When I was young and as yet unformed as a theoretical physicist, cosmology was in a transitional period. We had certainly moved beyond the relatively barren landscape of the 60’s and 70’s, when pretty much the only things one had to hang one’s hat on were very basic features like expansion, rough homogeneity, and the (existence of) the cosmic microwave background. By the late 80’s we were beginning to see the first surveys of large-scale structure, there was good evidence for dark matter, and the inflationary paradigm was somewhat developed. In the 90’s things changed quite rapidly, unbelievably so in retrospect. We detected primordial anisotropies in the CMB and began to study them in detail, large-scale-structure surveys really took off, we discovered the acceleration of the universe, and techniques like gravitational lensing matured into usefulness.
My students and postdocs will readily testify that I am fond of complaining how much harder it is to come up with interesting new ideas that aren’t already ruled out by the data.
In an interesting and provocative post, Peter Coles bemoans a generational shift among cosmologists: “When I was a lad the students and postdocs were a lot more vocal at meetings than they are now.” In particular, Peter is worried that people in the field (young and old) are “willing to believe too much,” and correspondingly unwilling to propose dramatic new ideas that might run counter to received opinion. Or even, presumably, just to express doubt that received opinion is on the right track. After all, even with all we’ve learned, there’s certainly much we don’t yet know.
I’m not sure whether there really has been a shift or not; there’s a big observational bias from the fact that I used to be one of those young folks, and now I am a wise old head. (Old, anyway.) But it’s completely plausible. Is it a bad thing?
There’s an argument to be made that widespread agreement with a basic paradigm is actually a good thing. People agree on what the important questions are and how to go about answering them. Ideas are held to a higher standard. Furthermore, it would be very hard to blame a young scientist who wanted to play by the rules rather than rocking the boat. It’s easy to say “challenge conventional wisdom!”, but the thing about conventional wisdom in a mature field is that it’s usually right. The exceptions are important and memorable (remember when everyone thought the cosmological constant was zero?), but most controversial new ideas are just wrong. Being wrong is an important part of the progress of science, but it’s hard to tell other people that they should be wrong more often.
At the end of the day, though, I agree with the spirit of Peter’s lament. I do think that the discourse within cosmology has become tamer and less willing to try out new ideas. Dark matter is well-established empirically, but we certainly don’t know that it’s WIMPs (or even axions). Inflation has had some successes, but we are very far indeed from knowing that it happened (and the problems with eternal inflation and predictability are extremely real). I have my own prejudices about what’s settled and what are interesting open questions, but the field would be healthier if youngsters would challenge people like me and make up their own minds.
Then again, you gotta eat. People need jobs and all that. I can’t possibly blame anyone who loves science and chooses to research ideas that are established and have a high probability of yielding productive results. The real responsibility shouldn’t be on young people to be bomb-throwers; it should be on the older generation, who need to be willing to occasionally take a bomb to the face, and even thank the bomb-thrower for making the effort. Who knows when an explosion might unearth some unexpected treasure?
The most vocal advocate for black holes as dark matter, at least recently, has been Mike Hawkins. (Primordial black holes, so they are non-baryonic and hence there is no conflict with limits on baryon density from big-bang nucleosynthesis.) The mass range he suggested has definitely been ruled out by microlensing.
I’ve read Hawkins’ work, but he is considerably less prolific and convincing than Paul Frampton and his several coauthors who suggest that roughly 1% of all black holes are in the 100,000 solar mass range, which certainly aren’t ruled out by microlensing or any other gravitational lensing. Or by the orbits of wide binary stars (a counter-argument that persists years after having been debunked) or by any particular features of the CMB, because every single theory of supermassive black hole formation requires at least thousands and usually on the order of tens of thousands of such 100,000 solar mass progenitors per Milky Way-sized galaxy, whether from coalescing interstellar media, or the interiors of supergiant population III stars, or per a arXiv submission from the past week, the collapse of irrotational (“non-vortical”) dark matter. Wherever they come from, I defy you to find any published theory of supermassive black hole formation which doesn’t posit thousands of intermediate mass black holes by z=8.
The “limits on baryon density from big-bang nucleosynthesis” is another profoundly weak argument against non-primordial intermediate mass black hole dark matter which is always framed by the “elders” (including undergrads steeped in the hegemony) as if it was certain, but it depends on specific attributes of inflation on which we have absolutely no information one way or another at all.
These questions are so sensitive to the WIMP hegemony that I have been repeatedly censored simply for asking about them and the heterodyne lunar VLBI telescope arrays with the resolution to distinguish an IMBH accretion from interstellar media from an ordinary stellar black hole. Ian O’Neill and Phil Plait both blocked me on Twitter years ago. Ian and Ethan Siegel have both blocked me on Google Plus for asking about black hole dark matter. Just a few months ago a cosmology postdoc whose fellowship is predicated on the existence of WIMPs told me that if I ever asked her about black hole dark matter again she would block me, after I asked which sources led her to disagree with her prestigious Princeton former advisor’s opinion that black holes are the second most mainstream explanation of dark matter after WIMPs.
As an amateur, I have the luxury of asking these questions without risk, but I believe I also have an implicit scientific duty to help end this absurd fear and censorship. So I put forth the following offer to all takers:
I challenge any proponent of WIMP (or axion or neutralino etc.; not MoND or similar or other black hole-based) dark matter to a one hour debate on Google Hangouts on Air, IRC, or any other recorded telecommunications medium, to be judged by Sean Carroll or any one of his willing designees. If I am judged to lose the debate I will pay my opponent $300 and the judge $100; if I win then the loser must pay the judge $100. Are there any takers?
In general, current astro postdocs seem to care really a lot about statistics like number of papers and number of citations. I think this more than anything else drives people to take incremental steps in established fields. After all, there are already seven other groups taking these steps, and they will all have to cite your version when they do theirs. Plus, you can write your work up in baby steps, without fear that a referee will challenge you for more justification about the basic ideas. Needless to say, this attitude is bad for science.
Accepting that this attitude does indeed exist, the question is, whose fault is it? If search committees really screen, rank, and ultimately hire their applicants by papers/citations, then it is their fault. With so few jobs around, it’s perfectly reasonable for postdocs to cater to those who control the jobs. But if committees instead carefully evaluate the scientific merit/promise of their applicants, by reading letters and consulting expects, then there is no excuse for (the above caricature of) postdoc behavior, and we postdocs have to accept that we’re just a bunch of nervous, whiny louts.
Which is it?
I think, it is bit difficult to make such comparison.now we have much more experimental evidences as before, we more sources of knowledge, youngsters are very well aware of the theoretical predictions and their harmony with experiments.so usually they know what to challenge.this paradigm shift from theoretical dominance to more balance situation between theory and experiment has made young students/scientists little bit more believer than otherwise,apart from the exceptions.although there are still many things which can be challenged easily especially in the field of cosmology. it is more like believing than true science.most of the evidences regarding expanding modal of universe are indirect and controversial, yet everyone is preaching them as truth.
Here is a 2010 paper on the topic which states that that the density of primordial black holes affects Big Bang nucleosynthesis light element ratios, and black holes formed later do not.
Where did the idea that non-primordial black hole dark matter is ruled out by light element ratios get started?
James,
You have to realize that as an amateur (which you stated you are), you have to go the extra mile to prove that you are worth discussing BASIC topics with. It would be difficult to have someone consider you an equal on those basic topics, much less a theoretical topic that the best and brightest are still working out. To attempt to discuss theoretical topics would be almost impossible. Pair that with anything that can be interpreted as belligerence or ignorance and you will be labeled a crackpot every single time, and understandably so. It’s equivalent to : You have no formal training, yet you’re convinced that you are more qualified to build a nuclear reactor because you watched The China Syndrome. Who would take the time to listen to that? Politicians work for the people, and even THEY have the option of choosing to ignore anyone they feel like ignoring. Tenured professors; enough said. Challenging people on the internet/email is the new age equivalent of shouting your beliefs on a street corner. Would Max Planck or Stephen Hawking take the time to entertain the “THE END IS NIGH!” guy they see on the street? no, they wouldn’t. You’re not being shut down based on your ideas; you are being shut down based on your approach. Mordehai Milgrom got his idea through and people listened to him because he did things the same way that Einstein did with relativity; he presented his ideas and then sat back and let people form their own opinions, defending his position when asked to do so or in an otherwise appropriate manner. He didn’t go knocking on every physicist’s door only to point his finger and shout “BULLSHIT!” when they open the door and then run away down the street.
Oh, the irony!
“…Challenging people on the internet/email is the new age equivalent of shouting your beliefs on a street corner…”
It isn’t, Meh. The blog is the soapbox. Comments are like some guy at the back talking back. So it would be better if you didn’t diss and dismiss James because of your hubristic arrogance.
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I thought there was a difference between email and blogs, John. no?
Also, this isn’t about random people with pop-science knowledge of cosmology or physics talking back. This is about students in the field or introductory professionals (in the field) talking back. If you are an amateur or have not dedicated enough time to get a basic degree in a scientific field, then this topic doesn’t apply to you. It also doesn’t apply to the internet where any random person with any level of understanding can make a comment. To rephrase that; scientists do not care (other than generalized discussion; strictly nonprofessional) what someone outside of their field thinks about their field. Sure, it’s interesting to see what someone thinks about it; but they aren’t going to uproot the fundamental pillars of physics, or any science, because of an abundance of internet comments. Anyone who thinks that is the case is just an idiot for lack of a better word.
That’s what I was saying to James. Of course nobody listens to you; you’re an amateur (as you claim to be). Admitting you’re an amateur, spamming professionals with emails, and then wondering why they block you and ignore you? You don’t understand what’s happening here? There always have and always will be filters on the type of information that gets through. There simply isn’t enough time to comb through every single idea from the billions of people that inhabit this planet. Just like particle accelerators; it isn’t possible to analyze every bit of information, you have to pick out the important parts and discard the rest.
To be clear, I have never been blocked or threatened with blocking by anyone because of private emails, only because of questions I’ve asked scientists in public on social media or blogs. These are questions in the general topic area of dark matter cosmology that such scientists usually delight in answering, and say that they consider to be an important part of their outreach work. But when it comes to specific explanations, or even citation of specific sources, on the question of why WIMPs are more likely dark matter candidates than Dr. Frampton and his colleagues’ explanation of intermediate mass black holes, the story changes quite a bit. And this from people who spend hours rightly explaining why MoND is unsatisfactory. Doesn’t it raise a red flag when cosmologists who will devote multiple well-referenced blog posts debunking MoND suddenly clam up when it comes to black hole dark matter, which is widely considered a more plausible explanation than MoND?
If the explanation on a particular topic is difficult, doesn’t that make it an even more important public outreach topic to elucidate? I’m willing to spend $400 to make that outreach happen. If I lose the debate, then at least there will be a record with the reasons why to fill the conspicuous gap in science communications. This isn’t just another “idea from the billions of people that inhabit this planet” — black hole dark matter explanations repeatedly pass peer review in the most pretentious cosmology and astrophysics journals.
I engage in detailed email and social media dialogs with astrophysicists and cosmologists on related topics, at a high level where I am often complimented on my background research. For example, Chuck Hailey at Columbia, the lead on NuSTAR’s Milky Way black hole population survey team, complemented me a few months ago on bringing this 2004 paper on the dynamics and resulting halo distribution of colliding intermediate mass black holes to his attention. I’ve engaged in a similarly productive discussion with the authors of this paper on detecting the nearest black holes who as you can see had not considered the use of the NuSTAR observations (which is promised on HEASARC next month) until I contacted them. I’m confident I can hold my own, but if I am so uninformed then prove it, take my money like candy from a baby, and score a victory for public science communications where one on either side is clearly needed.
Meh is correct. So many physicists get manuscripts from amateurs “disproving” QM or GR or other subjects which contain basic math errors or ignorance of basic experimental results that we generally ignore them. My advice to amateurs is:
1) Focus on experimental/observational science.
It’s always much, much harder to gainsay empirical results than it is for theoretical speculation. (I’m an experimentalist; of course I’ll give this advice!)
2) Get strong academic credentials.
It will help you make your arguments and give scientists confidence that you know what you are talking about.
3) Be polite and restrained.
A person will be taken more seriously if he/she doesn’t rant about conspiracy theories about how he/she is the Galileo to the mainstream Inquisition. In one collaboration I worked in, a professor with “heretical” beliefs insulted so many colleagues (he told me I should go kill myself, for example, as well as claiming that he is a modern Galileo) that no one felt comfortable talking to him. He had built his own wall preventing people from listening to his ideas.
4) Expect tough resistance.
Many people have spent many years crafting current paradigms. They aren’t going to give them up at the drop of the hat.
Now God only knows I have my own beefs with sections of the mainstream scientific community, mainly with scientists who say things like, “science has proven telepathy doesn’t exist!”, even though, except for a few outliers, experimental evidence taken as a whole is strongly in favor of telepathy (sorry, this is my pet peeve … and please don’t put your faith in Wikipedia). But the vast majority of amateurs are simply unaware of the amounts of evidence favoring current models and what is needed to overcome them.
James– To be clear, I have zero interest in judging the debate you propose. Also, you have wandered off-topic to ride an individual hobbyhorse, which is precisely the kind of behavior likely to get one banned. Fair warning.
For everyone else: all good cosmologists understand that black holes have not been completely ruled out as a dark matter candidate. However, unlike WIMPs or axions, there is no good way to produce the requisite density. (You can do it, by messing with perturbations in the early universe, but it’s typically very ad hoc.) The idea that you can make DM out of black holes in the post-recombination universe is a complete non-starter, as both BBN and the CMB rule out the idea that all matter was baryonic at early times.
An addendum to the previous comment: I am speaking very generally and do not have the background to critique James’ work.
you have wandered off-topic to ride an individual hobbyhorse, which is precisely the kind of behavior likely to get one banned. Fair warning…. The idea that you can make DM out of black holes in the post-recombination universe is a complete non-starter, as both BBN and the CMB rule out the idea that all matter was baryonic at early times.
So am I correct in assuming, Sean, that if I attempt to discuss the strength of the evidence pertaining to the ratio of the baryon density to critical and total matter densities of big bang nucleosynthesis, or similar comparisons of the CMB radiation evidence relative to the state of WIMP evidence, then you will ban me? Would I be banned if I linked to others’ work on the topic?
You are welcome to discuss those topics in the comment sections of posts that are about those topics.
Of course, I reserve the right to ban anyone at any point, without explanation, just for being annoying. It’s my blog.
“There is another Iain Brown in astronomy though – radio astronomy, I think.”
Yes, Ian Brown at Jodrell Bank; I used to work for him. 🙂
“I’ve been based in Oslo for the last three years”
OK, so you came to my talk there in May 2011. 🙂
“1% of all black holes are in the 100,000 solar mass range, which certainly aren’t ruled out by microlensing or any other gravitational lensing”
What about the argument from Ostriker and Vietri that they would be visible due to distortions in the images of jets from radio sources?
The “limits on baryon density from big-bang nucleosynthesis” is another profoundly weak argument against non-primordial intermediate mass black hole dark matter which is always framed by the “elders” (including undergrads steeped in the hegemony) as if it was certain, but it depends on specific attributes of inflation on which we have absolutely no information one way or another at all.
How does BBN depend on inflation?
“Are there any takers?”
Someone once replied to a similar taunt: “It would look good on your CV but not on mine. 🙂
“Where did the idea that non-primordial black hole dark matter is ruled out by light element ratios get started?”
Because BBN tells us the Baryon density so conventional (non-primordial) black holes formed by the accretion of baryons obviously cannot exceed the total baryon density, especially since there are many baryons not in black holes.
James Salsman’s link points to a page called “TalkNicer”. 🙂
@Prof. Carroll: “It’s my blog.” etc.
Aha! Methinks that might have something to do with the fact that we don’t see Tony Rz hanging around here anymore. 🙂
OK, so you came to my talk there in May 2011. 🙂
Aha! That sounds very likely 🙂
@Phillip, please correct me if I’m mistaken, but didn’t Ostriker and Vietri rule out AGNs too?
On BBN and CMB, Drees and Erfani (2011) and Lacki and Beacon (2010) might offer some insight.
I would love to read anything recent on PBHs as dark matter candidates. Who is working on the topic these days?
Well now I’m confused. Ostriker and Vietri (1986) say on page 75-6 that some of the quasars they studied had evidence of minilensing which may have been due to 1E+6 stellar mass objects.
James,
I don’t think that you are necessarily uninformed, I think that you’ll never get anyone to listen to you if your approach can be INTERPRETED as belligerent or ignorant. I don’t mean to insult you or make you feel like I have any hostility towards you in my analogies, I’m mostly just trying to present some funny imagery while “keepin’ it real” as it’s said. MOND, or its love child TeVeS, are good modern examples that relate to this topic of how to present information that doesn’t agree with a basic paradigm. This is from on old(er) 2006 article :
“””” In spite of the suggestions Milgrom had received—all from world-class scientists—getting the papers published became an ordeal. “I was a little naive,” Milgrom says. “I thought the papers would be welcomed. They were rejected by the journals at first. The reasons varied: ‘It was all nonsense’; ‘It’s too early to consider an alternative to Newton’; ‘There is no trouble yet; the flat rotational curves will be resolved in other ways.’ ”
Looking back on this period, Milgrom betrays no bitterness. “I went back and looked at the history of science and saw this happens again and again. The marketplace can only handle so many heretical ideas at one time. I think on the whole I have been treated fairly.” After Milgrom’s dogged persistence, all three of his original papers on modified Newtonian dynamics were published side by side in 1983 in Volume 270 of The Astrophysical Journal, a premier publication in the field.
As is often the case with radical ideas, the community’s reaction was not scorn but silence. “At first the work was not accepted, not even really looked at,” Milgrom recalls. By this time he had begun collaborating on MOND with fellow Israeli theorist Jacob Bekenstein. Bekenstein, who had already won some acclaim for his work on black holes, became a hard-core MONDista. “In 1986 we were invited to present a talk at a meeting in Princeton,” says Milgrom. “This made us really happy. At least we were getting noticed.” MOND began to make inroads. Its solution to the galaxy-rotation-curve problem was too elegant to ignore. For most galaxies it explained observations better than dark matter did.
But why did MOND work? What was the justification for changing Newton’s law other than that it made the rotation-curve problem disappear? There was no reason, and Milgrom knew it. His solution wasn’t a theory; it was simply a description and did not explain anything from first principles. Meanwhile, the dark-matter hypothesis had become ever more sophisticated. So while Milgrom and a handful of true believers continued to work on MOND, dark matter had attracted legions of supporters and became the subject of hundreds of research papers. “”””
You have to be patient, there is no other way around it. It is the way that it has always been done. Unless you have some sort of amazing experimental or observational evidence, then you are going to have to wait until they are ready. If you become impatient or are perceived as impatient or rude, then you’ll be rejected. It’s easy for a person to say that they are being rejected based on a conspiracy or bias, because then you don’t have to admit that you might be wrong. But it also shows that you have a certain amount of arrogance and that you aren’t a logical person; that you can’t remove yourself from the data. That doesn’t go over well in a field based on observation and logic. Why do cosmologists go with WIMPs over TeVeS or black holes? Because it’s easier for us to test quantum mechanics and get a conclusive yes or no. You can present a conclusion for a cosmological model and it will still be open for debate, which you are very aware of.
It should also be mentioned that even if you are correct, but are perceived as a jerk about it for the past x # of years; then chances are good that when the tides do turn in your favor, someone will repackage your idea in their own terminology and everyone will pretend like you never said anything because they don’t want you to be the spokesperson for it. Look at Vera Rubin and Fritz Zwicky.