Possible Dark Matter Signs At the Core

Scientific American has a piece on speculation that dark matter may be behind diffuse radiation in the galactic center. Beginning in 2003, researchers led by Douglas Finkbeiner noticed a curious excess of microwave radiation in the WMAP data, after all known sources of such radiation were accounted for. Data from NASA's Fermi Gamma-Ray Space Telescope resulted in a similar anomaly in gamma rays. "A paper posted to the physics preprint Web site arXiv.org on October 26 and submitted to the Astrophysical Journal points to a possible signature of dark matter in the Milky Way, although the study's authors are careful to keep their observations empirical and table such speculation... In the new paper [the researchers] describe the Fermi gamma-ray haze and make the claim that it confirms the synchrotron origin of the WMAP microwave haze. And as with the microwave haze, the authors argue that the electrons responsible for the gamma-ray haze appear to originate from an unknown astrophysical process. ... 'We are absolutely in the process of exploring the Fermi haze in the context of dark matter physics,' [one of them] says."

Comments

It's a black hole!

[shentino]

Of course it's dark matter in the middle

Re:It's a black hole!

[selven]

Black hole and dark matter have very precise meanings in physics. In fact, black holes aren't strictly black due to Hawking radiation and dark matter is transparent, not dark.

Re:It's a black hole!

[causality]

Of course it's dark matter in the middle

Dark matter is sort of like violence. If it doesn't work, just use more of it.

Re:It's a black hole!

[The_Wilschon]

Well shoot. You got us all figured out. We're all just a bunch of charlatan priests. I guess we'll just give up and go home now.

You want scientists to consider their theories falsified, question their premises, and come up with new ideas, eh? OK, when I find that galactic rotation curves don't line up with what I've predicted, I'll consider my theories (standard model with, as best we can manage, general relativity) falsified. I'll question my premises (for instance, the premise that I know exactly what particles exist in the universe). I'll come up with some new ideas (for instance, that there might be some type of particle that I don't know about). Looks OK so far, right? At what point do you have an objection to this?

One objection that I can see is that you might think that no other avenues of investigation have been explored. However, they have. Instead of questioning the standard model (giving us dark matter), we could question general relativity. This gives us a theory called MOND. It doesn't really work very well, but a lot of very smart people spent a great deal of time and effort investigating it.

In the end, in order to be a good scientist, you've got to come full circle. You take all the new ideas (new theories) that you've come up with, and you make predictions with them. Turns out that dark matter predicts something different from, say, MOND for a collision between two galaxy clusters which contain gas, stars, and dark matter. Well, we found such a collision (Bullet Cluster), and dark matter made the correct prediction, whereas MOND made the wrong prediction.

But that's not all. When you start to enumerate all the properties that dark matter ought to have in order to fit what we've observed in galactic rotation curves, the bullet cluster, etc, it turns out that there are not too many different ways in which to fit dark matter onto the standard model. And those ways in general predict different things about what astroparticle experiments like Fermi, ICECUBE, etc should see. Give it a few (~10) years, and these experiments will either have indirectly observed dark matter (and the characteristics of that observation will narrow down the particular type of dark matter dramatically), or they will have ruled out a large number of the candidate dark matter models, leaving even fewer. Give it long enough, and we'll have either made the indirect observation or ruled out all the models.

If we rule out all the models, then it's back to the drawing board. We'd have a falsified theory, we'd question our premises, and we'd come up with some new ideas. But until then, dark matter is a very good avenue for investigation. You shouldn't "believe" in it until it's been observed, but neither should you claim it's bad science. It isn't.

FWIW, I don't really expect to convince you of this, as you seem to be quite firmly decided that it is bad science, even though it fits your apparent criteria for what science should be. But hopefully I can prevent others who read both of our comments from being infected by you.

Re:Explanation Impossible

[wizardforce]

The difference is that dark matter and dark energy can be tested for in various ways; a deity can't be.
When physicists can't explain something they may use a place holder at times but there's no chance of just giving up like the "god did it" explanation does.

And it went a little something like this:

[Gizzmonic]

CAPTAIN KIRK: Spock, come in here, can you make sense of these readings?

SPOCK: Captain, it appears that dark matter may be behind diffuse radiation in the galactic center.

CAPTAIN KIRK: It's the most magnificent thing I've ever seen!

SPOCK: It is...fascinating.

CAPTAIN KIRK: But why would diffuse radiation need a starship?

DR. MCCOY: Come on over here, boys! This galactic dick ain't gonna suck itself!

Thanks for reading and supporting fan fiction.

Explanation Very Possible

[Roger W Moore]

Can't explain something, Dark Matter is the reason! Can't find a cause, Dark Matter is it!

This is completely incorrect. This work is the result of looking for Dark Matter. Dark Matter is the best explanation for galactic rotation curves and the cosmic microwave background. Depending on what the Dark Matter is it may annihilate with itself and produce, amongst other things, electron-positron pairs. In fact the paper is really a very beautiful and elegant bit of work since the first bit of evidence which lead to this comes from the background 'noise' of one of the major pieces of evidence for Dark Matter - the WMAP data! As such, far from noticing something and then attributing it to Dark Matter, this is actively looking for something that suggests evidence for Dark Matter. True the evidence does not show that it HAS to be Dark Matter but if you cannot attribute it to anything else which is known and you have models which suggest that Dark Matter might produce such a signal it is very interesting.

Arkani-Hamed et al have a model which may explain this and which, if correct, predicts jets of leptons (electrons or muons) at the LHC. This is actually one of the things which my colleagues and I are looking for on the ATLAS Experiment. If we do observe them then this will be further evidence for Dark Matter and not a "oh, something else we cannot explain and put down to Dark Matter". Until we have enough bits of evidence that, combined, show that Dark Matter is the only possible cause there will always be some doubt but that should not be construed as flailing around and using Dark Matter to explain every observation that is inexplicable. Indeed, the fact that we are using Dark Matter models to suggest observations and experiments to perform and then finding that these return "inexplicable" results is very, very interesting!

Re:Explanation Impossible

[sleeponthemic]

You're absolutely right. I therefore suggest we call it "Colorless Jesus Powder", in accordance with our new invisible overlord.

Re:Explanation Impossible

[wizardforce]

Simulations of stars in galaxies are approximations because:
1) there isn't an equation for an exact solution to any gravitationally bound system containing more than 5 objects.
2) stars in a typical galaxy are not uniform so the simulations must take this into account as a best guess. br />3) newton's equations are indeed incorrect however, Einstein's equations only dominate to a significant degree under unusual conditions.

In so far as dark matter is concerned, you are incorrect. Experiments like the Cryogenic Dark Matter Search are attempting to detect dark matter particles directly, we've got neutrino detectors looking for evidence of annihilation events... Particle accelerator experiments attempting to actually synthesize dark matter candidates.. To claim that there isn't a way to test the dark matter hypothesis would be grossly inaccurate.
Disclaimer: Physics isn't my major but I did study quite a bit of it in high school and college.

Re:Explanation Impossible

[yndrd1984]

This is more along the lines of "our equations don't explain the observed motion of galaxies, therefore, there's matter there we can't see or touch."

Wow! I never thought they would do things like that! I would have expected things to go like this:
"our equations don't explain the observed motion of galaxies, therefore, it's reasonable to hypothesize that there's matter there we can't see or touch, let's test it."
And then they'd go and look for evidence or something. Thanks for correcting me!

That's just not a logical conclusion. It leaves out the much more likely answer that our understanding of the equations of motion is wrong.

So all that stuff I heard about MOND was just in my head? Thanks for grounding me in reality!

Most galaxy motion simulations are based on either Newtonian mechanics or "modified Newtonian" mechanics, even though both are known to be wrong. Einstein showed them to be wrong over a hundred years ago!

You're right! It's quite likely that thousands and thousands of astrophysicists have spent decades researching a problem that has such an obvious solution. You're a veritable font of wisdom!

I studied physics at University, and both me and a friend of mine noted during our studies that Physics seems to overuse simplified equations ... Those simple equations are the ones we learned about also. They're wrong. In many practical cases, the error can exceed 30%!

O M G ! - W T F ! Low level physics classes use lots of simplifications? That explains why I can't find massless ropes and frictionless pulleys on E-Bay!

Can we please just call it by its traditional name

[BitZtream]

Magic?

Re:Explanation Impossible

[Dachannien]

The difference is that dark matter and dark energy can be tested for in various ways; a deity can't be.

Well, technically you can test for existence of a deity.... you just can't come back to tell the rest of us about it afterwards.