Fermi and dark matter

[ben m]

The only thing that has to do with Fermi images are "gamma rays". Select any energy state Fermi can see, and that is now what you're going to claim relates to "dark matter".

That's funny, when I go to the ArXiV looking for recent gamma ray papers, I find dozens and dozens of Fermi discoveries of gamma ray pulsars, gamma rays from supernovae, and gamma rays from cosmic-ray proton collisions.

When I look at the specific Fermi paper on the Galactic Center excess, I see them describing most of the gamma rays as a mix of electron-inverse-Compton-on-starlight (with an electron spectrum like E^-3, resembling that near Earth) and pion decay from CR proton-proton collisions. It's only the gamma rays that fit neither of these non-dark-matter models that are declared to be possibly interesting for further investigation.

Really, you seem to be subscribing to a bizarre fantasy of what Fermi could do wrong if they were unscientific morons. They are not, in fact, doing any of those things wrong---you're inventing them all out of whole cloth.

 

[ben m]

I am in fact "stuck" by playing "by the rules" of empirical physics. I realize that larger sized objects would be detected by our current technologies but I also recognize that smaller particles will not be seen by such techniques.

You again ignored the fact that smaller particles would be seen by other techniques.

gravitating dark matter: not star-mass, not planet-mass, not rock-mass, not dust-mass, not gases. What do you think it is when you don't ignore the data?

 

[Michael Mozina]

Listen: you know that all mainstream astronomers/astrophysicists/physicists think that EC is bunk when it tries to "explain" stars, solar flares, planets, the ISM, and whatever else. Don't imagine that we suddenly give it more credence when you get around to "explaining" dark matter.

This statement just seems utterly irrational from my perspective. We point Rhessi and Fermi at the Earth and we observe gamma rays from "powerful electrical discharges" in the Earth's atmosphere. Alfven looked at skylab x-ray images of sun and attributed these high energy events to "discharges' in the solar atmosphere, as did Birkeland before him and Bruce and many other folks as well. They "explained" these solar events in terms of discharges in plasma.

Birkeland and his team (it wasn't just one guy by the way) actually created/simulated "coronal loops", "jets", all the same high energy events we see in the solar atmosphere in a lab in real experiments. He did so "empirically" in real "experiments" with real control mechanisms. You *REFUSE* to accept what has already been "explained" empirically. You can't explain coronal loops. You can't explain what they individually reach millions of degrees and stay that way for hours on end. Birkeland certainly could do so. He even "predicted" them in real physical experiments. He "predicted" high speed solar wind. He "predicted" jets. The mainstream *refuses* to embrace these "solutions" because they are part of EU theory. Your biases are utterly irrational. It's making your beliefs systems become "irrational" too. You'd rather put your faith in "dark matter gamma rays" than the gamma rays we see from our own sun and our own atmosphere. It makes no sense.

 

[Michael Mozina]

You again ignored the fact that smaller particles would be seen by other techniques.

What technique would see our own moon?

gravitating dark matter: not star-mass, not planet-mass, not rock-mass, not dust-mass, not gases. What do you think it is when you don't ignore the data?

From my perspective Ben you're simply "assuming" that you can already be "so certain" that you haven't missed anything that you "put your faith" in a hypothetical particle with a half dozen required "properties" to make your beliefs systems work. That's bizarre IMO. Our technologies simply are not that sophisticated or that precise. We don't even know what we don't know. Hell, we're still finding satellite galaxies around our own galaxy and we've been underestimating the amount of light being blocked by dust by at least a factor of 2! Come on. There is no way that you can claim to have already eliminated all possible forms of baryonic matter. You just "think" you have.

 

[Michael Mozina]

That's funny, when I go to the ArXiV looking for recent gamma ray papers, I find dozens and dozens of Fermi discoveries of gamma ray pulsars, gamma rays from supernovae, and gamma rays from cosmic-ray proton collisions.

You don't hear me bitching about those papers do you?

When I look at the specific Fermi paper on the Galactic Center excess, I see them describing most of the gamma rays as a mix of electron-inverse-Compton-on-starlight (with an electron spectrum like E^-3, resembling that near Earth) and pion decay from CR proton-proton collisions.

You didn't hear be complain about that either.

It's only the gamma rays that fit neither of these non-dark-matter models that are declared to be possibly interesting for further investigation.

The fact you can't explain them is not a justification for 'dark matter did it".

Really, you seem to be subscribing to a bizarre fantasy of what Fermi could do wrong if they were unscientific morons. They are not, in fact, doing any of those things wrong---you're inventing them all out of whole cloth.

You know Ben, when I was in my 20's, fresh out of college, I had the greatest respect for astronomers. Since that time however I've watched what used to be a wonderful branch of physical science go to hell in a metaphysical hand basket. I've see the industry make about every bad decision that I can possibly think of when it comes to cosmology theory. What used to be a branch of empirical physics has turned into a faith based religion that is 96% useless metaphysical mumbo jumbo that is about as useful as numerology, and only 4% actual physics.

I'm certainly not "inventing" the fact that astronomers have stuffed the "Big Bang" theory that I was taught in college with metaphysical entities galore like "inflation", "dark energy" and now exotic forms of mythical matter, none of which can be empirically verified in any sort of actual experiment. Many of the astronomers I've met online recently and in this conversation (including you evidently) can't even tell the difference between a real physics "experiment" (with actual control mechanisms) and a pure "observation" where we have no control at all.

Sorry Ben, but I've seen this industry in action now for a long time.

 

[Tubbythin]

If you folks weren't promoting what Alfven called "pseudoscience", and you (collectively) weren't doing everything possible to smear Alfven's PC/EU theories, I might actually believe you.

I don't recall having smeared Alfven's theories of PC/EU. I've just at various times that your PC/EU theories are inconsistent with the data. Which is all that really matters.

 

[Tubbythin]

Birkeland's "control mechanism" was an on/off switch and dial.

That's nice. An astronomer can stop observing whenever they like. What exactly is your point?

What are you using to "control" dark matter?

Nothing. If I had some dark matter in my possession I'd probably have a Nobel prize. Sadly, I don't have either. We're talking about a controlled experiment not a controlled manipulation of matter. "We" can do a controlled experiment to search for dark matter using the basic principles I outlined above. I'm fast coming to the conclusion that you don't know what a controlled experiment is.

Er, ditto?

???

It's entirely "possible" to create gamma rays from discharges. Why did I need hypothetical entities to explain gamma rays?

Can you quantitatively explain the whole observed gamma ray spectrum with discharges?

 

[ben m]

What technique would see our own moon?

See this post: http://www.internationalskeptics.com/forums/showpost.php?p=5304563&postcount=443 If you try to make the gravitating dark matter out of a collection of moons (that's the 2nd-to-last column of my table) you expect 0.2% of these moons to collide with one another per gigayear; 2% collide over the life of the Galaxy. That's not dark matter, that's a completely absurd quantity of metal-rich (no, make that absurdly metal rich), opaque, trivially-detectable dust---that's a Galaxy with more dust than stars and about as much dust as gas altogether. That is not the galaxy we live in.

From my perspective Ben you're simply "assuming" that you can already be "so certain" that you haven't missed anything

Thirty years of constantly-improving, dead-on-consistent data can get you that kind of certainty.

How long have you been proving that SUSY is a false hypothesis? How many papers and cross-checks have you used to reinforce your certainty that the Standard Model is 100% complete and cannot additional sub-TeV particle content? You sound pretty certain about it.

 

[ben m]

You don't hear me bitching about those papers do you?

You said "select any energy Fermi can see" and they'll attribute it to dark matter. Would you like to retract that statement in face of evidence to the contrary?

 

[Michael Mozina]

So, to borrow your term, what is the "control" for our universe?

There obviously isn't one.

But that is my point.

The fusion that happens in the core of the Sun is NOT the same as the fusion that happens here on Earth in our labs.

They are not the same processes.

That would be "your" assumption but not necessarily mine.

So by that argument, logically, if I claim that fusion of uranium is what powers the Sun then by virtue of the fact that we have a version of fusion happening here on Earth any type of fusion can possibly happen anyway and it should be given serious credence.

no?

If you can show me an example of uranium fusing to anything else, sure. If not, no.

By the way White Dwarfs were brought up.

Can you show me where here on Earth the experiments show the degenerate matter as evidence in White Dwarfs?

Or Neutron Stars?

No, but these are basically just reconfigurations of known and standard baryonic materials. Neutrons certainly exist in nature.

That is what was at the heart of my statement that "This constant statement about having to be able to repeat the experiment on Earth is a misnomer."

I hope I have put myself across a little more clearly this time.

I'm not even complaining about "quark stars" or "black holes"!

Keep in mind that I have never had a problem with "scaling' any known entity to size, nor am I adverse to any reconfiguration of known forms of matter that you might postulate. It's only if you intend to introduce some other new form of matter or new type of energy that I will require additional support of that specific claim. That hardly seems "unreasonable", particularly in the case of "dark energy" which supposedly makes up 70+
% of the universe and "dark matter" that is supposedly many time more abundant than the dirt in my backyard.

 

[Michael Mozina]

You said "select any energy Fermi can see" and they'll attribute it to dark matter. Would you like to retract that statement in face of evidence to the contrary?

So the fact that they USED to attribute annihilation signatures to "dark matter', but now they don't do so any longer is supposed to erase the fact that they did it in the first place? Would you be you happier if I said "every high energy gamma ray they can think of (and can't otherwise explain)" they will now try to attribute to "dark matter"?

 

[Reality Check]

I am in fact "stuck" by playing "by the rules" of empirical physics. I realize that larger sized objects would be detected by our current technologies but I also recognize that smaller particles will not be seen by such techniques.

Wrong:
You are actually ignoring the rules of empirical physics.

ben_m already pointed out the empirical physics of the collision rates of clouds of rocks many days ago (13 November 2009, see below). This empirical physics is easy to understand. It shows that your "smaller particles" collide at a rate that turns them into hot plasma in cosmologically short times.

Another chunk of of empirical physics that you are ignoring is the question of where do your rocks come from?

And then there are all the other questions that you are ignoring.

I went ahead and did a calculation: how collisionless would "rocky" dark matter be?

rock size (m) vs. time between collisions (gigayears)
0.001 1.93013e-09
0.003 5.79039e-09
0.009 1.73712e-08
0.027 5.21135e-08
0.081 1.5634e-07
0.243 4.69021e-07
0.729 1.40706e-06
2.187 4.22119e-06
6.561 1.26636e-05
19.683 3.79907e-05
59.049 0.000113972
177.147 0.000341917
531.441 0.00102575
1594.32 0.00307725
4782.97 0.00923175
14348.9 0.0276952
43046.7 0.0830857
129140 0.249257
387420 0.747772
1.16226e+06 2.24331
3.48678e+06 6.72994
1.04604e+07 20.1898
3.13811e+07 60.5695
9.41432e+07 181.709
2.8243e+08 545.126
8.47289e+08 1635.38

That calculation is done for the Earth's "local" dark matter: isotropic 220 km/s orbits through a 0.3 GeV/cm^3 mean density. I gave it 5g/cm^3 density, somewhere between stone and iron.

Look at those numbers. If you built the Milky Way using Volkswagen-sized rocks as the dark matter, they'd last four thousand years between collisions; they'd be dust and plasma. Use 500 m asteroids, they'd last a million years before colliding and pulverizing. (Remember, these are 220 km/s collisions; they make Shoemaker-Levy look wimpy.) A 10^6 m planetoid could last for a gigayear---at least that survives a full Galactic orbit!---but at that point we're into the stuff that the EROS surveys have ruled out. Sub-meter-scale dust, of course, is not collisionless at all which is why it's never been even in the ballpark of viable dark matter candidates.

MM might object to these numbers all being so small: how has Earth survived for 4 Gy, he might ask, if Earthlike objects are supposedly so collision-prone? The answer is twofold: (a) dark matter is much DENSER than regular matter. The number density of actual rocks/planets/Earths is much, much lower than the number density I need to hypothesize to make them dark matter. (b) Dark matter is isotropic---it seems to orbit the Milky Way in a spherical halo, which implies orbits that intersect one another all over the place. The Earth (and most of the Galaxy's baryonic matter) is in the Galactic Disk, where intersections are much, much sparser than those in the halo.

Conclusion: rocks cannot be dark matter. Anything small would be highly collisional, and could not possibly remain "rocky" in a dense halo full of other rocks. Anything large would have been seen by EROS. The two ranges overlap generously.

and

I just showed you that dust doesn't pass through. The mean free flight time of sub-meter dust, IF there's enough of it to make up the dark matter halo, is measured in years---look at the early entries of the table. It orbits a short distance and then it collides. The collisions (a) make it NOT neutral dust anymore, they make it a hot plasma which is trivially visible in both absorbtion and emission. (The mean collision kinetic energy is over 200 eV per nucleon, far above ionization energies.) The collisions (b) remove material from halo orbits and drop it into non-intersecting disk orbits. Dark matter is not in the disk, it's in the halo.

Don't like my assumptions? Propose your own. Can you find *any* configuration of dust, rocks, and planets which can peacefully fill the Galactic halo for more than a gigayear or so?

 

[Tubbythin]

Keep in mind that I have never had a problem with "scaling' any known entity to size, nor am I adverse to any reconfiguration of known forms of matter that you might postulate.

Bosons exist with masses below the TeV range. I propose scaling this up to get bosons in the TeV range. That ok with you?

 

[Michael Mozina]

That's nice. An astronomer can stop observing whenever they like. What exactly is your point?

Hoy. So you really mean to tell me that you can't personally tell the difference between "observation" and a "control mechanism"? A control mechanism isn't created by "looking away". A control mechanism is a variable that you can change *WHILE STILL OBSERVING THE EXPERIMENT* so you can see what happens as the result of your changes to the control mechanism.

In Birkeland's case, he didn't "stop looking" at the experiment. He changed variables. He modified the surface of the sphere. He changed the magnetic field strength inside the sphere. He changes the "current flow" coming from the sphere. He changed the amount of gas inside the chamber. These are "control mechanisms" that have an effect on the experiment. "Looking away" isn't a "control mechanism".

 

[Tubbythin]

Hoy. So you really mean to tell me that you can't personally tell the difference between "observation" and a "control mechanism"? A control mechanism isn't created by "looking away". A control mechanism is a variable that you can change *WHILE STILL OBSERVING THE EXPERIMENT* so you can see what happens as the result of your changes to the control mechanism.

In Birkeland's case, he didn't "stop looking" at the experiment. He changed variables. He modified the surface of the sphere. He changed the magnetic field strength inside the sphere. He changes the "current flow" coming from the sphere. He changed the amount of gas inside the chamber. These are "control mechanisms" that have an effect on the experiment. "Looking away" isn't a "control mechanism".

Exactly! Its no more or less a control mechanism than an on/off switch. And yet you just claimed:

Birkeland's "control mechanism" was an on/off switch and dial.

 

[Michael Mozina]

I don't recall having smeared Alfven's theories of PC/EU. I've just at various times that your PC/EU theories are inconsistent with the data. Which is all that really matters.

That depends. It depends on *why* something might be inconsistent with whatever data we're discussing. IMO you folks don't even *TRY* to make it work with any creativity before going back to playing around with metaphysics. With you guys it's like "Oh look, we found a mathematical flaw in this EU paper. EU is obviously bunk and dark stuff obviously did it."

Birkeland IMO puts us *ALL* (myself certainly included) to shame as an example of "real astronomer". The guy risked his very life (and the lives of his best friends) to take in-situ measurements in the most hostile environments on Earth so that he could then compare his measurements to his exhaustive experiments. He (actually they) conducted *real* experiments too. He didn't just point at the sky and add math although he certainly quantified his ideas. He built real life "working models" of this theories. He created "real aurora' around 'real spheres' by bombarding the sphere with cathode rays. He then turned his sphere into a cathode and watched it "work" in a 'real world experiment'. He use "actual control mechanisms" in his experiments too, he didn't just "stop looking".

 

[Michael Mozina]

Exactly! Its no more or less a control mechanism than an on/off switch. And yet you just claimed:

Man. I've seen people cling to a sinking ship before but you're close to winning a cyber-award or something.

Come on. You mean to tell me you can't honestly tell the difference between a control mechanism and "blinking"?

 

[Michael Mozina]

Wrong:
You are actually ignoring the rules of empirical physics.

How ironic. This coming from the guy that probably hasn't even read Birkeland's work, let alone Alfven's work.

ben_m already pointed out the empirical physics of the collision rates of clouds of rocks many days ago (13 November 2009, see below). This empirical physics is easy to understand. It shows that your "smaller particles" collide at a rate that turns them into hot plasma in cosmologically short times.

What kind of assumptions was he making anyway? We'll have to save that conversation for the other thread because unless you can show some correlation between "dark matter" and "gamma radiation", it has nothing whatsoever to do with this thread.

Another chunk of of empirical physics that you are ignoring is the question of where do your rocks come from?

Supernova events.

 

[ben m]

So the fact that they USED to attribute annihilation signatures to "dark matter', but now they don't do so any longer is supposed to erase the fact that they did it in the first place?

That's how science is supposed to work. The 511-keV-from-dark-matter claim was a hypothesis, posed in response to data. That particular hypothesis made further predictions for future data. In this case, the new data (thanks to higher spatial resolution) ruled out the 511-kev-from-dark-matter hypothesis.

Would you be you happier if I said "every high energy gamma ray they can think of (and can't otherwise explain)" they will now try to attribute to "dark matter"?

They will try to explain the actual observed properties of the gamma rays, including spectral, spatial, and timing data. If dark matter is a better explanation than the alternatives, then this will be taken seriously. If not, it won't. Just like it has been so far. If higher resolution and more careful future work really nails it down, you may find people calling it a "discovery" rather than a "candidate" or a "hypothesis".

 

[Tubbythin]

Man. I've seen people cling to a sinking ship before but you're close to winning a cyber-award or something.

Come on. You mean to tell me you can't honestly tell the difference between a control mechanism and "blinking"?

We were talking about controlled experiments...

The ability to blink does not make the experiment a controlled experiment.

Looking away does not make the experiment a controlled experiment.

An on/off switch does not make the experiment a controlled experiment.

A controlled experiment is one in which we can vary one parameter and keep all other independent variables constant (or as near as damn it).
This is neither an exclusive property of a lab-based experiment nor a guarantee certainty in a lab based experiment.