Fermi and dark matter

[Michael Mozina]

A dusty plasma is a plasma with dust. Putting quotes around the dusty does not change the definition.
The ICM is a plasma. By definition most (99%) of the plasma is not neutral.

Just out of curiosity, where did you get this number? I can see how you might be sure that 99% of the light emitting material is ionized, but how do you know that 99% of *all* the material present in the cloud is ionized again?

I really need to understand where you believe the 'normal' stellar core infrastructure is located relative to the various "blobs" in these images. You seem to believe you can separate out the heavy objects (like stars) from the plasma regions, but I fail to see how you think you're doing that.

 

[Tubbythin]

http://www.space.com/scienceastronomy/090608-aas-black-hole-masses.html

It actually goes beyond simply our knowledge of stellar populations, but also what goes on at the core of galaxies in general.

This doesn't help your case in the slightest. To make the galactic rotation curves flat at large distances from the centre of a galaxy (which is what we observe) we need to add mass at large distances. Adding mass in the middle I think just makes things worse!

 

[DazzaD]

Hmmm

My expertise is outdated (it has been 10 years since I did any research in Cosmology) but even at that time it was pretty well accepted that the "missing" mass, at least in galaxies and halos, could not be "ordinary" baryonic matter by a long shot.

MACHOs simply cannot account for a significant proportion of the mass that is evidenced by galactic rotation and gravitational lensing.

Also scientists are a very suspicious bunch by nature and every possible effort has been made with respect to "you know what, there might just be a load of junk between us and that galaxy". Short of the typical corrections made (when I was at Uni) I am not aware of how underestimating the amount of say, interstellar dust, could account for a significant fraction of baryonic matter in the galaxies (given the errors/constraints on the theories and experiments that I knew about even back then).

Or have I misread your position on this MM?

Of your two news stories quoted above one increases the total mass of stars in a galaxy by 20% at most and the other is talking about ratios of different sized stars, not necessarily changing the total mass of the galaxy.

Being as the baryonic matter accounts for a such a low proportion of the "budget" even a change of mind which leads to ten times as much stuff would hardly make a dent in the "what the hell do we do with the rest" problem.

 

[Michael Mozina]

This doesn't help your case in the slightest. To make the galactic rotation curves flat at large distances from the centre of a galaxy (which is what we observe) we need to add mass at large distances. Adding mass in the middle I think just makes things worse!

In terms of "explaining" dark matter based upon the galaxy rotation method, I agree with you. In terms of what the lensing data might show us, that's another story.

In fact I don't see how the lensing data actually demonstrates evidence of "dark matter" since most of the "dark matter" is expected to be located in the exterior of the galaxy, not the core.

 

[Michael Mozina]

Hmmm

My expertise is outdated (it has been 10 years since I did any research in Cosmology) but even at that time it was pretty well accepted that the "missing" mass, at least in galaxies and halos, could not be "ordinary" baryonic matter by a long shot.

I would agree that our "estimation" of "baryonic matter" (does an electron/positron "count" as a "baryon" in this "method" by the way?) does not jive with the mass requirement suggested by galaxy rotation patterns (assuming no flow of current through the galaxy). I fail however to see how our technology could possibly allow us to account for "all" the "normal matter" in a distant galaxy. We can't seem to accurately measure the black hole that sits at the core of a galaxy, so how can we be sure how much mass is actually missing to allow us to explain those rotation patterns? If the dust of the universe blocks more light than we expect, wouldn't we first want to factor in these changes *before* deciding how much "missing mass" there really is?

MACHOs simply cannot account for a significant proportion of the mass that is evidenced by galactic rotation and gravitational lensing.

It could account for some of it, particularly if we grossly underestimated the number of point sources in a given galaxy.

Also scientists are a very suspicious bunch by nature and every possible effort has been made with respect to "you know what, there might just be a load of junk between us and that galaxy". Short of the typical corrections made (when I was at Uni) I am not aware of how underestimating the amount of say, interstellar dust, could account for a significant fraction of baryonic matter in the galaxies (given the errors/constraints on the theories and experiments that I knew about even back then).

Well, let's play the "if" game for a second. If there are "dusty threaded regions" between us and a given galaxy, it could cause us to underestimate the amount of light coming from a galaxy. It could have a more significant effect on distant galaxies than it has on closer ones, but due to the threaded nature of the galaxy, it could have more of an effect on some galaxies than on others. A "typical correction" make grossly underestimate the amount of light that is actually being blocked, and thereby make us grossly underestimate the number of visible light sources and normal baryonic material in any given galaxy.

How can you be so certain that a "typical correction" is anything more than "gross oversimplification" that already grossly underestimates the amount of light emitted by various galaxies.

It seems to me that in light of recent "discoveries", it would be "prudent" to go back to the drawing board. Even deciding what to do with that information has a "subjective" component to it as Tubbythin pointed out to me earlier. We can "subjectively' decide to simply increase the size and light output of the existing point sources *or* we can subjectively increase the number of point sources. Given the amount of "missing mass" that we're trying to account for, it seems "prudent" to increase the number of point sources and stuff as much "normal matter" into these equations as we can fit *before* we claim this material is some sort of exotic matter with ad hoc properties galore.

Of your two news stories quoted above one increases the total mass of stars in a galaxy by 20% at most and the other is talking about ratios of different sized stars, not necessarily changing the total mass of the galaxy.

Where did you come up with that 20% figure "at most"? If half the light is being blocked and we thought it was only 10%, would not we want to increase the point sources, not simply the sizes of various objects? Wouldn't we want to be "cautious" on the side of "normal matter" rather than simply trying to minimize the effect on current theory?

Being as the baryonic matter accounts for a such a low proportion of the "budget"

Well, if we increase it significantly (like a factor of two), it's not such a "significant" percentage of the budget any longer. If the core contains a more massive amount of matter than we realize, then it too isn't quite as "insignificant" in terms of the budget.

even a change of mind which leads to ten times as much stuff would hardly make a dent in the "what the hell do we do with the rest" problem.

At worst case it's still a "missing mass" problem. It still makes little sense to "assume" that missing mass has any unique or "special properties" until and unless otherwise demonstrated empirically.

There are many reasons why galaxies might emit an excess of gamma rays, including shock waves and discharges and other more "likely" sources than "hypothetical" forms of matter with hypothetical properties galore.

 

[Reality Check]

Before I continue, perhaps you could answer a few questions about where you percieve the the galaxy infrastructure is located in its relationship to these "blobs". Where in your opinion is the "black hole" or "large mass object" from the galactic core, and/or the main core of stars in relationship to any of the "blobs"?

I will ignore this since you are back to your delusion that the Bullet Cluster and MACS J0025.4-1222 and Abell 520 observations are of galaxies and stars (and "black hole" or "large mass object").

How about that iron 'cloud' in relationship to the blobs?

There is no "iron cloud". It has no relationship to the blobs.
The observation that Fe increases in abundance from ~0.1% to ~0.3 % in the ICM is not for any of the colliding galactic clusters. However it is probably the situation for galactic clusters in general.

I gave the example of the paper as a possible explanation for whatever you think is "that iron core around the central mass of the galaxy".
First asked 8 November 2009:
What is your source for an iron core around the the central mass of the galaxy?

 

[Reality Check]

Just out of curiosity, where did you get this number? I can see how you might be sure that 99% of the light emitting material is ionized, but how do you know that 99% of *all* the material present in the cloud is ionized again?

The number is a guess on my part.
But the intracluster medium is hot and heavily ionized:

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.

A small bit of physics that you are ignoring is that whether the gas is neutral or ionized has little effect in the collisions. The mean free path of the particles (whether ionized or not) is about a lightyear.

• Neutral atoms also collide.
• Colliding neutral atoms also interact electromagnetically. To be more exact their electrons and protons interact electromagnetically during the collision.
• Neutral atoms that collide in colliding galactic clusters will lose kinetic energy and slow down.
• Neutral atoms that collide in colliding galactic clusters will heat up and emit light.

I really need to understand where you believe the 'normal' stellar core infrastructure is located relative to the various "blobs" in these images. You seem to believe you can separate out the heavy objects (like stars) from the plasma regions, but I fail to see how you think you're doing that.

The 'normal' stellar core infrastructure is located in the galaxies.
The galaxies are in the images taken by the astronomers.
The galaxies in the colliding galactic clusters have nothng to do with the observation which is about the ICM.

The Bullet Cluster and MACS J0025.4-1222 and Abell 520 are observations of the intracluster medium.

 

[Reality Check]

So these heavier elements, are the "more likely", or "less likely" to "pass through" the process?

By heavier elements do you mean the ~.1% of the ICM that is Fe ions?
I would guess that a larger particle would have a smaller mean free path (because it has a larger cross section) and so would collide more often then a smaller particle.

Does that number you quoted (9 times) also describe the amount of material you believe to be contained in what we'll call the "plasma cloud" as compared to the stars and planets, neutron stars, binary stars, black holes, etc that might be in any particular core of any particular galaxy? Aren't most galaxies expected to have "black holes' near their core?

There is no "plasma cloud". There is the ICM. That is the name that astronomers use.
The ICM has on average 9 times the mass of the galaxies.

Sagittarius A*: 4 million solar masses.
Milky Way: 5.8 × 10¹¹ solar masses.

You do the math.

 

[DazzaD]

I would agree that our "estimation" of "baryonic matter" (does an electron/positron "count" as a "baryon" in this "method" by the way?) does not jive with the mass requirement suggested by galaxy rotation patterns (assuming no flow of current through the galaxy).

I was referring really to nucleosynthesis constraints, so in the strictest (and proper) sense an electron is not a baryon, it is a lepton.

I fail however to see how our technology could possibly allow us to account for "all" the "normal matter" in a distant galaxy. We can't seem to accurately measure the black hole that sits at the core of a galaxy, so how can we be sure how much mass is actually missing to allow us to explain those rotation patterns? If the dust of the universe blocks more light than we expect, wouldn't we first want to factor in these changes *before* deciding how much "missing mass" there really is?

There could be a shipping container full of unknown objects sitting on a weighbridge. The weighbridge could give you a very good estimate of the total mass involved in the shipping container. If you knew the container was full of footballs, and you knew the average mass of a football, and you could work out how many could be squashed in the container, and if the total mass of the footballs and the container itself only came to 5% of what the weighbridge said the weight was, then you could have to give your head a serious scratch.

You don't need to know the exact mass of the clump of footballs in the centre to work out how much mass in footballs there is overall.

Ok ok ok.. terrible analogy I know, but I was struggling to understand your point here MM.. truly.

Well, let's play the "if" game for a second. If there are "dusty threaded regions" between us and a given galaxy, it could cause us to underestimate the amount of light coming from a galaxy. It could have a more significant effect on distant galaxies than it has on closer ones, but due to the threaded nature of the galaxy, it could have more of an effect on some galaxies than on others. A "typical correction" make grossly underestimate the amount of light that is actually being blocked, and thereby make us grossly underestimate the number of visible light sources and normal baryonic material in any given galaxy.

Forgive me if you have already answered this, but these dusty threaded regions, are they distributed evenly? Could we not infer their presence statistically? I.e. would we not have already discovered this after 40 odd years of looking at dust and gas in space to see how it affects light from stars and galaxies and notice this "unusual" effect you put forward?

How can you be so certain that a "typical correction" is anything more than "gross oversimplification" that already grossly underestimates the amount of light emitted by various galaxies.

Because I have seen and dealt with the research and statistics and it would be doing a generation of scientists and theorists and experimenters a great disservice to call it a "gross oversimplification".

In that sense most of what we do in cosmology or astrophysics would be a gross oversimplification but I think to a laymen that would imply it is next to useless and pretty much something somebody just guessed as they got out of bed one morning... i.e. I don't quite think it is fair.

It seems to me that in light of recent "discoveries", it would be "prudent" to go back to the drawing board. Even deciding what to do with that information has a "subjective" component to it as Tubbythin pointed out to me earlier. We can "subjectively' decide to simply increase the size and light output of the existing point sources *or* we can subjectively increase the number of point sources. Given the amount of "missing mass" that we're trying to account for, it seems "prudent" to increase the number of point sources and stuff as much "normal matter" into these equations as we can fit *before* we claim this material is some sort of exotic matter with ad hoc properties galore.

But. We. Have.

I may be completely misunderstanding you but please understand that the last thing on the mind of any cosmologist is to just go round saying "here... we aint got a clue what this is .. it must all be stuff we dont know and cant understand".

The concepts evolved were forced by very tight restrictions on theory and experimental results, not a consequence of being lax and lazy in applying known ideas and theories.

What I think you are suggesting has been pretty much to death over the last 20 odd years with no real hint of success. We are left with these strange ideas because we have pretty much exhausted everything else we can think of (not to say we are not still trying).

But if you accept the constraints on baryonic matter by nucleosynthesis and other bits and bobs then it dont matter how much you messed up on how many stars a galaxy has, or how much dust there is, or how many MACHOs there are, the simple fact is you can add that stuff til the cows come home but you are still not going to match everything else we see... not by a long shot.

Where did you come up with that 20% figure "at most"?

Your link:

http://www.nytimes.com/2008/05/17/science/space/17univ.html?_r=1

The results also mean that there is about 20 percent more mass in stars than previously thought. But since stars make up such a small percentage of the universe to begin with — dark matter and dark energy account for 95 percent or so — it is a small adjustment over all.

At worst case it's still a "missing mass" problem. It still makes little sense to "assume" that missing mass has any unique or "special properties" until and unless otherwise demonstrated empirically.

If a part in a car's engine is not performing as expected, how do you demonstrate its properties until you have identified which part in the car is the one that is "faulty" and compared it to what you would expect to happen in a normal car engine?

You seem to be claiming a mechanic can just look a car engine, identify the part that is wrong without hearing the engine work or looking under the bonnet, and then instantly detail how that part would behave without even touching it or playing with it.

Or am I being unfair?

There are many reasons why galaxies might emit an excess of gamma rays, including shock waves and discharges and other more "likely" sources than "hypothetical" forms of matter with hypothetical properties galore.

Indeed there is. There are many ways of emitting gamma rays.

The trick is to look for the details and not just on whether gamma rays are emitted or not.

I think maybe there is too much concentration on the simple fact that gamma rays are observed or expected. That, alone, tells you next to nothing.

It is all in the details

 

[Tubbythin]

I would agree that our "estimation" of "baryonic matter" (does an electron/positron "count" as a "baryon" in this "method" by the way?) does not jive with the mass requirement suggested by galaxy rotation patterns (assuming no flow of current through the galaxy). I fail however to see how our technology could possibly allow us to account for "all" the "normal matter" in a distant galaxy. We can't seem to accurately measure the black hole that sits at the core of a galaxy, so how can we be sure how much mass is actually missing to allow us to explain those rotation patterns?

Well its actually easier to measure properties of at least some of the other galaxies easier than it is our own. Think for example, about the red/blue shift of a spectral line if we look in the direction of the Milky Way centre. Compare that to what you would see for a line from an edge-on or obliquely angled spiral outside our Milky Way's plain.

If the dust of the universe blocks more light than we expect, wouldn't we first want to factor in these changes *before* deciding how much "missing mass" there really is?

Its going to have to be pretty special additional dust to make sphericalish shaped galaxies look disk-like.

 

[Michael Mozina]

I will ignore this since you are back to your delusion that the Bullet Cluster and MACS J0025.4-1222 and Abell 520 observations are of galaxies and stars (and "black hole" or "large mass object").

Your answer is "less than helpful". My question was legitimate and it deserves an answer. Black holes are thought to exist at the core of most if not all galaxies. The core contains many stars, not only plasma. Prior to collision both galactic cores contained these objects. Where did they go? They didn't just "disappear". Specifically where are they *now* located in relationship to any of the "blobs" in your opinion?

There is no "iron cloud".

http://chandra.harvard.edu/photo/2005/felines/
http://en.wikipedia.org/wiki/Accretion_disc

There's an accretion disk around the black hole. It contains man heavy elements. Where did they go in relationship to your blobs?

It has no relationship to the blobs.

Unless they instantly disappeared they *must* have a relationship to the blobs, specifically the blobs that "passed right on through". The mass of the stellar and black hole infrastructure had to go somewhere.

I gave the example of the paper as a possible explanation for whatever you think is "that iron core around the central mass of the galaxy".
First asked 8 November 2009:
What is your source for an iron core around the the central mass of the galaxy?

Evidently the central mass/black hole is a collector of heavy elements from around the galaxy.
http://en.wikipedia.org/wiki/Accretion_disc

I've provided the link to the Chandra data now twice for you to verify this fact. What's with the denial song and dance routine? These MACHO items like the "black hole" in the core would have "passed on through" along with the stellar infrastructure. The stellar infrastructure didn't just vanish. It has to still exist and have some relationship to those "blobs" you keep discussing. I'm asking you a legitimate scientific question, one that deserves a direct answer. In your opinion, where are the stars and other "condensed" forms of matter from the ICM located in relationship to the blobs?

 

[sol invictus]

Your answer is "less than helpful". My question was legitimate and it deserves an answer. Black holes are thought to exist at the core of most if not all galaxies.

We're not discussing colliding galaxies, MM. These are colliding clusters of galaxies, each containing hundreds of individual galaxies.

The core contains many stars, not only plasma. Prior to collision both galactic cores contained these objects. Where did they go? They didn't just "disappear". Specifically where are they *now* located in relationship to any of the "blobs" in your opinion?

When these collisions happen, massive compact objects like stars are more or less unaffected and pass straight through. That's because the density of stars is low compared to their cross section, and because diffuse gas has little effect on them. Most of the stars are in the blue (outer) blobs (and yes, they're visible - they didn't just "disappear").

There's an accretion disk around the black hole. It contains man heavy elements. Where did they go in relationship to your blobs?

I would expect that most black holes along with their accretion disks also passed through along with the stars and dark matter. It's not a very relevant issue because the mass in those holes is a tiny fraction of the total mass in a galaxy, let alone in a cluster.

By the way, we know very accurately how much the black hole at the center of the Milky Way weighs, because astronomers have imaged complete orbits of stars around it. It's about 4 million solar masses. The Milky Way has about 200 billion stars in it, and its total mass is much larger than the total mass of those stars.

 

[Michael Mozina]

I was referring really to nucleosynthesis constraints, so in the strictest (and proper) sense an electron is not a baryon, it is a lepton.

Well then, I already know where the mainstream is missing some of their mass. Since the mainstream cannot even account for "current flow" properly inside even our own solar system, I have zero confidence they account for the effect of current flow outside of the solar system.

There could be a shipping container full of unknown objects sitting on a weighbridge. The weighbridge could give you a very good estimate of the total mass involved in the shipping container. If you knew the container was full of footballs, and you knew the average mass of a football, and you could work out how many could be squashed in the container, and if the total mass of the footballs and the container itself only came to 5% of what the weighbridge said the weight was, then you could have to give your head a serious scratch.

I personally would tend to be suspicious of what that balls are made of, but that's just me. The problem here is that while there may be ample evidence that something else is in the container, it's not likely to be anything other than 'normal matter' that we haven't accounted for by counting up the number of balls. You wouldn't immediately assume that "non-bayronic dark matter" was in that container would you?

Forgive me if you have already answered this, but these dusty threaded regions, are they distributed evenly?

Not likely, at least not in every case. "Some" sort of 'averaging' process might be possible, but it would still just be an "average". Plasma tends to mass separate and form "threads" in the presence of "current flow". Even "dark matter" studies show a mass concentration pattern that looks very 'threaded'. We would still have to be careful when studying any specific galaxy due to these threaded patterns.

Could we not infer their presence statistically? I.e. would we not have already discovered this after 40 odd years of looking at dust and gas in space to see how it affects light from stars and galaxies and notice this "unusual" effect you put forward?

Until I looked at Hubble images of space I had no idea how 'dusty' the universe really was. I'm not convinced we've even had the technology to understand the problem until Hubble. According to that article and paper, the 'dust' in the universe blocks considerably more light than we realized when a lot of these formulas were first put forth. If there is double the light than we realized (on average) , then there there could easily be more "normal" mass in those galaxies. It just seems prudent to factor in what we've learned over the past few years before we start attributing every bit of missing mass to some exotic form of matter.

Because I have seen and dealt with the research and statistics and it would be doing a generation of scientists and theorists and experimenters a great disservice to call it a "gross oversimplification".

In that sense most of what we do in cosmology or astrophysics would be a gross oversimplification but I think to a laymen that would imply it is next to useless and pretty much something somebody just guessed as they got out of bed one morning... i.e. I don't quite think it is fair.

I guess a part of this issue is "age" related. I'm old enough to have been taught an "empirical" brand of "Big Bang" theory in school. I've since watched that theory be hacked and kludged with every new 'discovery'. 12 years ago, nobody had ever heard of "dark energy" for instance. Today it presumably makes up 70+ percent of the universe. They oversimplify everything, and they constantly fudge the numbers to fit when new observations don't jive with previous theories. I happen to know this from a historical perspective.

The basic problem is that nature is "messy". It's not always 'simple" and "easy". Not every event in nature lends itself to easy mathematical quantification. Birkeland's mathematical explanations of Aurora weren't as 'elegant' as Chapman's theories from a mathematical point of view. They weren't as easy to convey to student in the classroom. 70 years of time had to pass before it become clear that Birkeland's approach was correct and superior in terms of accurately describing the flow patterns of energy from the sun to the Earth.

I'll respond to the rest of your post after some coffee.

 

[Michael Mozina]

We're not discussing colliding galaxies, MM. These are colliding clusters of galaxies, each containing hundreds of individual galaxies.

That does not alter my point one iota, in fact it makes my question that much more important. The physical infrastructure of each galaxy is going to "pass on through" just like your presumed "dark matter". RC seems to be under the impression that he can distinguish between "baryonic' and "non-baryonic" matter in these images, but that is simply *impossible*. You have no way to differentiate various types of matter in these sorts of lensing studies. Sooner or later I will drive that point home, but you'll have to stop skirting the direct questions.

When these collisions happen, massive compact objects like stars are more or less unaffected and pass straight through. That's because the density of stars is low compared to their cross section, and because diffuse gas has little effect on them. Most of the stars are in the blue (outer) blobs (and yes, they're visible - they didn't just "disappear").

So they are going to act just like "dark matter" in their ability to "pass through' other objects and they will necessarily be inside that same blue blob where you claim "dark matter' is located.

I would expect that most black holes along with their accretion disks also passed through along with the stars and dark matter. It's not a very relevant issue because the mass in those holes is a tiny fraction of the total mass in a galaxy, let alone in a cluster.

You *assume* that *all* forms of MACHO dark matter account for a tiny fraction of the mass, but how do you actually know that?

By the way, we know very accurately how much the black hole at the center of the Milky Way weighs, because astronomers have imaged complete orbits of stars around it. It's about 4 million solar masses. The Milky Way has about 200 billion stars in it, and its total mass is much larger than the total mass of those stars.

That may be (probably is) the case with our own galaxy because we can track individual stars in our own galaxy, but how do we figure out what a distant black hole might contain in terms of total mass?

The bottom line is that your trying to 'sell' our technology as being better than it is, and our knowledge of the universe as being 'more advanced' than it actually is. We can't even count stars in a distant galaxy so how can we be sure how much "normal" (identified) matter exists there? Until recently we didn't even believe that neutrinos had mass, yet now we believe they do. Surely that must account for some of that "missing mass", without resorting to "unknown" and "theoretical" forms of matter?

 

[Michael Mozina]

But if you accept the constraints on baryonic matter by nucleosynthesis and other bits and bobs then it dont matter how much you messed up on how many stars a galaxy has, or how much dust there is, or how many MACHOs there are, the simple fact is you can add that stuff til the cows come home but you are still not going to match everything else we see... not by a long shot.

You seem to have touched upon a very key point. The operative word of the first sentence is the word "if". I personally don't have a "favorite" explanation of the universe. Over the past 30+ years of studying this topic in earnest I've read a ton of different theories. They all have interesting aspects to them, and they all seem to lack empirical support without resorting to metaphysics in some way. I'm really not convinced that there ever was a "creation event", where all matter and energy were condensed to a single "lump" (happy sol?). I tend to believe that if there was a "bang" it was probably more along the lines of of a cyclical matter/antimatter contraction/expansion process as Alfven suggested. I personally doubt that all matter and energy came from a singular event. It's "possible' I suppose, but if the evidence doesn't lead me there, I'm willing to try something else too.

I'm personally much more interested in explaining astronomical events that are closer to home using empirical forms of 'science'. That is why I find EU theory so attractive by the way.

It personally doesn't matter to me one iota whether all matter and energy was once collected to a single place in spacetime, therefore I'm not emotionally attached to the nucleosythesis limitation arguments you're concerned about. I'm not sure how we will bridge that particular theological gap.

 

[DazzaD]

You *assume* that *all* forms of MACHO dark matter account for a tiny fraction of the mass, but how do you actually know that?

Now this I can answer a bit.

This is what I did at university.

If you are talking about MACHOs in galaxies/halos then they cannot be above a certain proportion of the mass that is known to exist in the galaxy (because of say, galactic rotation curves) because when you stare at a star (many stars, but one at a time) for a long while, you can have a look see and see how many "blinks" occur because something passed along your line of sight.

Do that properly, over a very large sample size, in many ways and you can account, statistically, for how many of these MACHO type objects you expect to have in a galaxy.

Sadly (for me) they cannot represent much more than a few percent of the mass we infer to be present in the galaxy/halo.


If you wish to borrow the word MACHO for your own purposes to talk about electrons or "filament threads" then you would have to make that clear, else most of the bods on here would then be talking at cross purposes with you.

 

[Michael Mozina]

Well its actually easier to measure properties of at least some of the other galaxies easier than it is our own.

I'm sure that is true, but sol cited an example where the reverse can also be true with his black hole example.

Its going to have to be pretty special additional dust to make sphericalish shaped galaxies look disk-like.

Well, as I understand the rotation method (feel free to correct me if I'm mistaken), the "missing mass" would be likely to be located mostly in the galactic accretion disk, and mostly concentrated on the outside of the disk. I therefore don't see how lensing data related to the collision process of the ICMs of galaxies really supports a 'dark matter' theory.

 

[DazzaD]

They all have interesting aspects to them, and they all seem to lack empirical support without resorting to metaphysics in some way.

But the standard model is purely driven by empirical support.

I.e. the whole kit and caboodle that we use as our best explanation is only that that matches the extensive set of observations that range from particle physics to deep field cosmology.

I know, because I was that theorist who had to throw away months of work because the latest set of observations made it all just a jolly idea with no real grounding in reality.

I'm really not convinced that there ever was a "creation event", where all matter and energy were condensed to a single "lump" (happy sol?). I tend to believe that if there was a "bang" it was probably more along the lines of of a cyclical matter/antimatter contraction/expansion process as Alfven suggested. I personally doubt that all matter and energy came from a singular event. It's "possible' I suppose, but if the evidence doesn't lead me there, I'm willing to try something else too.

Ahh excellent.

With that then we are all pretty much in agreement.

I dont know a single cosmologist who truly believes literally in a singular event. I think every single one recognises the limit of their abilities and the abilities of the tools/theory/maths they currently use.

It personally doesn't matter to me one iota whether all matter and energy was once collected to a single place in spacetime, therefore I'm not emotionally attached to the nucleosythesis limitation arguments you're concerned about. I'm not sure how we will bridge that particular theological gap.

Hmm.. I would disagree vehemently on the "theological" aspect there.

Now all the electric universe stuff I have read is probably about 10 years old but I am not aware of how the EU predicts to within a significant degree of precision elemental abundances.

The little that I know of it (which as I say is probably outdated) simply flies in the face of well known and well tested particle physics theories (which are tested right here on the Earth, as I think you stated you would prefer to happen).

 

[DazzaD]

I guess a part of this issue is "age" related. I'm old enough to have been taught an "empirical" brand of "Big Bang" theory in school. I've since watched that theory be hacked and kludged with every new 'discovery'. 12 years ago, nobody had ever heard of "dark energy" for instance. Today it presumably makes up 70+ percent of the universe. They oversimplify everything, and they constantly fudge the numbers to fit when new observations don't jive with previous theories. I happen to know this from a historical perspective.

The basic problem is that nature is "messy". It's not always 'simple" and "easy". Not every event in nature lends itself to easy mathematical quantification.

All I can say is I wish they had oversimplified everything... my ride through university would have been a damn sight easier then!



I suppose it really truly doesnt help when people on the "outside" of the academic circle dont get to see first hand the arguments, fights, decades of dedicated work going down the drain, the many many instances of scientists picking apart other theories with a vengeance.

It may come across (from the outside) as a serene place where they sit in their watchtowers patting each other on the back for a job well done - writing a few equations on the back of an envelope down the pub.

But in reality it is a vicious fight for survival, and while the last standing predator may not be the best suited to fight its next adversary, it has certainly ripped all its other foes to pieces and is standing pretty tall on top of the pile.

For the moment, those dark eyes stalking it in the long grass are just that, eyes watching it from a distance. The hulking predator that dominates the pile of food at the moment is the standard model, even if he still doesnt know how to open those tins of dog meat.

 

[Tubbythin]

I'm sure that is true, but sol cited an example where the reverse can also be true with his black hole example.

He's probably right, he usually is. I actually read your statement as:

We can't seem to accurately measure the black hole that sits at the core of our galaxy

rather than what you actually said which was "a galaxy". I was pointing out that this wasn't, in general, a very good argument. But since I no longer think you were making that argument (though I'm not 100% certain) its a bit of a moot point. SI's argument on the other hand still stands.

Well, as I understand the rotation method (feel free to correct me if I'm mistaken), the "missing mass" would be likely to be located mostly in the galactic accretion disk, and mostly concentrated on the outside of the disk. I therefore don't see how lensing data related to the collision process of the ICMs of galaxies really supports a 'dark matter' theory.
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I don't know what you mean by "galactic accretion disk". I'm not even sure what you mean by "outside".