark matter seems to me to be the modern equivalent to Aether. They still both feel like placeholders used because the known science doesn’t fit the reality of observations.

  17. Joseph G

    Ok. Fine. Well played.
    You think you’re so powerful, Dark Matter, you smug bastard.
    Oh you may have won this round, yes. You may have won this skirmish, but don’t you worry, we’ll be back! We’ll build another towering edifice of mathematics, this time even more convoluted and daunting! We’ll invoke extra dimensions and brane interactions, yes, we’ll bring in the string theorists, oh, it’s going to be epic. It’ll take the best cosmologists years to sift through our equations. As long as you insist on being so damned elusive, we will haunt you, nipping at your heels, poisoning the lay public’s mind against you, and you’ll be forced to step out of the shadows – that, or collapse into a singularity of obscurity, you MACHO bastard.
    Curse you, Dark Matter, you haven’t won yet!
    Sincerely,
    –MOND

  18. Dmpalmer

    | If we assume dark matter exists, where is the detector?
    | It be that hard to cobble together a box that detects darkness. Right?

    We have a dark matter detector. The problem is that whenever it detects dark matter, a black light lights up black to tell you it has detected something.

  19. Dark matter is NOT like the Aether. More on that here:

    http://365daysofastronomy.org/2010/06/26/june-26th-dark-matter-not-like-the-luminiferous-ether/

    The reason some of us snort or act frustrated at the whole MOND business is because once upon a time it was a good idea as an alternative to Dark Matter, but now it’s an explanation for SOME of the things Dark Matter explains, but that doesn’t explain anything that Dark Matter doesn’t also explain. This doesn’t mean there isn’t some form of MOND out there, but there’s absolutely no need for it right now.

    Meanwhile, the evidence that Dark Matter is real is EXTREMELY strong, and even MOND proponents admit that there is some kind of dark matter. Yet, you get comments like the one above about Dark Matter being like the aether, and you get people who think that MOND is a viable *alternative* to Dark Matter. Then you start to get that tired old narrative about how scientists aren’t really critically thinking and evaluating all the evidence if they don’t give MOND full consideration alongside Dark Matter. That’s the standard fallacy of balance. You hear people arguing the same thing about completely nutty ideas like Plasma Cosmology. (To be clear, MOND is *not* crackpottery like Plasma Cosmology. That being said, there’s no need for it, and it should effectively be dead right now.)

    Effectively, MOND *has* been considered as an alternative to Dark Matter, and it’s been found wanting.

    Dark Matter exists. We know that now.

  20. Blizno

    6. Ray Says:
    March 1st, 2011 at 2:41 pm

    “If we assume dark matter exists, where is the detector? Shouldn’t be that hard to cobble together a box that detects darkness. Right?”

    Studying distant galaxies that behave in ways that can’t be explained by traditional understanding of gravity is the “detector”.

    4. Ryan Brown Says:
    March 1st, 2011 at 2:12 pm

    “… than Dark Matter theory did…”

    I wish that serious posters would be much more rigorous with their terminology. Of course the existence of dark matter is not a scientific theory. It is at best a hypothesis.

    The casual misuse of technical terminology only gives ammunition to the antiscience people who love to say things such as “evolution through natural selection is only a theory” and “scientists defend their theories religiously, therefore science is a religion”, etc.

    For technically trained people discussing important findings, carefully correct use of terminology is crucial to avoid misunderstandings.

  21. Joseph G

    @#3 Jason Dick: Can you explain a little more about this CMB signature that you (and the link Phil posted) speak of? I’m probably slow or mathematically challenged, but I’m still not able to picture the whole anisotropy distribution = dark matter link.

  22. Derrick Billings

    Is MOND in itself a Special Pleading writ large?

    “Dr Newtonius, Professor Schwarzdinge says that the inverse-square law doesn’t accurately predict galactic rotation!”

    “Well, maybe gravity’s equations change at very small values, eh?”

    I dunno, it just seems like the Step 2 that Needs More Detail in that cartoon.

  23. Brian137

    Good article, Phil; nice complement to Sean’s piece.

  24. Hierro

    I’ve always found Dark Matter to be interesting, but it always seemed like a cop-out to me.
    “Well, there’s some crazy stuff going on that we’re not sure about, so it must be stuff that we just can’t see.”
    Kinda reminds me of the invisible dragon in the garage that Sagan wrote in one of his books.

    I remember seeing a book talking about another alternative to the Dark Matter hypothesis called MOG by a guy named John Moffat. I’ve yet had a chance to read it but I’ve also not seen any critiques about it.
    Anyone know how well it matches with the data? Anyone got any links about if it’s wrong?

  25. MadScientist

    Hardly anyone remembers seeing the gorilla – just ask Richard Wiseman (or anyone else who studies how people think and how to fool people).

    Ethan Siegel also has a number of posts about dark matter and why MOND just doesn’t work.

    @9: It may not be trivial to dismiss, but when there are a number of phenomena which it cannot explain at all while a competing idea does explain the phenomena, then at best this “serious theory” is deficient. Unless the MOND people can somehow come up with a simple explanation which works, that idea isn’t going anywhere.

  26. Peter

    Well, so spacetime is warped where we see dark matter. But, suppose, suppose, there isn’t any energy or matter that warps spacetime there. Suppose spacetime there is warped all by itself. Suppose, suppose, the Big Bang hasn’t given the universe a clean, smooth sheet of spacetime to work with, but suppose, suppose the Big Bang instead gave the universe a sheet of spacetime to live in that is all bumpy and wobbly all by itself. How would that work out?

    Just a thought. Yes, I like viewing things at a different angle. :)

  27. Robert

    What I’ve never understood about dark matter is that it seems that the mass of a galaxy is somehow calculated from its luminosity, then compared to the amount of mass/gravity needed to make a galaxy spin as it does, and found deficient. How on earth does this lead to the conclusion that there is some exotic form of matter out there instead of that your calculation of the mass from the luminosity of a galaxy contains some huge uncertainties?

    How do we know that we haven’t underestimated the amount of interstellar dust for example? Could dark matter not be just a form of ordinary matter which isn’t luminous?

  28. Dan I

    Phil;

    I understand what you’re saying when you say you aren’t dismissing “MOND” but still I think “snorting” is a little over the top.

    MOND, while certainly not the best explanation, is an alternative scientific theory. I don’t think “snorting” at it is an appropriate response. It’s way to easy for the anti-vaxxers and creationists to seize on that kind of dismissive reaction and use it was ammo against you in a

    “See, he automatically dismisses ANYTHING even things that fit HIS definition of ‘science’ it he doesn’t believe them, so why should anyone listen to him!” argument.

    Obviously neither you nor I really care what the “true believers” in those camps think, but that kind of argument can go a long way towards getting people who are on the fence to dismiss you as well.

  29. Aubri

    At least for me, “dark matter” is unsettling because the term might as well be “magic”. As in, “We know this happens, but we don’t know why or what’s causing it. So we’ll call it ‘magic’ until we figure out what ‘magic’ is made of.” Don’t get me started on dark energy.

    But, as you say, it’s very hard to dismiss the observations out of hand. As Justice Louis Brandeis once said, “If we would guide by the light of reason, we must let our minds be bold.” As uncomfortable as the conclusion might be, you mustn’t shy away from it just because it doesn’t match your preconceived notions, or is something you consider “blasphemous”. (That’s my favorite quote, and words I try to live by.)

  30. Here is a link to an online talk I gave a year or so ago entitled “How We Know that Dark Matter Exists” :

    http://vimeo.com/4559703

    Robert @29 — Other kinds of “normal matter” that we just haven’t accounted for when converting luminosity to mass was, in fact, a real possibility for dark matter for a long time. Indeed, when Zwicky started talking about dark matter in galaxy clusters in the 1930′s, a fraction (though it turns out not that much of a fraction) of his missing mass was intracluster ionized gas that we’d later see once we observed things with X-rays.

    The reason we know that dark matter isn’t baryonic comes from observations of the light element ratios and putting them together with calculations of element formation in the very early universe. The primordial rations of deuterium, helium, lithium, and beryllium, all compared to hydrogen, can be predicted by big-bang nucleosynthesis. However, they’re all sensitive to the total density of baryons (i.e. normal matter)… and to be consistent with the observations, we can only have a small fraction of the mass we know is in the universe (from gravitational lensing and dynamics observations) in baryons. Thus, the conclusion is, dark matter has to be something else.

  31. AThinkingScientist

    Interesting and partially sad discussion here. Once upon a time not too long ago everyone knew for a fact that there was phlogiston and an aether . . .

    Peeles & Nusser quite nicely show that LCDM doesn’t really work to make the Local Volume (they find one needs to introduce extra forces or some modified gravity): “Nearby galaxies as pointers to a better theory of cosmic evolution” (2010, Nature):
    http://adsabs.harvard.edu/abs/2010Natur.465..565P

    Independently, Kroupa et al. quite nicely show that LCDM doesn’t really work to make the Local Group (they find one needs to introduce extra forces or some modified gravity): “Local-Group tests of dark-matter concordance cosmology. Towards a new paradigm for structure formation” (2010, A&A): http://adsabs.harvard.edu/abs/2010A%26A…523A..32K

    And finally, there is a science blog with some interesting contents as to overall issues with the current cosmological scenario: The Dark Matter Crisis:
    http://www.scilogs.eu/en/blog/the-dark-matter-crisis
    There is also a discussion of the Bullet Cluster – that it “proves” the existence of Dark Matter or the LCDM model would be quite a silly statement.

    So in view of this, Prof. Stacy McGaugh’s work is quite brilliantly pointing into a very specific direction we should be taking very seriously indeed.

    Dark-Matter advocates are likely to ridicule all of this, of course.

  32. réalta fuar

    @Rob Knop I can’t disagree with anything you said on science terms, I think it’s just that I found the word “snort” extremely distasteful and to use a word academics love, uncollegial.
    Personally, I think MOND is nearly at the same stage as work on “anamolous redshifts”, not quite there yet but getting close. Still, I read those papers closely, and didn’t dismiss them out of hand after glancing at their titles.

  33. shunt1

    Phil;

    There is a need for people to simply stand back from their computer models and study what the real world is trying to teach them. Computer models are not reality.

    Dark matter is a result of computer models, but this is something that has never been detected in the most advanced nuclear physics experiments. Why is that?

    Just like the Michelson-Morley Experiment proved wrong, the current astronomical “knowledge” at that time could only explain the nature of light with the concept of an hypothetical Ether.

    When (if?) this hypothetical “dark matter” can be captured and measured by something like the Large Hadron Collider (CERN LHC), then I will trust in the computer models.

    Until then, these computer models are nothing but “PlayStation physics” and have no basis in reality.

    As with the problem with “global warming”, the first priority is to establish the accuracy of the original raw data.

  34. shunt1

    During the 1970′s, there was a theory that the speed of light changed in steps. When the red shifts of galaxies were plotted, they formed shell like bands instead of a smooth transition with distance.

    Was this a measurement error or an actual property of the speed of light?

    When something unusual is being observed in astronomy, the first priority is to test the accuracy of the raw data.

  35. The neutrino existed only as a mathematical model — a “placeholder particle” — for 26 years from Pauli’s proposal in 1930 until their final discovery in 1956. When he first proposed it, he was loathe to do it. When it was finally discovered, nobody reproduced the experiment for a while because by then, nobody was surprised that it really existed.

    Just because you haven’t directly detected something, that doesn’t mean that you can’t have high confidence that it’s out there.

    And, to repeat, Dark Matter is NOT like the aether, even though people love making that comparison. The aether was a hypothesis that made predictions… predictions that experiment did not confirm. Dark Matter is a hypothesis that makes predictions, predictions that observations DO confirm.

  36. Ema Nymton

    shunt1 would be a perfect example of how wrong tends to collect in a single individual. He’s not content to be a denialist, he needs to go to other sciences and try to embrace the crackpottery.

  37. shunt1

    I fully agree that the theory and computer models of quantum jumps in the speed of light did fit the raw data. And with that theory, it was rather easy to predict which ring galaxies would fall into.

    The Aether was a prediction that a laboratory experiment was able to falsify. The ability to falsify a theory, is a basic requirement of all honest science.

    To my knowledge, I have not seen a single laboratory experiment that has verified the “dark matter” particle.

    When I see the term “dark matter” in astronomy, I simply substitute the word “Angels” and enjoy the debate.

    How many Angels can dance on the head of a pin in the LHC?

    What is the actual mass of these Angels?

    Can we actually measure the mass of an Angle in our most advanced physical experiments?

    Personally, compared to the Angel theory, the quantum decay of light speed had much more data to support it.

    One of my first jobs was to analyze spectral photo plates back in 1972. I am not exactly ignorant about our current theories of astronomy and how that data was obtained.

    However, from first hand experience, I have learned to question the raw data first, before modifying our concepts of basic Physics.

  38. shunt1

    Ema:

    “perfect example of how wrong tends to collect in a single individual”

    I have no clue what you were even trying to say….

    At the moment, I am trying to talk about our computer models and how well thay can reproduce the actual physical reality, if the raw data that they analyze is not accurate.

    Why is this basic concept of science even debatable?

  39. CB

    @Aubri Says:

    At least for me, “dark matter” is unsettling because the term might as well be “magic”. As in, “We know this happens, but we don’t know why or what’s causing it. So we’ll call it ‘magic’ until we figure out what ‘magic’ is made of.” Don’t get me started on dark energy.

    Why is it unsettling that astronomers would humbly acknowledge that they don’t understand what is happening by giving it, essentially, a placeholder-name? As Neil de Grasse says, astronomers are simple people. Spots on the sun ? Sun Spots. It’s a hole, it’s black, it’s a Black Hole. It’s (maybe) matter, and we can’t see it? Dark Matter. Especially when they first came up with the idea, and the simplest explanation really was that it’s just be regular matter that is too dim to see, like brown dwarfs etc.

    @ shunt1

    Dark matter is a result of computer models, but this is something that has never been detected in the most advanced nuclear physics experiments. Why is that?

    Just like the Michelson-Morley Experiment proved wrong, the current astronomical “knowledge” at that time could only explain the nature of light with the concept of an hypothetical Ether.

    If we lived in a universe where the Michelson-Morley Experiment had shown as much success as hunts for Dark Matter, as opposed to literally nothing, then we’d probably be teaching Aether Theory in schools today if not as current theory then at least as a step in the right direction. The evidence does not just exist in computer models, but in real-world observations. Or does astronomical observation of gravitational lensing not count as the “reality”. Are you one of those who only believes in phenomenon that can be generated in repeatable lab experiment? Do you not believe in geology? Is the existence of the stars up for grabs?

    As to why nothing has shown up in our most advanced physics experiments, and why that null result isn’t sufficient to refute dark matter — it’s because they have not yet been sophisticated, powerful, and sensitive enough. However we have entered an era where that is no longer the case, and multiple experiments are running right now to detect dark matter. In the coming years we will have strong evidence one way or another, and a null result will be sufficient to rule out nearly every dark matter hypothesis.

    This is because scientists already know that they have to look at what the real world is telling them, long before you came along to remind them. In fact they are anxious to compare their models and theories with the real world, which is why they’ve spent decades developing these experiments.

  40. AThinkingScientist

    @RobKnob: “The aether was a hypothesis that made predictions… predictions that experiment did not confirm. Dark Matter is a hypothesis that makes predictions, predictions that observations DO confirm.”

    … something here not quite right: I would claim to be an expert on nearby galactic astrophysical systems, and I do not know of a single prediction of the dark matter hypothesis which has been verified observationally, but I know that each computation has been falsified.

    The claimed verification of the dark matter hypothesis on large scales are mostly post-adjustments, so are far overstated.

  41. shunt1

    CB Says:

    I have absolutely no arguments about gravitational lensing. That is an actual physical measurement that can be made and verified. That theory was was falsifiable and has achieved the status of a physical fact.

    Your other argument has supported exactly what I was tring to say:

    “it’s because they have not yet been sophisticated, powerful, and sensitive enough.”

    Amazing, no matter how advanced the science is, nobody was able to prove the existence of the Aether or Angles!

    Please learn to question the raw data first. That will make you a true scientist.

    And yes, I can honestly predict that nobody will be able to prove the exhistance of Angels and how many can dance on the head of a pin.

  42. CB

    Your other argument has supported exactly what I was tring to say:

    “it’s because they have not yet been sophisticated, powerful, and sensitive enough.”

    Amazing, no matter how advanced the science is, nobody was able to prove the existence of the Aether or Angles!

    Are you just being obstinate as indicated by ending the quote where you did, or did I fail in my effort to communicate what I thought was a fairly simple point?

    The equipment in the M&M experiment was sufficiently advanced to detect the planet’s motion through the Aether, if it existed, which means the null result is strong evidence for the aether’s non-existence.

    The equipment for detecting weakly interacting particles was not sufficient to detect most of the theorized dark matter particles, if they exist, so a null result means very little. It means as much as your bathroom scale not demonstrating the existence of light pressure.

    However new experiments are sufficiently sensitive, which means they can detect dark matter, which means a null result would be significant.

    Please learn to question the raw data first. That will make you a true scientist.

    If you questioned the raw data then you would have concluded that in previous experiments a true dark matter signal would have been below the noise floor, and thus the non-detection of dark matter does not mean anything. You would conclude that we need new experiments to conclusively detect, or rule out, dark matter particles.

    Instead, you just jump to your a-priori conclusion, without questioning whether the data actually supports that conclusion.

    This hypocrisy is tediously predictable.

  43. me

    “We have a dark matter detector. The problem is that whenever it detects dark matter, a black light lights up black to tell you it has detected something.”

    Is it mounted on the dashboard of the Disaster Area stunt-ship by any chance?

  44. AThinkingScientist

    @CB: The point being made here is quite nonsensical.

    It is well known that the entire preferred parameter space for dark matter particles has already been excluded well and thoroughly.

    The only hope that remains now is that the dark matter particle has properties far away from these originally expected ones.

    So new experiments are being build, which are more sensitive, but this process can go on indefinitely because whenever the experiments fail to find the particle this null result is merely taken to mean that the experiment was not sensitive enough … thus shunti is right.
    Check out: http://www.astro.umd.edu/~ssm/darkmatter/WIMPexperiments.html

  45. shunt1

    Do you honestly understand how most red-shift data was obtained?

    I would sit in front of a microscope and view a glass photo plate of a gallaxy spectrum. Moving the wheel on my right side, the plate would be moved in 10 micron steps. As each spectral line crossed the lines in my microscope optics, I would then write down the numbers on the wheel.

    For the majority of redshift data, which current astronomy models are based upon, this is how that raw data was obtained!

    My very first computer program was to reduce those spectral lines into actual measurements, so that they could be accepted into the official records.

    This was damn hard work!

    I soon learned that my computer skills in 1972 were much more valuable than astronomy, so I switched. However, astronomy has always been my love and has never ignored.

    If you are a scientist, please study how the raw data was obtained!

    Before you start inventing new things like “dark matter”, ask yourself a very sinple question:

    Is this something new, or a result of data sampling and computer processing?

  46. shunt1

    CB Says:

    “Instead, you just jump to your a-priori conclusion, without questioning whether the data actually supports that conclusion. This hypocrisy is tediously predictable.”

    Sadly, as I have been trying to explain to you, the raw data may not actually support your conclusion.

    Honest debates like this is what I truely enjoy. Your postings are respected and thought about in detail. You should consider this as respect, which you have earned.

    Now, can you explain to me how our current data has been able to measure the mass of an Angel?

  47. I do not know of a single prediction of the dark matter hypothesis which has been verified observationally, but I know that each computation has been falsified.

    Two words: Bullet Cluster.

    If Dark Matter exists and is real, then it might (should?) be possible to find a system where most of the mass is not where most of the baryonic mass is. That’s the bullet cluster: most of the baryonic mass in between the two clusters that have passed through each other, whereas most of the mass is outside of where most of the baryonic mass is, as Dark Matter is effectively collisionless.

    Calculations using CDM also reproduce large-scale structure extremely well. Yes, there are problems with the models on smaller scales, and that’s an area of active research.

    It’s simply false to say that Dark Matter doesn’t predict or explain anything.

    Also, “each computation has been falsified”… what is that supposed to mean?

  48. I would sit in front of a microscope and view a glass photo plate of a gallaxy spectrum. Moving the wheel on my right side, the plate would be moved in 10 micron steps. As each spectral line crossed the lines in my microscope optics, I would then write down the numbers on the wheel.

    For the majority of redshift data, which current astronomy models are based upon, this is how that raw data was obtained!

    As somebody who verified the redshift measurements for everything on this Hubble Diagram, I must admit to being rather surprised to find out that the majority of redshift data that we supposedly use nowadays comes from 1972 techniques….

    Believe it or not, technology has advanced quite a bit in the last four decades, and science has taken advantage of that. I think it’s pretty safe to say that the HUGE number of redshifts coming out of the Sloan survey, for example, didn’t use methods anything like what you’re talking about.

  49. shunt1

    Never mind, every astronomical measurement has been obtain with 0.000001 percent precision. Therefore, any computer models based upon this infinitely accurate data is absolutely perfect.

    Those of us who grew up in the “real world” know how this will end up being false.

  50. shunt1

    I am willing to listen to a decent scientific debate.

    Please explain to me, in full detail, what has been learned from this…

    Two words: Bullet Cluster.

    Please provide all links to websites that support your views of how important the Bullet Cluster is to your concept of basic Physics.

    What is correct and wrong with the current knowledge of physics, as demonstrated with the “images” of the Bullet Cluster.

    Oh, did I mention “images” of the Bullet Cluster? Please provide all images that you are basing your scientific research upon, and how they can support our currenent Physical particle knowledge.

    What, you can find this “Dark Matter” which can move Galaxies, but nobody can on find this on our planet Earth?

    Are you freeking kidding me?

  51. CB

    @AThinkingScientist:

    Obviously as your own link shows only a subset of the original theoretical space has been ruled out. However that link also seems to be dated, and missing a lot of recent and ongoing experiments, like DAMA or CDMSII, which also put constraints on DM while showing tantalizing preliminary results. That article also seems to be written by someone who favors MOND, but is not aware that MOND has had to adopt dark matter or effects very much like it to explain observations that predate that article by years. So… Yeah.

    @ Shunti:

    The only conclusion I’m reaching is that previous experiments did not have sufficient sensitivity to rule out dark matter to any reasonable degree, which is true. The real experiments that will confirm or refute the hypothesis are being conducted now. I will draw conclusions about DM from those experiments as warranted. You on the other hand have already decided what the result of these experiments will be, but are saying it’s I, and every scientist working on the problem, who isn’t looking at the real world.

    And then comes the sarcasm. Awesome. Yes, let’s honestly debate about Angels. And Pink Unicorns. And Maxwell’s Caloric Aether Phlogiston Demon who holds the Philosopher’s Stone. If you replace the thing you don’t like with things known to not be real, that means the thing you don’t like doesn’t exist! This is clearly a sincere and honest level on which to debate. So let’s keep doing that!

  52. AThinkingScientist

    @Rob Knop:
    The Bulet Cluster turns out to be a real problem for LCDM:
    “Bullet Cluster: Chanllenge to LCDM Cosmology” (2010, ApJ):
    http://adsabs.harvard.edu/abs/2010ApJ…718…60L

    This is an excellent example of how hype overstates the meaning of scientific data with the added aftertaste that relevant research results that do not fit a pre-defined concept of reality are simply ignored.

    The Bullet cluster works fine with MOND, in fact better than in LCDM.

    And yes, in MOND a hot dark matter component may be needed, but this turns out to be nicely conistent with what other clusters also require, and what in fact the CMB also requires, as has been published (Rob: do you know those papers?)
    MOND and Bullet Cluster (2006, MNRAS): http://adsabs.harvard.edu/abs/2006MNRAS.371..138A
    Note that the hot dark matter emerges naturally in some ideas on how neutrino masses are generated.

    However, perhaps hot dark matter may not be needed, since most of the normal matter, which is supposed to be around given primordial nucleosynthesis, has mysteriously gone missing in our universe (this is called the unsolved “Missing Baryon Problem”). So Milgrom suggests in research papers that perhaps the dark matter needed in MOND is just this missing baryonic matter.

    MOG (another alternative) and Bullet Cluster: Yes, works without any dark matter:
    http://adsabs.harvard.edu/abs/2007MNRAS.382…29B

    Conclusion: It is false to state that the Bullet Cluster is a convincing supporting case for LCDM. In truth, it can be used as an example of where LCDM does not work well.

    Concerning falsification of computations: In my first contribution here I provided a few references to research papers which would clarify this. The failure of LCDM is on a massive scale despite very major efforts by many independently working research groups to solve the problems.

  53. AThinkingScientist

    @CB: Re: dark matter searches:

    Even if some of the contents of the link were slightly dated the exclusion of the originally expected dark matter particle properties is fact.

    To put it more blatantly: there was a prediction/expectation of what the dark matter particle ought to look like. The search gave a null result.

    So theoreticians invent other properties of the particle so experimenters can build other (expensive) detectors. Meanwhile, astronomical observations are showing a failure of the LCDM hypothesis on Local Volume scales and below. There are no theoretical options left to get LCDM into line with the observations, unless unphysical treatment of e.g. feedback or star-formation rates way too high are invented.

    Here is a thought guidance for you on one example of broad/generic failure of the LCDM hypothesis:
    nearly 80 percent of all galaxies are disk galaxies. Of these, about 60 percent do not have a classical bulge.

    Astrophysicists do not have a clue how to make so many thin large disk galaxies in a theory where dark matter clumps hit a growing galaxy all the time. The typical galaxy, which tries to grow up in the computer, bloats and thickens leading to a fairly small thick disk with a major bulge.

    In order to make a large thin disk galaxy without a bulge, a LCDM cosmologist is forced to select only such dark matter halos that do not have a violent merging history. But such cases are the very exception. And, the cosmologist is forced to include unphysical levels of supernova energy to heat the gas so it does not fall into the dark halo quickly.

  54. shunt1

    Absolutly everything that I have seen has looked like fluid dynamics to me.

    Physics tells me that this is impossible, but even the radial velocity of the galaxies follow something like a fluid.

    So, we invent something called “Dark Matter” to explain why things fail to follow the simple 1/ r^2 laws as expected from gravity.

    When people open their eyes and quit following thier computer models, then we will learn what is actually going on.

    Do I know the answer? Heck no!

  55. Joseph G

    Question: The current hypothesis seems to be that dark matter consists of particles that don’t interact electromagnetically with normal matter, interacting only via gravity and the weak force, right? And, per the Bullet Cluster observation, that said dark matter doesn’t interact with other dark matter electromagnetically, either.
    Thing is, wouldn’t it then be very easy for DM particles to collide (or rather, not “collide” as baryonic matter would and instead move through each other)?
    Here’s what I wonder – would this, combined with the putative massiveness and abundance of that they exceed the critical mass for a given (tiny) Schwarszchild radius? ‘Nother words, these particles, lead to a number of them ultimately occupying a small enough volume of space wouldn’t large concentrations of dark matter eventually lead to the creation of micro-black holes? If so, could the tiny flashes of gamma radiation from the evaporation of these black holes be observed?

  56. CB

    @ AThinkingScientist:

    Even if some of the contents of the link were slightly dated the exclusion of the originally expected dark matter particle properties is fact.

    No it isn’t, as that very link shows. Some of the original parameter space has been excluded. Not all.

    Maybe you should read your own link? I mean more than figuring out that it says “MOND good, CDM bad”.

  57. mike burkhart

    Dark matter is strange its invisable and passes thro regular matter . Its the dark side of the universe. This is what I meen when I say the universe is strange. Dark matter is the werdest thing there is.

  58. mike burkhart

    The belef in Aether emerged in aceint Greece .The Greeks thought Earth was made of four elements: Earth,Air,Fire and Water the heavens were made of Aether a fifth element.

  59. Brian137

    I consider MOND/MOG/TeVeS as reasonable attempts to explain the same set of observations that dark matter is supposed to explain. Both ideas, modified gravity and dark matter, possess at least a prima facie level of plausibility and deserve to be pursued as long as anyone is interested in doing so. I am impressed by the fact that no third possible explanation seems to have intrigued a large enough segment of the scientific community to hold much sway in the discussion despite the typical human zest to conceive alternatives.

    Here is a link to another recent essay on the subject.

    http://scienceblogs.com/startswithabang/

    I realize that some might see this linked article as supporting the same “side” as Phil’s and Sean’s, but my motive in providing the link is not to “pile on” but to call attention to something I enjoyed reading.

  60. Brian137

    On Snorting:
    Phil says,
    I couldn’t help it; I literally snorted a bit.

    Candid remark – adds a bit of spice. Sort of thing you would say to a friend but avoid in a context in which you felt constrained to be diplomatic. So which describes the milieu here? I prefer being informal enough to be ourselves. Perhaps the snort betrays a measure of disdain, but I think we already know that we do not all agree about everything anyway.

  61. Ema Nymton

    Yup.

    In general, if you give them time, the nutters will out themselves.

    shunt1 has definitely come out of the closet.

  62. Joseph G

    WOW, my sentences got scrambled somehow. Must be this new medication my doc put me on :P
    Can someone delete my last post?
    Let me try that again:
    (regarding the presumed nature of dark matter as particles that only interact gravitationally)
    Wouldn’t it then be relatively easy for DM particles to collide (or rather, not “collide” as baryonic matter would and instead move extremely near each other)?
    Here’s what I wonder – would this, combined with the putative massiveness and abundance these particles, lead to a number of them ultimately occupying a small enough volume of space that they exceed the critical mass for a given (tiny) Schwarszchild radius?
    ‘Nother words, wouldn’t large concentrations of dark matter eventually lead to the creation of micro-black holes? And if so, could the tiny flashes of gamma radiation from the evaporation of these black holes be observed?

  63. David George

    #63 Ema Nymton,

    I would say in general the nutters prefer to hide themselves in a herd of nutters, and point wherever the lead nut points. At which point the sociopathic powers simply co-opt the lead nut! It seems to work quite well in the case of nationalism, fascism, communism, corporatism, etc. Even in scientism!

  64. Gary Knoeppel

    Phil,
    Could Dark Matter, be caused by loops of gravitons pulling outside our three dimensional universe, back into our own universe, and the curvature of space-time created as time passes and mass coalesces regionally in a collapsing universe?
    If a small amount of matter is trapped equally in between the gravitational pull of two galaxies, a time distortion, would warp space. Viewed on time axis like pizza dough dripping between fingers,galaxies would pull toward each other in Deep Space.( outside our three dimmensional space ) and the effect would increase over time.
    If gravatons act as I have heard described, they pull outside our three dimmensional universe and back in. Space would overlay itself, incongruently in it’s shape and time.
    Would folded space act like a second universe completely independent of ours?
    If so Dark Matter, and Dark Energy could simply be a function of time, and a regionally collapsing universe.
    Due to the near prefect distribution of matter in the early universe, I would think the vectoring of gravitational pull outside three-dimensional space would be very difficult to differentiate from a cosmic constant.
    The way time incongruence could explain galaxy rotation.
    As matter is pulled into a black hole, it would not pour like a funnel hole in a table to the floor, but should pull on the future of the surrounding space.
    Two suns gravitationally bond fall toward black hole, one falls in, other orbits for two thousand years, as inner sun is mashed, and time slows it will still have an attraction to it’s twin that has not fallen into the hole. This would also cause an incongruent time distortion similar to that of two galaxies. Dark matter would gather toward the forward path of the galaxy, and have an orientation specific to the rotation of its stars.
    Both the black hole and the galaxy should pull toward each other folding over, reducing its mass on the surface of three-dimensional space while leaving its true mass in Deep Space unaffected. The simple reason stars rotate faster at the periphery of galaxies would be they are much closer to the super black holes at their center than can be seen by looking across three-dimensional space.
    Time incongruence to explain inter- galactic expansion.
    I need to make up some terms to explain my thoughts.
    As described above gravitational pull outside three-dimensional space would occur as time passes between any two or three galaxies. If this continued, surface mass would reduce and correct time incongruence. I would like to call this a nub galaxy pair.
    If two sets of paired up galaxies joined up the mid point time distortions could be trapped, making reduction of surface mass to three-dimensional space permanent. I would like to call this a galaxy nodule set.
    If two -? Nodules set join up a sphere would be created greatly reducing the surface mass of region on surrounding space and stabilize time in-congruencies. Causing a Space Vortex, leading to a Black Brain, and a regional collapse of the universe. Regional time would differ, but would appear consistent due to vast size of neighborhoods of galaxies being described.
    Requirement: For a regionally collapsing universe to exist, caused by bands of gravity reaching through three dimensional space to pull back on incongruant folds of our own universes fabric to occur, Both Dark Energy, and Dark Matter will have to increase with time,up to the point that the region of space they contain begins it collapse.
    I know I am missing something, yetI feel like the kid in Al Gores class 40 years ago saying it looks like South America, and Africa used to fit together. Then having the teacher say that’s just stupid. I can accept my idea is silly and wrong.
    I would just be grateful if someone would explain why.
    Why can’t Dark Matter and Dark Energy simply be a function of the warping of visable space over time.

  65. “Can we have a bit of credit for Professor McGaugh for trying to disprove MOND, getting results that didn’t back her original idea and still publishing them rather than losing them down the back of the sofa.”

    That should be “his”. Stacy is a name like Lynn or Lee or Tracy or Jamie or Chris which can be masculine or feminine.

    Yes, MOND’s success at explaining galaxy rotation curves didn’t carry over to things like galaxy clusters. But that doesn’t mean that MOND is completely wrong. The universe might contain dark matter and MOND might also be true at some level. This happens all the time: neutrinos have mass but, guess what, they aren’t the dominant component of dark matter (far from it). A few years ago, Phil’s logic would have said: either neutrinos are the dark matter, or they are massless. Similarly, a few years ago, many people believed that the universe was not spatially flat or the cosmological constant was non-zero, but not both. Yes, we should stick with the simplest theory which explains all the data. But there are several things to keep in mind: 1) there is no guarantee that the simplest theory is correct, 2) “simplest” is open to interpretation and 3) it is dangerous to assume, on the basis of today’s data, that the simplest theory is the best, and then not even consider alternatives when much better data are available.

    There are other issues. Conventional cosmology (i.e. dark matter, no MOND, concordance model) overpredicts the abundance of small galaxies whereas MOND does not. Yes, maybe there is some reason that we don’t detect them even if they are there, but the jury is still out on this one. Some folks thought it was due to the lack of perfection in n-body similations (all are imperfect to some degree, of course) but better simulations made the overprediction problem worse, so that can’t be the answer. The third alternative (and this list is not exhaustive) is that MOND works better here.

    Personally, I’m somewhat sceptical about MOND, but both the theory itself and the people who support it are much more detailed than the straw men many people set up.

  66. AThinkingScientist

    #58 @CB:

    “No it isn’t, as that very link shows. Some of the original parameter space has been excluded. Not all.

    Maybe you should read your own link? I mean more than figuring out that it says “MOND good, CDM bad”.”

    A typical and often seen trivialisation by a dark-matter enthusiast. CB’s statements sound as if the exclusion of the vast region of originally expected/predicted dark-matter properties is not particularly meaningful. Far from it. If the astronomical evidence were not so against standard-cosmologically relevant cold dark matter one could perhaps argue that we need a new generation of more sensitive experiments. But given the null result of the originally predicted dark-matter parameters plus the astronomical evidence it is becoming more an exercise of artificially upholding a belief system and denying rather than facing the evidence.

  67. Brian137

    Hello Thinking Scientist,
    First let me say that I am far from “a dark matter enthusiast.” There are so many aspects of life that I enjoy so much more than astrophysical theories that I would be trivializing the term enthusiast by applying it to the world of ideas about physics.

    The blue-colored area in this diagram
    http://xenon.astro.columbia.edu/images/XENON_sensitivity_w1T.png
    shows a region of parameter space that would be favored if dark matter particles were supersymmetric and cooperated with a particular model of Ruiz et al. But, of course, dark matter particles may not be supersymmetric, and, in fact, supersymmetry itself may not even be a valid theory. Dark matter particles might well be of a type that we have never even thought of. They may be WIMPS from a completely different part of the parameter space, or they may not react via the weak force (by exchanging W and Z bosons) at all. If they do not, the ENTIRE parameter space would become irrelevant.

    Note, that I am not arguing in favor of the existence of dark matter. I am merely disputing the significance of the “favored part of the parameter space.”

  68. Messier Tidy Upper

    @ 19. Dmpalmer :


    | If we assume dark matter exists, where is the detector?
    | It be that hard to cobble together a box that detects darkness. Right?
    We have a dark matter detector. The problem is that whenever it detects dark matter, a black light lights up black to tell you it has detected something.

    LOL. ;-)

    Looking for dark matter is certainly challenging – like finding a black cat wearing a blindfold in a black cave full of coal! ;-)

    Of course, you might frequently feel the cat brush against your legs but its still fairly hard to catch!

    We did find the neutrino and the black hole eventually; similarly I suspect we’ll unravel the mysteries of dark matter one day too – through science as we know it. :-)

  69. AThinkingScientist — the Bullet Cluster isn’t necessarily the challenge to ΛCMD that you say it is. Here’s a paper with somebody else’s models that say it’s no problem to see a few clusters like this in a ΛCDM universe: http://arxiv.org/abs/1007.3902

    There’s also the fact that “Dark Matter” does not equal ΛCDM. ΛCDM is in fact the dominant paradigm for the constituents of our Universe, and there are reasons to suspect it might be right. Dark Matter, however, is broader than that, and the existence of nonbaryonic Dark Matter is itself more sure than the particular paradigm of ΛCDM. And, indeed, the Bullet Cluster shows most of the mass not being where most of the baryonic mass is. Whether or not a given cosmological model means that the existence of a colliding cluster like this is is probably, you DO have a basic observation of most of the mass not being where most of the baryonic mass is. Thus, Dark Matter.

  70. AThinkingScientist

    @71 Rob Knob

    The Bullet Cluster was not expected in LCDM (the relative velocity of the two clusters is too high), while in MOND it comes out naturally with a hot dark matter or dark baryonic component (e.g. cold gas which cannot be found) needed which is at the same time also needed for all other galaxy clusters as well as the cosmic background (in MOND).

    As ever, the LCDM community is now turning knobs to try to make the observed effects appear to be consistent and they call the calculations they do “predictions”, although they are post-adjustments. There are many LCDM research papers around playing various scientific tricks to make the results appear consistent with the data – the length of the list of such publications would be very long.

    If you write that dark matter does not equal LCDM then you perfectly right and I agree entirely.

    BUT: _only_ with LCDM (i.e. Einstein’s General Relativity plus cold dark matter – and inflation and dark energy by the way) can you get anywhere close to what our universe actually looks like.

    So if you argue that you see the universe dominated by dark matter (which now does not need to be cold dark matter) then you left with no theory whatsoever which works unless you return to MOND (with hot dark matter or baryonic dark matter).

  71. JR

    You should look at the train wreck cluster. If the bullet cluster is proof for dark matter, the train wreck cluster is disproof.

    Seriously, look it up. I think at the end of the day you -do not- have a clear passage to simply affirm DM’s existence. It’s still up in the air all things considered.

    In my opinion, it doesn’t exist. And I don’t really feel that the bullet cluster taken by itself (ignoring all other astronomical data) challenges that opinion.

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