Non-baryonic cold dark matter ("CDM"), the observational evidence
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Hellbound
Merchant of Doom
Thank you for comfirning your lack of understanding.
Either that, or creating a strawman.
You talk about semantic arguments, but that's the majority of what you've been doing.
Heres a clue for you:
That's basically what the words "dark matter" mean. EVERY PROPERTY put forth for dark matter comes from the observations, and the limitations on those observations, and the implications of those limitations in regards tot he laws of physics.
Instead of saying "evidence for invisible matter that does not act like matter that we know of has been observed" everyt ime, which would make scientists sound like idiots besides being a mouthful, that's been shortened to "dark matter". You, however, seem to have some objection to the word (since, from your statements, it's clear you don't object to the meaning..assuming you understand it). It's not like we had this word called dark matter that had this whole, well-defined set of attributes associated with it that we simply slapped on the first unseen gravitational lensing effect we found.
DeiRenDopa
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I'm curious ...
This very recent arXiv preprint uses both "infer" and "large detectable magnetic field" in the abstract (see below; I added bold).
How do you think the authors should have written their abstract robinson?
Skwinty
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Hi DRD
In a nutshell, why I am not happy with the "Dark matter has been directly observed" statement although I accept the inferred conclusions from the observational data.
DAMA in 2000 stated the dark matter had been directly observed using a sodium iodide detector.
This statement only raised eyebrows in the scientific community.
DAMA in 2008 restated this claim with a better data and a bigger detector. The scientific community accepted the results as real effect but not convinced that it indicated dark matter.
There was very little or no corroborating evidence from CERN, Fermilab or COUPP with respect to any WIMP detection. Maybe LHC willl produce a WIMP.
No corroborating evidedence from CDMS, XENON10 or 100.
No corroborating evidence from ADMX for axions or ICE-CUBE for neutrinos.
GLAST will give good data in the near future as will all the other experiments I mentioned above.
So, in my opinion, the dark matter issue has not been sufficiently resolved for us to celebrate.
My main problem is the headline hype and not the inferred data from direct or indirect observations which indicate the presence of dark matter regardless of whether dark matter is indeed matter or energy.
In a nutshell, why I am not happy with the "Dark matter has been directly observed" statement although I accept the inferred conclusions from the observational data.
DAMA in 2000 stated the dark matter had been directly observed using a sodium iodide detector.
This statement only raised eyebrows in the scientific community.
DAMA in 2008 restated this claim with a better data and a bigger detector. The scientific community accepted the results as real effect but not convinced that it indicated dark matter.
There was very little or no corroborating evidence from CERN, Fermilab or COUPP with respect to any WIMP detection. Maybe LHC willl produce a WIMP.
No corroborating evidedence from CDMS, XENON10 or 100.
No corroborating evidence from ADMX for axions or ICE-CUBE for neutrinos.
GLAST will give good data in the near future as will all the other experiments I mentioned above.
So, in my opinion, the dark matter issue has not been sufficiently resolved for us to celebrate.
My main problem is the headline hype and not the inferred data from direct or indirect observations which indicate the presence of dark matter regardless of whether dark matter is indeed matter or energy.
Did you just make that up? DM was theorized to explain Gravity rotation which didn't match Kepler's equations for the planets orbits. It is assumed Galaxy rotation has to follow Kepler's laws, which they don't, so there had to be some missing matter to explain it. A LOT of missing matter.
It is amusing to consider that while the third law was the one that got the head scratching started, the first one seems to be ignored.
1. The orbit of every planet is an ellipse with the sun at one of the foci.
2. A line joining a planet and the sun sweeps out equal areas during equal intervals of time as the planet travels along its orbit.
3. The squares of the orbital periods of planets are directly proportional to the cubes of the semi-major axes of their orbits.
Assuming a plasma dominated system of hundreds of billions of stars, as well as many times more plasma and hydrogen/helium, would act like a solar system, in terms of rotation and orbits, seems kind of silly now.
"Non-baryonic cold dark matter", from the thread title, is a made up term. It is a placeholder until we figure out what is really going on. There is no such thing as "Dark Matter", (just like there is no such thing as "Baryonic hot light matter").
At some point it will be called neutralinos, axions, axinos or Majorons, or something. The problem is wikiality hasn't decided what to call it. much less what it is. Once consensus is reached, all will be well.
Hellbound
Merchant of Doom
robinson:
That's exactly my point. Dark matter is a place holder, or more accurately a term to include a grouping of matter that's different from regular matter.
Saying it doesn't exist because we don't know all the elements that make it up is as non-sensical as saying beetles don't exist because we haven't found and classified every beetle yet.
It's a semantic argument, rather than an argument based on anything of substance.
But by all means, continue to play word games.
That's exactly my point. Dark matter is a place holder, or more accurately a term to include a grouping of matter that's different from regular matter.
Saying it doesn't exist because we don't know all the elements that make it up is as non-sensical as saying beetles don't exist because we haven't found and classified every beetle yet.
It's a semantic argument, rather than an argument based on anything of substance.
But by all means, continue to play word games.
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Nobody said that, except you, just now.
Hellbound
Merchant of Doom
Well, then, let me state it better.
Claiming we haven't directly detected dark matter is like claiming we haven't directly detected beetles because we haven't seen every variety.
We have directly detected dark mater, we just don't have all the answers as to exactly what it is yet.
DeiRenDopa
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Oh?
What would you say cosmic rays are then?
After all, they:
* are composed of protons (and other atomic nuclei) ... "baryonic"
* travel at relativistic speeds .... "hot"
* 'feel' the electromagnetic force ... "light"
* and are a form of "matter"!
May I ask robinson, to what extent are you actually (really, truly) interested in learning how modern physics (including astrophysics) works?
DeiRenDopa
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OK ...
... may I ask a hypothetical then? What sorts of circumstances do you feel would constitute "sufficiently resolved", so that you could celebrate?
And during the ~40 years it took to resolve the "solar neutrino issue" (if I may call it that), how did you feel? Were you aware of the issue? of its resolution? of the details of that resolution?
What other issues - in astrophysics, astronomy, or cosmology do you feel are also insufficiently resolved?
Hype can be quite annoying, can't it?
Do you find the hype about DM particularly more annoying than that about some other aspect(s) of astrophysics?
Skwinty
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Hi DRD
Firstly, my satisfaction in this matter is irrelevant.
For the scientific community at large I would say that its time to pop corks when:
1.WIMPS are directly detected. See end of post for a examples of direct and indirect detection.
2.When local and relic densities of WIMPS have been directly measured.
3. When WIMP masses have been directly detected.
Then we can say that at least some part of dark matter has been directly observed.
40 years ago I had no interest in Astronomy or Science.
But, in the last 10 years I have. I do recall that the resolution of solar neutrinos involved neutrino oscillation and a change to the standard model of particle physics. I dont recall hyped headlines though, perhaps there were, I just dont remember.
Goodness, there are so many unresolved issues. A bit naive to expect that there would be none.
Sure, hype is bound to lead to disappointment.
Not particularly.
Examples of Large Surveys:
Sloan 1 & 2, Deep 2, Gravitational lensing(MegaCam, Panstar, LSST)
Example of Direct detection/searches:
Experiments such as CDMS2, EDelweiss 2,Cresst 2, Liquid Xenon, Argon/Neon, Pressurised Gas, COUPP, Picasso, Simple.
Direct detection involves elastic scattering.
WIMP interacting with detector.
Examples of Indirect detection/searches:
GLAST
IceCube Antares/Nemo/Nestor
Indirect detection involves annihilation.
WIMP to Gamma rays/positrons/antiprotons.high energy neutrinos.
Pretty much what I said here in an earlier post
"Perhaps the HESS is a bad example as the gamma rays do not penetrate the atmosphere and reach the earth 's surface as they interact with the atmosphere and produce cerenkov radiation. The link between the gamma ray and cerenkov radiation is inferred, so the direct observation is the cerenkov radiation and the gamma ray observation is indirect. And its a good solid inferrence.No problem there. "
Firstly, my satisfaction in this matter is irrelevant.
For the scientific community at large I would say that its time to pop corks when:
1.WIMPS are directly detected. See end of post for a examples of direct and indirect detection.
2.When local and relic densities of WIMPS have been directly measured.
3. When WIMP masses have been directly detected.
Then we can say that at least some part of dark matter has been directly observed.
40 years ago I had no interest in Astronomy or Science.
But, in the last 10 years I have. I do recall that the resolution of solar neutrinos involved neutrino oscillation and a change to the standard model of particle physics. I dont recall hyped headlines though, perhaps there were, I just dont remember.
Goodness, there are so many unresolved issues. A bit naive to expect that there would be none.
Sure, hype is bound to lead to disappointment.
Not particularly.
Examples of Large Surveys:
Sloan 1 & 2, Deep 2, Gravitational lensing(MegaCam, Panstar, LSST)
Example of Direct detection/searches:
Experiments such as CDMS2, EDelweiss 2,Cresst 2, Liquid Xenon, Argon/Neon, Pressurised Gas, COUPP, Picasso, Simple.
Direct detection involves elastic scattering.
WIMP interacting with detector.
Examples of Indirect detection/searches:
GLAST
IceCube Antares/Nemo/Nestor
Indirect detection involves annihilation.
WIMP to Gamma rays/positrons/antiprotons.high energy neutrinos.
Pretty much what I said here in an earlier post
"Perhaps the HESS is a bad example as the gamma rays do not penetrate the atmosphere and reach the earth 's surface as they interact with the atmosphere and produce cerenkov radiation. The link between the gamma ray and cerenkov radiation is inferred, so the direct observation is the cerenkov radiation and the gamma ray observation is indirect. And its a good solid inferrence.No problem there. "
Acleron
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So what hypothesis do you have to explain the non-Newtonian if not non-Einsteinian orbiting of visually detectable matter in galaxies?
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Skwinty
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No, it would be like claiming there is a new kind of life form that doesn't fit into any known category, because something is eating the leaves of a tree, and we don't know what it is, but we are sure it isn't any known animal.
And the tree is so far away we can only see it with a telescope, and we don't see any other animals eating the tree, so it has to be a new kind of life form, one that has never been seen, and doesn't act like any known animal, and there are more of these animals than all the other species combined.
DeiRenDopa
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After all this time, you still don't get it robinson?!?
What part of "matter" don't you understand?
It walks like (cold) mass, talks like (cold) mass, fights like (cold) mass ... sure must be a new species of sith then ...
Skwinty
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After all this time, you still don't get it robinson?!?
What part of "matter" don't you understand?
It walks like (cold) mass, talks like (cold) mass, fights like (cold) mass ... sure must be a new species of sith then ...
Robinson might well ask of you, "What dont you get about the"allegory".
Check the meaning of the word and "The allegory of the cave"
Now I understand why people, who are highly educated in "science" cant agree with "philosophy" or the more figurative trains of thought.
Not everything has to be black and white all the time.
There is actually a lesson or moral in robinsons story here which is flying right over your heads.
Just a thought here.
DeiRenDopa
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If you say so.
However, this part of the JREF forum is entitled "Science, Mathematics, Medicine, and Technology". I can't see where "philosophy" fits in, for this section. In fact, the forum has a whole section called "Religion and Philosophy", so why do you think it appropriate to have discussions of philosophy here (and not in the section explicitly devoted to it)?
But thanks, I think you have put your finger on one possible reason for miscommunication ('talking past each other') - some people post here with a default perspective other than that of contemporary science.
Acleron
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My bolding.
First of all, being highly educated doesn't mean anything at all. A highly educated scientist can be as stupid as a highly educated anything else.
Secondly, in science, it has to be black and white. If you cannot clearly describe what you are talking about it is not science. If you don't see that point, you have no idea about how scientists think or work.
Thirdly, if you think that Robinson's use of English to describe or interpret deeper parts of scientific thought is of any use at all then you must be part of the modern philosophers movement. Unfortunately, the universe does not operate according to responses and reflexes learned when the maximum speed and mass approximate to that attained by a human being.
I could ask my question again ie What does philosophy have to offer to our understanding of the universe? But why should I wait for an answer?
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Acleron
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Precisely
Skwinty
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Agreed, stupidity has no limitations.
Agreed, but with some reservation. For example, the brain is divided into two hemispheres and I believe that logical thinking uses one hemisphere predominately. Lateral thinking predominately uses the othe hemisphere.
My point is that surely a balance is required. You dont have to be in the lab all the time. Same for philosophers, they dont have to be in the mind all the time.
I'm not part of any movement, just that I try to maintain a balance and overall understanding. Call me a fence sitter. Also , your objection to philosophy being discussed even as an aside is puzzling. Does philosophy only have something in common with religion? I thought philosophy was the seed of science. I have no interest in religion. My interest is in the science with a smattering of philosophy.
It is not so much that philosophy can offer specific answers to the facts of the universe, but rather to apply some understanding to the non scientist as to why etc.
Coming back to what is discussed in this thread, I thought I made myself clear about dark matter and direct and indirect observations. You then come along and say
Originally Posted by Acleron
So what hypothesis do you have to explain the non-Newtonian if not non-Einsteinian orbiting of visually detectable matter in galaxies?
Lets get back onto this topic instead of bashing non scientists.