Is it evil to sell MOND over Dark Matter?

Earlier this week, I wrote about an article that appeared in Nature, New Scientist and other places. The article — and especially the popular writeups — talked about a problem with dark matter and how MOND (MOdified Newtonian Dynamics) solves those problems.

And I’m livid about it. Another physicist/scienceblogger thinks my anger is misplaced, and left me the following in my comments section:

Ethan – this is not a creationism debate.

Hong Sheng is a top dynamicist and he knows perfectly well what the issues are.
The whole point of science at this level is to test models and propose falsifiable alternatives.

MOND may be wrong, but it is not evil.

Cold Dark Matter is a likelier hypothesis, by far, but it has some serious problems in detail, and the underlying microphysics is essentially unknown and plagued with poorly motivated speculation.

MOND has always approached the issue from a different perspective: that you start with What You See Is What You Get, and then look for minimal modifications to account for the discrepancies.

It is a phenomenological model, and makes little attempt to be a fundamental theory of anything.

Observers tend to like it because it gives direct comparison with data and is rapidly testable.

I think Leslie Sage knew what he was doing when he published this paper.

First off, here’s the deal as far as the science goes. Whatever you choose as your theory of gravity, there are certain things it needs to explain.

1.) Earth-based phenomena. Falling, rolling, acceleration, etc., basically any motion that happens under the influence of gravity must be explicable by our theory of gravity. This includes the speed at which clocks run at different elevations and at different speeds. The only theory we’ve ever found that can do all of it? Einstein’s General Relativity. Well, and other people’s versions of General Relativity that don’t deviate too drastically from Einstein’s.

2.) The bending of starlight by matter and energy. From the apparent positions of stars during a solar eclipse to weak and strong gravitational lensing, the fact is that space gets bent by all types of energy, such as mass. By how much? And where? That’s something a theory of gravity will tell us. Einstein’s General Relativity gets this right, too, and it’s the only one that does.

3.) The orbits of massive bodies. From the planet Mercury to binary stars, calculating the orbits of objects in space is a vital test of any theory of gravity. Not only does Einstein’s General Relativity get this right, but even slight modifications to it (such as Brans-Dicke gravity) fail miserably.

There are plenty of other experiments and observations that confirm Einstein’s General Relativity as the correct theory of gravity. If we want for cosmology to work, too, we need to add dark matter to the theory. This one addition — dark matter — successfully allows us to explain a whole host of observations, including the large-scale structure in the Universe, the cosmic microwave background, the elemental abundances of hydrogen, helium, lithium and deuterium, the motion of galaxies within clusters, collisions between galaxy clusters, the observed expansion rate of the Universe, and the internal motions of spiral and elliptical galaxies.

So Einstein’s General Relativity and dark matter together explain what we see. Dark matter is the key addition that provides the extra gravitational force we need to make the Universe do what it does. Here’s what the total matter looks like — reconstructed — inside a galaxy cluster:

Yes, you’ll notice the big spikes where the galaxies are. But you’ll also notice this big, diffuse central blob that goes all the way to the outskirts. That’s what our observations tell us the dark matter looks like. You can read more about why dark matter works so well in parts I, II, III, 3.5, and IV of my series.

But out of all of these observations, one presents a small amount of difficulty for dark matter. When we simulate what the dark matter should look like at the center of individual spiral galaxies, we get an answer that’s slightly at odds with what we observe. Dark matter predicts the outer reaches of the rotation curve very well, but the very inner regions — especially of low-mass galaxies — look like they need a slight tweak. It’s a detail of dark matter theory that many people are trying to work out. An apt analogy is that the whole theory of dark matter is a beautiful boat, and these observations of the centers of spiral galaxies are like a broken oar. The boat’s in great shape, but the oar needs to be repaired.

Now, MOND comes along. MOND starts with Newton’s gravity — not Einstein’s General Relativity — and says that if we tweak Newton’s gravity, it can explain these rotation curves. It says it can do it better than General Relativity and Dark Matter together can do. And it’s right. It is, for reasons we do not fully understand, a fabulous oar.

But it’s a fabulous oar that does not fit our boat. It not only is incompatible with the cosmic microwave background, large-scale structure, galaxy cluster observations, colliding cluster observations, the elemental abundances, and the expansion history of the Universe, it’s also incompatible with the three basic tests of the theory of gravity outlined above. MOND is an oar with no boat to attach itself to. And the attempted modifications to General Relativity do not solve all (or even most of) the problems that dark matter does.

And nobody disputes these facts. The MOND people don’t, the dark matter people don’t, the simulators don’t, the observers don’t, the theorists don’t, nobody does.

And I don’t have a problem with pointing out a difficulty that dark matter has; I think that’s a good plan. But what ruffled my feathers was that the authors held up MOND like it was a reasonable alternative to dark matter. In fact, quoting from the New Scientist article:

Alternatively, they say our understanding of gravity may need modification to eliminate the need for dark matter entirely. Some existing theories, such as MOND (modified Newtonian dynamics) attempt to do just that, suggesting that gravity does not fade away as quickly as current theories predict.

And this is just contrary to fact. This idea that you can “eliminate the need for dark matter entirely” is not true. We’ve been trying. We continue to try. We cannot do it. The attempts all fail, and they fail spectacularly. While dark matter is unsettling in a lot of ways, the simple fact is that we cannot explain the things listed above (and there are a lot of them, I know) without dark matter, no matter what we’ve done to our theory of gravity. A functional boat with a broken oar is unequivocally better than a good oar with no boat. But is it evil to say otherwise?

This brings me back to Steinn‘s comment. Yes, Steinn, it is evil to present MOND as though it is a viable alternative to dark matter.

It is evil to spread information about science based only on some tiny fraction of the available data, especially when the entire data set overwhelmingly favors dark matter and crushes MOND so as to render it untenable. It isn’t evil in the same way that creationism is evil, but it is evil in the same way that pushing the steady-state-model over the Big Bang is evil.

It’s a lie based on an unfair, incomplete argument. It’s a discredited theory attacking the most valid model we have at — arguably — its only weak point. Or, to use a favorite term of mine, it is willfully ignorant to claim that MOND is reasonable in any sort of way as an alternative to dark matter. It’s possibly worse than that, because it’s selectively willful ignorance in this case.

And then I look at the effect it has. It undermines public understanding of dark matter, gravity, and the Universe, by presenting an unfeasible alternative as though it’s perfectly valid. And it isn’t perfectly valid. It isn’t even close. It has nothing to do with how good their results as scientists are; it has everything to do with the invalid, untrue, knowledge-undermining conclusions that the public receives.

And yes, I find that incredibly evil. Do you?


We have an entire empty comment thread down here waiting for your input and your thoughts. What are you waiting for?!

Comments

  1. #1 sean hogge
    October 8, 2009

    Ethan-

    In general I agree. I would dispute what can be seen as a moral judgment, however.

    To say that someone is evil for spreading disinformation tends to imply not only a knowledge if the inadequacy of the ideas being promoted, but a further knowledge of the harmful effect as well as that effect being the ultimate goal. While those who promote MOND as more than it is certainly are doing bad science, I hesitate to imply that the damage they are doing is intentional.

    Of course, that opens the debate on whether evil can be done unintentionally. Is manslaughter equal to homicide, etc. By most accounts, unintentional evil is a lesser crime than intentional. Therefore, perhaps this is gross negligence rather than evil.

    I know this may be splitting hairs, but if we’re going to demand such rigor from scientists with pet theories, shouldn’t we be doubly sure that our terminology is as accurate as possible when criticizing them?

  2. #2 Brian
    October 8, 2009

    Evil is such a vague and loaded term. I prefer to keep it restrained to casual banter, and drop it if challenged on the point. “Willfully ignorant”, on the other hand, is a precise description, and IMHO no less damning.

  3. #4 Brian
    October 8, 2009

    You’ve opened a can of worms on what is the very nature of evil itself? That’s not easy to answer. Sean’s comment couldn’t have been better, so I defer to it.

    It may be irresponsible, misleading, and downright selfish to present something that isn’t true, but that doesn’t necessarily make it “evil.” Such a severe moral judgment requires a higher level of intended harm, and I have a hard time believing the authors of MOND intentionally want to wreak havoc.

  4. #5 Robert
    October 8, 2009

    I also agree with Sean Hogge and have little to add.

    If you’re trying to say that selling MOND is harmful, then you should use the word “harmful.”

  5. #6 Sili
    October 8, 2009

    Will you go into detail on what the issue is the non-fitting parts of the rotationcurves? Can it be solved by … ‘shifting the DM around’ for lack of a better description? I mean, is it possible to model the rotation by using a non-isotropic distribution of DM (I’m not sure isotropic is the right word – it’s been too long)? If it is one could then start to look at why the distribution is as it is. That might lead to a better understand of the dynamics and nature of DM.

    Of course, if it’s completely impossible to describe the rot curves, then we have a problem.

    “Evil” is a strong word, but it’s certainly unhelpful. But you explain the situational interpretation well enough that I’ll go along with the first option.

  6. #7 sean hogge
    October 8, 2009

    I’d like to second Sili’s questions. As I’ve said elsewhere, I’d love to hear more detail about the problems we’ve yet to solve with dark matter. As well as any proposed methods to find the answers. It’s just as fun to hear about what we hope to discover as it is to hear about what’s already been discovered.

  7. #8 Nathan Myers
    October 8, 2009

    Sorry, you’re way off base. MOND as expressed has problems. DM as expressed has problems. Saying your preference is better is not evil. Saying the other is worse is not evil. They both need modification to account for present observations, and it’s almost certain that additional observations will fail to be accounted for by either.

    MOND as presently expressed is a very naïve approach that will need major work to turn into a real theory. That’s OK, there’s time.

    In the meantime, it’s very nice that you can place arrangements of DM to explain things seen. Please let us know when something DM predicts is looked for and found, after the fact. (Has that happened?)

  8. #9 dave w.
    October 8, 2009

    I’ll chime in on the moral debate by stating my firm belief (which has NOT been subjected to the scientific method) that “willful ignorance” IS “evil”. So I think you got it right.

  9. #10 Scooty Puff Jr.
    October 8, 2009

    I’m curious to know what the current thoughts are on scalar tensor vector gravity.

  10. #11 ChrisZ
    October 8, 2009

    Quibbling over whether Ethan should have used the word “evil” (a word that someone else brought into the conversation, mind you) misses the point of this post I think. No one is trying to say it’s equivalent to genocide or slavery or murder, that’s clear to anyone with a brain.

    Ethan’s point is that it’s NOT OKAY to talk about MOND as a reasonable alternative to Dark Matter. I agree. Dark Matter is the kind of thing that people want scientists to be wrong about. It plays to the popular (and incorrect) image of scientists making up crazy ideas to explain observations that are much more simply explained. People want to think, “No Dark Matter isn’t real scientists just got a number wrong in their gravity equations. Those silly scientists making stuff up again, you can never trust them.” Without actual knowledge of the evidence for Dark Matter (which the vast majority of people (even scientists) don’t have, that’s the impression you get from the article, and that’s a very bad impression to send in a society where half the population wants very badly to not believe scientists already and another 40% or so only believes them as authority figures and not because they understand how science works.

    I think what these articles do is really bad. I think it’s more than just harmful, or incorrect, it contributes to a real and important problem in our country. You don’t want to call that evil? Fine, who cares? It’s not important. What’s important is that there is a big problem with that kind of representation in a science journal or magazine, and they should know better.

  11. #12 sean hogge
    October 8, 2009

    Nathan-

    I don’t think the MOND/DM debate can be expressed as a simple preference. Ethan has shown that the failures of MOND far outweigh its successes, and in fact MOND currently fails where 200-year-old theories succeed. MOND is a step backward in ten ways, and a step forward in one.

    I don’t declare that MOND will never be viable. However, it needs so much work to even explain what’s already been explained that it can’t be the explanation for what remains to be explained. How’s that for a catch phrase?

    With DM, the problems aren’t in direct conflict with the sum of knowledge we currently possess.

    Part of what Ethan is trying to say is that it’s NOT about preferential treatment for any one theory. It’s about viability, scientific validity, and the maintenance of science as an “-ology” instead of an “-ism.”

  12. #13 sean hogge
    October 8, 2009

    ChrisZ-

    You argue about the merits of not only how science is performed, but how it is presented. Then you refuse to apply those same ideals to the criticism of (poor) science.

    If science needs to be presented correctly, our criticism of it must be held to the same standard. For criticism is an integral part of science. If it is inappropriate to present MOND’s viability as more than it is, then should it not be equally inappropriate to present the misrepresentation of MOND as more than it is?

  13. #14 Helioprogenus
    October 8, 2009

    I refuse to take this poll because evil is such an empty word, bereft of any descriptive qualities. It doesn’t do much to help in reasonable discourse and I believe, takes substance away from a reasoned argument. Describing MOND as evil, does little to engage a conversation. There are hundreds of apt adjectives in describing MOND, such as poorly reasoned, weak, bereft of data, almost unscientific, not even wrong, etc. I guess it’s a question of semantics, and I do understand your frustration with MOND, Ethan. I’m as combative and frustrated at creationism as yourself, but I still wouldn’t describe it as evil. It’s disingenuous, unreasonable, cowardly, naive, manipulative, hypocritical, hateful, misogynistic, and counterproductive. Yet, notice that all these descriptives are better suited for a reasoned argument against than evil.

  14. #15 ChrisZ
    October 8, 2009

    Sean-

    No, I don’t think it is equally inappropriate. You argue very abstractly, trying to compare two things without context. I like looking at context, that’s why I talked about the greater problem that over representation of the viability of MOND contributes to, which is a mistrust of science. Ethan’s above criticism may be slightly hyperbolic, but is certainly not equally inappropriate to the New Scientist article he was criticizing.

  15. #16 Robert
    October 8, 2009

    A previous question asked:

    –> Is String Theory an Unphysical Pile of Garbage?

    If string theory isn’t evil, then nothing else in physics is evil either.

    :D :D :D

  16. #17 creeky belly
    October 8, 2009

    I haven’t seen the formal structure of MOND, but presumably it would need to predict, well, relativistic phenomena. For me it’s a non-starter, I couldn’t use it even if I wanted to. I put it in the same category as aether theory, it would be intellectually dishonest to say that it’s tenable theory of gravity. Maybe not evil.

  17. #18 daedalus2u
    October 8, 2009

    I agree with Ethan that it is evil to push MOND over dark matter.

    As scientists the one true evil is intellectually dishonesty. To push your own ideas for your own gratification over the data and over other ideas that explain the data better is evil.

    Nathan is not saying that MOND is evil, just that it is evil to pretend that MOND explains more than it really does, and to say that dark matter does not explain what it really does explain.

    That is exactly what the creationists are doing when they use creation science to explain the fossil record, the genomes of extant organisms, radioactive dating and all the other data that science has generated. They ignore the single explanation that fits extremely well with every piece of data that is available and say their idea is a viable substitute. Anyone who does that is not a scientist, they are the same as creationists They lack the intellectual honesty to be a scientist. If you can’t see and admit where your ideas are wrong, you don’t have the temperament to be a scientist and should find other work before you damage it.

    It is ok to work in things that are far out, things that are on the edge. It is not ok to misrepresent the data and other explanations of the data that you happen to not like. It is not ok to misrepresent ideas in the popular press. A non-scientist reading the newscientist article might think that dark matter research should be defunded because MOND explains it all better.

  18. #19 MadScientist
    October 8, 2009

    I asked this before (but lost track of the thread it was in without seeing an answer): what is the distribution of Dark Matter like? Would we expect to have an abundance of this stuff within our own solar system? I just think it would be awfully funny if we did expect loads of the stuff around our little star – that would mean that the ether was there – it just doesn’t seem to have an easily measured effect and of course no demonstrated link with the transmission of light (except for gravitational lensing). I’m also curious about whether is agglomerates due to gravity or if it can pass through itself as well as other matter and thus mainly swirls around and forms huge diffuse blobs here and there.

  19. #20 James E Gambrell
    October 8, 2009

    MOND is simple speculation.
    Dark matter is a complicated speculation.
    Scientists of the future will laugh at both.
    Proponents of dark matter will realize their foolisness.

    Soon dark energy will be renamed and its quantity and qualities recognized.

    James E Gambrell, October 2009

  20. #21 Anonymous Coward
    October 8, 2009

    Ethan,

    I thought your article was well-written and fun to read.

    I would suggest – as a kindness on your part – exercising a bit of caution when judging individual scientists by what gets written up in the “popularizer” magazines. It’s certainly possible that these guys are overly into self-promotion, but I’ve always found it astonishing how things can get distorted or blown out of proportion by the popular press or university PR departments, despite efforts to the contrary from the researcher.

    Of course scientists should try to correct misleading overstatements made by journalists concerning their research, but after witnessing some of the PR statements released by my institution (from PR folks who had agreed to run their article by the researchers for fact-checking, then neglected to do so), I’m predisposed to give folks the benefit of the doubt.

  21. #22 Adrian Morgan
    October 8, 2009

    The best presentations of MOND don’t present it as an alternative to dark matter; they present a choice between “dark matter” or “dark matter plus MOND”. Presenting it as an alternative is, indeed, evil. But I’d like to know more about your views on MOND when it’s presented as a supplement (as it is, a reasonable proportion of the time).

    The case for dark matter plus MOND seemed very convincing to me this time last year. Without MOND, I thought, you have to assume that in each and every galaxy, the dark matter just happens to be distributed in such a way as that the velocity of a star is independent of its distance from the galactic centre. Obviously, any theory in which this phenomenon is just a great big cosmic coincidence is not viable. William of Ockham never shaved; in reality, every hair in his beard independently and spontaneously got shorter, and it’s just a coincidence that they all did so at exactly the same time.

    I changed my mind when I read on some website that velocity independent of radial distance is what you’d expect if the density of matter throughout the galaxy is more or less uniform. I then saw that if the galaxy is dominated by dark matter and if dark matter has some preferred density (plausibly due to some aspect of its physical properties), then dark matter could explain galaxy rotation without the need to invoke any wildly improbable cosmic coincidence.

    I don’t know if this reasoning is right in its particulars, or if there’s a better way to get to the same conclusion. I am curious about what properties of dark matter are necessary, or can be hypothesised, to explain the way galaxies rotate. For example, it occurs to me that a tendency to accumulate at a particular density might be explained by assuming that dark matter particles exhert a repulsive but short-ranged force on each other. Or if this is wrong, what alternatives are there?

  22. #23 Cody
    October 8, 2009

    As many others have remarked, “evil” seems an inappropriate word–I find the hyperbole decidedly off-putting and counter-productive.

    Also it seems to me that you count GR+DM (specifically exotic DM), as confirmatory of GR, whereas I interpret the need for an exotic DM postulate as falsifying GR.

    Also, aren’t you overstating the power of DM? I was under the impression that galaxy rotation and intergalactic motion required different distributions of DM? And isn’t it dishonest to say “[t]his one addition — dark matter — successfully allows us to explain a whole host of observations, including the large-scale structure in the Universe, the [CMB], …the observed expansion rate of the Universe…”, since large-scale structure, CMB and expansion all require the additional postulates of dark energy and inflation? And if 90% of the mass in the universe is exotic DM, why does GR work so well in the solar system without DM?

    Nathan Myers (comment 8) represented my view perfectly. Anonymous Coward (#21) has a really good point too.

  23. #24 Crazy
    October 9, 2009

    I have simplistic vision that try to make connection between the dark matter and the dark energy. The vision is if you play in accordion, in one part of the accordion the folds draw far from each other (the dark energy) and in other part of the accordion the folds draw close to each other (the dark matter).

  24. #25 zottel
    October 9, 2009

    The point you miss is clearly that it is easier to hit someone with an oar than to hit this person with a boat …

  25. #26 Diablo
    October 9, 2009

    Oh so you science geeks can’t agree on even gravity? Ya know what ain’t never wrong? My Bible. See that’s what ya science boys need to learn…some bible. Don’t got no worries bout no test or nothing not working with my bible. Sheeooot…can’t figure out dark matter…and yaw want my young’uns thinking their grandma was a monkey. Ya need to stop wasting the government money on the think’n and do a bit more pray’n.

  26. #27 Naked Bunny with a Whip
    October 9, 2009

    See that’s what ya science boys need to learn…some bible.

    But that archaic LOLSpeak is so hard to read!

  27. #28 Bjoern
    October 9, 2009

    @MadScientist: As Ethan already pointed out in another part of this series (part 3, IIRC), the total mass of Dark Matter in the whole solar system is only about the same as a small asteroid.

    @James E Gambrell: Why do you think that Dark Matter is a more complicated speculation than MOND? I’d say that hypothesizing that there may be particles which we can’t observe directly is way more parsimonous (especially in light of the fact that e. g. supersymmetrical Quantum Field Theories already predict the existence of such particles!) than saying that a well-tested law of nature maybe isn’t corrected on large scales.

  28. #29 sean hogge
    October 9, 2009

    Sean-

    No, I don’t think it is equally inappropriate. You argue very abstractly, trying to compare two things without context. I like looking at context, that’s why I talked about the greater problem that over representation of the viability of MOND contributes to, which is a mistrust of science. Ethan’s above criticism may be slightly hyperbolic, but is certainly not equally inappropriate to the New Scientist article he was criticizing.

    I’m trying to remove abstraction. let me try further.

    MOND fails where Newtonian gravity succeeds. Newtonian gravity’s failure to work in extreme circumstances was later fixed by general relativity (without completely undermining Newtonian physics). MOND can’t even do what Newtonian gravity can do – it’s more than a theory with problems. It’s a theory that doesn’t move us forward, it moves us backward.

    Dark matter doesn’t have a lock as a viable solution, I agree. But at least it doesn’t attempt to invalidate the discoveries of the last two centuries when one observation seems out of whack (versus the literal thousands of observations that support the 200+ years of work).

    Is that less abstract?

  29. #31 Spaceman Spiff
    October 9, 2009

    I agree with those who find the use of the descriptor ‘evil’ as misplaced, and counterproductive. However, I do find the willful “ignoration” of the grand scale of the evidence in favor of the current paradigm and the shortcomings of the newcomer, to be rather “troubling”. And for many of the reasons that were mentioned here.

    That’s not to say we should rest on our laurels — and science isn’t apt to do that anyway. We certainly do not have the full story on gravity (space-time).

    And that’s not to say that we shouldn’t let clever people push something reasonable like MOND as far as it will go. Jacob Beckenstein apparently had a go in making it relativistic.

    But we should not mistake the likes of MOND for the likes of the current standard model, or mischaracterize their relative stature with respect to their explanatory powers.

  30. #32 Robert
    October 9, 2009

    It’s not willful ignorance. To be honest, I’m not qualified to evaluate the Gentile et al. paper, but I trust the reviewers and editors of Nature enough to consider this paper a valid attempt to make the DM defenders work harder to prove their point. Leaving DM unopposed at this time is no less dangerous than letting the MOND supporters have the freedom to publish their ideas.

    I found it most interesting that DM defenders have been relying on some data where the uncertainty is greater than the value being measured. I had suspected that was true, but now the Gentile paper confirms it.

  31. #33 acı çehre
    October 10, 2009

    I found it most interesting that DM defenders have been relying on some data where the uncertainty is greater than the value being measured.

  32. #34 acı çehre
    October 10, 2009

    I found it most interesting that DM defenders have been relying on some data where the uncertainty is greater than the value being measured.

  33. #35 acı çehre
    October 10, 2009

    I found it most interesting that DM defenders have been relying on some data where the uncertainty is greater than the value being measured.

  34. #36 acı çehre
    October 10, 2009

    I found it most interesting that DM defenders have been relying on some data where the uncertainty is greater than the value being measured.

  35. #37 acı çehre
    October 10, 2009

    I found it most interesting that DM defenders have been relying on some data where the uncertainty is greater than the value being measured.

  36. #38 acı çehre
    October 10, 2009

    I found it most interesting that DM defenders have been relying on some data where the uncertainty is greater than the value being measured.

  37. #39 Sweetwater Tom
    October 10, 2009

    I don’t like the word “evil” — it has religious connotations. Also to me to claim evil-ness requires an investigation into the motives of the evil-doer.

    To knowingly (intention again) spread false information is definitely a Bad Thing!

  38. #40 Crazy
    October 10, 2009

    Even in GR there have energy and space. Energy say to space how to twist and space say to energy how to move. But yet, space is space and energy is energy. It seems to me that it must that energy in some way is space and space in some way is energy. may be energy is some sort of dense and twist space and space is some embodiment of energy and time is reciprocal relation in what I call space-energy, when energy can turn to space and space can turn to energy. Antimatter and matter give us hints that to the matter have geometrical property- the interference between antimatter and matter.

  39. #41 Spaceman Spiff
    October 10, 2009

    @32 : Just to clarify — I used the phrase “willful ignoration”, which is to willfully ignore for one’s convenience.

  40. #42 MadScientist
    October 11, 2009

    @Bjoern: Thanks.

    So is dark matter that sparse throughout star systems? At one small asteroid per sun-like system the odds of studying the stuff in our own star system seems too small. Wouldn’t this also mean that the lensing observed at those galaxy collisions is really orders of magnitude weaker in the regions of dark matter than around the area with the visible matter?

  41. #43 Bjoern
    October 12, 2009

    @MadScientist:

    At one small asteroid per sun-like system the odds of studying the stuff in our own star system seems too small.”

    Well, that’s why they use such huge detectors for trying to find that stuff…

    Wouldn’t this also mean that the lensing observed at those galaxy collisions is really orders of magnitude weaker in the regions of dark matter than around the area with the visible matter?

    What do you mean with “regions of dark matter”? Dark matter is essentially everywhere in the galaxy clusters; denser in some places, less dense elsewhere.

    And why should the lensing of the Dark Matter be orders of magnitudes weaker? Even if you have only about one asteroid’s worth of Dark Matter in the whole solar system – on large scales, you nevertheless have about four to five times more Dark Matter than baryonic matter.

  42. #44 Lotharloo
    October 12, 2009

    From what I have read, pushing MOND over DM willingly is evil, specially if it boosts your career. It is spreading half-truths and misinformation just to make your research area sound cooler.

    As researchers, we can do a little bit of exaggeration when describing our research (I’m pretty much quoting Hardy here) but that does not mean an open season on academic morality.

  43. #45 shane
    October 13, 2009

    At the moment I think the author makes some good points, but not that representing MOND as a viable alternative to DM is evil. It might be wrong. But DM might be wrong too. At the moment I think the greater evil would be not suggesting any possible alternatives to DM. It already seems to have enough of a monopoly in adademia as it is. I seem to recall another example of an orbital anomoly that called for some speculation on gravitational theory back in the day…the perihelion of Mercury. Prior to GR people were wondering how to explain that. People were wondering if there was an unseen moon for mercury (unseen mass), or if there was some modification of Newtons laws. GR turned out to provide the “correct” Modification. Ironically the debate with MOND vs DM has a similar flavor. Is there unseen mass in galaxies, or do gravitational laws need to be modified (again)?

  44. #46 JJ
    October 13, 2009

    Say MOND is a nice oar with no boat… maybe it’s an oar for an improved type of boat that doesn’t exist yet. Somebody found a great oar that works better than existing oars, and wants to build a boat to take advantage of this oar.

    Right now that boat doesn’t float, but is there any proof that it will never? Why not let people work on it, and see what comes up? Perhaps the MOND Einstein is yet to be born.

  45. #47 Spaceman Spiff
    October 13, 2009

    @41: Science is interested in “useful” models that explain and unify what is known (data in hand). Useless oars are, well, useless — at least to science.

  46. #48 Thomas Neil Neubert
    October 14, 2009

    Evil in this context, is a rather silly description; and voting on evil is even sillier science. As Galileo says, “In questions of science the authority of a thousand is not worth the humble reasoning of a single individual.” I for one believe that the astronomical evidence suggests that both MOND and “dark matter” theory are incorrect. I grant that “dark matter” theory is the best in town; but what is lacking is a credible interpretation that doesn’t depend upon a foundation of extraordinary assumptions and the consensus of a thousand “dark matter” theorist (I don’t hear any solid state physicists saying, “Yes dark matter.”) The only thing about “dark matter” that is exactly correct is the observational data. When and if “dark matter” theory becomes established bedrock physics; then it will be recognized as bedrock physics by all subspecialties of physics. Does any subspecialty of physics seriously doubt general relativity, quantum mechanics, quarks, antiparticles etc? In contrast which subspecialties of physics seriously consider “dark matter” theory as bedrock physics? Maybe one, depending what you include or not in the subspecialyt of “dark matter” physics.

  47. #49 The Big Dumb Weirdo
    October 16, 2009

    In response to the following…
    “To say that someone is evil for spreading disinformation tends to imply not only a knowledge if the inadequacy of the ideas being promoted, but a further knowledge of the harmful effect as well as that effect being the ultimate goal. While those who promote MOND as more than it is certainly are doing bad science, I hesitate to imply that the damage they are doing is intentional.”
    It’s time to invoke Godwin’s Law. (For those who don’t know, it states that as any internet discussion continues over time, the probability of a comparison to the Nazi party approaches 1.)
    The Nazi doctrine was intended to create a Utopian society. Its goal was not to kill undesirable people, that was merely a means to achieve it. This does not make their actions any less evil, however.
    For any physicist, or even any well educated autodidact, hobbyist or science reporter to offer up MOND as a replacement for theories which invoke dark matter is a very similar thing. The pushing of misinformation upon the public is not their goal, but a means to achieve their goal of furthering science.

    Creating a Utopian society and furthering our understanding of the universe are both noble goals. It is the methods by which we achieve them which determine whether or not we are behaving in an evil fashion.

    As for what evil is, I prefer to think of it as any behavior which is not in keeping with a level of morality which can be agreed upon by a majority of informed individuals. Sure, there are different levels of evil, from stealing $20 out of your mother’s purse to go play games at the arcade to torturing and killing millions of people. But in the end, it’s all bad, it’s all evil.

  48. #50 Scientist
    November 3, 2009

    I think there is some confusion about the way science works.

    Science is about making experiments (or observations in the case of astronomy) to verify/test the predictions of theories. These tests have to be performed with an open mind, without being dogmatic or blindly following mainstream ideas.

    Ethan: it is incorrect to say that “Galaxy rotation curves are the only thing MOND has ever been good for” and that “MOND completely fails” on low surface brightness galaxies.

    In fact, before they were even discovered, MOND predicted that low surface brightness galaxies should follow the same Tully-Fisher relation (luminosity vs. rotation velocity) as other galaxies. And that’s exactly what they do, whereas in cold dark matter this is completely unexpected.

    The same holds for the rotation curves of low surface brightness galaxies: MOND can explain them, cold dark matter (in most cases) fails to do so.

    And how about tidal dwarf galaxies? MOND explains their kinematics with zero free parameters, whereas the cold dark matter prediction is completely off.

    The paper by Sanders & McGaugh (2002, Annual Reviews of Astronomy and Astrophysics, available here: http://arxiv.org/abs/astro-ph/0204521) is very instructive about the MOND predictions other than rotation curves (the existence of a preferred surface density in galaxies, the predicted colour-stellar mass-to-light ratio relation, etc.).

    Of course MOND has problems on scales larger than galaxies, but none of them is lethal (the bullet cluster? see http://arxiv.org/abs/astro-ph/0609125; the CMB? see http://arxiv.org/abs/astro-ph/0511591), and cold dark matter has serious problems too, in particular on galaxy scales.

    In conclusion, considering MOND (despite its problems) as an alternative framework is the exact opposite of evil, it is a healthy scientific approach that can only help the advancement of science.

  49. #51 33
    November 3, 2009

    Ethan, I guess you are referring to this press release from Zhao http://www.research.leiden.edu/news/new-light-on-dark-matter.html , where the authors quote at the end “But such theories have their own problems on a cosmic scale”, when speaking about modifying gravity. I also see the authors speculate in this press release on a new long-range force in the dark sector, that has nothing to do with modifying *gravity*. Is it evil on your side to ignore these statements from the press? Furthermore, did you read the Nature paper you are talking about? Or do you think being a blogging scientist is only about reading the accounts that New Scientist journalists make of the scientific papers? So, could you comment on the content of the scientific Nature paper rather than on the press releases? And tell us what is wrong with it. I think being over-emotional as you are is not doing any good to science…

  50. #52 Scientist
    November 3, 2009

    I think that some people have misconceptions about the scientific approach. It is about testing/verifying theories through experiments (observations in the case of astronomy) and modifying theories or even adopting new ones according to what the data say, without being dogmatic or blindly following mainstream theories.

    In this particular case, there are two frameworks (MOND and Cold Dark Matter) which both have their successes and their failures in explaining observations. It is fair to say that none of them is the perfect theory.

    So isn’t it the best scientific approach to take the observations and see which framework explains the data better?

    In my opinion this is the exact opposite of an “evil” approach…

    Ethan: it is incorrect to say that “Galaxy rotation curves are the only thing MOND has ever been good for” and that “MOND completely fails” on low surface brightness galaxies. For the first statement, have a look (without preconceptions) at Sanders & McGaugh (2002). For the second statement, the kinematic properties of low surface brightness galaxies were predicted by MOND even before these galaxies were discovered. Cold dark matter does not manage to explain the kinematics of these galaxies.

    So why not be open-minded and adopt the healthy scientific attitude of letting the actual observations decide which framework works best?

  51. #53 34
    November 4, 2009

    I should add that Ethan sounds more and more like Lubos Motl by attacking “ad hominem” his fellow scientists. We know how the career of Lubos Motl ended up, and I couldnt warn Ethan enough to be very careful about the agressive tone he has chosen to adopt if he doesnt want to follow the same path as Motl. If he thinks he is smarter than all the people who have published research on relativistic mond in the past few years, including Scott Dodelson (Fermilab), Glenn Starkman (Case Western) or Jacob Bekenstein, that is fine, but he should not attack them personally because of their interest in mond.

  52. #54 33
    November 7, 2009

    Does Ethan think that, in addition to Nature, the journal Science is now also willing to be evil? Haha, funny how many evil astronomers and cosmologists, with a whole lot more credibility than Ethan will ever have (how many papers with how many citations did you write Ethan?) are publishing evil things these days, isnt it? And of course, *nobody* is saying that these relativistic MOND approaches do not have any problems…

    http://www.sciencemag.org/cgi/content/abstract/326/5954/812

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