Dark matter detected?

[Reality Check]

FYI, as I understand it, they are not making the claim of having discovered WIMP's, just that they have two detection events that "could be" candidates.

I suppose their claim that there is only a 1 in 4 chance these two specific events 'could be" related to "dark matter" seems rather suspect to me, but I have not been through the whole paper yet, or done any investigating of the detectors. I don't have any idea how they intend to distinguish between a WIMP and an ordinary gamma ray for instance.

It looks like you have not even read the abstract yet !
You have their conclusion the wrong way around.
Results from the Final Exposure of the CDMS II Experiment

We report results from a blind analysis of the final data taken with the Cryogenic Dark Matter Search experiment (CDMS II) at the Soudan Underground Laboratory, Minnesota, USA. A total raw exposure of 612 kg-days was analyzed for this work. We observed two events in the signal region; based on our background estimate, the probability of observing two or more background events is 23%. These data set an upper limit on the Weakly Interacting Massive Particle (WIMP)-nucleon elastic-scattering spin-independent cross-section of 7.0x10^{-44} cm^2 for a WIMP of mass 70 GeV/c^2 at the 90% confidence level. Combining this result with all previous CDMS II data gives an upper limit on the WIMP-nucleon spin-independent cross-section of 3.8x10^{-44} cm^2 for a WIMP of mass 70 GeV/c^2. We also exclude new parameter space in recently proposed inelastic dark matter models.

(emphasis added)
Their claim is that there is 23% chance that the 2 events that they report are background events (i.e. not caused by dark matter recoil).

BTW: Cosmic rays (0.04 background events) and gamma rays ("estimated background is between 0.03 and 0.06 events") are accounted for in page 3 of this 6 page paper.

Just remember that no scientist thinks that these 2 events are evidence for the detection of dark matter particles. See for example "A Tantalizing Hint of Dark Matter?" No for the scientific point of view and the bad reporting of this from news outlets. There would have to be at least 5 events before the results were statistically significant.

 

[MattusMaximus]

Thanks to those who posted the link to the paper. I look forward to reading it over the next few days

Just remember that no scientist thinks that these 2 events are evidence for the detection of dark matter particles. See for example "A Tantalizing Hint of Dark Matter?" No for the scientific point of view and the bad reporting of this from news outlets. There would have to be at least 5 events before the results were statistically significant.

Ah, so I see we were right to express a bit of skepticism earlier in the thread. Leave it to the media to screw up the science with a fluffed-up headline

 

[Zeuzzz]

Thats tight Zeuzzz, when it comes to backing your statements with evidence, you run away.

Oh I wonder why

Some admissions are best unspoken. To read between the lines can often be easier than to follow the text.

But then you don't think nutrinos exist either.

Wrong. Theres ample evidence for neutrinos.

 

[Reality Check]

Wrong. Theres ample evidence for neutrinos.

There is ample evidence for dark matter also.

 

[Dancing David]

Oh I wonder why

Some admissions are best unspoken. To read between the lines can often be easier than to follow the text.




Wrong. Theres ample evidence for neutrinos.

Gee, Zeuzzz, what is the current candidate for dark matter and what does it have in common with dark matters? In fact nutrinos are one form of Weakly interacting massive particles^WPs.

But you don't seem to like that, despite the fact that there very easily could be other WIMPs just like nutrinos.

 

[shadron]

Gee, Zeuzzz, what is the current candidate for dark matter and what does it have in common with dark matters? In fact nutrinos are one form of Weakly interacting massive particles^WPs.

But you don't seem to like that, despite the fact that there very easily could be other WIMPs just like nutrinos.

Ummm, except that neutrinos aren't massive, in fact have no rest mass at all, like photons. You wiki article points that out - it compares WIMPs to neutrinos, but doesn't actually call the neutrino one.

Oops. They do have a very small mass, and are said to travel "quite close" to the SoL. I guess they are WILPs, then.

 

[ben m]

Oops. They do have a very small mass, and are said to travel "quite close" to the SoL. I guess they are WILPs, then.

The point is not "neutrinos are the dark matter", the point is: there is no good reason to assert, as the dark-matter-is-absurd crowd does, that WIMP-like "invisible matter" is implausible and unscientific; any set of statements you make to give a blanket condemnation of WIMPs would also count as a blanket condemnation of neutrinos.

 

[GreyICE]

Wrong.
It is an observed fact that three-quarters of the matter in the universe" is missing- WMAP tells us that the universe is flat, GR tells us that there missing mass & energy.

Dude, when your math says the mass of the universe is 4 times the observed mass of the universe, Occam's Razor notes there's a flaw in your math or a flaw in your observations. 3/4ths of the universe being dark matter is pretty automatically the less likely scenario. It'd be nice, because our current math and observations would work, but that's all it is. Nice. It's by no means close to proven.

 

[ben m]

Dude, when your math says the mass of the universe is 4 times the observed mass of the universe, Occam's Razor notes there's a flaw in your math or a flaw in your observations. 3/4ths of the universe being dark matter is pretty automatically the less likely scenario. It'd be nice, because our current math and observations would work, but that's all it is. Nice. It's by no means close to proven.

The mass of all matter is 4 times the mass of stars and gas. There are five or six independent measurements of the mass of all matter (CMB, lensing, galaxy kinematics, cluster kinematics, LSS, etc.) and three or four independent measurements of the mass of the stars and gas (CMB, BBN, disk kinematics, star counting). All of them basically agree.

It would be plausible, if Occam's Razor demanded it, to imagine that *one* such measurement might be subtly flawed. Imagining that they're all wrong but that they just happen to all agree with a single picture? That's not simplification, that's a conspiracy theory.

 

[Floyt]

(

[...]Take Jupiter or Neptune, they both have an appreciable radio frequency emission.[...]

How come, BTW? Is that a direct output of the core, or the magnetosphere interacting with the atmosphere, or what?

)

 

[ben m]

(



How come, BTW? Is that a direct output of the core, or the magnetosphere interacting with the atmosphere, or what?

)

It's the Jupiter equivalent of the Van Allen belts; electrons (largely stripped from gases erupting from Io) trapped in a magnetic bottle in Jupiter's magnetic field.

 

[Reality Check]

Dude, when your math says the mass of the universe is 4 times the observed mass of the universe, Occam's Razor notes there's a flaw in your math or a flaw in your observations. 3/4ths of the universe being dark matter is pretty automatically the less likely scenario. It'd be nice, because our current math and observations would work, but that's all it is. Nice. It's by no means close to proven.

Dude,
To emphasis what ben_m replied - the existence of dark matter has overwelming support (nothing in science is ever "proven").

I just cited one bit of evidence. The fact is that the WMAP data allows us to measure the curvature of the universe. It is within 2% of being flat. General relativity then tells us how much mass and energy would create a flat universe. We then measure the mass of the universe and see that there missing mass & energy. This is quite simple.

For more evidence read: Dark matter (or just read my signature).

P.S.
You should also learn what Occam's Razor is. It is not that a simple (or more "likely" according to the prejudices of a person) theory is right. It is that if you have competing theories that predict the same things then the one that postulates the fewer entities is to be preferred. It states nothing about the possibility of flaws in math or observations.

 

[GreyICE]

Uh yes. An invisible, undetectible mass three times the mass of the observed universe would qualify as an 'entity.' Whether it is unnecessary (or non-existent) remains to be seen, but at the moment, color me skeptical. A whole lot of evidence that relies on the same theories and the same techniques just demonstrates that the flaw is fundamental to me.

And my theory that there's a flaw in our understanding (which honestly happens quite a lot) requires rather less entities than yours that there's invisible matter three times the mass of visible matter. Hence Occam's Razor. Which apparently one of us understands...

 

[Reality Check]

Uh yes. An invisible, undetectible mass three times the mass of the observed universe would qualify as an 'entity.' Whether it is unnecessary (or non-existent) remains to be seen, but at the moment, color me skeptical. A whole lot of evidence that relies on the same theories and the same techniques just demonstrates that the flaw is fundamental to me.

Uh yes. You do not know the basic facts.

• Dark matter is not undetectible - it can be detected because of its mass.
• A whole lot of evidence that relies on different theories and different techniques just demonstrates that the dark matter exists.

And my theory that there's a flaw in our understanding (which honestly happens quite a lot) requires rather less entities than yours that there's invisible matter three times the mass of visible matter. Hence Occam's Razor. Which apparently one of us understands...

You are wrong. Which apparently one of us understands...

There is the scientific theory that is backed up by several sources of evidence. There is 1 entity postulated in this theory (dark matter).


There is your theory which is basically that each of these several sources of evidence is flawed. That requires an entity for each source of evidence. The observational evidence for dark matter comes from the following sources:

1. Motion of galaxies in clusters.
2. Velocity dispersions of galaxies
3. Galaxy clusters and gravitational lensing
   Observations of colliding galaxy clusters.
4. Cosmic microwave background
5. Structure formation

You notice that your theory has postulated 5 entities. Thus Occam's Razor would favor dark matter.

 

[Dancing David]

Ummm, except that neutrinos aren't massive, in fact have no rest mass at all, like photons. You wiki article points that out - it compares WIMPs to neutrinos, but doesn't actually call the neutrino one.

Oops. They do have a very small mass, and are said to travel "quite close" to the SoL. I guess they are WILPs, then.

yes they are very low mass, I understand that. The point is that they are very similar to the SUSY partciles hypothesized to be dark matter, and the tau nutrino is measured to have a mass of 15.5 MeV compared to the 2.2 eV of the 'normal' nutrino.

(I know the common spelling is neutrino, but I think Fermi spelled it without th e)

 

[Dancing David]

Uh yes. An invisible, undetectible mass three times the mass of the observed universe would qualify as an 'entity.' Whether it is unnecessary (or non-existent) remains to be seen, but at the moment, color me skeptical. A whole lot of evidence that relies on the same theories and the same techniques just demonstrates that the flaw is fundamental to me.

And my theory that there's a flaw in our understanding (which honestly happens quite a lot) requires rather less entities than yours that there's invisible matter three times the mass of visible matter. Hence Occam's Razor. Which apparently one of us understands...

Not really, in this case Ockhams razors (William of Ockham^WP) would include the observed data that the dark matter hypothesis is based upon. So you still have to explain the Galaxy rotation curve^WP or say that something replaces the dark matter hypothesis. So your

Current theory is flawed has to have a hypothesized 'something' to replace and explain the galaxy rotation curve observations.

So some new partciles or a form of physics that totaly reright the rules of gravitation?

Ockham's razor is not a goff tool in this situation.

 

[jsfisher]

Current theory is flawed has to have a hypothesized 'something' to replace and explain the galaxy rotation curve observations.

Demonstrating a theory to be flawed does not require there be a replacement theory waiting in the wings. The replacement can come along later.

(By the way, I am in no way suggesting the current theory involving dark matter is flawed.)

 

[Dancing David]

Demonstrating a theory to be flawed does not require there be a replacement theory waiting in the wings. The replacement can come along later.

(By the way, I am in no way suggesting the current theory involving dark matter is flawed.)

I argue differently in this case because universally people who say 'dark matter can't be right' do not understand the basis of it. They need to come up with another hypothesis that is more elegant than adding some particles.

They need to explain why the galaxy rotation curves look the way that they do, dark matter was originally conceived of as baryonic material until it began to not be observed (MACHOs), then the WIMPs became the preffered candidate. In that case Ockham would have applied except the data did not find MACHOS in the needed amount.

I think that again Ockham does not apply because 'there is a flaw' is not really a hypothesis. They have not shown a flaw in rotational geometry and orbital vectors that applies only to these observations.

 

[Michael Mozina]

Demonstrating a theory to be flawed does not require there be a replacement theory waiting in the wings. The replacement can come along later.

That is absolutely true. The mainstream needs to get over the idea that it's automatically right until proven wrong by something else that explains things exactly the same way it explains them. It's doesn't work that way.

 

[ben m]

That is absolutely true. The mainstream needs to get over the idea that it's automatically right until proven wrong by something else that explains things exactly the same way it explains them. It's doesn't work that way.

I repeat what many others have said: please get used to the idea of a "hypothesis". Nobody is saying WIMP dark matter is automatically right. We're saying that it is a hypothesis (or a family of hypotheses) that fit everything we know so far, and which we furthermore plan to compare to ongoing and future measurements.

The process is called "science". The MACHOs and MOND hypotheses got thrown out by the data, the WIMP and axion hypotheses remain on the table.

The Electric Universe hypotheses was also thrown out, not because WIMPs were assumed correct by default, but because it's an incoherent pile of nonsense that doesn't even *pretend* to agree with modern data and has not done so for decades.