Fermi and dark matter

[DeiRenDopa]

No, it's that electrical discharges are already a known and demonstrated source of gamma rays on Earth, and gamma rays around larger bodies in the solar system. What do we need dark energy for?

[...]

Indeed.

But do the numbers add up?

Or is it - once again - a case of "who the **** cares about ****ing numbers! " ?

In short, have you not, for the umpteenth time, demonstrated that the MM worldview is blind to quantitative analyses? Or, to be blunt, that your approach is antithetical to science?

 

[Michael Mozina]

Well it doesn't unify the three non-gravitational forces. It doesn't really explain the neutrino masses. And it does contain quite a few free parameters.

Fair enough. I think most folks figure that will come about via QM sooner or later. How does SUSY theory solve any of those issues?

I'm going to skip the irrelevant stuff if you don't mind.

I personally had no evidence for the existence of the top quark in the early 1990's. What's your point?

My point is that even in the early 1990's there was a 'likelihood' that it would be found. There is no such likelihood as it relates to SUSY theory. I guess I may not understand what specific issue you believe SUSY theory will solve and I probably need to hear that answer before I can continue.

And you think there is no evidence of gamma rays from high-energy particle interactions?

Sure. I don't have any problem with you attributing gamma rays to anything that can be empirically demonstrated.

Where? Either you have a quantitative model to defend or you have nothing. Which is it?

http://www.sciencemag.org/cgi/content/summary/307/5712/1054

If you mean have I personally sat down to explain the Fermi data with electrical discharges and known solar activities, no, I have not done that. I haven't even seen a full solar cycle in Fermi data yet, so how would I know what is "normal" output for our own sun?

 

[Michael Mozina]

Please define "electricity".

Inside a mostly plasma universe is I would describe it as "current flow". Moving ions can contain a charge as well as electrons, and protons.

Even if this were the case, still doesn't explain galactic rotation curves. Oh and I'm expecting to see a full quantitative explanation of the data. SInce you are so sure you're right that must be pretty straightforward.

I'm willing to accept that there is "missing mass" in a galaxy that our current mass estimates cannot account for based on the lensing data I have seen. I therefore prefer a "missing mass" theory over a MOND theory for instance. That does not mean that any of the "missing mass" in located in any form of exotic materials that do not show up in particle physics experiments and/or the periodic table.

What are you talking about? My argument was that your assertion that dark matter didn't exist because it hadn't been seen in a lab was, based on history and common sense, a ridiculous one. This has nothing whatsoever to do with Occam's razor.

I'm saying that there is already a known and demonstrated "natural" way to generate gamma rays. There is no need for DM. It's not going to survive an Occum's razor argument.

 

[Michael Mozina]

Indeed.

But do the numbers add up?

Or is it - once again - a case of "who the f*** cares about f***ing numbers! " ?

In short, have you not, for the umpteenth time, demonstrated that the MM worldview is blind to quantitative analyses? Or, to be blunt, that your approach is antithetical to science?

I guess if I *had* to choose between the two, I'd rather be blind to the quantitative analysis than to be blind to the qualitative analysis like you.

How exactly would you suggest that we go about computing a number of photons counts to expect from a sun and from the planets when we haven't a full solar cycle to work with?

http://www.space.com/scienceastronomy/080515-galactic-dust.html
http://cmarchesin.blogspot.com/2009/08/galaxies-demand-stellar-recount.html

Have these more recent discoveries even been factored into current galaxy estimates in terms of the number of stars there are in a given galaxy, including our own? How many gamma ray emitting planets shall we assume for every star in your opinion?

I know how much you love to simply ignore the qualification side of empirical physics and all that matter to you is the math, but don't you get tired of just pulling these numbers out of thin air and then seeing them be demonstrated to be wrong over and over again?

From a 'qualitative" side of science, you haven't a leg to stand on and your math is just fancy window dressing. It's still just mathematical lipstick on a metaphysical pig.

 

[Tubbythin]

Fair enough. I think most folks figure that will come about via QM sooner or later.

Such as supersymmetry.

How does SUSY theory solve any of those issues?

It allows the coupling constants of the three forces to meet at a single distance/energy scale which would allow for a "natural" GUT. I guess this would also lead to less free parameters although I'm a little rusty here.

My point is that even in the early 1990's there was a 'likelihood' that it would be found. There is no such likelihood as it relates to SUSY theory.

Best tell all those people at CERN who are wasting there time then. They certainly seem to believe its a distinct possibility.

I guess I may not understand what specific issue you believe SUSY theory will solve and I probably need to hear that answer before I can continue.

Google it. I'm sure you can find better sources than me.

Sure. I don't have any problem with you attributing gamma rays to anything that can be empirically demonstrated.

But a number of these things were empirically demonstrated from measuring the gamma-rays in the first place! If you rule out the empirical evidence that something exists based on the fact that its never been shown to exist before then you're never going to discover anything new at all.

http://www.sciencemag.org/cgi/content/summary/307/5712/1054

I can't read the paper. But based on the abstract, the phenomena described are too low in energy by a factor of at least 50 compared to the data in the FGST paper. So I'm not sure what the relevance is.

If you mean have I personally sat down to explain the Fermi data with electrical discharges and known solar activities, no, I have not done that. I haven't even seen a full solar cycle in Fermi data yet, so how would I know what is "normal" output for our own sun?

I'm not sure why you need a full solar cycle.

 

[Tubbythin]

Inside a mostly plasma universe is I would describe it as "current flow". Moving ions can contain a charge as well as electrons, and protons.

So what did you mean by

If we need more of them, all we have to do is turn up the "electricity" and a known source of gamma rays in nature will produce more gamma rays.

?

I'm willing to accept that there is "missing mass" in a galaxy that our current mass estimates cannot account for based on the lensing data I have seen. I therefore prefer a "missing mass" theory over a MOND theory for instance. That does not mean that any of the "missing mass" in located in any form of exotic materials that do not show up in particle physics experiments and/or the periodic table.

Actually it does, precisely because of the successes of the Standard Model. It cannot be explained by anything that interacts electromagnetically. That leaves neutrinos. But neutrinos are too light.

I'm saying that there is already a known and demonstrated "natural" way to generate gamma rays. There is no need for DM. It's not going to survive an Occum's razor argument.

a) This was not my argument (not at the time anyway).
b) There is from the galactic distribution curves etcetera.
We have no simple explanation of the source of the gamma rays. You are unable to provide a quantitative explanation. And neither has anybody else.
Therefore dark mater is a possibility. But even if its something more mundane there's still those galactic rotation curves, those cluster rotation curves and various other things supporting the existence of DM.

 

[DeiRenDopa]

I guess if I *had* to choose between the two, I'd rather be blind to the quantitative analysis than to be blind to the qualitative analysis like you.

How exactly would you suggest that we go about computing a number of photons counts to expect from a sun and from the planets when we haven't a full solar cycle to work with?

http://www.space.com/scienceastronomy/080515-galactic-dust.html
http://cmarchesin.blogspot.com/2009/08/galaxies-demand-stellar-recount.html

Have these more recent discoveries even been factored into current galaxy estimates in terms of the number of stars there are in a given galaxy, including our own? How many gamma ray emitting planets shall we assume for every star in your opinion?

I know how much you love to simply ignore the qualification side of empirical physics and all that matter to you is the math, but don't you get tired of just pulling these numbers out of thin air and then seeing them be demonstrated to be wrong over and over again?

From a 'qualitative" side of science, you haven't a leg to stand on and your math is just fancy window dressing. It's still just mathematical lipstick on a metaphysical pig.

So tell me, MM, what was the proper - i.e. kosher according to the MM worldview of science - thing to have done wrt the original dark matter (i.e. Neptune)?

And would you have railed vociferously against all those who sought to test GR (the solution to the second lot of solar system dark matter, a.k.a. the anomalous advance of the perihelion of Mercury), because it had not been demonstrated in any earthly labs?

Wrt your quantitative questions: pick a number (or ten), MM, as long as it is consistent with all relevant observations, turn the handle, and produce for us an upper estimate of the gamma ray SED you'd expect Fermi to observe, from all the kings horses (the MW stars) and all the kings men (the MW planets).

And when you've done that, compare it to what Fermi has actually observed, write up your work, and submit the paper to ApJ (or similar).

Wait! You don't even need to do that ... the back of an old envelope would do, wouldn't it?

 

[Reality Check]

And since ordinary suns release these same exact gamma rays on a regular basis you have absolutely nothing to support your claim.

Stars do emit a small amount of gamma rays.
I do not make the claim that there is a Fermi haze. The paper does.
You make the claim that this invalidates the paper. Now give your evidence that it does.

So what? Based on what evidence? Point at the sky claims?

Based on actually reading their paper.

The fact that these authors make exactly the same mistake you're making doesn't justify the error.

What error? Citation please. Or a fully worked example of the gamma sources that they missed.
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.

So suns are a perfectly "natural" source for such emissions and we have no need for anything exotic.

They are not a perfectly "natural" source for such emissions until you give evidence for that they are.

Uh, yes, but what does that have to do with anything? You asked for evidence that Fermi could see a sun. I provided that evidence. Gamma rays are definitely coming from our sun and likely all suns in the galaxy. It's hardly a surprise then when we can observe the galaxy in gamma rays in a Fermi image.

I asked for evidence that the Ferrm data sees gamma radiation from stars - a plural.


It is clear that stars emit gamma rays. We detect them from the Sun. The questions is:

• Is the amount of gamma rays emitted by the stars in the galaxy large enough to be detected by Fermi?

My guess is no.

• If it was then the NASA movie would show the stars moving, especially the nearer stars.
• People who know about this stuff (unlike you and me, MM!), take account of strongly emitting objects like X-ray binaries, pulsars, etc.
  They then confirm that there is no contribution from other point sources to the spectrum of the Fermi haze .

Point sources in the paper :

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.

Appendex A is all about the effects of unresolved point sources! This includes normal stars (AFAIK).
It concludes

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.

 

[Beerina]

I don't know if anyone's mentioned this, yet, but the galaxy's star rotation indicates the existence of matter well in excess of that of adding up the mass of the stars.

Galaxies look like a bunch of stars swirling down a drain. In this case, the supposition is they're all in orbit, more or less, about the center of the galaxy, which has the vast bulk of mass, and thus gravity.

Except that when scientists measured how fast stars were going around the center of the galaxy, it was much closer to a solid disc rotating than a bunch of swirling stars.

The only way that can happen is if there's a lot more mass way outside the core of the galaxy so there's a counterpull of gravity that counteracts a lot of the swirliness. There isn't that much swirliness if you're being pulled from both sides almost equally.

Now stars are huge, and a hundred billion are a massive amount of mass, but it's no way near enough to account for that observed behavior.

SO, there must be a lot more mass, i.e. matter somewhere, but we can't see it, so "dark matter" it is. The rest so far is trying to derive characteristics of it -- doesn't interact with observable frequencies, etc.

Any ideas? Have fun! But it's not just pulled out of their ass. And other theories besides matter are being considered, I'm sure, from measurement errors to new forces that act on massive scales and so on.

 

[Michael Mozina]

I don't know if anyone's mentioned this, yet, but the galaxy's star rotation indicates the existence of matter well in excess of that of adding up the mass of the stars.

Galaxies look like a bunch of stars swirling down a drain. In this case, the supposition is they're all in orbit, more or less, about the center of the galaxy, which has the vast bulk of mass, and thus gravity.

Except that when scientists measured how fast stars were going around the center of the galaxy, it was much closer to a solid disc rotating than a bunch of swirling stars.

The only way that can happen is if there's a lot more mass way outside the core of the galaxy so there's a counterpull of gravity that counteracts a lot of the swirliness. There isn't that much swirliness if you're being pulled from both sides almost equally.

Now stars are huge, and a hundred billion are a massive amount of mass, but it's no way near enough to account for that observed behavior.

SO, there must be a lot more mass, i.e. matter somewhere, but we can't see it, so "dark matter" it is. The rest so far is trying to derive characteristics of it -- doesn't interact with observable frequencies, etc.

Any ideas? Have fun! But it's not just pulled out of their ass. And other theories besides matter are being considered, I'm sure, from measurement errors to new forces that act on massive scales and so on.

As I have explained in the past, due to the lensing data I've seen, the concept of "unidentified mass" or 'missing mass' is more appealing to me than say MOND theory.

IMO that simply demonstrates we grossly underestimate the amount of mass in a galaxy. Those links I cited for DRD demonstrate the recent discoveries suggest we have grossly underestimated the amount of dust in the universe as well as the number of smaller stars in a galaxy. Have these more recent discoveries even had a chance to be factored into our galaxy mass estimates?

The term "dark matter' as I was taught it in school was mostly though to be standard matter our technologies could not yet identify, more along the lines of MACHO orientation of 'dark matter". Today's new and improved brand is being created in an "ad hoc" manner and being assigned various "properties" that have never been demonstrated. The term "dark matter" has changed from being associated with standard material, to being mostly associated with hypothetical SUSY theory with hypothetical and metaphysical properties galore.

When we look at the Fermi images, the material doesn't seem to be concentrated in any one place around the galaxy, instead the entire galaxy seems to glow as though every star and every planet is emitting these wavelengths. That's confirmed too by the fact we can observe the sun traversing the Fermi data set quite clearly. It should hardly be surprising then that we see gamma rays from stars in a galaxy and even planets are known to emit gamma rays inside our own solar system.

There's absolutely no need for 'dark matter' to explain 'gamma rays' from a galaxy. There's no empirical link established between 'dark matter" and "gamma rays". The whole thing is "assumed", the material itself, the gamma link, the areas of concentration of DM (which don't even jive with observation), all of it. DM theory is not a "simpler" explanation for gamma rays than suns and planets. It's not supported by any observation in a controlled experiment. There is not one single instance of "dark matter" emitting gamma rays inside out solar system, so what in the world would lead me to believe it occurs "out there somewhere else"?

I'm afraid the DM source of gamma ray theory doesn't survive the first Occum's razor argument. In fact it falls apart over the simplicity factor alone. It lacks empirical support of any kind, and it's not even viable compared to the simpler and *demonstrated* sources of gamma rays.

 

[Tubbythin]

As I have explained in the past, due to the lensing data I've seen, the concept of "unidentified mass" or 'missing mass' is more appealing to me than say MOND theory.

IMO that simply demonstrates we grossly underestimate the amount of mass in a galaxy.

The lensing data explicitly removes the possibility that the missing mass (or rather excess mass) is in the the form of massive objects.

Those links I cited for DRD demonstrate the recent discoveries suggest we have grossly underestimated the amount of dust in the universe as well as the number of smaller stars in a galaxy. Have these more recent discoveries even had a chance to be factored into our galaxy mass estimates?

Can you show they're even in the right ballpark to make a significant difference?

The term "dark matter' as I was taught it in school was mostly though to be standard matter our technologies could not yet identify, more along the lines of MACHO orientation of 'dark matter".

Which has now been ruled out by the lensing data. Hence the transition to WIMP type objects.

Today's new and improved brand is being created in an "ad hoc" manner and being assigned various "properties" that have never been demonstrated.

Not in the slightest. For example the MSSM assigns properties (or rather a range of possibilities for the properties (mass etc)) to particles based on what we already know from the Standard Model and experiment with the added assumption of supersymmetry - something we have independent reasons for believing in. This is anything but ad hoc. In fact the properties of SUSY particles would be the same whether we'd observed DM or not.

The term "dark matter" has changed from being associated with standard material, to being mostly associated with hypothetical SUSY theory with hypothetical and metaphysical properties galore.

They don't really have any hypothetical features not observed in other particles. At least none that I can think of. And I dunno where you get the idea they are "metaphysical" properties from.

When we look at the Fermi images, the material doesn't seem to be concentrated in any one place around the galaxy, instead the entire galaxy seems to glow as though every star and every planet is emitting these wavelengths. That's confirmed too by the fact we can observe the sun traversing the Fermi data set quite clearly. It should hardly be surprising then that we see gamma rays from stars in a galaxy and even planets are known to emit gamma rays inside our own solar system.

I don't see your point.

There's absolutely no need for 'dark matter' to explain 'gamma rays' from a galaxy. There's no empirical link established between 'dark matter" and "gamma rays".

The give us a quantitative alternative.

The whole thing is "assumed", the material itself, the gamma link, the areas of concentration of DM (which don't even jive with observation), all of it.

Wrong. See above.

DM theory is not a "simpler" explanation for gamma rays than suns and planets. It's not supported by any observation in a controlled experiment.

Define "controlled experiment".

There is not one single instance of "dark matter" emitting gamma rays inside out solar system, so what in the world would lead me to believe it occurs "out there somewhere else"?

There's not a single instance of a supernova event inside our solar sytem, so what in the world would lead me to believe it occurs "out there somewhere else"?

I'm afraid the DM source of gamma ray theory doesn't survive the first Occum's razor argument. In fact it falls apart over the simplicity factor alone. It lacks empirical support of any kind, and it's not even viable compared to the simpler and *demonstrated* sources of gamma rays.

You really don't get the idea of quantitative[\B] analysis do you?

 

[Michael Mozina]

So tell me, MM, what was the proper - i.e. kosher according to the MM worldview of science - thing to have done wrt the original dark matter (i.e. Neptune)?

You mean "unidentified mass"? When did anyone claim that this particular missing mass was able to pass through walls in a single bound? Emit gamma rays on a whim? When did anyone claim it could puke out positrons anywhere and everywhere? I'm afraid you only serve to demonstrate the obvious here. There's a lot we cannot observe directly and there is every reason to believe that we grossly blew the mass estimates as it relates to the "normal" amount of material in a galaxy. There is at least twice the "dust" we expected to find and four times as many small stars in a galaxy than we realized. You haven't even had time to factor in these changes to our understanding of a makeup of a galaxy, but you still expect me to believe you have everything so figured out that you can estimate the amount of exotic new material in distant galaxy. Come on. Your story isn't even believable. Like Neptune, I'm sure your "missing mass" is made of ordinary matter and baryonic materials.

And would you have railed vociferously against all those who sought to test GR (the solution to the second lot of solar system dark matter, a.k.a. the anomalous advance of the perihelion of Mercury), because it had not been demonstrated in any earthly labs?

No because "gravity" shows up on Earth and does its thing right here on Earth. I'm sure that gravity exists "out there" in space too. Compare and contrast that with hypothetical brands of SUSY particles with hypothetical properties galore that are entirely based on faith, starting with the claim of "longevity".

Have the "professionals" in your industry even revised their mass estimates of normal material in a galaxy based on these new findings? Yes or no? If so, which paper would you cite for us? Has the Fermi team cited these new numbers in any single paper to date?

 

[Michael Mozina]

The lensing data explicitly removes the possibility that the missing mass (or rather excess mass) is in the the form of massive objects.

How do you figure that? It certainly doesn't remove the possibility that ISM and IGM is "dustier" than we thought.

http://www.space.com/scienceastronomy/080515-galactic-dust.html

If it's "twice as bright" as we realized, why wouldn't that equate to a doubling of the number of stars and solar systems in a galaxy?

Even more damaging IMO:
http://cmarchesin.blogspot.com/2009/08/galaxies-demand-stellar-recount.html

Given these facts, how can you expect me to believe that we already know how much ordinary matter exists in a distant galaxy?

 

[Tubbythin]

How do you figure that?

The weak gravitational lensing data shows that the mass cannot be largely in the form of large objects.

It certainly doesn't remove the possibility that ISM and IGM is "dustier" than we thought.

http://www.space.com/scienceastronomy/080515-galactic-dust.html

If it's "twice as bright" as we realized, why wouldn't that equate to a doubling of the number of stars and solar systems in a galaxy?

Even more damaging IMO:
http://cmarchesin.blogspot.com/2009/08/galaxies-demand-stellar-recount.html

Given these facts, how can you expect me to believe that we already know how much ordinary matter exists in a distant galaxy?

You do know we not only know how much dark matter there is but what shape it takes right?

 

[DeiRenDopa]

[...]

There's a lot we cannot observe directly and there is every reason to believe that we grossly blew the mass estimates as it relates to the "normal" amount of material in a galaxy. There is at least twice the "dust" we expected to find and four times as many small stars in a galaxy than we realized.

Evidence?

Start with our own, the MW galaxy, and then either of the Magellanic Clouds, followed by any other MW satellite galaxy, followed by M31 and/or M33.

[...]

Like Neptune, I'm sure your "missing mass" is made of ordinary matter and baryonic materials.

I have no doubt whatsoever that you are, indeed, sure of this.

However, it has never been the case that the answer to a scientific question like this can be answered by asking MM what he is sure about ...

Perhaps you can put fingers to keyboard, and write a paper actually demonstrating this? And backing it up with quantitative analyses, unbiased sets of references, etc?

If you can't, what do you have, other than a personal, subjective opinion?

And would you have railed vociferously against all those who sought to test GR (the solution to the second lot of solar system dark matter, a.k.a. the anomalous advance of the perihelion of Mercury), because it had not been demonstrated in any earthly labs?

No because "gravity" shows up on Earth and does its thing right here on Earth.

Are you so grotesquely ignorant of the relevant history?

The original "dark matter" (Neptune) worked out just fine, in terms of the then prevailing theory of gravity (Newton's).

Starting around the middle of the 19th century, just the same sort of solution was sought to some new "dark matter" (i.e. the anomalous advance of the perihelion of Mercury) ... and it was even given a name (Vulcan).

Einstein's new theory of gravity did away with the need for a "dark matter" solution, but at the expense of a "dark energy" one (i.e. a theory which could not - then - be empirically tested in any lab on Earth).

An MM clone at the time (1918, say) would have railed most vociferously against this "dark energy" (i.e. an unsubstantiated theory of gravity), and insisted that astronomers lift their game in terms of searching for Vulcan.

And it was not until some four decades later - well after many of the leading astronomers of the day were dead, or had ceased any astronomical research - that GR was tested in a lab here on Earth.

Had MM been the ultimate authority on physics, at the time, no one would even have tried to test GR!

I'm sure that gravity exists "out there" in space too.

Indeed.

The only thing - wrt gravity - that you're not sure about is whether a cosmological constant is required to adequately describe it ...

... well, you also are not sure of the validity of gravitational lensing, of the ISW, of the nature of the EFE, of ...

Compare and contrast that with hypothetical brands of SUSY particles with hypothetical properties galore that are entirely based on faith, starting with the claim of "longevity".

Just like the hypothetical Neptune (as it subsequently became known) and Vulcan (which remains entirely hypothetical)?

Oh, and the "faith" basis is the same as the "faith" basis for GR, the Standard Model (of particle physics), ...

Have the "professionals" in your industry even revised their mass estimates of normal material in a galaxy based on these new findings?

I was not aware that any of these "new findings" referred to our own galaxy (the Milky Way) - can you point me to where, exactly, this reference is to be found?

Yes or no? If so, which paper would you cite for us? Has the Fermi team cited these new numbers in any single paper to date?

Why should they need to, if they have no relevance?

 

[Reality Check]

The term "dark matter' as I was taught it in school was mostly though to be standard matter our technologies could not yet identify, more along the lines of MACHO orientation of 'dark matter". Today's new and improved brand is being created in an "ad hoc" manner and being assigned various "properties" that have never been demonstrated. The term "dark matter" has changed from being associated with standard material, to being mostly associated with hypothetical SUSY theory with hypothetical and metaphysical properties galore.

I think I see your problem - you are stuck with the science that was taught to you in school many years ago. You have forgotten to learn, especially about the new discoveries that changed this original concept for dark matter.

Dark matter was considered to be "missing matter" from 1933 when Zwicky found that there as not enough matter measured in galactic clusters to explain the orbital motion of galaxies. This is the concept that was taught in schools for the next 40 years.

Then in 1975, came Rubin's observation that the velocity dispersions of galaxies also needed dark matter. This could also be "missing matter" but 40 years of improving observational techniques made this doubtful. Further advances in observation techniques since then finally broke the association of dark matter with "missing matter". The biggest observational straw was that fact that the leading candidate for this (MACHO's) have been detected but not at a level high enough to explain dark matter.

The real observations that showed that dark matter could not be normal matter (i.e. "missing matter") are the colliding galactic clusters of Bullet Cluster and MACS J0025.4-1222 (and even Abell 520).
Here is the situation in the observations in a simplified form:

1. A is a big blob of gas.
2. B is a bib blob of gas.
3. Blob A hits blob A.
   • If the gas is all the same stuff then the result will be another blob of gas.
     It is probable that some of the gas will not not collide. In that case there will be blobs of gas to each side. The size of these outlying blobs will reflect the amount of gas that did not collide.
   • If the gas is a mixture of two kinds of gas , one of which interacts weakly with the other, then the result will be 3 blobs since the weakly interacting gas passes through the other gas.
     The size of these outlying blobs will reflect the amount of gas that did not collide plus the amount of weakly interacting gas.
4. We see 3 blobs.
   The outlying blobs contain most of the matter.
5. Thus the gas is made of two kinds of gas, one of which interacts weakly with the other.

You may want to read Starts With a Bang's clear description of Dark Matter in his blog entries.

• Dark Matter Part I: How Much Matter is There?
• Dark Matter Part II: How much Normal Matter is there?
• Dark Matter Part III: Dark Matter or Modified Gravity?
• Dark Matter Part 3.5: When Clusters Collide!
• Dear MOND: Time for a New Song! (Dark Matter pt. IV)

He also mentions the fact that astronomers measure the mass distribution of galactic clusters and see that the majority of matter is not visible. Have a look at The Camera that Changed the Universe: Part 4

What can you learn from this? Well, other than all sorts of things about the lensed galaxies, you can learn about dark matter! You see, gravitational lensing only cares about mass, and so we can figure out where -- in a cluster like this -- the mass is distributed. The results are breathtaking.

What this shows you is that yes, there are spikes where the individual galaxies are. But the cluster is dominated by this giant spherically-distributed mass that's present everywhere, both where there are galaxies and where there aren't. And that has got to be dark matter.

 

[sol invictus]

There's a very close analogy to the topic of this thread, one that demonstrates the absurdity of MM's position (and the danger it would pose to progress were anyone else to subscribe to it). The analogy is the solar neutrino problem.

Must as Fermi (and other experiments) have detected an unexplained excess of positrons and photons produced by electron-positron annihilation, neutrino detectors starting in the 60's found a strange deficit in the flux of solar neutrinos (specifically, they detected about 1/2 the number expected based on the standard solar model).

Then as now, there were a few possibilities:

1) the experimental results were wrong

2) the standard solar model was wrong, and once that mistake was corrected the measured flux would agree with theory

3) something really new was responsible

Possibility 1) was largely eliminated by more experiments (which found consistent results). Possibility 2) was looked at very closely over many years, but no one could find a problem in the solar model that explained the deficit.

At the same time theorists proposed a far more radical idea fitting into 3): that neutrinos have mass, and moreover that their mass eigenstates do not line up with their flavor eigenstates, which means one type of neutrino can spontaneously turn into another type (thereby avoiding detection in some types of detectors and reducing the measured flux).

Of course that radical theory is now know for certain to be correct. In this case the final confirmation was provided by "lab" experiments (you produce neutrinos at a nuclear reactor, beam them a long distance at an angle that takes them through the crust of the earth, detect them far away when they emerge, and note that some have oscillated into others). If these theories of dark matter being responsible for the excess gamma rays and positrons are correct, it's possible that they will eventually be established in accelerators. But that possibility is irrelevant to whether or not the theories are correct now - they either are or are not, whether or not we can tell. MM's insane criteria - which is that we should not look for anything that hasn't already been found - would preclude any such search, and so we would never know. In the case of solar neutrinos, since there was no evidence (apart from the observed deficit) that neutrinos had mass, MM's criterion would have prevented any experiment from being built to test it, or for that matter any theorists to come up with the idea in the first place. All of that is literally antithetical to science.

I think a good term for the position MM advocates: "antiscience".

 

[Tubbythin]

There's a very close analogy to the topic of this thread, one that demonstrates the absurdity of MM's position (and the danger it would pose to progress were anyone else to subscribe to it). The analogy is the solar neutrino problem.

Sadly the analogy doesn't work on anyone "sceptical" of neutrino oscillations.

 

[sol invictus]

Sadly the analogy doesn't work on anyone "sceptical" of neutrino oscillations.

Neutrino oscillations have been confirmed in lab experiments.

But anyway, I'm not trying to convince MM - that's useless. I'm assuming other people might read this thread, and neutrino oscillations are a very good example of the kind of fundamental particle physics that can be learned from astrophysical observations. The correction to the standard model of particle physics that resulted from that was the first one in something like 30 years.

 

[DeiRenDopa]

[...]

http://www.space.com/scienceastronomy/080515-galactic-dust.html
http://cmarchesin.blogspot.com/2009/08/galaxies-demand-stellar-recount.html

Have these more recent discoveries even been factored into current galaxy estimates in terms of the number of stars there are in a given galaxy, including our own? How many gamma ray emitting planets shall we assume for every star in your opinion?

[...]

Can you please confirm that The energy output of the Universe from 0.1 micron to 1000 micron and Evidence for a Non-Uniform Initial Mass Function in the Local Universe are the papers you are referring to?