Fermi and dark matter

[Michael Mozina]

Nope, they haven't been tested.

At least we both agree there is a logical way to do so.

What?

What?

Which has to do with this topic.... how?

Holy Cow. There are hundreds of billions of confirmed sources for annihilation signatures in a galaxy! They are called "suns". What makes you think "DM did it"?

 

[Davidlpf]

I'm curious why astronomers as a group are allowed to simply point at the sky and make stuff up in an ad hoc manner? What empirical evidence demonstrates that "dark matter" releases gamma rays or positrons? Without such empirical validation, what it the world are they doing pointing at the sky with the Fermi telescope and claiming "dark matter did it" ?

You kind of started the insults in your first post so stop trying to point fingers at everywhere else.

Theorists thought a part of dark matter would emit gamma ray bursts. They got others to build observatory to look for it. They found bursts where the scientists thought the bursts would be, so more evidence for dark matter. They are not saying it has to be dark matter, it is just more evidence for dark matter.

 

[Reality Check]

I used exactly the same logic you did! I took an ordinary observation and turned it into "evidence" of whatever I want.

I already told you the name of the fallacy. It's called "affirming the consequent". You're right, it's a "bad" one.

Gah! That's my whole point!

Then you are wrong.
Affirming the consequent

Affirming the consequent, sometimes called converse error, is a formal fallacy, committed by reasoning in the form:

1. If P, then Q.
2. Q.
3. Therefore, P.

Arguments of this form are invalid, in that the conclusion (3) does not have to follow even when statements 1 and 2 are true. The simple reason for this is that P was never asserted as the only sufficient condition for Q, so, in general, any number of other factors could account for Q (while P was false).
The name affirming the consequent derives from the premise Q, which affirms the "then" clause of the conditional premise.
One way to demonstrate the invalidity of this argument form is with a counterexample with true premises but an obviously false conclusion. For example:
If Bill Gates owns Fort Knox, then he is rich.
Bill Gates is rich.
Therefore, Bill Gates owns Fort Knox.
Owning Fort Knox is not the only way to be rich. There are any number of other ways to be rich.

Nobody asserts that the Fermi data can only be produced by dark matter.
What they assert is that all known sources of the gamma rays have been eliminated (including the hundreds of billions of confirmed sources for annihilation signatures in a galaxy called "suns"!). That leaves unknown sources of gamma rays. Dark matter is one of the ways that the excess gamma rays may have been produced.

The last step in the fallacy is missing. It is not "Therefore, P". The last step in the logic used in this case is "Maybe, P (among other possibilities)".

 

[Michael Mozina]

You kind of started the insults in your first post so stop trying to point fingers at everywhere else.

Okey-dokey.

Theorists thought a part of dark matter would emit gamma ray bursts.

Ok, but why? Based on what empirical evidence did they theorize that DM emits gamma rays? How did they confirm that theory prior to pointing at the sky?

They got others to build observatory to look for it. They found bursts where the scientists thought the bursts would be, so more evidence for dark matter. They are not saying it has to be dark matter, it is just more evidence for dark matter.

http://www.nasa.gov/images/content/397293main_Fermi_1_year_revised.jpg

The problem is that common, ordinary suns are a known and demonstrated source of annihilation emissions and they too are spread around the whole galaxy. Coincidentally (actually not) Fermi does see gamma ray emissions coming from our whole galaxy, not just the core. What makes an exotic "dark matter" theory a "better" explanation than the obvious one (suns) to explain ordinary positron/electron annihilation?

 

[Michael Mozina]

Nobody asserts that the Fermi data can only be produced by dark matter.

Gah! You can't even demonstrate that dark matter *DOES* actually do what you claim it does and that it's even a logical option!

What they assert is that all known sources of the gamma rays have been eliminated (including the hundreds of billions of confirmed sources for annihilation signatures in a galaxy called "suns"!). That leaves unknown sources of gamma rays.

Hell, until tonight I don't think sol even realized that suns emitted annihilation signatures! What makes you think I have any confidence that astronomers actually eliminated suns from consideration? This industry has an extremely bad habit of eliminating logical possibilities based on absurdly weak arguments.

Dark matter is one of the ways that the excess gamma rays may have been produced.

Let me see you empirically demonstrate that claim *WITHOUT* affirming the consequent.

The last step in the fallacy is missing. It is not "Therefore, P". It is "Maybe, P (among other possibilities)".

"Maybe P" is a "belief" that is born of "pure faith" because you can't demonstrate that DM exists, that it emits *ANY* form of light, let alone gamma rays. The 'maybe p" claim was pure ad hoc speculation in the first place. It's like me claiming that "maybe God did it" and therefore my argument is completely "Ok" so long as I remember to use the term "maybe". Maybe you forgot to demonstrate that DM exists. Maybe you forgot to demonstrate it emits anything, particularly gamma rays. Maybe you forgot to demonstrate your claim that it's even a legitimate "maybe".

 

[temporalillusion]

Is this about the scientific method or just DM?

Every MM thread is about the scientific method. Ultimately it boils down to "if it hasn't been tested in a lab it doesn't exist", MM rejects natural experiments as valid science.

So while everyone goes round and round about specific things, it always comes back to that.

 

[Reality Check]

Gah! You can't even demonstrate that it dark matter *DOES* actually do what you claim it does!

Gah! What do you mean? What do you think scientists claim that dark matter *DOES*?

The claim in this case is that dark matter may be a weakly interacting massive particle that may annihilate producing elections and positrons that would then produce gamma rays. This might be detected by Fermi if we subtract all other known mechanisms for generating gamma-rays at the energies observed by Fermi. But Fermi might be detecting another mechanism producing the same gamma rays.
I do not claim that dark matter is weakly interacting massive particles that do annihilate producing elections and positrons that would then produce gamma rays.

Let me see you actually demonstrate that claim *WITHOUT* affirming the consequent.

I just did but lets make it clearer: "Maybe P or X or Y or Z or ..." is the last assertion.

"Maybe P" is a "belief" that is born of "pure faith" because you can't demonstrate that DM exists, that it emits *ANY* form of light, let alone gamma rays. The 'maybe p" claim was pure ad hoc speculation in the first place. It's like me claiming that "maybe God did it" and therefore my argument is completely "Ok" so long as I remember to use the term "maybe". Maybe you forgot to demonstrate that DM exists. Maybe you forgot to demonstrate it emits anything, particularly gamma rays. Maybe you forgot to demonstrate your claim that it's even a legitimate "maybe".

"Maybe P (among other possibilities)", i.e. "Maybe P or X or Y or Z or ...", is exactly what astronomers assert. Thus there is no fallacy and you are wrong in thinking that there is a fallacy. The fallacy only exists if there can only one conclusion ("Therefore P").

ETA:
Actually the conclusion of the authors is closer to "Therefore, this is new physics, such as the decay or annihilation of dark matter; or new astrophysics".
Using the the Wikipedia article example:

1. If Bill Gates owns Fort Knox, then he is rich.
2. Bill Gates is rich.

"Therefore, Bill Gates owns Fort Knox." produces the fallacy.
"Therefore, Bill Gates owns Fort Knox or has some other source of wealth" does not produce the fallacy.

Dark matter is a valid possibility because the observational evidence for the existence of dark matter is very strong.

It looks like the gamma rays emitted from stars are either too weak or at the wrong energies. From the paper:
The Fermi Haze: A Gamma-Ray Counterpart to the Microwave Haze

There are three well-known mechanisms for generating gamma-rays at the energies observed by Fermi. First, at low (1 GeV) energies, gamma-ray emission is dominated by photons produced by the decay of pi⁰ particles generated in the collisions of cosmic ray protons (which have been accelerated by SNe) with gas and dust in the ISM. Second, relativistic electrons colliding with nuclei (mostly protons) in the ISM produce bremsstrahlung radiation. Finally, those same electrons interact with the interstellar radiation field (ISRF) and inverse Compton scatter (ICS) CMB, infrared, and optical photons up to gamma-ray energies.

They then go onto subtract these contributions from the Fermi data.​

If you have a citation that states that the Fermi data includes contributions from stars then I would be interested in it.​

 

[Michael Mozina]

http://www.nasa.gov/mp4/397394main_NEW_Blazar_Galactic__NP_with_labels_640x480.mp4

If you watch the right side of this Fermi video, you'll notice a bright object moving from the top toward the bottom of the image. Would anyone care to guess what that moving bright spot corresponds to?

 

[Michael Mozina]

Gah! What do you mean? What do you think scientists claim that dark matter *DOES*?

They claim that "dark matter" emits gamma rays. Care to demonstrate that claim without relying on a logical fallacy or an act of pure faith?

The claim in this case is that dark matter may be a weakly interacting massive particle that may annihilate producing elections and positrons that would then produce gamma rays. This might be detected by Fermi if we subtract all other known mechanisms for generating gamma-rays at the energies observed by Fermi. But Fermi might be detecting another mechanism producing the same gamma rays.
I do not claim that dark matter is weakly interacting massive particles that do annihilate producing elections and positrons that would then produce gamma rays.

So let me understand your logic. As long as you toss in enough disclaimers you figure that is going to make it better? Well, in my hypothetical theory, "God" "may" exist and "may" emit gamma rays and "may" do so in space. Does that make my "God did it" theory more palatable to you personally?

If you have a citation that states that the Fermi data includes contributions from stars then I would be interested in it.

Great. How about identifying that object for us on the right side of that Fermi movie that travels from top to the bottom of the image during the movie.

http://www.nasa.gov/mission_pages/GLAST/news/first_year.html
http://www.nasa.gov/mp4/397394main_NEW_Blazar_Galactic__NP_with_labels_640x480.mp4

 

[Davidlpf]

Why can there not be gamma rays produced by stars and DM? Because in some peoples minds it has to be one or the other. It is not the scientist claim all the positrons are coming from dark matter but just the excess of what they were expecting if it was just coming from stars alone.

 

[Michael Mozina]

Why can there not be gamma rays produced by stars and DM?

Because DM has never been shown to actually emit gamma rays in the first place!

Because in some peoples minds it has to be one or the other. It is not the scientist claim all the positrons are coming from dark matter but just the excess of what they were expecting if it was just coming from stars alone.

I'm willing to let you posit *ANY* and *multiple* "known" source(s) of gamma rays, including electrical discharges, the one thing in nature that has been shown to emit gamma rays right here on Earth. What I won't let you do is simply *assume/claim* that DM had anything to do with it unless you can demonstrate that DM exists and actually emits gamma rays.

Here, I'll give you folks a hint about that moving arc on the right side of the image:

http://esciencenews.com/articles/20...elescope.reveals.best.ever.view.gamma.ray.sky

The map includes one object familiar to everyone: the sun. "Because the sun appears to move against the background sky, it produces a faint arc across the upper right of the map," Michelson explained. During the next few years, as solar activity increases, scientists expect the sun to produce growing numbers of high-energy flares. "No other instrument will be able to observe solar flares in the LAT's energy range," he said.

 

[Michael Mozina]

Every MM thread is about the scientific method. Ultimately it boils down to "if it hasn't been tested in a lab it doesn't exist", MM rejects natural experiments as valid science.

So while everyone goes round and round about specific things, it always comes back to that.

Well, it does seem to always come back to the fact that astronomers cannot empirically demonstrate their claim and 96% of Lambda-CDM theory is based upon hypothetical entities. How is that my fault?

 

[Davidlpf]

I'm willing to let you posit *ANY* and *multiple* "known" source(s) of gamma rays, including electrical discharges, the one thing in nature that has been shown to emit gamma rays right here on Earth. What I won't let you do is simply *assume/claim* that DM had anything to do with it unless you can demonstrate that DM exists and actually emits gamma rays.

Electricity does produce gamma rays, but do you have proof that is causing gamma rays in space. It looks like you are jumping to conclusions. Scientists say there is something in space but they do not have proof of what exactly what it is. The gamma rays is just evidence of what it might be.

 

[Michael Mozina]

Electricity does produce gamma rays, but do you have proof that is causing gamma rays in space.

Well, since Earth is in fact located in "space" and gamma rays occur here on Earth and other planets, yes, as a matter of fact I have proof that discharges cause gamma rays in space.

It looks like you are jumping to conclusions.

Not me. I can see that sun traverse the Fermi image with my own eyes. I know for a fact that a sun will emit annihilation signatures. I know for a fact that discharges create gamma rays too. I have zero evidence that DM does exists or does squat in terms of gamma ray emissions.

Scientists say there is something in space but they do not have proof of what exactly what it is. The gamma rays is just evidence of what it might be.

The gamma rays "might be" caused by any KNOWN force of nature. It's not possible however for these wavelengths of light to have been created by dark matter because dark matter has never been shown to emit such wavelengths. My "God did it" theory is at least as "scientific" as any "dark matter did it" theory in that respect.

 

[Davidlpf]

Well, since Earth is in fact located in "space" and gamma rays occur here on Earth and other planets, yes, as a matter of fact I have proof that discharges cause gamma rays in space.
There is no evidence to back up that electricity are causing the ones being observed by fermi.
Not me. I can see that sun traverse the Fermi image with my own eyes. I know for a fact that a sun will emit annihilation signatures. I know for a fact that discharges create gamma rays too. I have zero evidence that DM does exists or does squat in terms of gamma ray emissions.

The sun does produce annihilation signatures but no one here has said the gamma ray bursts are created by DM. You are claiming that scientists claim all gamma ray bursts are created by DM and no one actually is. Matter/antimatter annihilation has been observed here on Earth and some nuclear processes in the sun can create positrons and electrons, so the most likely process to emit gamma rays is positron/electron annihilation.

The gamma ray emissions that scientist think are caused by DM are the excess that they expect from what the stars produce.

 

[Michael Mozina]

The sun does produce annihilation signatures but no one here has said the gamma ray bursts are created by DM. You are claiming that scientists claim all gamma ray bursts are created by DM and no one actually is.

Could you quote me where I actually stated that "scientists claim "all" gamma ray bursts are created by DM? That seems to be your misconception if that is how you interpret my statements. My complaint is not that scientists claimed that *ALL* gamma ray burst come from DM. My complaint is that they claimed that *ANY* gamma ray bursts come from DM because that claim has never been demonstrated empirically.

Matter/antimatter annihilation has been observed here on Earth and some nuclear processes in the sun can create positrons and electrons, so the most likely process to emit gamma rays is positron/electron annihilation.

Ok.

The gamma ray emissions that scientist think are caused by DM are the excess that they expect from what the stars produce.

What exactly do they "expect" and why? Wouldn't solar cycle changes and all sorts of unknown factors have some influence on these "expectations"? Since Fermi has only been in space for a little over a year, how exactly did they even decide what to "expect" from our own sun over a typical 11 year cycle?

The key issue here is that suns are a known source of annihilation signatures, and even planets can emit gamma rays from their atmosphere. Since there are literally hundreds of billions of stars and planets in a galaxy why do we need to look further than stars and planets and typical objects in space as a "source" of gamma rays? How do we even know what to "expect" in the first place?

 

[Reality Check]

They claim that "dark matter" emits gamma rays. Care to demonstrate that claim without relying on a logical fallacy or an act of pure faith?

There is a theory that dark matter may be made of particles that annihilates to electrons and positrons and that this produces gamma rays. There is no "demonstration" of this except a possibility that Fermi has detected these gamma rays.

So let me understand your logic. As long as you toss in enough disclaimers you figure that is going to make it better? Well, in my hypothetical theory, "God" "may" exist and "may" emit gamma rays and "may" do so in space. Does that make my "God did it" theory more palatable to you personally?

My logic is that you do not know what the authors of the paper acually said in their conclusion.
Their conclusion was not that dark matter emitted the gamma rays.

Their conclusion was that new physics (e.g. the decay or annihilation of dark matter) or new astrophysics is the mechanism producing the excess gamma rays.

So your original logic was wrong and there is no fallacy.

Great. How about identifying that object for us on the right side of that Fermi movie that travels from top to the bottom of the image during the movie.

http://www.nasa.gov/mission_pages/GLAST/news/first_year.html
http://www.nasa.gov/mp4/397394main_NEW_Blazar_Galactic__NP_with_labels_640x480.mp4

It is the Sun.
Did you know that the Sun is a bit closer to us than other stars?
Have you heard of the inverse square rule for the intensity of radiation?

Fermi's Best-Ever Look at the Gamma-Ray Sky

The top five sources within our galaxy are:

The sun. Now near the minimum of its activity cycle, the sun would not be a particularly notable source except for one thing: It's the only one that moves across the sky. The sun's annual motion against the background sky is a reflection of Earth's orbit around the sun.

"The gamma rays Fermi now sees from the sun actually come from high-speed particles colliding with the sun's gas and light," Thompson notes. "The sun is only a gamma-ray source when there's a solar flare." During the next few years, as solar activity increases, scientists expect the sun to produce growing numbers of high-energy flares, and no other instrument will be able to observe them in the LAT's energy range.

You have still not produced the citation that I asked for:

If you have a citation that states that the Fermi data includes contributions from stars ( to be clear: the stars in the galaxy - not just our Sun or specific high energy sources) then I would be interested in it.​

It is obvious that astronomers know about the various point sources (X-ray binaries, pulsars, etc.). Now show that the paper incorrectly ignored these.

ETA:
Found it! I remember reading something about point sources in the paper and here it is:​

In this fit, we mask out all of the Fermi 3-month point source catalog as well as the LMC, SMC,Orion-Barnard’s Loop, and NGC 5090.

And Apendex A is all about the effects of unresolved point sources! Itconcludes

As Fig. 13 shows, at low energies we find values of R consistent with a significant point source component (although the point source fraction cannot be precisely determined without knowing the luminosity function). Above 10 GeV, however, the value of R is consistent with entirely diffuse emission, and at 95% confidence, the fraction of emission from unresolved point sources cannot exceed ~ 5% and remain consistent with the measured value of R. Therefore,even for these conservative assumptions, the hard spectral shape of the Fermi haze cannot be caused by point source contamination.

​

​

​

​

 

[Davidlpf]

What would the 11 year cycle have to do with the particles created in the center of the sun?
I would imagine that scientist have modeled how many gamma rays would be produced by stars and other objects, so they would know if there are excess gamma rays.

 

[Reality Check]

What would the 11 year cycle have to do with the particles created in the center of the sun?
I would imagine that scientist have modeled how many gamma rays would be produced by stars and other objects, so they would know if there are excess gamma rays.

The situation is that solar gamma rays are produced in solar flares and so their intensity is cyclic.
As in MM's link:
ANNIHILATION RADIATION OBSERVATIONS: IMPLICATIONS FOR CONDITIONS IN THE FLARING SOLAR CHROMOSPHERE

Flare-accelerated ions interact with the solar atmosphere to produce radioactive nuclei (Kozlovsky et al. 1987) and pions (Murphy et al. 1987) that decay, yielding positrons. Positrons slow down by interactions with the ambient medium prior to directly annihilating with electrons or forming the hydrogenlike positronium atom. Direct annihilation and annihilation from the singlet state of positronium give rise to two 511 keV photons, while annihilation from the triplet state yields three photons with varying energies below 511 keV.

This means that the Sun is a strong point source of gamma radiation beacuse it is close to us. Other normal stars are not sources but there are the other strong point sources like pulsars and X-ray binaries.

I suspect that these point sources were ignored since the paper is analyzing the general radiation.

 

[Davidlpf]

The situation is that solar gamma rays are produced in solar flares and so their intensity is cyclic.
As in MM's link:
ANNIHILATION RADIATION OBSERVATIONS: IMPLICATIONS FOR CONDITIONS IN THE FLARING SOLAR CHROMOSPHERE

This means that the Sun is a strong point source of gamma radiation beacuse it is close to us. Other normal stars are not sources but there are the other strong point sources like pulsars and X-ray binaries.

I suspect that these point sources were ignored since the paper is analyzing the general radiation.

My bad. I should not try to a lot of things at once.