I mentioned in an earlier post that Stephano Profumo gave an excellent departmental colloquium here at USC on the subject of Dark Matter, addressing the questions of what it is, what some of the promising models and theories of particle physics have to say about it, and the prospects for (relativity) near future experiments and observations.
What is the Dark Matter?
The matter content of the Universe appears to be dominated by a form of matter whose existence is inferred on the basis of its gravitational effects, and whose fundamental microscopic nature is at present unknown. This form of matter must be qualitatively different from the ordinary matter (neutrons, protons, electrons) that accounts for planets, stars and galaxies, and must couple very weakly to the known particles of the Standard Model. In this colloquium, I will review and outline the wide ensemble of evidence for dark matter, the best motivated dark matter candidates, and the ongoing experimental and theoretical effort in the quest for the identification of this elusive, and yet fundamental, constituent of the Universe.
His penultimate slide (shown above) was really an excellent summary of the two key approaches to learning more about out universe’s complement of Dark Matter. [Update: That slide is actually due to Sean Carroll. See this comment, and this link.]
Here’s a slide with what he meant in more traditional scientific terms:
-cvj
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No, still nothing new to add from the last time 🙂
Peter,
We will be watching closely for your award.
It will be an amazing event to see that you alone have figured out, what noone else has been able to.
Elliot
Clifford writes:
It is no trouble at all to understand introductory textbook physics. When I started out 30 years ago I unofficially audited for four or five years several times over every introductory & sophomore physics class I could. I know where physicist are coming from. (its is where they are going that I am having trouble with).
After failing to get a decent response from commenting on other peoples blogs, I decided submit my work to the April 1st Gravitational Research Foundation competition. The awards will be announced May 15th.
Maybe I can get my point across about scientist not using their “mind’s eye” in their work with some quotes:
The Nobel laureate Szent-Gyorgyi stated that a scientists should
“see what everybody else has seen and think what nobody has thought.”
Mark Twain writes:
“What gets us into trouble is not what we don’t know. It’s what we know for sure that just aint so.”
This quote from Mark Twain is from Stacy McGaugh (astro-ph/0606351) who also writes:
“i.e., we shouldn’t be overly confident that the universe is filled with some
new form of invisible, non-baryonic mass (such as WIMPs) until we
actually detect the stuff directly in the laboratory. Current cosmology
(ΛCDM) invokes not one but two aethers (dark matter and dark energy);
let us be careful not to fall into the same conceptual trap that led classical
physicists to infer that Maxwell’s theory required aether. It is at least
conceivable that there could be a theory which captures the successes of
cosmology without the excess baggage.”
Fair enough. I see what you are saying, but the key point that I was worried was getting lost is that at the end of the day, real experimental results determine the outcome, and whether a model that was suggested continues to hold sway or not. It is not entirely a matter of sociology and belief in one’s favourite things.
Cheers,
-cvj
No. You are absolutely right. And I loved your example of dark matter and I used it here: http://alphysics1.blogspot.com/2007/04/dark-matter.html
My statement though, was based on a list that I have seen once, but I couldn’t locate now. If we make a list of cosmological models proposed by physicists and the physicists’ specialty, there will be a correlation between the speciality and the proposed models.
So Alfven is a plasma physicist and he sees the universe as plasma, […] is specialist on fractals and he sees a fractal universe. A particle physicist uses his particle physics specialty to interpret the universe as such.
Big Bang was originally proposed as the mother of all nuclear explosions by Nuclear physicists. So there is a social element to physics. This is not surprising. Since the beginning of history cosmology has been the projection of local observations to cosmic scale.
It is hard to blame physicists. They spend about a dozen years to specialize in a field and universe is the most generic platform where physicists can apply and monetize their specialty.
Really? I can think of numerous counterexamples from the history of physics that just do not fit your broad statement…..And in fact in this example, you’re both then spectacularly wrong about what you say since in this case the physicists are saying that the universe is made of stuff they *don’t know*. That’s the whole point of the dark matter problem -using many independent pieces of data from astronomy, astrophysics and cosmology we’ve been able to characterize the problem to the extent that we know that the matter in the universe is mostly (some 85% or so) made of unknown stuff….unknown– …so your central (rather sociological) thesis seems to be falling over its own feet even before getting within sight of the first hurdle, no?
I must admit I’m very puzzled by the attitude that someone would just come in from another field, and before even getting their basic facts right, would declare that everyone in another field is doing something manifestly stupid. This is remarkable to me.
Or perhaps I misunderstood you… could you explain your point more carefully, is there some subtlety I’m missing, or is it pretty much as I characterized it in the above paragraph?
-cvj
I am sorry, I did not exactly understand the discussion here, but I have noticed that there is a trend among physicists to see the universe in their own specialty.
So someone whose specialty is fractals publishes a paper saying that the universe is fractals. Someone whose specialty is plasma physics publishes a paper saying that universe is plasma. The same for particle physics.
So I agree with Peter Fred that When physicists don’t know what the universe is made of, they make the universe made of what they know.
My apoligies if this is out of topic.
If you click on the link to Sean’s post on Preposterous Universe, and the comments, you will see why I recognize the article Clifford posted today. I’d be following a while now. I am not just a couch potato 🙂
LOL
e.
If you have an alternative theory that fits the data, that’s really excellent.
Nope, nothing more to add.
Thought people interested in dark matter would like “any other” information to do with dark matter/energy as well?
Yes, the Law and Order people must be really pissed…… 😉
-cvj
I smell a copyright infringement lawsuit in the making.
😉
Elliot
That’s between you and Stephano’s business manager.
-cvj
All I ask for is 15% of the gross.
Hi Sean,
Ha! You know, I had my suspicions….. since it had more than a whiff of your sense of humour (and I seem to recall you liking that show), but it was impolite to me to ask him whether he’d got it from somewhere else, and since he did not volunteer any information about the slide (probably too busy wrapping up and fielding questions, to be fair to him) I probed no further.
Definite update of the post to be done.
Cheers,
-cvj
Stefano knows good stuff when he sees it!
Peter, Plato,
There are very many accounts of the case for dark matter’s existence, and several cross checks. I’ve talked about some of these matters in other posts on this blog too. Search for dark matter using the engine. If you have an alternative theory that fits the data, that’s really excellent. Please present it to your scientific peers to review in the appropriate forum, and publish it somewhere, and the world will be very excited by your findings.
In the meantime, Stephano was not obliged to give the standard talk on the introduction to the dark matter problem and all the various evidence (in fact, he did a great job of reviewing it a little at the beginning), otherwise he’d never get to anything new in his talk -the models, etc, he wanted to talk about.
Cheers,
-cvj
As a lay person I am having trouble orientating a “reductionistic view” of what could be expressed in the development of this universe. Turning to a microperspective view in terms of the microseconds(string theory?), where is dark matter/energy in relation?
So how do you not see the relationship of particle research not coming from “this background?” How is it being fuelled?
What is the Dark Matter?
Cosmic Tug of WarCredit: NASA, ESA, and A. Feild (STScI)
Hubble Maps the Cosmic Web of “Clumpy” Dark Matter in 3-D
The dark matter filaments began to form first and provided an underlying scaffolding for the subsequent construction of stars and galaxies from ordinary matter. Without dark matter, there would have been insufficient mass in the universe for structures to collapse and galaxies to form.
In my first course as a graduate student in psychological statistics at Ohio State, the professor in educational psychology said, “This course will be based on a joke and this joke is The experimental psychologist is like the moron who looks under the street lamp for the lost coin because that is where the light is.” We had to write essays every week or so that confirmed or contradicted this joke.
I flunked my first several essays that contradicted the sense of the joke. But then to pass the course I started writing essays that confirmed the its sense. Then towards the end of the course I realized that the joke had a lot of truth in it.
There is another phrase that similar to it: When generals don’t know what to do, they do what they know.
Now we have these physicists like Stephano Profumo who has been well-schooled in particle physics and we listen to him go on and on about how dark matter may be related to this or that finding in particle physics. We do not get any decent treatment from him that dark matter may not exists–that is may be like the aether–just some construct to keep the old and trusted theory alive. Since there is no body of knowledge that supports the idea that dark matter is like the aether, that possibility gets little airing in his talk.
So an individual like myself has had to spend the last 30 years at my own expense collecting a body of knowledge that supports the idea that dark matter is like the aether so that point of view so that point of view will some day get a decent airing in one of these colloquiums where eager graduates students will try to learn something of value in their field of endeavor.