Quarks, [OIII], neutron stars, black holes OK; CDM not OK - Huh?

This is a thread to explore an attitude (or opinion) that I continue to find hard to understand every time I encounter it, which is rather often.

You are talking with someone who is not an astronomer, nor a physicist (and also not an astrophysicist, etc), and who also does not have a BSc (or higher) with a major in either of these fields^. You know from earlier conversations that they do not bat an eyelid when 'quarks' get discussed, nor when 'neutron stars' nor 'black holes; if they have some interest in astronomy, perhaps you have also discussed some of the beautiful nebulae, including those with a delightful green colour due to something known as the [OIII] 5007 emission line.

Later the conversation turns to 'dark matter', and after clearing up confusion over 'ordinary' dark matter (i.e. things like stars too faint to be visible, and rocks, and planets), and 'hot' dark matter (i.e. neutrinos, in this case), you start talking about 'cold dark matter', a.k.a. non-baryonic cold dark matter, CDM, and how it seems that for every gram of ordinary ('baryonic') matter in the universe there is ~5 grams of CDM. Then the eyes glaze over; disbelief is expressed, perhaps forcefully; and so on.

And that brings me to the point of this thread.

Why?

How does it come about that an apparently intelligent, educated, thoughtful person can be quite OK with 'quarks' (which have not be 'seen' in any experiments), [OIII] 5007 (which has never been produced in any lab), neutron stars (ditto), and black holes (double ditto!), yet balk at the very thought of non-baryonic cold dark matter (CDM)?

From the point of view of the astronomy, the observational evidence for neutron stars and black holes is no different than that for CDM: millions (billions?) of independent observations, made using multiple, independent techniques, and relying on several, independent, parts of physics to get from observation to conclusion.

Our apparently intelligent, educated, thoughtful person seems perfectly at ease with accepting that there is a great deal between what comes out the back of some telescope and a conclusion 'here be a neutron star', and that the astronomers and physicists who did the work to connect the dots did so competently, etc, etc, etc. Yet when it comes to CDM, no such acceptance is to be found!

To some extent this goes to 'argument from authority' that is being discussed in a separate thread; our apparently intelligent, educated, thoughtful person certainly could be walked through a good summary of how observations are connected to conclusions, for CDM*, just as they could for neutron stars, or black holes; in principle, the issues in doing such a successful walk-through are the same.

Footnotes:
^ 'CDM no way!' issues with people with this background are, I have found, very different; they are NOT what I want to cover in this thread.

* if anyone is interested, I'll write a post or two on this

I have the same problem. For some reason there seem to be some topics that pretty much everyone feels the need to have an opinion on, even if they have no qualifications, no experience and, often, no clue what they're talking about. Dark matter is one, global warming another and evolution probably falls here as well.

My first thought was that it comes from a lack of any common ground with every day experience, which often leads to horrible misinterpretations due to poor analogies. For example, people have no problem accepting quarks because they already understand that everything is made up of little balls, so being told that some of those little balls are made up of even smaller ones isn't a big problem, and the weird properties can be largely ignored. When it comes to dark matter however, there really is nothing like it in human experience, so it's a lot harder to swallow. The obvious problem here is that neutrinos should suffer the same problem, but very few people have a problem accepting that they exist.

Possibly the problem is just the need for controversy. Most people don't seem to understand the difference between scientific debate and controversy. People rarely discuss the evidence either way for global warming, they argue about politics and supression of ideas. Same with evolution, it's not the science that's usually argued, it's the claimed controversy, even though there isn't one. I think dark matter has the same problem. There is no argument about neutrinos. Physicists know they exist and it's just a matter of working out exactly how they work. Dark matter, on the other hand, has many different ideas covering it, and plenty of other ideas, both mainstream and crackpot, which don't require dark matter at all. This means that it gets presented as a controversial subject to the general public, who go on to argue about the controversy without ever understanding the actual science involved.

Cuddles said:

I have the same problem. For some reason there seem to be some topics that pretty much everyone feels the need to have an opinion on, even if they have no qualifications, no experience and, often, no clue what they're talking about.

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That has bugged me to no end on this board, especially in regards to cosmology. I am brutally unqualified to prognosticate on cosmology, so I find it irritating when people who have even less education in physics post convoluted polemics on the subject.

Possibly the problem is just the need for controversy. Most people don't seem to understand the difference between scientific debate and controversy.

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CNN does this. I noticed the other day that they made a mountain out of a molehill about the problematic Soyuz landing (not that it wasn't serious for those involved), where the comments by NASA officials in the article clearly contradicted the alarmist headlines!

Um, weeeell, some of the resident insert name here do find exception to neutron stars and black holes. And when you try to talk to them about pions and Yukawa particles they have a very strange impression of the way that physics works. They will tell you that these things were predicted and that people never denied that they existed.
They will also get insulted if you ask them if nutrinos exist but then say dark matter does not.

So go figure...

Well, let’s remember the name of the website that sponsors this forum, The James Randi Educational Foundation, with education being the operative term. Certainly most of the people who have already posted on this thread have clearly demonstrated (on many other threads) their willingness and patience when it comes to educating others (and I believe be by others themselves). However, education requires a personal commitment in one’s desire to be educated by one’s self and by others. Speaking for myself, I have no BS degree nor have I worked in the fields of astronomy or physics (mostly technology and mechanical engineering). Yet, I have an interest in those fields and the desire to educate myself. I for one, have no problem in trying to educate others or being educated by others. Some on this forum (present company excluded) feel the only application of education on this forum is to educate others in their particular point of view, without displaying any real interest in being educated by others (other then to make their presentations better) or in admitting, at least to themselves if not to others, that they might have been wrong. The conversations usually degrade from that point with the thread continually going around in circles. Without a desire to be educated by others (other then reinforcing their current point of view) no amount of information or argument will create that desire in them. Although I enjoy a good debate and can debate form points of view I do not particularly agree with, I have no interest in unproductive debates that simply go around in circles solely for the sake of having an argument (or helping someone improve the presentation of their dogma). But we should not give up trying, though, even if active posts on a thread may not seem to be going anywhere, hopefully other people reading and not posting may be educating themselves with the information provided. Some people are never really comfortable with being wrong and therefore not really interested in educating themselves. Others might be more comfortable finding out they are wrong themselves then being told by someone else and therefore have little real interest in being educated by others. My self, I Just like to know if I am in fact or possibly wrong, regardless of the source, because it means I might just learn something. Just some of my thoughts on this phenomenon.

The Man said:

Speaking for myself, I have no BS degree nor have I worked in the fields of astronomy or physics (mostly technology and mechanical engineering). Yet, I have an interest in those fields and the desire to educate myself. I for one, have no problem in trying to educate others or being educated by others.

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Rationally, if a person truly wants knowledge, the respectful (and useful) thing to to do is to ask questions, and not to barge into a room and start blathering on (in this case) about plasma cosmology.

Absolutely, but anyone proposing that all people are rational, clearly is not.


ETA : Maybe irrationality is a requirement of or the effect of long exposure to plasma cosmology (I wouldn’t doubt either conclusion).

The Man said:

Absolutely, but anyone proposing that all people are rational, clearly is not.

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Interestingly enough, all of the readings in the last philosophy course I took presumed that the cases under study had 'rational actors.' Although the specifics are fading in memory, it still troubles me that most of the arguments fell apart if we just admitted to a single 'irrational action,' much less 'actor.'

Maybe irrationality is a requirement of or the effect of long exposure to plasma cosmology (I wouldn’t doubt either conclusion).

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DeiRenDopa said:

You are talking with someone who is not an astronomer, nor a physicist (and also not an astrophysicist, etc), and who also does not have a BSc (or higher) with a major in either of these fields^.

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I do not have a degree in these fields, so take my following comments with that fact in mind.

You know from earlier conversations that they do not bat an eyelid when 'quarks' get discussed,

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Good theoretical models for quarks exisit, and those models gave good predictions for the "finding" of the top and bottom quarks, for example. AFAIK, there is no convincing predictive model for what constitutes CDM.

nor when 'neutron stars' nor 'black holes

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Again, it seems to me that the theoretical, and observational evidence for these is strong. For example, we postulate that pulsars are actually rotating neutron stars, and luckly we have a theoretical framework that we can use to describe matter under these conditions, and make reasonable extrapolations from our theory, and our experiences with normal matter, to discuss neutron starts and black holes with what I would consider reasonable scientific certainty.

AFAIK, this is in stark contrast to CDM, of which the fundamental constiuents are just a vague postulate at this time.

if they have some interest in astronomy, perhaps you have also discussed some of the beautiful nebulae, including those with a delightful green colour due to something known as the [OIII] 5007 emission line.

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Isn't the science behind this example well understood, though? Can the same be said for the non-baryonic dark matter that supposedly makes up CDM? And I mean real, concrete predictions as to what CDM really is, not just that it accounts for X% of the matter in the universe, based upon our standard cosmology models.

Later the conversation turns to 'dark matter', and after clearing up confusion over 'ordinary' dark matter (i.e. things like stars too faint to be visible, and rocks, and planets), and 'hot' dark matter (i.e. neutrinos, in this case), you start talking about 'cold dark matter', a.k.a. non-baryonic cold dark matter, CDM, and how it seems that for every gram of ordinary ('baryonic') matter in the universe there is ~5 grams of CDM. Then the eyes glaze over; disbelief is expressed, perhaps forcefully; and so on.

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This paragraph is telling:

Ordinary dark matter: stars, rocks, planets
"Hot" dark matter: neutrinos
"Cold" dark matter: we have no idea what it might be, but our models show that it is 5x more prevalent then those things you can actually see and describle, like stars, galaxies, planets, rocks, birds, leptons, Mini Coopers, etc. But believe us, it's out there, in some mysterious form!

And you wonder why the eye's glaze over?

And that brings me to the point of this thread.

Why?

How does it come about that an apparently intelligent, educated, thoughtful person can be quite OK with 'quarks' (which have not be 'seen' in any experiments), [OIII] 5007 (which has never been produced in any lab), neutron stars (ditto), and black holes (double ditto!), yet balk at the very thought of non-baryonic cold dark matter (CDM)?

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Perhaps because, as I mention before, the quarks, doubly-ionized Oxygen, neutron stars, and black holes can be discussed in terms of what they are, not what they might be, as in CDM.

From the point of view of the astronomy, the observational evidence for neutron stars and black holes is no different than that for CDM: millions (billions?) of independent observations, made using multiple, independent techniques, and relying on several, independent, parts of physics to get from observation to conclusion.

Our apparently intelligent, educated, thoughtful person seems perfectly at ease with accepting that there is a great deal between what comes out the back of some telescope and a conclusion 'here be a neutron star', and that the astronomers and physicists who did the work to connect the dots did so competently, etc, etc, etc. Yet when it comes to CDM, no such acceptance is to be found!

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When someone looks in the back of a telescope, and says "here be a neutron star", his observation is backed by physics that describes how such a star may come to be, what it might consist of, and how our current understanding of physics would allow a neutron star to exist.

AFAIK, when someone says "here be CDM", that observation is lacking concrete physics that says how such CDM may come to be, what it might consist of, and our hour current understanding of physics would allow the CDM to exist.

Notice, I qualify my statements with AFAIK a lot; if anyone has information about what CDM might actually be, I would be excited to hear about it.

Λcdm

These two descriptions prefectly sum up my opinion on ΛCDM. Both are written from a strong plasma cosmology type viewpoint, holding the things we do know for certain from direct observation and experiment in much higher regard then the mathematical abstractions and untestable foundations that modern cosmology is replete with.

ΛCDM cosmology: how much suppression of credible evidence, and does the model really lead its competitors, using all evidence? by Professor of Astrophysics at The University of Alabama, Richard Lieu.

Astronomy can never be a hard core physics discipline, because the Universe offers no control experiment, i.e. with no independent checks it is bound to be highly ambiguous and degenerate. Thus e.g. while superluminal motion can be explained by Special Relativity. data on the former can never on their own be used to establish the latter. This is why traditionally astrophysicists have been content with (and proud of) their ability to use known physical laws and processes established in the laboratory to explain celestial phenomena. Cosmology is not even astrophysics: all the principal assumptions in this field are unverified (or unverifiable) in the laboratory, and researchers are quite comfortable with inventing unknowns to explain the unknown.

How then could, after fifty years of failed attempt in finding dark matter, the fields of dark matter {\it and now} dark energy have become such lofty priorities in astronomy funding, to the detriment of all other branches of astronomy? I demonstrate in this article that while some of is based upon truth, at least just as much of $\Lambda$CDM cosmology has been propped by a paralyzing amount of propaganda which suppress counter evidence and subdue competing models. The recent WMAP3 paper of Spergel et al (2007) will be used as case in point on selective citation. I also show that when all evidence are taken into account, two of the competing models that abolish dark energy and/or dark matter do not trail behind $\Lambda$CDM by much. Given all of the above, I believe astronomy is no longer heading towards a healthy future, unless funding agencies re-think their master plans by backing away from such high a emphasis on groping in the dark.

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And Michael Mozina gives what I believe is the true skeptics approach to ΛCDM, an approach that I often feel should be much more prominent on a skeptics forum such as this.

http://www.physicsforums.com/showpost.php?pp=1493877&postcount=27

At present, Lambda-CDM theory relies upon no less than three different forms of metaphysics. It is therefore quite difficult for me to accept that this is the "best" cosmology theory available, or that it should be the only cosmology theory that is taught to astronomy students in college. IMO MOND theories, and PC/EU theories deserve equal consideration.

There's a bigger problem however. The math we have done with Lambda-CDM theory turns out to have a gaping hole in it, despite a nearly homogeneous prediction of inflation.

I can see why Einstein called the introduction of this constant as his greatest blunder, because even if there are external forces of nature acting on mass bodies, these forces will have mathematical properties that are directly related to the force involved, that are not necessarily even related to the gravitational component. IMO the Lambda-CDM theory isn't "pure" GR. It's a loosely GR oriented theory with a liberal dose of metaphysics mixed in, it's about 96% metaphysics in fact.

I'm always hearing astronomers talk about metaphysical constructs as though we are certain that they exist, and that's the way things happened in some distant past. I keep hearing things like "The universe is about 13.7 billion light years old, plus or minus a few billion years." The only way that could possibly be true is *if* all the various metaphysical hypothetical entities of Lambda-CDM theory pan out. If even one of them does not exist in nature (particularly inflation), that age estimate will be completely meaningless. It is not "fact" that there was ever a "big bang". It is not "fact" that DE and non-baryonic DM exist, or that inflation ever existed in nature. I tend to ruffle a lot of feathers when I say that in public, but it's certainly true that Lambda-CDM theory is not fact, nor is the age of the universe "fact", nor is the notion that there was a "big bang', a factual statement. These are all "theories", or as you said "hypothesis" that may or may not be fact. The "fact" is that inflation has not be demonstrated, and that DE has not been demonstrated, and that non-baryonic forms of DM have not been demonstrated. Lambda-CDM is but one theory among many competing theories. Those are the facts. [...]

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and he concludes later in the post;

Well, hope does spring eternal, but IMO it's a poor substitute for hard empirical evidence. If and when I see someone demonstrate the existence of non-baryonic forms of mass, I'll be quite happy to entertain non-baryonic form of matter in GR theory. Of course I will still need to see some evidence that "dark energy" causes "space" (whatever that is) to expand, and that inflation actually exists before I'll buy into those aspects of the Lambda-CDM theory. I'm not imposing any special requirements on any particular theory, but I will require that each and every theory meet basic scientific requirements. One of those requirements is that extraordinary claims always require extraordinary evidence. So far I see lots of extraordinary claims in Lambda-CDM theory (DE, DM, inflation), and very little in the way of supporting evidence. That is not to say that non-baryonic forms of mass *cannot* exist, it's just that I do have any evidence that the *do* exist. That is also true of DE and inflation. I can't disprove a negative, so the burden of proof must fall to the individual that makes the claim. If someone makes the extraordinary claim that non-baryonic forms of mass exists, they will need to support that statement with solid empirical evidence. That is SOP (standard operating procedure) for all branches of science.

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He took the words right out of my mouth. Certainly saves me the time . The rest of that thread at PF is worth a look also, the discussion was lively and interesting, with both sides making very good points and consessions, and reaching a 'have to agree to disagree' situation by the end (until Neried came along at the very end, got very angry with someone doubting her cosmological preference, banned Mozina permanantly from the forum before he could respond to her fully, and locked the thread [thank heavens for JREF not being so dogmatic]) You can get a good sense of how plasma cosmology advocates approach standard cosmology from Mozina's posts, and what the problems are with Lambda-CDM from this perspective.

First, Zeuzzz, you are on record as having at least a BSc with a major in physics (if I'm wrong, please say so); as such, I thought the OP was perfectly clear ... this thread is NOT, repeat NOT about any problems, issues, worries, concerns, objections, etc, etc, people like you may have with CDM. If you are interested, I will start a specific thread just for you (and anyone else); alternatively, you could start just such a thread.

Second, Zeuzzz, this thread's scope was explicitly restricted to CDM, and I thought that was perfectly clear in the OP; to repeat, this thread is NOT, repeat NOT, about ΛCDM, or even about cosmology. If you are interested, I will start a specific thread on just that topic; alternatively, you could start just such a thread.

Third, for all those who've posted so far, thank you; I'll comment and respond shortly.

I should have been more explicit in the OP: this thread is NOT, repeat NOT, about plasma cosmology (PC); nor do I wish to have anyone who is a proponent of that idea post in this thread, from that perspective ... the PC objections to CDM have been spammed into far too many JREF forum threads already.

Finally, on PC: it is my opinion that this is, at its core, no different than ID (as sol invictus said, elsewhere): I think it can be shown that PC rests on a perversion (distortion, if you prefer) of a number of principles and methods at the heart of branches of science such as physics and astronomy. In a later thread I would like to expand on this opinion, and discuss it. However, not here, not now.

DeiRenDopa said:

First, Zeuzzz, you are on record as having at least a BSc with a major in physics (if I'm wrong, please say so); as such, I thought the OP was perfectly clear ... this thread is NOT, repeat NOT about any problems, issues, worries, concerns, objections, etc, etc, people like you may have with CDM. If you are interested, I will start a specific thread just for you (and anyone else); alternatively, you could start just such a thread.

Second, Zeuzzz, this thread's scope was explicitly restricted to CDM, and I thought that was perfectly clear in the OP; to repeat, this thread is NOT, repeat NOT, about ΛCDM, or even about cosmology. If you are interested, I will start a specific thread on just that topic; alternatively, you could start just such a thread.

Third, for all those who've posted so far, thank you; I'll comment and respond shortly.

I should have been more explicit in the OP: this thread is NOT, repeat NOT, about plasma cosmology (PC); nor do I wish to have anyone who is a proponent of that idea post in this thread, from that perspective ... the PC objections to CDM have been spammed into far too many JREF forum threads already.

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Fair enough, just thought I would add my opinion on mainstream cosmology. I didn't read the OP fully, and I should have done. My post was more a reaction to the title of the thread than the contents. Sorry for the brief hijack, I did get a bit carried away there Exam stress is getting to my head at the mo. I'll start a thread myself for this subject then when i've more time available.

And, re-reading you OP, your correct, I shouldn't have talked about lambda-CDM, I'm just so used to arguing against this on various other fora I went straight into my usual points, without fully considering the context. I could have (and probably should have) written that post without mentioning PC, just the critiques of cosmology would have done, but they are not really on topic I admit now reading back. Appologies.




....And to point this back in the right direction, I personally am sceptical of all of those things you listed in the OP (possibly not so much quarks as the rest). I think that one reason that other scientists are not as accepting of CDM than the others is that they learnt the others from a very early age, everyone has heard about black holes since they were a kid, and possibly neutron stars and pulsars too, so these idea’s are considered more common knowledge and are more popular topics of conversation than CDM, so you would expect them to have gained more widespread approval. Quarks and CDM are more college/uni level, but I think that it requires less faith to believe in the existence of miniscule subatomic scale particles than to accept CDM on a universal scale.

DeiRenDopa said:

I should have been more explicit in the OP: this thread is NOT, repeat NOT, about plasma cosmology (PC); nor do I wish to have anyone who is a proponent of that idea post in this thread, from that perspective ... the PC objections to CDM have been spammed into far too many JREF forum threads already.

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DRD, I can't help but notice that you remained silent when earlier posters specifically introduced the notion of plasma cosmology to this thread and attacked it and it's advocates. So I think your statement here rings rather hollow. Don't expect advocates of plasma cosmology to remain silent on *your* thread when you allow that to happen.

Zeuzzz said:

Fair enough, just thought I would add my opinion on mainstream cosmology. I didn't read the OP fully, and I should have done. Sorry for the brief hijack, I did get a bit carried away there

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Don't apologize Zeuzzz. You didn't introduce the topic of plasma cosmology to this thread. Another poster did. And DRD had nothing to say about that ... just because that poster happened to agree with DRD. Now that might be worthy of a study ...

I wonder why some people get so upset, so emotional, when there theory is challenged, or disbelieved, or questioned.

robinson said:

I wonder why some people get so upset, so emotional, when there theory is challenged, or disbelieved, or questioned.

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Did you read, actually read, the OP, robinson?

I wonder why you get so interested when you read things such as what BAC and Zeuzzz wrote, yet by your own admission you cannot understand, much less appropriately process, anything beyond a very minimal gloss of the (physics, astronomy) material which is presented in threads such as this?

Do you enjoy the controversy? Do you get your jollies from seeing heat in posts?

Is your lifeforce sustained by expressions of anger? of disgust? of ignorance?

DeiRenDopa said:

And that brings me to the point of this thread.

Why?

How does it come about that an apparently intelligent, educated, thoughtful person can be quite OK with 'quarks' (which have not be 'seen' in any experiments), [OIII] 5007 (which has never been produced in any lab), neutron stars (ditto), and black holes (double ditto!), yet balk at the very thought of non-baryonic cold dark matter (CDM)?

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I wonder the same thing. Why do some people get so upset when somebody just doesn't believe them? Why is it so important to some people for everybody to believe them?

BeAChooser said:

DRD, I can't help but notice that you remained silent when earlier posters specifically introduced the notion of plasma cosmology to this thread and attacked it and it's advocates. So I think your statement here rings rather hollow. Don't expect advocates of plasma cosmology to remain silent on *your* thread when you allow that to happen.

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Welcome to this thread, BeAChooser; I look forward to your (non-PC) contributions to finding answers to the questions in the OP.

I can't help but notice that you remained silent when asked questions about the ideas you forcefully presented, many times, in quite a few threads and attacked me for merely following your exemplary example. So I think your statement here rings rather hollow.

However, in order to not further derail this thread from its clearly stated purpose, I have started a new thread, specifically designed to cater to your express concerns: A collection of questions that BeAChooser has not answered (but I hope he now will).

In conclusion, to borrow a word from a prolific JREF forum poster, don't be coy now, jump right in and start answering all those unanswered questions ...

robinson said:

I wonder the same thing. Why do some people get so upset when somebody just doesn't believe them? Why is it so important to some people for everybody to believe them?

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Thanks.

And what do you think some of the answers to these questions might be?

Have you expressed a belief, in this section of the JREF forum, which has met with a vigorous response? If so, did you get upset (after spending dozens and dozens of posts clarifying you belief, and answering hundreds of questions)?

How important is it to you that everybody believe you?

The Man said:

Well, let’s remember the name of the website that sponsors this forum, The James Randi Educational Foundation, with education being the operative term. Certainly most of the people who have already posted on this thread have clearly demonstrated (on many other threads) their willingness and patience when it comes to educating others (and I believe be by others themselves). However, education requires a personal commitment in one’s desire to be educated by one’s self and by others. Speaking for myself, I have no BS degree nor have I worked in the fields of astronomy or physics (mostly technology and mechanical engineering). Yet, I have an interest in those fields and the desire to educate myself. I for one, have no problem in trying to educate others or being educated by others. Some on this forum (present company excluded) feel the only application of education on this forum is to educate others in their particular point of view, without displaying any real interest in being educated by others (other then to make their presentations better) or in admitting, at least to themselves if not to others, that they might have been wrong. The conversations usually degrade from that point with the thread continually going around in circles. Without a desire to be educated by others (other then reinforcing their current point of view) no amount of information or argument will create that desire in them. Although I enjoy a good debate and can debate form points of view I do not particularly agree with, I have no interest in unproductive debates that simply go around in circles solely for the sake of having an argument (or helping someone improve the presentation of their dogma). But we should not give up trying, though, even if active posts on a thread may not seem to be going anywhere, hopefully other people reading and not posting may be educating themselves with the information provided. Some people are never really comfortable with being wrong and therefore not really interested in educating themselves. Others might be more comfortable finding out they are wrong themselves then being told by someone else and therefore have little real interest in being educated by others. My self, I Just like to know if I am in fact or possibly wrong, regardless of the source, because it means I might just learn something. Just some of my thoughts on this phenomenon.

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Thanks.

I agree that for some people the eye-rolling response to CDM (and many, more vigorous, responses) comes from a firmly held belief in what we may term 'alternative physics' or 'alternative astronomy', and that these people will give similar responses to any aspect of physics or astronomy that does not fit in the alternative.

As you note, this forum can serve as a place to have a discussion of these alternatives, and in that respect CDM is merely one part of a broader discussion, and that discussion should be based on a mutually accepted basis of method, principles, and theories.

However, what I am particularly interested in is not the fellow travellers of PC, ID, or whatever alternative, but those who will respond, almost like clockwork, to posts on CDM, but will rarely (if ever) post on quarks, [OIII] 5007, neutron stars, black holes, or the like.

For example, robinson.

Cuddles said:

I have the same problem. For some reason there seem to be some topics that pretty much everyone feels the need to have an opinion on, even if they have no qualifications, no experience and, often, no clue what they're talking about. Dark matter is one, global warming another and evolution probably falls here as well.

My first thought was that it comes from a lack of any common ground with every day experience, which often leads to horrible misinterpretations due to poor analogies. For example, people have no problem accepting quarks because they already understand that everything is made up of little balls, so being told that some of those little balls are made up of even smaller ones isn't a big problem, and the weird properties can be largely ignored. When it comes to dark matter however, there really is nothing like it in human experience, so it's a lot harder to swallow. The obvious problem here is that neutrinos should suffer the same problem, but very few people have a problem accepting that they exist.

Possibly the problem is just the need for controversy. Most people don't seem to understand the difference between scientific debate and controversy. People rarely discuss the evidence either way for global warming, they argue about politics and supression of ideas. Same with evolution, it's not the science that's usually argued, it's the claimed controversy, even though there isn't one. I think dark matter has the same problem. There is no argument about neutrinos. Physicists know they exist and it's just a matter of working out exactly how they work. Dark matter, on the other hand, has many different ideas covering it, and plenty of other ideas, both mainstream and crackpot, which don't require dark matter at all. This means that it gets presented as a controversial subject to the general public, who go on to argue about the controversy without ever understanding the actual science involved.

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Thanks.

I think you've identified two important aspects: what 'matter' is composed of, and controversy.

Taking 'matter' first. The atomic theory has been such a resounding success, in terms of how deeply it is accepted by intelligent, educated, and thoughtful people that 'matter' has come to have a strong implication of 'composed of atoms' or 'composed of particles'. The intricate, complicated, and numerous paths, evidence, etc that lead to this strong acceptance of what is, after all, 'just another theory' remains almost completely unconscious, if not downright unknown to most such intelligent, educated, and thoughtful people.

Hence 'matter' whose particle composition cannot (yet) be specified (never mind that almost all intelligent, educated, and thoughtful people have next to no appreciation of the relevant parts of quantum physics) creates discomfort, and, possibly, disbelief.

'Controversy' is certainly alive and well as an element of journalism that helps boost circulation. Yet many (most?) serious journalists are not so careless with science as to whip up controversy where it truly does not exist in the physics or astronomy communities. So maybe 'quarks' caused eye-rolling a few decades ago, between the first proposal of the ideas and the widespread acceptance of QDC? And neutron stars are not controversial because those who froth at the mouth at their mention are not even on the fringes of contemporary physics or astronomy?

That certainly helps explain why neutrinos don't cause eyes to glaze over; with the possible exception of neutrino oscillations, there's no controversy any more. And neutrino oscillations are so hopelessly esoteric that even the best journalist would surely have qualms about even attempting to write a circulation-boosting story based on any 'neutrino oscillation' controversy.

Or perhaps not; it took several decades to solve the 'solar neutrino problem'; how much controversy was there, during that period, about astrophysics or particle physics?

Zeuzzz said:

These two descriptions prefectly sum up my opinion on ΛCDM. Both are written from a strong plasma cosmology type viewpoint, holding the things we do know for certain from direct observation and experiment in much higher regard then the mathematical abstractions and untestable foundations that modern cosmology is replete with.<>

And Michael Mozina gives what I believe is the true skeptics approach to ΛCDM, an approach that I often feel should be much more prominent on a skeptics forum such as this.

http://www.physicsforums.com/showpost.php?pp=1493877&postcount=27

I can't disprove a negative, so the burden of proof must fall to the individual that makes the claim. If someone makes the extraordinary claim that non-baryonic forms of mass exists, they will need to support that statement with solid empirical evidence. That is SOP (standard operating procedure) for all branches of science.

Click to expand...

He took the words right out of my mouth.

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Took the words out of your mouth, did he? Interesting, since that quote displays a breathtaking ignorance of particle physics.

Typical woo garbage - talk about subjects you're utterly ignorant of as if you knew something.

Sorry for the threadjack - I couldn't let that pass.

DeiRenDopa said:

.And what do you think some of the answers to these questions might be?

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You only asked one question in your OP. You went on and on, making a claim, a statement, about your own opinion, then asked:

DeiRenDopa said:

Why?

How does it come about that an apparently intelligent, educated, thoughtful person can be quite OK with 'quarks' (which have not be 'seen' in any experiments), [OIII] 5007 (which has never been produced in any lab), neutron stars (ditto), and black holes (double ditto!), yet balk at the very thought of non-baryonic cold dark matter (CDM)?

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See? You are asking why people are "OK with" some things, but reject current theory about Dark Matter, and perhaps Dark Energy as well. Or more exactly, why they "balk" at the very thought of Dark Matter. By setting up your own situation, in which you imagine a state of somebody else's mind, or beliefs, then asking why, you have created a strange situation. You created a scenario, then want somebody to explain it to you.

DeiRenDopa said:

.
Have you expressed a belief, in this section of the JREF forum, which has met with a vigorous response?

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Maybe, I don't know. I rarely express "beliefs", I try to stick with science and evidence. Unfortunately, many people think belief is more important than scientific inquiry, and when their "beliefs" are threatened by evidence, they get all emotional and angry, which isn't scientific at all. I don't know why.

DeiRenDopa said:

.
Have you expressed a belief, in this section of the JREF forum, which has met with a vigorous response? If so, did you get upset (after spending dozens and dozens of posts clarifying you belief, and answering hundreds of questions)?

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Again, I try to avoid beliefs, and present evidence, or questions, both of which have certainly caused a few people discomfort. They even become insulting and personal, rather than discuss the science or reality of something. I don't really know why.

I think I can help you and a few others out with one problem however. It is obvious from your phrasing of that last question.

did you get upset (after spending dozens and dozens of posts clarifying you belief

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See? Getting upset because someone doesn't buy into your belief, isn't really scientific at all. Beliefs are not the same things as facts, or even theories. Belief depends on faith, or something. Defending your belief system certainly can get some people upset. I think we all know why.

DeiRenDopa said:

.How important is it to you that everybody believe you?

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It depends on the situation. Here, on these forums, it isn't important at all. In reality, especially in regards to finances, health and security issues, it is very important that those I count on and deal with believe me. As well as being able to believe them. For this reason the truth is paramount, as is trust and dependability.

By comparison, chatting online with a bunch of people who don't even use their real names, it just isn't that important. It is however, a lot of fun, if you can find the time.

If it isn't fun for you, you might want to ask why you keep doing it, over and over, without a break. Why would anyone keep chatting online if they didn't enjoy it?

DeiRenDopa said:

How does it come about that an apparently intelligent, educated, thoughtful person can be quite OK with 'quarks' (which have not be 'seen' in any experiments),

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I'm not sure what you mean by here by they haven't been 'seen'. Confinement in QCD explains why we've never seen a free quark. But deep inelastic scattering experiments 'see' them all the time as constituents of the nucleons.

Tubbythin said:

I'm not sure what you mean by here by they haven't been 'seen'. Confinement in QCD explains why we've never seen a free quark. But deep inelastic scattering experiments 'see' them all the time as constituents of the nucleons.

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Just as measurements of the mass of galaxies, gravitational lensing, CMB data, and large scale clustering "sees" dark matter?

sol invictus said:

Just as measurements of the mass of galaxies, gravitational lensing, CMB data, and large scale clustering "sees" dark matter?

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Sees dark matter = possibly

Sees cold dark matter = who knows?

sol invictus said:

Just as measurements of the mass of galaxies, gravitational lensing, CMB data, and large scale clustering "sees" dark matter?

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But that is dark matter as a whole. No one has observed a (non-baryonic, non-neutrino) 'dark matter particle' in a lab... yet.

Tubbythin said:

But that is dark matter as a whole. No one has observed a (non-baryonic, non-neutrino) 'dark matter particle' in a lab... yet.

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But the same goes for quarks - that was the whole point! The observations of both are indirect, and in neither case has an individual particle ever been observed.

"Seeing" DM via gravitational lensing is just as direct as "seeing" quarks by inferring their existence from the properties of baryon scattering.

Wangler said:

DeiRenDopa said:

You are talking with someone who is not an astronomer, nor a physicist (and also not an astrophysicist, etc), and who also does not have a BSc (or higher) with a major in either of these fields^.

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I do not have a degree in these fields, so take my following comments with that fact in mind.

You know from earlier conversations that they do not bat an eyelid when 'quarks' get discussed,

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Good theoretical models for quarks exisit, and those models gave good predictions for the "finding" of the top and bottom quarks, for example. AFAIK, there is no convincing predictive model for what constitutes CDM.

nor when 'neutron stars' nor 'black holes

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Again, it seems to me that the theoretical, and observational evidence for these is strong. For example, we postulate that pulsars are actually rotating neutron stars, and luckly we have a theoretical framework that we can use to describe matter under these conditions, and make reasonable extrapolations from our theory, and our experiences with normal matter, to discuss neutron starts and black holes with what I would consider reasonable scientific certainty.

AFAIK, this is in stark contrast to CDM, of which the fundamental constiuents are just a vague postulate at this time.

if they have some interest in astronomy, perhaps you have also discussed some of the beautiful nebulae, including those with a delightful green colour due to something known as the [OIII] 5007 emission line.

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Isn't the science behind this example well understood, though? Can the same be said for the non-baryonic dark matter that supposedly makes up CDM? And I mean real, concrete predictions as to what CDM really is, not just that it accounts for X% of the matter in the universe, based upon our standard cosmology models.

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Thanks very much Wrangler!

So far, this is right in line with what Cuddles wrote: if it's "matter" you are OK if there's something fundamental, something elementary at the bottom of it, somewhere (though 'black holes' doesn't quite fit).

Two new aspects are predictive power and extrapolation of well-established theories.

To cover the first in more detail (which I am most interested in doing, in a later post or two), we'd need to look into how you arrived at your intuitive guide of 'prediction', and (perhaps) the extent to which it corresponds with objective history.

For now, how about this: from Zwicky's and Rubin's discoveries/landmark papers onward, 'prediction' has, in fact, been what's driving astronomers (and physicists) in constructing their hypotheses, which they went and used observations to test. Perhaps the most stunning example of predictive success might be that the CMB angular power spectrum matches ΛCDM cosmological models amazingly well, despite the fact that CDM, prior to the actual CMB observations, had not been 'observed' in a cosmological setting.

In terms of extrapolation of well-established theories, how about this (for now): IF (rich cluster CDM, from virial theorem) THEN (rich cluster weak and strong gravitational lensing, from GR). Also, there's the extrapolation from the Standard Model (of particle physics): it's been known for some time now that it cannot be a complete theory of particle physics, because there are 'holes' in it. Further, it's also been known, for a much longer time, that the universe can create particles with energies many, many, many orders of magnitude greater than the best we have been able to do in our own particle accelerators, and every time we explored a new (higher) energy regime, we found some new physics. So a strong 'astronomical' signal suggesting a form of matter not (yet) seen here on Earth hints at that new physics, and it has, of course, several historical precedents (positrons and muons, for example).

Have you come across these considerations before? Does this reduce your incredulity at CDM any?
.

Later the conversation turns to 'dark matter', and after clearing up confusion over 'ordinary' dark matter (i.e. things like stars too faint to be visible, and rocks, and planets), and 'hot' dark matter (i.e. neutrinos, in this case), you start talking about 'cold dark matter', a.k.a. non-baryonic cold dark matter, CDM, and how it seems that for every gram of ordinary ('baryonic') matter in the universe there is ~5 grams of CDM. Then the eyes glaze over; disbelief is expressed, perhaps forcefully; and so on.

Click to expand...

This paragraph is telling:

Ordinary dark matter: stars, rocks, planets
"Hot" dark matter: neutrinos
"Cold" dark matter: we have no idea what it might be, but our models show that it is 5x more prevalent then those things you can actually see and describle, like stars, galaxies, planets, rocks, birds, leptons, Mini Coopers, etc. But believe us, it's out there, in some mysterious form!

And you wonder why the eye's glaze over?

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That's great too - in addition to the point Cuddles made (that 'matter' requires something elementary, in particle form, to have a hook to), would you say more on this please?

For example, what makes non-baryonic CDM any more mysterious than the detailed mechanisms that give rise to the jets seen in quasars (as AGNs), YSOs (young stellar objects), and (possibly) GRBs (gamma ray bursts)? or how UHECRs (ultra-high energy cosmic rays) are accelerated? or the asymmetrical distribution of 511 keV (electron-positron annihilation radiation) gammas around the Galaxy core? or ...?

.

And that brings me to the point of this thread.

Why?

How does it come about that an apparently intelligent, educated, thoughtful person can be quite OK with 'quarks' (which have not be 'seen' in any experiments), [OIII] 5007 (which has never been produced in any lab), neutron stars (ditto), and black holes (double ditto!), yet balk at the very thought of non-baryonic cold dark matter (CDM)?

Click to expand...

Perhaps because, as I mention before, the quarks, doubly-ionized Oxygen, neutron stars, and black holes can be discussed in terms of what they are, not what they might be, as in CDM.

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.
Another tick for Cuddles' point.

Could you please say more on how you perceive (or conclude) that quarks etc 'can be discussed in terms of what they are'? In what way(s) can you discuss a neutron star in terms of what it is, that makes it intellectually satisfying, recognising that it takes only a few questions to get to the limit of what's known about them?
.

From the point of view of the astronomy, the observational evidence for neutron stars and black holes is no different than that for CDM: millions (billions?) of independent observations, made using multiple, independent techniques, and relying on several, independent, parts of physics to get from observation to conclusion.

Our apparently intelligent, educated, thoughtful person seems perfectly at ease with accepting that there is a great deal between what comes out the back of some telescope and a conclusion 'here be a neutron star', and that the astronomers and physicists who did the work to connect the dots did so competently, etc, etc, etc. Yet when it comes to CDM, no such acceptance is to be found!

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When someone looks in the back of a telescope, and says "here be a neutron star", his observation is backed by physics that describes how such a star may come to be, what it might consist of, and how our current understanding of physics would allow a neutron star to exist.

AFAIK, when someone says "here be CDM", that observation is lacking concrete physics that says how such CDM may come to be, what it might consist of, and our hour current understanding of physics would allow the CDM to exist.

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Great, thanks very much!!

If I may paraphrase, CDM is hard to swallow because there's no 'story' to go with it - where it comes from, what it's made of, and how it behaves ... OK?

If an astronomer pointed to some other entity, derived as the conclusion of a long chain of logic and analysis, which, like CDM, lacked a 'story' of this kind, would you be equally incredulous?

For example, how about the super-massive black holes in the nuclei of so many 'normal' (i.e. not dwarf) galaxies? (no story on origins)

And does the 'requirement for credulity' apply to only things labelled 'matter'? For example, if the mechanisms for the formation and maintenance of the bars in barred spirals could be said to be lacking in a 'story' about origins and maintenance ("how our current understanding of physics would allow the bars to continue to exist"), to what extent would that put bars into the same category as CDM?
.

Notice, I qualify my statements with AFAIK a lot; if anyone has information about what CDM might actually be, I would be excited to hear about it.

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Stay tuned!

DeiRenDopa said:

.
Or perhaps not; it took several decades to solve the 'solar neutrino problem'; how much controversy was there, during that period, about astrophysics or particle physics?

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Well I think there you have it, even though the neutrino had been detected in the lab and on earth from the sun, there was still significant controversy with the ‘solar neutrino problem’ because the numbers did not workout. We still have not reacted that phase with CDM yet, we know it can help the current numbers work out better but we have not detected (at least not that has be verified) it in a lab or on earth yet (WIMP just as an example). When (and if) that happens we may also find some CDM problem based on the number or nature of the WIMPs that may be detected (like the 'solar neutrino problem'). But of course we are not even up to that point yet to know if the detection and a better understanding of the nature of CDM creates more problems then it solves. I think Cuddles makes an excellent point as to “a lack of any common ground with every day experience” hell we really can’t even give it much common ground in particle physics experience other then to call it non-baryonic matter and Weakly Interacting Massive Particles (again ignoring MACHOs in this example). Which really just signify its differences to the particles we normally consider in the standard model (ignoring supersymmetry for this example as well). Maybe when we can directly detect it and produce it here on earth and have a better understanding of its nature then for some, it might be an easier pill to swallow. But of course, like the 'solar neutrino problem' detecting it directly and a better understanding of its nature might lead to more problems that we all end up choking on for quite some time.

Tubbythin said:

I'm not sure what you mean by here by they haven't been 'seen'. Confinement in QCD explains why we've never seen a free quark. But deep inelastic scattering experiments 'see' them all the time as constituents of the nucleons.

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.

Already covered to some extent, by others, but I'm making a somewhat arbitrary distinction between an 'atom' (which can be 'seen' using an AFM, for example), an 'electron' (which registers in certain instruments as a 'click'), and a 'quark' (which has never been detected as an isolated entity, anywhere, anyhow).

It's a somewhat artificial distinction since all three (atom, electron, quark) - and many more - are, in one sense, merely the labels applied to parts of highly successful theories ... highly successful (in this case) in the sense that we all talk, all the time, as if these things are 'real'.

However, in this thread, I don't want to get into the relationship between hugely successful theories (models, etc) and 'reality'; quarks, neutron stars, and black holes all share one characteristic with (non-baryonic) CDM - we infer their existence indirectly, and we rely on the success of a very large number of exacting experiments and observations, of many different kinds, done by a great many different individuals/teams/facilities, over several decades (at least), etc to conflate inference with reality.

sol invictus said:

But the same goes for quarks - that was the whole point! The observations of both are indirect, and in neither case has an individual particle ever been observed.

"Seeing" DM via gravitational lensing is just as direct as "seeing" quarks by inferring their existence from the properties of baryon scattering.

Click to expand...

I'd call high energy electron scattering a pretty direct mechanism myself but maybe thats just me. Does 'direct' viewing of a particle explicitly mean it must be a free particle?

Tubbythin said:

I'd call high energy electron scattering a pretty direct mechanism myself but maybe thats just me. Does 'direct' viewing of a particle explicitly mean it must be a free particle?

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I don't see why gravitational lensing is any more or less direct than that. Remember, baryons must be characterized by parton distribution functions - you never know for sure which quark interacted with what, whether it was a virtual or a real quark, whether there were some nearly coincident particles in the jet you observed or just one, soft gluons, etc. It's rather indirect.

In any case, it's pointless to argue about semantics. We have some mathematical models, and they either do a good job agreeing with data or not. QCD does a good job; so does CDM. What the OP (and I) find mystifying is why the data supporting DM is regarded as less compelling, or the DM hypothesis as so much more exotic.

sol invictus said:

I don't see why gravitational lensing is any more or less direct than that.

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I would probably classify them both as direct for what its worth (not a lot).

Remember, baryons must be characterized by parton distribution functions - you never know for sure which quark interacted with what, whether it was a virtual or a real quark, whether there were some nearly coincident particles in the jet you observed or just one, soft gluons, etc. It's rather indirect.

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I suppose. But we still observe that protons and neutrons have substructure and that sub-components have the right charges and as far as we can tell are points.

In any case, it's pointless to argue about semantics.

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Agreed.

We have some mathematical models, and they either do a good job agreeing with data or not. QCD does a good job; so does CDM. What the OP (and I) find mystifying is why the data supporting DM is regarded as less compelling, or the DM hypothesis as so much more exotic.

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Because we can create quarks in labs but not dark matter? Because we can construct other theoretical hadrons by sticking together different combinations of quarks and then go out and look for them in our accelerators? I think if and when ATLAS or CMS or some other collaboration create/find a 'dark matter particle' the debate will be over. And Nobel prizes will be handed out all round. But perhaps I'm being naive.

Tubbythin said:

Because we can create quarks in labs but not dark matter? Because we can construct other theoretical hadrons by sticking together different combinations of quarks and then go out and look for them in our accelerators? I think if and when ATLAS or CMS or some other collaboration create/find a 'dark matter particle' the debate will be over. And Nobel prizes will be handed out all round. But perhaps I'm being naive.

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But we can do the equivalent in astrophysics. We can look at a galaxy which hasn't been observed before and predict how much DM there will be, what the rotation curve will be, etc. and then observe it. We can run simulations with or without DM and see that with DM we get results consistent with observation. We can make predictions about the acoustic peak in the power spectrum of galaxies, based on the existence of DM, and then go out and observe it. Etc.

Granted, one can't produce DM particles in a lab - but one can't produce a star in a lab either. Does that make the physics of stars more suspect than the physics of quarks?

Obviously the detailed properties of DM are less well understood than quarks, but the fact of its existence is all but irrefutable.

sol invictus said:

But we can do the equivalent in astrophysics. We can look at a galaxy which hasn't been observed before and predict how much DM there will be, what the rotation curve will be, etc. and then observe it. We can run simulations with or without DM and see that with DM we get results consistent with observation. We can make predictions about the acoustic peak in the power spectrum of galaxies, based on the existence of DM, and then go out and observe it. Etc.

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But until we observe it in a lab there's still the "but it could be something we haven't thought of yet" option. Or the conspiracy theory option: "my theory explains rotation curves without the need for matter we can't see yet". In the latter case the proponents seem to ignore the fact that the alternative must be consistent with the observations of the universe around us.

Granted, one can't produce DM particles in a lab - but one can't produce a star in a lab either. Does that make the physics of stars more suspect than the physics of quarks?

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We can recreate 'bits' of stars in labs. We can find the Q values of various stellar reactions. We can measure reaction cross sections (usually with big error bars and very indirectly but nevertheless its possible). We can measure neutrino cross-sections and look for oscillations. We can study hydrogen plasmas.
Do you think we'd be so sure the Sun was powered by nuclear fusion if we couldn't do nuclear fusion in a lab?

sol invictus said:

Obviously the detailed properties of DM are less well understood than quarks, but the fact of its existence is all but irrefutable.

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DRD and Sol, it is the statement like this that makes me uneasy.

Sol, I have not read the CMB paper you linked me to in it's entirety, but if I understand, one of the reasons that the lambda-CDM model is favored is due to it's ability to accurately predict the appearance of the CMB.

Now, the mathematical processes that are used to derive the CMB appearance/properties seem to me to be somewhat complex, in terms of the total amount of variables that are all brought together.

According to my laymans' understanding, the current lambda-CDM model is in part assembled due to certain constraints, or limits:

For example: I thought that for inflation to work, with the universe being flat, it means that certain parts of your cosmology must be constructed a certain way.

Another example: For the large and small scale structure to be explained, there are certain other limits to the cosmology that must be considered.

Now, there are certain other limits to the cosmology, but of observational nature: the gas in the Bullet cluster, the galaxy cluster velocities, galaxy rotation curves. These also set certain limits.

What makes me (as a layman) uneasy is that I see a cosmological model that depends upon a number of variables; some are well known, some less so. And the solution that is derived as the "virtually irrefutable" one is the one that needs new physics or new entities.

Is it really true that all of these variables are such that the only "irrefutable" solution is for one of those variables to point to CDM? I find that hard to believe, as a layman.

Does anyone who isn't a crackpot consider different cosmologies that don't depend upon some strange unknown form of matter? Shouldn't we pull out all of the stops to examine all those cosmologies that don't require this addition to our physics, or other strange additions? Shouldn't exotic forms of CDM be the last straw, and not the leadoff hitter?

Doesn't QCD tell us how quarks work? Can't we do all sorts of calculations about black holes, rotating, non-rotating, charged, non-charged? Doesn't this make us all feel better about these theories?

Can anyone one say that they feel as confident about CDM as they do about black holes, white dwarfs, barred spiral galaxies, and all of that stuff? Really, as confident as they feel about processes involving photons, or the decay of radioactive elements? As confident as they feel about the periodic table, and what physics are behind it?

If yes, than I must be missing something big.

If no, why then so quick to invoke CDM of an exotic form? Maybe the analysis of the cosmological models that says: "this must be it" are flawed?

It just seems like we are throwing up our hands in frustration when we invoke CDM in this way. It reminds me of the struggles to predict planetary positions: we didn't have gravity as a theory, so we assumed that epicycles were nearly irrefutable based upon observational evidence and predictive power.

I am certain that this way of thinking, my opinion, must be frustrating to people like DRD (that's why he started the thread).

I am sorry if this seems like an approach from ignorance, but it is, in my case.

I have read, and could possibly argue from authority somewhat, on problems that I have seen presented about CDM, but this isn't the thread for that.

I just want to make clear the roots of my personal misgiving about the seeming "rote acceptance" of the need for something new and exotic.

Thank you all for your patience in hearing me out.

Wangler said:

DRD and Sol, it is the statement like this that makes me uneasy.

Sol, I have not read the CMB paper you linked me to in it's entirety, but if I understand, one of the reasons that the lambda-CDM model is favored is due to it's ability to accurately predict the appearance of the CMB.

Now, the mathematical processes that are used to derive the CMB appearance/properties seem to me to be somewhat complex, in terms of the total amount of variables that are all brought together.

According to my laymans' understanding, the current lambda-CDM model is in part assembled due to certain constraints, or limits:

For example: I thought that for inflation to work, with the universe being flat, it means that certain parts of your cosmology must be constructed a certain way.

Another example: For the large and small scale structure to be explained, there are certain other limits to the cosmology that must be considered.

Now, there are certain other limits to the cosmology, but of observational nature: the gas in the Bullet cluster, the galaxy cluster velocities, galaxy rotation curves. These also set certain limits.

What makes me (as a layman) uneasy is that I see a cosmological model that depends upon a number of variables; some are well known, some less so. And the solution that is derived as the "virtually irrefutable" one is the one that needs new physics or new entities.

Is it really true that all of these variables are such that the only "irrefutable" solution is for one of those variables to point to CDM? I find that hard to believe, as a layman.

Does anyone who isn't a crackpot consider different cosmologies that don't depend upon some strange unknown form of matter? Shouldn't we pull out all of the stops to examine all those cosmologies that don't require this addition to our physics, or other strange additions? Shouldn't exotic forms of CDM be the last straw, and not the leadoff hitter?

Doesn't QCD tell us how quarks work? Can't we do all sorts of calculations about black holes, rotating, non-rotating, charged, non-charged? Doesn't this make us all feel better about these theories?

Can anyone one say that they feel as confident about CDM as they do about black holes, white dwarfs, barred spiral galaxies, and all of that stuff? Really, as confident as they feel about processes involving photons, or the decay of radioactive elements? As confident as they feel about the periodic table, and what physics are behind it?

If yes, than I must be missing something big.

If no, why then so quick to invoke CDM of an exotic form? Maybe the analysis of the cosmological models that says: "this must be it" are flawed?

It just seems like we are throwing up our hands in frustration when we invoke CDM in this way. It reminds me of the struggles to predict planetary positions: we didn't have gravity as a theory, so we assumed that epicycles were nearly irrefutable based upon observational evidence and predictive power.

I am certain that this way of thinking, my opinion, must be frustrating to people like DRD (that's why he started the thread).

I am sorry if this seems like an approach from ignorance, but it is, in my case.

I have read, and could possibly argue from authority somewhat, on problems that I have seen presented about CDM, but this isn't the thread for that.

I just want to make clear the roots of my personal misgiving about the seeming "rote acceptance" of the need for something new and exotic.

Thank you all for your patience in hearing me out.

Click to expand...

The indirect evidence for Dark Matter in at the link.

There is one direct observation of dark matter in the Bullet Cluster which from some reaons you do not know about or maybe trust (may I suggest a bit of research?).

The mathematical processes that are used to derive the CMB are complex because the universe is complex. There are many processes that have to accounted for when considering the early universe.

The observational and theoretical basis for the existence of dark matter is (IMHO) as good as those for stellar sized black holes and only slightly less than that for super-massive black holes.


There was no "rote acceptance" of the need for dark matter. Our observations of the universe indicate that its curvature is very close to zero. We can not account for all of the mass (or energy) that is required to make the curvature zero. The indirect evidence for dark matter supports this. This leads to one of 2 possibilities:

1. There is other energy or mass that we cannot see that makes the curvature zero or
2. We need a "new and exotic" theory of the universe to account for the flatness and the evidence for DM.

The first option was used because there are no viable cosmological theories that are as good as the Big Bang theory. The actual observation of dark matter is a confirmation that the right option was taken.
This does not rule out the possiblity that someone in the future may work out a "new and exotic" theory of the universe that explains dark matter, makes the same predictions as BB cosmology and makes other falsifiable predictions.

Wangler said:

Sol, I have not read the CMB paper you linked me to in it's entirety, but if I understand, one of the reasons that the lambda-CDM model is favored is due to it's ability to accurately predict the appearance of the CMB.

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Just a quick response for now. I think you're coming at this a bit backwards. The CMB is only one of many pieces of evidence for DM, and it's more complex and less direct than some others. Probably if the CMB were the only evidence, there would be significant skepticism among the pros.

The first evidence for DM was the rotational velocity (as a function of distance from the galactic center) of the matter in galaxies. Gravity within a galaxy is not strong enough to require general relativity, so we can use Newtonian gravity to a very good approximation. If you'll recall, the velocity of a body orbiting a central mass as a function of radius is determined by how much mass there is inside the radius of the orbit (this has been known since Johannes Kepler). When we observe the velocity of orbiting matter we see that it's orbiting much too fast if the visible matter in the galaxy were the only thing in play, indicating that there is some additional mass. We can use this discrepancy to measure the amount of additional mass and its distribution (density as a function of radius).

So Newtonian gravity and galaxy observations tell us there is DM. The only possibilities are:

1) the observations are wrong (very hard - this has been seen in thousands of galaxies over 30 years of observations);

2) Our theories of gravity (Newton and Einstein) are wrong, and there are large corrections to Newton's law in galaxies (the only models like that which might have worked were killed by the recent Bullet cluster observations);

3) There is some extra matter in galaxies which isn't emitting or absorbing enough light for it to be visible to us (even with no other data, this is by far the most plausible).

That was the starting point, and there are now four or five independent types of observations (like the CMB) which all agree on this extra mass. If you want to understand the evidence, I would go in this order:

1) galactic rotation curves
2) bullet cluster
3) CMB
4) structure formation simulations (need DM to reproduce what we see)
5) weak lensing
6) observed acoustic peak in large-scale structure power spectrum

Probably there are more...

First off, let me say: Thanks for the useful responses, folks.

Reality Check said:

There is one direct observation of dark matter in the Bullet Cluster which from some reaons you do not know about or maybe trust (may I suggest a bit of research?).

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I actually did mention the Bullet cluster in my post, in terms of this observation setting limits on any cosmology model that one chooses. By wording it this way, I meant that any cosmology model that one chooses to support needs to explain this observation.