Fermi and dark matter

[Michael Mozina]

When two objects collide inelastically, they convert bulk kinetic energy into heat. The more bulk kinetic energy, the higher the final temperature. Galaxy clusters are very massive, so infalling gas is coming in very fast, hence has a lot of kinetic energy, hence a high temperature.

So, if I understand you correctly, this is kinetic energy that is being transferred to ICM particles due to collisions from incoming fast moving charged particles? Why is it that the mainstream refuses to call "current flow", "current flow"? How dense is this "incoming" particle stream anyway?

If there is all this kinetic energy due to incoming particles why doesn't this inflow heat the interplanetary plasma to these temperatures?

I can see that I will definitely need to compare these "collision equations" with some scrutiny.

One also has to ask how efficiently a high-temperature gas can cool down or escape, as this should also affect the observed temperature.

Well, it seems to me that every ion is capable of emitting photons. Unless there is a continuous collision process from incoming particles the whole thing would tend to "cool off' rather rapidly. I wouldn't expect it to keep that heat for billions of years.

This tells you that more massive clusters (=more kinetic energy) should be hotter than less massive clusters. It does not tell you whether clusters should be hotter than the ISM, or hotter than the solar wind, or hotter than the fluorescent light bulbs in my office, or hotter than ITER, because there are different energy sources (and different cooling mechanisms) in these different places.

Essentially any moving charged particle is a form of "current flow". What you're doing is taking a moving charged particle (current flow) and slamming it into another relatively stationary (charged) particle and creating "resistance" to that incoming "current flow". I really love how astronomers create all these clever euphemisms to avoid using the term "current flow" and "resistance".

 

[Reality Check]

Can Micheal Mozina answer a simple question about intercluster medium?

 

[Reality Check]

Could you point me to the page and paper where that number was calculated?

Intracluster medium does not have a citation. If you knew how to follow links then you would have read mean free path section on kinetic theory which is also covered in physics textbooks.
Hyperphysics has a neat mean free path calclator.

 

[Michael Mozina]

Intracluster medium does not have a citation

Um, RC, you can't keep pulling numbers out of thin air (99% ionization, 3M collisions) and expect me to simply agree with you. Where did you get that number and who did the calculation? What densities were used in terms of the ICM and/or the incoming particle stream? Was the number "realistic" in terms of the actual conditions of space, or was it one of those "gross oversimplifications" that assume a constant density of material and stuff like that?

Your 'mean free path' formulas seem to be apply primarily to molecules and non ionized matter. In high speed plasma physics they tend to use the term "attenuation" typically in reference to the length the particle beam can travel before being significantly degraded by the plasma medium (something like 2/3rd of the beam has been absorbed by the plasma).

http://en.wikipedia.org/wiki/Attenuation_length

 

[Michael Mozina]

Can Micheal Mozina answer a simple question about intercluster medium?

Yes, but evidently you don't like the answers. Number 1 - whatever are all "gross oversimplifications". A) is not a "blob of gas". A) is full of a "lot of stuff" that probably includes MACHO forms of matter as well as "ions" (not neutral gas). From there it goes down hill in a hurry. You absolutely refuse to embrace the fact that your "blob" is not simply a "blob of gas", but rather it is composed of a "bunch of stuff including ions". That seems to be where you're stuck.

 

[DazzaD]

From the horses mouth (or at least his mate):

http://www.symmetrymagazine.org/breaking/2009/11/05/dark-matter-at-the-fermi-symposium/

"To determine if there is an excess of gamma rays, you first need to define what is normal. Scientists can use models to approximate the number of gamma rays we should see coming from individual point sources in the galaxy and the rest of the universe, and add them all up. When researchers subtracted that total from the EGRET data, they found that there were more gamma rays than they had accounted for. That immediately suggests that either an as-yet-unidentified source, possibly dark matter, is emitting gamma rays, or more likely that the model needs to be refined in any number of ways. Any claim of an excess relies heavily on the strength of the model, which relies on an ever-growing understanding of astrophysics and a growing library of observations."

I have emboldened the bit I think is important in this thread.

 

[Dancing David]

That comment wouldn't sound so utterly ironic were it not for the fact that
"modern" astronomers cannot explain something as simple as sustained high energy coronal loops, solar jets, and high speed solar wind, something that was "explained" and "predicted" by Birkeland over 100 years ago.



Ya, astronomers know it so well in fact that they still practice a form of what Alfven himself called "pseudoscience". More importantly they can't/won't (refuse to) recognize a "discharge' in solar plasma when they see one. No wonder they "failed" so miserably to explain the universe with electricity and gravity. They keep calling an electrical discharge process a "magnetic reconnection" process and treat the whole thing as a "neutral" plasma.



Indeed. It is 100% ad hoc wiggle room in fact and only the most recent installment of metaphysics into BB theory. Without it, gravity theory (without electricity) is indeed a miserable failure at describing the universe. Dark matter and dark energy are essentially fudge factors of epic proportions and with inflation providing the last of the metaphysical 'wiggle room' anyone will ever need to explain anything. Need gravity to do repulsive tricks? No problem. Need "space" (physically undefined no less) to "expand" somewhere out there we we can never reach, but have no effect here on Earth? No problem! Need to account for faster than light expansion from a single lump? No problem. Need an "accelerating' universe when you first 'predicted' a decelerating one? No problem. That "new and improved" BB theory has all the fine wiggle room a mathematician could ever ask for.

Lambda-CMD theory today is 96% "wiggle room" and only 4% actual physics. Is it any wonder that the numbers can be fudged to fit anything and everything? The last time it didn't "fit right" BB theory was stuffed with 70%+ more metaphysics, and that was just in the last 12 years or so. Holy cow, if we never have to physically demonstrate anything, "magic energy", "magic matter", and "magic inflation" do exactly the same "excellent job" of describing the universe. [qimg]http://www.internationalskeptics.com/forums/images/smilies/mazeguyemotions/jaw-dropping.gif[/qimg]

Off topic, please stop.

 

[Michael Mozina]

From the horses mouth (or at least his mate):

http://www.symmetrymagazine.org/breaking/2009/11/05/dark-matter-at-the-fermi-symposium/

"To determine if there is an excess of gamma rays, you first need to define what is normal. Scientists can use models to approximate the number of gamma rays we should see coming from individual point sources in the galaxy and the rest of the universe, and add them all up. When researchers subtracted that total from the EGRET data, they found that there were more gamma rays than they had accounted for. That immediately suggests that either an as-yet-unidentified source, possibly dark matter, is emitting gamma rays, or more likely that the model needs to be refined in any number of ways. Any claim of an excess relies heavily on the strength of the model, which relies on an ever-growing understanding of astrophysics and a growing library of observations."

I have emboldened the bit I think is important in this thread.

Thank you for the link and for highlighting some of the key points of the article.

I think this point was also worth commenting on:

A prime motivator for building the Fermi Gamma-ray Space Telescope was to search for signals of dark matter.

It seems to me that the "pressure is on" now to justify the Fermi program, and it's expectations of "success" are predicated on some rather interesting "assumptions" at the start of the program. It seems to me that there is now a need to justify this program and evidently the program was intended by design to find evidence of 'dark matter'. That makes me extremely nervous.

What if DM isn't in any way responsible for these gamma ray emissions? If we can't explain some seeming overabundance of gamma rays, is that automatically evidence that 'dark matter did it'? It seems to me that the "assumption" of the Fermi team was based upon a premise that has never been empirically demonstrated or justified.

It's also quite interesting that their results don't seem to jive with previous observations. Does that mean that their model is different/better, or there is an important difference between the two types of gamma ray detectors, or both?

 

[Tubbythin]

That's too bad IMO. IMO that is one of the more important books ever written on astronomy, Birkeland's work being *the* most important IMO.

Keep in mind that what Birkeland, Bruce and Alfven attributed to "electrical discharges" in plasmas, the mainstream now calls "magnetic reconnection". Alfven personally rejected that term as pseudoscience, but what does he know, he just wrote MHD theory. Only grudgingly has the mainstream "accepted" the parts of EU theory they could not live without, like Birkeland's aurora "predictions".

You're just arguing over semantics and opinions.

Note that all of Birkeland's "predictions" were actually, real and true predictions that were derived from empirical experimentation. He actually learned things from his experiments and wrote about them. His theories all worked in the lab too.

Some of them don't, however, work on a large scale.

You have some odd ideas about what EU theory is by the way. I've never even heard of that one before. Most EU proponents use the term "electromagnetic field", and yes most of us believe that current flows "could have an influence" on the galactic rotation pattern. I don't think anyone claims that gravity isn't also important or relevant in the process.

The fact that anyone could claim that EM fields could have any impact on galactic rotation curves when the maths trivially shows this not to be the case is baffling.

FYI, one could call MOND theory "ridiculous" simply for claiming that GR theory was invalid. It's all a very subjective call.

Its not subjective at all. Its all about there is evidence for and against.

I think it would be better to stay on topic in this thread and keep this on focused

Fine.

Unfortunately for the mainstream they rejected parts of Birkeland's theories that were also "right", like those solar atmospheric discharges they keep calling "magnetic reconnection". They seem to ignore the fact that he actually "predicted" those jets and solar wind particles that the mainstream still struggles with.

Except the only real objection you've ever had with magnetic reconnection has been a semantic one.

Did you ever check out any of Peratt's work by any chance? He attempted to create a computer model to mimic the behaviors of plasmas on a large scale and succeeded in creating many of the same galaxy type structures we observe in space. Pure coincidence in your opinion?

Pretty much. The gaps in the spiral arms contained no matter, unlike rwal galaxies and, IIRC, he didn't include gravity!

Now I personally have reason to believe that a "missing mass" alternative is probably more viable than this simply being a result of an EM influence. The lensing data does convince me that a "missing mass" theory is preferable over a MOND theory or even an EU oriented option theory per se. That does not mean I believe that any of the missing matter is contained in exotic SUSY particles.

I don't think anyone has said it has to be SUSY particles.

I'm actually complaining about the fact that astronomers 'created' the parameters in an ad hoc manner, they did not use a known parameter or a know force of nature. That's been done now on at least three occasions in just the last 35 years or so. First we got inflation, then exotic forms of dark matter, and the most recent addition now makes up 70%+ of the whole universe no less! Your parameters are a little "too free" for my liking.

By all means come up with a better, quantitative, explanation for the accelerating expansion of the Universe, the flatness and horizon problems and the galactic/cluster rotation curves.

With or without, inflation, dark energy and dark matter?

Yes, with or without.

I can't technically build a completely working star in a lab, no, but then I'm not asking you to do that either. I can empirically demonstrate that neutrons exist in nature and that gravity has an effect on them.

There's a large difference between neutrons exist and neutron degenerate matter exists!

That's a lot more than you can do with "dark matter".

Not really. I can empirically demonstrate that dark matter exists.

It's "stunning" to me that you find it "stunning" that a constantly modified and postdicted theory, filled with metaphysical fudge factors galore, actually matches observation with some precision.

The CMBR was predicted in the 1940's. It was measured in the 1960's.

Nope. Neither can you without fudge factors galore starting with inflation.

Incorrect. The CMBR intensity spectrum has no dependency on inflation.

The really incredible thing to me about modern Lambda theories is the fact that they all rely upon inflation and you all accept the notion that inflation doesn't exist anymore, just "once upon a time".

No, they don't

That makes this theory about as close to a deistic religion as one could possibly make it IMO.

This is just bizarre. There are lots of things who's existence depends on the density and temperature of the environment. To suggest they can't possibly have ever existed because the density and temperature is wrong now is just plain ridiculous.

 

[Reality Check]

Yes, but evidently you don't like the answers. Number 1 - whatever are all "gross oversimplifications". A) is not a "blob of gas". A) is full of a "lot of stuff" that probably includes MACHO forms of matter as well as "ions" (not neutral gas). From there it goes down hill in a hurry. You absolutely refuse to embrace the fact that your "blob" is not simply a "blob of gas", but rather it is composed of a "bunch of stuff including ions". That seems to be where you're stuck.

Are you kidding ?

I have been linking to the Wikipedia article that states that the ICM is a bunch of stuff - mostly ions.
I know that the ICM is mostly ions.
I know that the ICM is not simply a blob of gas (it is a plasma).

This does not make any difference to the behaviour of the blobs of ICM. The mean free path of the ICM applies to all of its particle (charged or not).
That is where you are stuck.

Can you answer the question or are you going to continue to avoid it?
Any problems with this analysis with what is going on with the majority of the matter (i.e. ICM) in the Bullet Cluster and MACS J0025.4-1222 (and even Abell 520)?

P.S. Massive compact halo object.

 

[Tubbythin]

http://www.astronomy.com/asy/default.aspx?c=a&id=4245

As Tubbythin pointed out earlier, it can be very difficult even determining how much 'normal matter' is contained in our own galaxy. It's therefore not the least bit surprising to me that we have a difficult time accounting for all the mass in a distant galaxy.

Hmm. Which post are you referring to?

I still see no evidence that any of these lensing or rotational "methods" provides us with any insight into the actual composition of the mass.

Weak lensing experiments tell us that it isn't in machos. Rotation curves tell us where it is. The fact that it doesn't radiate and isn't in massive objects tells us it must be non-baryonic.

 

[Reality Check]

Did you ever check out any of Peratt's work by any chance? He attempted to create a computer model to mimic the behaviors of plasmas on a large scale and succeeded in creating many of the same galaxy type structures we observe in space.

Peratt's work is fatally flawed: Anthony Peratt's Plasma Model of Galaxy Formation

 

[Tubbythin]

So let's see....

We observe gamma rays from Earth that are directly linked to electrical discharges in the Earth's atmosphere. We point the same equipment at the sun, see the same annihilation signatures and we call it "magnetic reconnection"? Huh?

Either way you look at it folks annihilation signatures are completely 'natural' and they come from "normal matter". These emission wavelengths occur "naturally' inside our solar system. There simply is no need for any form of exotic matter to explain annihilation signatures from space, just 'current flow' and normal matter that is located on physical bodies like planets and suns. There is no way in hell that a "dark matter' explanation of annihilation wavelengths in space is going to survive a simple Occum's razor argument.

You don't seem to know what Occam's razor is.

 

[ben m]

So, if I understand you correctly, this is kinetic energy that is being transferred to ICM particles due to collisions from incoming fast moving charged particles? Why is it that the mainstream refuses to call "current flow", "current flow"? How dense is this "incoming" particle stream anyway?

The infalling clouds are net neutral. Moving neutral stuff around is not a "current". Anyway, kinetic energy has to do with mass and velocity, not with net charge, and is therefore the correct thing to put into an energy budget.

Well, it seems to me that every ion is capable of emitting photons. Unless there is a continuous collision process from incoming particles the whole thing would tend to "cool off' rather rapidly. I wouldn't expect it to keep that heat for billions of years.

Fully-ionized ions (bare nuclei) and electrons are the dominant species in these plasmas, and they radiate very weakly. Atomic plasmas are better at emitting radiation, but also better at absorbing it.

Essentially any moving charged particle is a form of "current flow". What you're doing is taking a moving charged particle (current flow) and slamming it into another relatively stationary (charged) particle and creating "resistance" to that incoming "current flow". I really love how astronomers create all these clever euphemisms to avoid using the term "current flow" and "resistance".

So when Alex Rodriguez slides into home base I guess the announcers are using "clever euphemisms" like sliding, friction, barreling, momentum, collide. What they ought to say is that a pair of 10^27 Ampere currents encountered a giga-giga-ohm resistor and ... um ... wait, that doesn't work at all, does it? There are mechanical forces, kinetic energy, and inertia, and treating it like a circuit is stupid.

 

[Michael Mozina]

You don't seem to know what Occam's razor is.

Yes I do and it's your worst enemy.

 

[Tubbythin]

Yes I do and it's your worst enemy.

I beg to differ.

 

[Michael Mozina]

I beg to differ.

There have to be at least a half dozen different ways that gamma rays could have been created in the amounts and locations specified that either show up in the lab, happen on Earth, or do not require exotic matter. In fact it's not even clear from the data that there is actually an 'overabundance' in the first place, and there are many known sources for such emissions.

There is absolutely no empirical link between gamma rays and "dark matter". That is an "act of faith" on the part of the "believer".

Almost *all* other theories that do not require "new forms of matter" are going to be preferable to a "dark matter" explanation, if only due to the fact that nothing new or exotic is necessary to explain it. DM isn't necessary and there is no link between DM and gamma radiation in the first place. You'll never win that argument.

 

[Tubbythin]

There have to be at least a half dozen different ways that gamma rays could have been created in the amounts and locations specified that either show up in the lab, happen on Earth, or do not require exotic matter.

Do their? Don't just stand there then. Show us. Because Occam's razor is a tool for differentiating between two different theories that explain the facts. And the fact are numerical quantities. Blind assertions like "There have to be" do not and cannot explain the facts.

In fact it's not even clear from the data that there is actually an 'overabundance' in the first place, and there are many known sources for such emissions.

But not enough apparently. Unless you can quantitatively show otherwise.

There is absolutely no empirical link between gamma rays and "dark matter". That is an "act of faith" on the part of the "believer".

If you want to start with all this religious crap then can I suggest you go over to the religion and philosophy forum.

Almost *all* other theories that do not require "new forms of matter" are going to be preferable to a "dark matter" explanation, if only due to the fact that nothing new or exotic is necessary to explain it.

Dark matter is needed to explain other observations anyway. Hence, the idea that we're adding an extra free parameter goes away entirely.

DM isn't necessary and there is no link between DM and gamma radiation in the first place. You'll never win that argument.

DM is necessary from other observations. Like galactic rotation curves etc. You've not been able to provide the first piece of quantitative evidence to refute this. And remember its the quantitative observations that constitute the facts.

 

[Michael Mozina]

Do their? Don't just stand there then. Show us.

Certainly.

http://www.nature.com/nature/journal/v451/n7175/abs/nature06490.html

Tell me how your "dark matter" solution is "simpler".

Because Occam's razor is a tool for differentiating between two different theories that explain the facts. And the fact are numerical quantities.

Sorry but a numerical "theory" related to "magic stuff" isn't much of an "explanation" IMO to begin with, so how in the heck are you going to tell me that DM solutions are better than a binary star solution to the exact same observation?

 

[Michael Mozina]

The infalling clouds are net neutral.

And exactly how do you know that?

Moving neutral stuff around is not a "current".

FYI, I've actually had people actually tell me that a lightening bolt is "neutral" too. You folks also claim that he plasmas in the solar system are "neutral" when in fact they are "current carrying" plasmas.

http://www.nasa.gov/mission_pages/themis/auroras/northern_lights.html

Angelopoulos was quite impressed with the substorm's power and he estimated the total energy of the two-hour event at five hundred thousand billion Joules. That's equivalent to the energy of one magnitude 5.5 earthquake . Where does all that energy come from? THEMIS may have found the answer.

"The satellites have found evidence of magnetic ropes connecting Earth's upper atmosphere directly to the sun," said David Sibeck, project scientist for the mission at NASA's Goddard Space Flight Center, Greenbelt, Md. "We believe that solar wind particles flow in along these ropes, providing energy for geomagnetic storms and auroras."

A quote from Alfven about a "magnetic rope" would be in order:

"However, in cosmic plasmas the perhaps most important constriction mechanism is the electromagnetic attraction between parallel currents . A manifestation of this mechanism is the pinch effect, which was studied by Bennett long ago (1934), and has received much attention in connection with thermonuclear research. As we shall see, phenomena of this general type also exist on a cosmic scale, and lead to a bunching of currents and magnetic fields to filaments or `magnetic ropes' . This bunching is usually accompanied by an accumulation of matter, and it may explain the observational fact that cosmic matter exhibits an abundance of filamentary structures (II .4 .1) . This same mechanism may also evacuate the regions near the rope and produce regions of exceptionally low densities."

I'm not convinced that your industry knows the difference between a "neutral" plasma and one that "carries current". According to Alfven that magnetic rope is a "current carrying" plasma. Everything he chalked up to "current flow" in the solar system, you now attribute to something he called "pseudoscience".