Fermi and dark matter

[Reality Check]

Michael Mozina rocks = dark matter idea (Question 3)

RC, you simply do not need any "special/exotic" kind of matter to be present in these regions. All you need is ionized and non ionized particles spread out heterogeneously. In no way is Occum going to be kind to your claim of a need for 'special' matter. All we need is 'dusty plasma", "clumpy" non ionized particles and some ordinary rocks distributed in a heterogeneous layout. There is absolutely *NO* need for 'exotic matter' to explain why some material "passes through" and why some matter interacts. The whole mainstream position is based upon the argument of "we can't figure it out, therefore exotic matter did it".

Wrong. The whole mainstream position is based upon the argument of "we can figure out what normal matter (in various configurations) would do and this does not explain the observations. Thus it is not normal matter.".


'Dusty plasma" and "clumpy" non ionized particles will act just like the ICM plasma. This has been covered before. All particles in the ICM have a mean free path of about a lightyear. This means that a particle (ionized or not) will collide about 3 million times to pass through 1 megeparsec of the ICM (a typical galactic cluster diameter). The particle will

• Slow down.
• Heat up and emit light.

Dark matter is observed to not slow or emit light as you may know.

Rocks are a really bad idea that is easy to rule out: Michael Mozina rocks = dark matter idea (reposted since you seem to be ignoring the questions in it )

And now let's get really, really local:

First asked 13 November 2009
Astronomers have measured the distribution of matter in galactic clusters using gravitational lensing. This distribution has a massive, roughly spherical background (dark matter) with the spikes of galaxies poking out from the background.

Dark matter is present everywhere. This includes inside galaxies. This includes inside the Milky Way. This includes inside the Solar System . Thus there are experiments in labs here on Earth trying to detect dark matter with one lab reporting success (but this is contested).

We can ignore the rocks in the asteroid belt (they formed with the Solar System).


Michael Mozina:
Why have astronomers not found enormous numbers of rocks

• Passing through the Solar System?
• Floating in interstellar space?

 

[Michael Mozina]

Ahh.. thank you... beat me to it.

That is why I raised the issue.

The "existence or nonexistence of monopoles" requires Maxwell's equations to be "rewritten" just in the same way that the "existence or nonexistence" of dark matter requires the general relativity solutions to be modified to take that into account (in fact the "rewriting and redoing" for the monopoles is actually a damn sight easier with less things that can affect it, yet MM doesnt seem to be overly worried about that compared with the issue in this thread, and yet it hits at the heart of his preferred explanation).

You might elaborate here for me a bit because your argument seems completely illogical from my perspective. I guess I'm missing something.

It seems to me that what you're doing is saying *if* x exists *then* we get to rewrite the laws of physics another way. Well.....ok.....but do you have any evidence x exists or that the laws of physics as we understand them are flawed? "Right now" we have no evidence that "laws" of physics work differently than they do, or work differently "out there somewhere" than they do right here on Earth.

Gamma rays come from discharges in the Earth's atmosphere and have been seen by Fermi. Even annihilation signatures specifically have been seen by Fermi due to discharges in the Earth's atmosphere. The discharge process is a known and "natural' source of annihilation wavelengths. The sun is also a "known and natural" source of gamma ray and specifically annihilation wavelengths. I even provided you folks with an extremely impressive (to me at least) paper with all sorts of mathematical support that demonstrates that binary stars can explain an excess of annihilation wavelengths.

As I see it there is absolutely no need whatsoever for any sort of 'exotic' matter to explain gamma rays in Fermi images. The same laws of nature apply to planets and suns in our galaxy and universe as apply to the Earth and our own sun. Binary stars might be able to produce "extra" gamma rays if we need them. There is *absolutely no need whatsoever* for any form of exotic matter to explain gamma rays in a Fermi image. We have all the math, physics and "natural sources" of gamma rays that we need to explain virtually any quantity of gamma rays from a galaxy. Occum is not going to be kind to any sort of theory that requires "exotic" variables in terms of explaining gamma rays in space. In fact Occum's razor is going to slice it and dice it and cut it to shreds. Even Alfven's "prediction" of an "ambiplasma" separating matter from antimatter isn't as "simple" to explain as what is already available to us today.

Ok, sure, 'monopoles' and unicorns may exist, "magnetic reconnection" may not be "pseudoscience* in spite of Alfven's protestations, and "dark matter' might emit gamma rays for breakfast. Anything and everything is "possible".

Empirical physics however deals with what "is known empirically" to work in a lab. There are ample empirical tools at our disposal to explain gamma rays in space that do not require any leaps of faith whatsoever. Why would we even consider *any* theory that introduces a variable (be it a monopole or dark matter) that lacks empirical support when we already have "better" empirically demonstrated options on the table, math, physics and everything?

Sure "laws" of physics might fall in the future, but then they have already stood the test of time. I'll assume the absence of monopoles and unicorns until I see them running through my backyard, or at least I see some valid empirical evidence.

I thought it prudent to point it out because we are in a dodgy position if we have argued that our "knowledge of x precludes y" if in fact precluding y was a vital step in reaching x in the first place.

Our knowledge of natural sources of gamma rays does not preclude there from being another "possibility". It doesn't make much sense however to simply abandon what is known to work in nature in favor of an act of pure faith on the part of the "believer" in the complete absence of empirical support.

That is why scientists are actually being very open minded and sensible about allowing (possibly, until you can convince them otherwise) for the existence of dark energy and dark matter.

There's a difference between being "open minded" and being "gullible". If I need to explain an "acceleration" of plasma, "electricity" is likely to be my first choice. If I need to explain gamma rays, "electricity" is again my first choice. If I need to explain something that I cannot explain, I don't automatically assume that the laws of physics need to change. I typically assume that I need a "better" scientific understanding of the problem and more information.

 

[ben m]

Rocks are a really bad idea that is easy to rule out: Michael Mozina rocks = dark matter idea (reposted since you seem to be ignoring the questions in it )

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.

 

[Michael Mozina]

Wrong. The whole mainstream position is based upon the argument of "we can figure out what normal matter (in various configurations) would do and this does not explain the observations. Thus it is not normal matter.".

No RC, you *DID NOT* figure it out, so you stuffed the gaps of your own ignorance with an "exotic" form of "dark matter"! You didn't even *TRY* to figure it out before LEAPING to the conclusion that your plasma body is homogeneously distributed, 99% ionized, and without any form of "clumpy" matter at all! You aren't open to any criticism. You aren't listening to reason either. Nobody is claiming *ALL* the matter is made of rocks or MACHOS. That is your own pathetic strawman RC. The plasmas of the ICM are "heterogeneous", "dusty" and include normal material objects galore of every shape and size. When you add them all together, some of them "pass through", some of them "slam together" and all it combined adds up to the total mass we're looking for. As long as you resist *ANY* sort of alternative explanation for matter that "passes through" the collision process, you only make yourself look bad IMO.

Never once did you even offer me a source for your 99% ionization claim. Not once did you offer me a legitimate "bone" in terms of "giving an inch". Pretty much everyone else in this conversation has been more open to alternative than you. Why is that? Are you so afraid of questioning your own beliefs that you can't consider alternatives?

 

[Michael Mozina]

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

Woah! I never claimed even a majority of the missing mass was found in "rocks". That might account for a small portion of the mass whereas the heterogeneous layout of "dusty plasma" may be responsible for the vast majority of the matter that "passes through" the collision. I have no idea where all the "missing mass" is located, but I also have no evidence whatsoever from these lensing studies that any of that missing mass is found in any form of exotic matter. Frankly I am *A LOT* more worried about your "assumptions* about ionization rates and the overall layout of material than I'm worried about rocks.

 

[ben m]

Woah! I never claimed even a majority of the missing mass was found in "rocks". That might account for a small portion of the mass whereas the heterogeneous layout of "dusty plasma" may be responsible for the vast majority of the matter that "passes through" the collision. I have no idea where all the "missing mass" is located, but I also have no evidence whatsoever from these lensing studies that any of that missing mass is found in any form of exotic matter. Frankly I am *A LOT* more worried about your "assumptions* about ionization rates and the overall layout of material than I'm worried about rocks.

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?

 

[ben m]

I have no idea where all the "missing mass" is located, but I also have no evidence whatsoever from these lensing studies that any of that missing mass is found in any form of exotic matter

This is a problem. You're not willing to think very hard about what it would mean for the missing mass to be regular matter, but you want to assume that it will work out somehow. Why? Because you intuit that such a working-out must be more plausible than the 70-year-old 70s-vintage idea that there must be particles beyond the Standard Model.

You do have to think about it a little bit. Dust---even ice-cold neutral dust with no IR emissions---is still a light absorber. The Milky Way's halo is not opaque---there are not even substantial opaque spots in it (whereas there are in the disk, due to real dust: http://apod.nasa.gov/apod/ap041219.html) Where, MM, are your denser dust clouds hiding?

Do you have some dust/rocks configuration in mind---anything at all---that you think looks like the actual Milky Way halo?

• Not opaque
• Not glowing
• Dynamically long-lived despite the intersecting nature of halo orbits[/I]
• total mass of ~1 trillion solar masses?
• No more than 8% of the mass in Moon-sized or larger bodies

 

[Reality Check]

No RC, you *DID NOT* figure it out, so you stuffed the gaps of your own ignorance with an "exotic" form of "dark matter"!

No MM , you *DID NOT* figure it out, so you stuffed the gaps of your own ignorance with an "exotic" form of "normal matter"!

I *DID NOT* figure it out is right. I am not an astronomer. Thus I have to rely on what actual astronomers state. As far as I can tell, the consensus in the scientific community is that the Bullet Cluster, MACS J0025.4-1222 and Abell 520 obervations deomstarte that most of the ICM is not normal matter.

You didn't even *TRY* to figure it out before LEAPING to the conclusion that your plasma body is homogeneously distributed, 99% ionized, and without any form of "clumpy" matter at all!

I did *TRY* to figure it using my general knowledge of physics.

• I never claimed that the ICM is homogeneously distributed.
• I never claimed that the ICM is exactly 99% ionized. I stated that 99% could be the mostly ionized part of the ICM as in:

  In astronomy, the intracluster medium (or ICM) is the superheated gas present at the center of a galaxy cluster. This plasma is heated to temperatures of between roughly 10 and 100 megakelvins and consists mainly of ionised hydrogen and helium, containing most of the baryonic material in the cluster. The ICM strongly emits X-ray radiation.

• By definition the ICM is without any form of "clumpy" matter at all. It is a plasma consisting of gas.

I know that intracluster space contains stars.
I know that intracluster space will contain rocks and "clumpy" matter from the intracluster stellar systems and possibly pulled out of galaxies.

You aren't open to any criticism. You aren't listening to reason either. Nobody is claiming *ALL* the matter is made of rocks or MACHOS. That is your own pathetic strawman RC. The plasmas of the ICM are "heterogeneous", "dusty" and include normal material objects galore of every shape and size.

I know that you are not claiming that.
You are still displaying your ignorance that the ICM by definition is a plasma.

The "normal material objects galore of every shape and size" are not part of the ICM. They are in intracluster space that includes:

• The ICM.
• Intracluster stars.
• Intracluster rocks.
• Intracluster dust.
• etc.

When you add them all together, some of them "pass through", some of them "slam together" and all it combined adds up to the total mass we're looking for. As long as you resist *ANY* sort of alternative explanation for matter that "passes through" the collision process, you only make yourself look bad IMO.

Any "lumpy stuff" will pass though. I know that. You know that.

What you cannot grasp is that all of the plasma that is the ICM in the colliding clusters in the observations of the Bullet Cluster, etc. has collided, heated up, formed shock waves and slowed down. This is what normal, electromagnetically interacting particles do whether ionized or not. So all of the normal matter in the ICM is in the central blob - except for the few stray atoms from the ICM that somehow managed to avoid millions of collisions.

That leaves your intracluster "lumpy stuff" to form the outlying blue blobs.
These blobs are 40 times more massive than the galaxies in the clusters. These blobs are 6 times more massive than the ICM in the clusters.
The issue is not the existence of "lumpy stuff" We know that there are intracluster stars and they are "lumpy stuff".

The issue is: Is there enough of this "lumpy stuff" to account for the mass in the blue blobs?

We can rule out most "lumpy stuff" to leave rocks and black holes and the questions that you are ignoring.

Astronomers have already ruled out MACHOs (one form of "lumpy stuff" according to MM) as a significant part of dark matter. They can be at most 8% of the dark matter in a galaxy.

Intracluster space contains the ICM. It also contains intracluster stars, planetary nebulae and globular clusters that are likely to have been removed from galaxies by gravitational forces. These visible intracluster objects emit 10-20% of the stellar light. Being charitable this is 20% of the mass of a galaxy.

So far we have "lumpy stuff" giving 0.28 of a galaxy per visible galaxy - only 39 galaxies to go!

Maybe "lumpy stuff" is dust? But Far-Infrared Emission from Intracluster Dust in Abell Clusters has measured no dust in 5 clusters and a low inferred dust mass in another.

That leaves the other candidates that MM has mentioned for "lumpy stuff": rocks and black holes.

• Michael Mozina rocks = dark matter idea
• Michael Mozina rocks = dark matter idea (Question 3)

 

[ben m]

I would like to point out, for clarity, that RC is citing constraints on the dark matter in galaxy clusters and I am citing constraints on the dark matter in galaxies themselves.

Personally, I chose to use the Milky Way halo only because I work in the field and have more of the relevant numbers at my fingertips. The same general calculations (opacity or lack thereof, collision rate, etc.) can of course be done for the galaxy cluster dark matter.

 

[Reality Check]

What you cannot grasp is that all of the plasma that is the ICM in the colliding clusters in the observations of the Bullet Cluster, etc. has collided, heated up, formed shock waves and slowed down. This is what normal, electromagnetically interacting particles do whether ionized or not. So all of the normal matter in the ICM is in the central blob - except for the few stray atoms from the ICM that somehow managed to avoid millions of collisions.

A correction: The Wikipedia article on the intracluster medium states that the mean free path of the ICM particles is "roughly 10¹⁶ m, or about one lightyear". But a light year is 9.461×10^15 m. Thus 10¹⁶ m is nearly 10.57 light years. Thus the above particles would be experience hundreds of thousands of collisions.

ETA
Since the article got the conversion from meters to light years wrong, I went looking for a better source of information. I found a couple of PDFs that look more trustworthy:
The Intracluster Medium
Gas Dynamics in Clusters of Galaxies
and give an actual equation: Mean free path = 23 kpc (T/10⁸)² (n/10^-3 cm^-3)^-1
Thus a typical ICM particle has a mean free path of 23 kpc. This is 1% of the usual scale of galactic clusters (~2 Mpc) or 2% if we keep with the 1 Mpc scale that I have been using based on the Bullet Cluster observation. That implies to me that the dark matter blobs could include as much as 2% from the ICM plasma. In other words the contribution from the ICM is insignificant.

In fact even if all of the ICM ended up in the dark matter blobs (it does not!), the contribution would still be minor. Someone would still have to find ~33 galaxies worth (for each visible galaxy) of "lumpy stuff" to make up the observed mass in the dark matter blobs.

 

[ben m]

A correction: The Wikipedia article on the intracluster medium states that the mean free path of the ICM particles is "roughly 10¹⁶ m, or about one lightyear". But a light year is 9.461×10^15 m. Thus 10¹⁶ m is nearly 10.57 light years. Thus the above particles would be experience hundreds of thousands of collisions.

Check your math---10^16 meters is 1.057 light years. Same conclusion, though.

 

[DazzaD]

You might elaborate here for me a bit because your argument seems completely illogical from my perspective. I guess I'm missing something.

Ok. I will have a go.

My point is that you seem to insist on having "something in your hand" before you are willing to believe it and that you insist that the "current laws" are enough to explain the effects, or at least we shouldnt be looking to expand on those laws and theories just yet.

But...

You may have been misinformed about these "laws and theories".

Maxwell's equations, as you may have seen them and been taught them, are in fact a "bodge job" if you will to fit the observation that at THAT time magnetic monopoles were not seen to obviously exist in abundance.

The simple fact is that if you accept that they are an excellent description of "all things magnetic and electric" then you have to accept that in their proper form they allow for the magnetic monopoles, in fact some might say even demand them.

For instance, if just a single monopole exists, and you trust that Maxwell's equations are valid, then ALL electric charges MUST be quantised. Which they are.

My point is that just arbitrarily throwing away monopoles seems to be doing the same thing that you criticise other people for when they refuse to throw away, say dark energy.

One might oversimplify the problem and say that the cosmological constant, which again is something that can be added to the equations describing general relativity (but which wasn't originally because it didn't seem to fit what they observer or what they wanted to observer back then) can "explain" why dark energy may exist.

For me the two situations are analogous.

With your favoured theory heavily based on electromagnetism you outright refuse to entertain the possibility of a magnetic monopole which is a perfectly valid predication of a theory that is amazingly successful in so many other ways. I find it hard to justify such picking and choosing. One might be crass and say that "absence of evidence is not evidence of absence ".

I brought it to your attention in the hope that you might begin to understand why cosmologists are willing to entertain such seemingly strange ideas as dark energy, precisely because they are so rooted in what is actually really going on.

If we were to go round using the simplified set of equations for electromagnetism that you see in undergraduate courses you would achieve an awful lot in physics but you would never understand the concept and problem of magnetic monopoles.

Similarly for general relativity. And particle physics. And the structure and evolution of stars. etcetc.

I just think that were we to fall into that rut we would never really have been willing to entertain ideas such as special relativity.

Ok, sure, 'monopoles' and unicorns may exist, "magnetic reconnection" may not be "pseudoscience* in spite of Alfven's protestations, and "dark matter' might emit gamma rays for breakfast. Anything and everything is "possible".


Sure "laws" of physics might fall in the future, but then they have already stood the test of time. I'll assume the absence of monopoles and unicorns until I see them running through my backyard, or at least I see some valid empirical evidence.

There's a difference between being "open minded" and being "gullible". If I need to explain an "acceleration" of plasma, "electricity" is likely to be my first choice. If I need to explain gamma rays, "electricity" is again my first choice. If I need to explain something that I cannot explain, I don't automatically assume that the laws of physics need to change.

There is indeed a difference. But the key thing is, do you truly think that cosmologists as a whole are being gullible in this case?

What I tried to explain above is that cosmologists first line of attack is NOT to change the laws of physics, that is exactly what I am arguing against! Yet I think you may have misunderstood or I may have misrepresented myself.

I typically assume that I need a "better" scientific understanding of the problem and more information.

That is an excellent soundbite but it means nothing in a practical sense.

If we are completely unable to explain away an effect using all known physics, and if the experimental evidence says that no matter what version of this theory you use you cannot account for the whole effect, we are left with the dramatic but necessary conclusion that we need a serious rethink.

I thank RC and others in this thread for patiently pointing out the issue raised originally and I apologise for this sidetrack.

I too would like to see a detailed response to RC's last few posts as he seems to raise a few simple but interesting questions about the nature of the matter within the ICM.

 

[Dancing David]

DazzaD I have to say you are a welcome addition to the forum, having followed these threads since BAC and the BiG Bang thread this is common to many many many of these threads in SMT.

MM carries the whole 'empirical' testing to a whole new level and then engages in special pleading when it comes to nutrinos, mesons and Yukawa particles, but then so did BAC.

Now MM has learned from the experience here, the posts are a little more careful in their construction.

But the data do not matter, it is the ideas and rather obsessive. Good luck, I have engaged in the same topic and have about twenty others.

 

[Michael Mozina]

Ok. I will have a go.

My point is that you seem to insist on having "something in your hand" before you are willing to believe it and that you insist that the "current laws" are enough to explain the effects, or at least we shouldnt be looking to expand on those laws and theories just yet.

Well, technically I will require some sort of "empirical support" to actually "believe" that something exists in nature. That does not mean that I will not entertain 'possibilities' which lack empirical support at the moment.

If however I am asked to "rank" or "judge" these various ideas, any "empirically viable" solution is going to be a "better" option than one that is based upon pure speculation about what *might* exist in nature.

In some instances that may not be possible. In other words, there may be no "natural" explanation based on empirical physics. The neutrino is an excellent example. There simply was no known particle, at that energy state, to explain "missing energy' from "controlled experiments". That kind of scenario does tend to suggest that there is "something new" to discover. Without "natural" options to choose from, a "new" idea makes a lot of sense.

In other cases, such as gamma rays seen in Fermi images, there are ample "natural" sources of gamma rays and other 'natural' solutions to this problem. There is no need to introduce another variable to explain gamma rays from our galaxy in any quantity. Occum's razor arguments now apply to this issue, unlike the neutrino scenario. I no longer need anything 'new' to explain what we observe. There could be multiple 'natural" solutions that I will have to choose from, all of which might be viable. In that case I may have to 'choose between competing empirical solutions'. All such options will necessarily be 'more scientifically attractive" than any options that rely upon 'acts of faith' in a "new" thing.

It's not as though I failed to provide you folks with a natural alternative, or failed to provide you with a "quantified" as well as a "qualified" explanation. I did provide you with a "natural" solution to this "mystery". There is no need to introduce "dark matter" to explain gamma rays in our galaxy. It is an absolutely unnecessary and unsupported assertion. No amount of math is going to "fix" the basic problem. Since there is no need to introduce a "new" variable, and there is no empirical support allowing me to validate the math, it's a nearly completely useless theory IMO. It has no empirical support whatsoever, whereas "electrical discharges" are well empirically supported. I simply see no need whatsoever for any non empirical theory at this point in time because there is a way to explain these observations without introducing any new variable. Occum's razor now applies to this argument.

As I said, there may be cases where there are no valid solutions to the problem using known forces of nature. In this case however, discharges and suns (binary ones as well) are able to 'explain' what we observe. In such scenarios, I have a much tougher time "believing" something else is required, or that something "unknown to mankind" is responsible for these emissions.

In the case of "monopoles", they too are "unnecessary". Electrical engineering is highly advanced to the point of being able to create these computers we're using right now. It works in the lab. Maxwell's equations have been able to "explain" everything we've observed "better than" any other option. *If* someone comes up with a scenario that requires them to exist, and can demonstrate they do exist, then I have a logical reason to "believe" in them. In the absence of such information, I will typically choose to "lack belief" in them. It's nothing personal. It's pure physics.

With your favoured theory heavily based on electromagnetism you outright refuse to entertain the possibility of a magnetic monopole which is a perfectly valid predication of a theory that is amazingly successful in so many other ways. I find it hard to justify such picking and choosing. One might be crass and say that "absence of evidence is not evidence of absence ".

My "bias" in that case is based upon "empirical physics". That "bias" can be overcome at any point in time by additional evidence. It's not 'set in stone', it's simply rooted in a bias toward empirical physics. That isn't "unusual" in most scenario, particularly when a "natural' solutions is available.

I brought it to your attention in the hope that you might begin to understand why cosmologists are willing to entertain such seemingly strange ideas as dark energy, precisely because they are so rooted in what is actually really going on.

I can understand them "entertaining" various ideas. In this particular case however, there's no need whatsoever to do that, and no empirical support whatsoever.

There is indeed a difference. But the key thing is, do you truly think that cosmologists as a whole are being gullible in this case?

Yes, in the case of the Fermi images I certainly do. In fact I would say that their own "anti EU bias" is likely to be the "cause" of that gullibility. It's more like "stubborn gullibility". They don't *want* to accept an "electrical" solution to that observation. They therefore "make up" a half dozen unsupported assertions and expect me to buy the idea. I find that sad and frankly very frustrating.

What I tried to explain above is that cosmologists first line of attack is NOT to change the laws of physics, that is exactly what I am arguing against! Yet I think you may have misunderstood or I may have misrepresented myself.

Like DD, I'm very happy that you opted to join this conversation. I've appreciated your input and your attitude. You've been highly logical, scientifically oriented, and completely professional. You need however to keep in mind however that I have a very *long* history with some of these folks, spanning many boards over many years. I've seen them in action on many occasions. I've seen their biases, and I've been victimized by those irrational biases.

*IF* their 'first line of attack' was skewed toward empirical physics, they would simply accept that there is a valid "explanation" for these Fermi images and DM is not responsible for those gamma rays. There bias however favors "dark" stuff, and "inflation" and they have a very strong *against* all things with an EU flavor. That is a deadly combo in my experience. They literally reject empirical physics only because they don't "like" that kind of empirical physics. In this case they reject a solution based upon pure empirical physics in favor of a "dark" solution that requires "faith" in their belief system. That is utterly absurd IMO, but I see it happen over and over and over and over again. IMO it's rooted in their dislike of EU/PC theory. Unfortunately for them we live inside an electric universe.

If we are completely unable to explain away an effect using all known physics, and if the experimental evidence says that no matter what version of this theory you use you cannot account for the whole effect, we are left with the dramatic but necessary conclusion that we need a serious rethink.

Whereas you might have an argument in terms of that lensing data, your argument points out the flaw in the mainstream position and attitude. There *IS* a "natural' explanation for gamma rays in Fermi images. The only reason they don't "like" that solution is that it favors EU theory and does nothing whatsoever to support their beliefs. The launched Fermi with the intent of "finding dark matter". IMO they now see 'evidence' for dark matter in everything they see, regardless of whether or not there are viable empirical solutions to the problem. They are going out of their way to misrepresent and mistreat "science" now only because it doesn't jive with their preconceived intent.

 

[Michael Mozina]

It think it is time to create a new thread.

We seem to be engaged in two different conversations at this point. This thread was specifically intended to discuss the topic of Fermi and whether "dark matter" has anything to do with gamma radiation.

There is also a larger debate taking place about the very existence of "any kind" of exotic matter based on any type of observation, including lensing data. I'm of the impression that this "larger" debate should take place in different thread, and this thread should stay focused on the Fermi data specifically.

IMO I have offered you a valid scientific 'explanation' for the gamma radiation. Discharges in the Earth's atmosphere generate gamma rays every day. Fermi has even seen annihilation wavelengths from such discharges. Our own sun can be clearly observed in the Fermi images. Binary star studies suggest that excess gamma radiation near the core of our own galaxy can be the result of binary star populations. There are "natural" explanations form what we observe in Fermi images, and no sort of exotic matter is necessary to explain these images.

I think I'd like to respond to Ben and RC in a new thread. You'll need to be patient with me today, I do have some work to finish before I can enjoy my weekend.

 

[ben m]

There is also a larger debate taking place about the very existence of "any kind" of exotic matter based on any type of observation, including lensing data. I'm of the impression that this "larger" debate should take place in different thread, and this thread should stay focused on the Fermi data specifically.

It's entirely relevant, when discussing whether Fermi is sensitive or insensitive to a particular dark-matter hypothesis, to establish that everyone knows what the dark matter hypothesis is.

If you want to continue discussing the Fermi data, can you allow for the sake of argument that the hypothesis in question, "dark matter is made of heavy WIMPs with a nonzero annihilation cross section to photons", is NOT RULED OUT BY ANY OTHER DATA, nor by Occam's Razor, nor by particle physics. If you'll accept that, we can discuss the Fermi sensitivity to that hypothesis.

 

[Michael Mozina]

It's entirely relevant, when discussing whether Fermi is sensitive or insensitive to a particular dark-matter hypothesis, to establish that everyone knows what the dark matter hypothesis is.

Agreed.

If you want to continue discussing the Fermi data, can you allow for the sake of argument that the hypothesis in question,

For the sake of argument....

"dark matter is made of heavy WIMPs

This will be considered "Claim A" and B. Wimps exist. They are "dark".

The next assumption/claim is that WIMPS (assuming the are found) are 'long lived'. We'll call that "Claim/Assumption C"

with a nonzero annihilation cross section to photons",

We'll call that "Claim D".

There's a "Claim E" coming that relates to where the WIMPS are presumably located/concentrated, but that will depend on which gamma rays in particular you are attempting to attribute to these hypothetical particles.

is NOT RULED OUT BY ANY OTHER DATA,

I agree.

nor by Occam's Razor,

I disagree. I handed you a perfectly logical "explanation' for gamma rays, and an excess of gamma rays near and around the core that require no 'hypothetical' entities.

nor by particle physics.

Ok, as long as you agree that WIMPS are a 'theoretical' particle from a 'non standard' branch of particle physics theory. They are not a part of standard theory, and no SUSY particle (or other theoretical particle) has been confirmed to exist. It's not "ruled out' in terms of SUSY theory, but it is not included in standard particle physic theory.

If you'll accept that, we can discuss the Fermi sensitivity to that hypothesis.

Well, for purposes of the discussion I can agree to pretty much all your assertions with the exception of the Occum's razor debate. That will become important as we review the various claims of your hypothesis, all of which must be 'true' for your theory to work.

 

[ben m]

You're not catching on to this "hypothesis" thing. The hypothesis is that WIMPs explain the mainstream, gravity-based dark matter observations. That includes their being stable, their being weakly-interacting, and their being where the dark matter is (halos, clusters, galaxy centers) with substructure ("clumpiness" or "cuspiness" are terms of art here) only as allowed by mainstream galaxy formation theory.

That---the whole thing---is the "dark matter is WIMPs" hypothesis.

Let's establish that, can we?

AFTER THAT we can make an additional hypothesis: if WIMPs are out there AND their mass is in range Y and they have a photon-annihilation channel with cross section X then Fermi would see Z. But let's get to that hypothesis/prediction pair after you've understood the prerequisite, please.

And all of that is still totally different from the reverse question: "given that Fermi saw W, what hypotheses are favored?" That is a data-analysis problem and an interesting one, but it's predicated on understanding the hypotheses---which you still don't. Start at the beginning.

 

[Michael Mozina]

You're not catching on to this "hypothesis" thing. The hypothesis is that WIMPs explain the mainstream, gravity-based dark matter observations. That includes their being stable, their being weakly-interacting, and their being where the dark matter is (halos, clusters, galaxy centers) with substructure ("clumpiness" or "cuspiness" are terms of art here) only as allowed by mainstream galaxy formation theory.

By "catching on", you mean I'm supposed to simply agree with everyone as one "complete package", inseparable, with exactly all the various "properties" you claim, including distribution which "just so happens" to coincide with the binary star populations near the core?

What you're suggesting here Ben includes all the following "assumptions" that are all part of your package 'hypothesis".

A new form of matter exists beyond the "standard" particle physics theory.
This new particle is "long lived" and doesn't deteriorate in say a millisecond.
It only interacts with other matter in the specific way that you claim at the "weak" level of particle physics. It "decay's" in some way that releases both an electron and a positron at whatever rate you evidently are allowed to "postdict" from whatever observation you're claiming they relate to now and into the future.

That---the whole thing---is the "dark matter is WIMPs" hypothesis.

Just out of curiosity, are you allowed to tinker with any of those variables for any particular observation? In other words, can you assume a different decay rate for various types of observations?

Let's establish that, can we?

AFTER THAT we can make an additional hypothesis: if WIMPs are out there AND their mass is in range Y and they have a photon-annihilation channel with cross section X then Fermi would see Z. But let's get to that hypothesis/prediction pair after you've understood the prerequisite, please.

It seems as though your "prerequisite" is that I accept a host of "assumed properties", and then you still intend to tinker around with the quantity, location, and that "photon-annihilation channel with a cross section x" variable. Do I understand your 'prerequisite" correctly? Am I allowed to challenge any of the those assumptions independently, or does that simply detract from your argument in a way you find personally offensive for some reason?

And all of that is still totally different from the reverse question: "given that Fermi saw W, what hypotheses are favored?" That is a data-analysis problem and an interesting one, but it's predicated on understanding the hypotheses---which you still don't. Start at the beginning.

As I see it Ben, "starting at the beginning" means I look for a valid empirical way to "explain" whatever it is I observe. If and only if I can't do that will I typically entertain "exotic" concepts. In this particular case I have shown you evidence that the excess gamma rays we're looking for can be explained by an excess of binary stars in the core, and the shape of that core and gamma ray excess just so happens to align itself pretty well with where we believe such stars are located. Fermi has already confirmed that it can see "stars", including our own, and even annihilation signatures at rate x from planetary discharges. If planets, suns and binary suns can explain what we observe, why do we need an 'exotic' alternative again?

 

[Michael Mozina]

You may have been misinformed about these "laws and theories".

Maxwell's equations, as you may have seen them and been taught them, are in fact a "bodge job" if you will to fit the observation that at THAT time magnetic monopoles were not seen to obviously exist in abundance.

Was Newtonian mechanics a 'bodge job' too once GR became popular?

Hypothetically speaking perhaps (assuming we find monopoles in the future), sure, maybe it's a "bodge job" to lack belief in monopoles. In practical application in the lab however, it's works quite well. In reality it's hardly a "bodge job" to correctly describe and accurately "predict" events in nature. So far those equations correctly describe nature, including the fact that nature does not seem to include any monopoles. I can't spend my life worrying about "what if" scenarios that might invalidate some part of my "empirically oriented belief system", I can only concern myself with the here and now and apply what I know (empirically) here and now to the topic at hand, in this case gamma rays seen in Fermi images.

It just so happens that nature does a wonderful job of emitting gamma rays via discharges on Earth and it produces them in the atmosphere of our own sun. We observe annihilation processes here on our own planet in the Fermi equipment. We observe them from our own sun in the Fermi equipment too. It's therefore not much of a "leap of faith" for me to believe that binary stars emit these same gamma rays in greater quantity due to their unique interactions. Nothing proposed in the explanation I offered you requires the existence of anything new "exotic'. It's a "simple" and elegant solution to explain those gamma rays.

We can take such an understanding now and apply such an understanding to distant galaxies as well and learn something about them from what we've learned from our own galaxy.

If however you (collectively speaking) wish to promote an alternative explanation, should it not be able to compete empirically with another empirical alternative? I mean sooner or later we may have to 'grade' these various proposals and "empirical qualification' has to count for something. When and where is it appropriate to apply Occum's razor if not to this specific scenario? If empirical physics can explain what we observe, why wouldn't it be considered a "superior" theory to one that is based on hypothetical entities a half dozen hypothetical "properties", none of which enjoy empirical support?