Non-baryonic cold dark matter ("CDM"), the observational evidence

[DeiRenDopa]

I've started this thread to avoid the Quarks, [OIII], neutron stars, black holes OK; CDM not OK - Huh? thread getting bogged down.

Of course the nature of the observational evidence, and the analysis that takes observations and concludes 'here be (lots and lots of) CDM' is relevant to that thread! And it has already been discussed, in an ad hoc way, starting with this post by sol invictus.

However, it is a separate topic, and one that could easily generate a dozen pages of posts ... and it is not central to the question I want to address in that other thread ("How does it come about that an apparently intelligent, educated, thoughtful person can be quite OK with 'quarks' (which have not be 'seen' in any experiments), [OIII] 5007 (which has never been produced in any lab), neutron stars (ditto), and black holes (double ditto!), yet balk at the very thought of non-baryonic cold dark matter (CDM)?").

I'll take the following approach to addressing the observational evidence:

* observations concerning CDM in our Milky Way galaxy, and other galaxies

* observations concerning CDM in rich clusters of galaxies

* CDM in cosmology.

For the first two, I will look at the different kinds of observations that lead to the conclusion 'lots of CDM', with an emphasis on the different physical mechanisms at work (a.k.a. the different physics theories involved in the observations themselves and in the analyses of those observations), the leading limitations and questions on these, and whether there are any viable alternative conclusions (to 'here be (lots and lots of) CDM'). Of necessity, most of the history will be omitted; this is, in some ways, a pity, because that history is really quite fascinating - the errors, the wrong turns, the prescient early insights, the slow elimination of all alternatives, the huge effort put into corroboration, etc, etc, etc.

The last one (cosmology) needs to be treated in a different way, partly because it is most powerful when considered in terms of consistency, rather than a set of independent classes of observation.

My approach deliberately omits all particle physics inputs; there is a very strong set of cases concerning the existence of CDM that arise from particle physics, and these help support the conclusion in terms of consistency.

I will also not even attempt to cover astronomical observations other than those under these three headings.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Key term: by "CDM" I will mean 'non-baryonic cold, dark matter'.

'Cold' refers to the average speed of this matter with respect to the CMB frame of reference; basically it just says this stuff isn't zipping round the universe nearly at the speed of light, unlike cosmic rays and neutrinos (the former is an example of 'hot matter', the latter 'hot dark matter').

'Dark' refers to transparency to all forms of electromagnetic radiation; DM and photons are like two ships in the night, they pass each other by without either noticing the other. In practical, astronomical, terms this simply means DM does not emit light (or gamma rays, or x-rays, or ... or radio), nor does it absorb it.

'non-baryonic' means the CDM is made up of stuff other than the molecules, atoms, nuclei, and electrons we are made up of (and the Sun, and cosmic rays, and neutron stars, and dust, and gas, and ...). Neutrinos are 'non-baryonic'; however, they are not 'cold'. The question of whether black holes get counted as non-baryonic or not will be covered in the cases where it is necessary to eliminate them as a possible explanation for the various observations.

OK, time to start.

 

[BenBurch]

Well, galaxies cannot hold together without CDM or a force that acts just like CDM. It has been a toothache in cosmology that gravitational simulations of galaxies based on the mass that we can see and the velocities we observe do not result in a galaxy that does not fly apart.

And it appears that when galaxies collide, the CDM, which does not appear to interact with baryonic matter (or itself) except gravitationally, shoots on past the parent galaxy as it experiences no drag in the interaction, but the stars and gas of the baryonic side of the galaxies DO interact mechanically and so slow. And you can detect the effects of this in analysis of these galaxies.

 

[fuelair]

I've started this thread to avoid the Quarks, [OIII], neutron stars, black holes OK; CDM not OK - Huh? thread getting bogged down.

Of course the nature of the observational evidence, and the analysis that takes observations and concludes 'here be (lots and lots of) CDM' is relevant to that thread! And it has already been discussed, in an ad hoc way, starting with this post by sol invictus.

However, it is a separate topic, and one that could easily generate a dozen pages of posts ... and it is not central to the question I want to address in that other thread ("How does it come about that an apparently intelligent, educated, thoughtful person can be quite OK with 'quarks' (which have not be 'seen' in any experiments), [OIII] 5007 (which has never been produced in any lab), neutron stars (ditto), and black holes (double ditto!), yet balk at the very thought of non-baryonic cold dark matter (CDM)?").

I'll take the following approach to addressing the observational evidence:

* observations concerning CDM in our Milky Way galaxy, and other galaxies

* observations concerning CDM in rich clusters of galaxies

* CDM in cosmology.

For the first two, I will look at the different kinds of observations that lead to the conclusion 'lots of CDM', with an emphasis on the different physical mechanisms at work (a.k.a. the different physics theories involved in the observations themselves and in the analyses of those observations), the leading limitations and questions on these, and whether there are any viable alternative conclusions (to 'here be (lots and lots of) CDM'). Of necessity, most of the history will be omitted; this is, in some ways, a pity, because that history is really quite fascinating - the errors, the wrong turns, the prescient early insights, the slow elimination of all alternatives, the huge effort put into corroboration, etc, etc, etc.

The last one (cosmology) needs to be treated in a different way, partly because it is most powerful when considered in terms of consistency, rather than a set of independent classes of observation.

My approach deliberately omits all particle physics inputs; there is a very strong set of cases concerning the existence of CDM that arise from particle physics, and these help support the conclusion in terms of consistency.

I will also not even attempt to cover astronomical observations other than those under these three headings.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Key term: by "CDM" I will mean 'non-baryonic cold, dark matter'.

'Cold' refers to the average speed of this matter with respect to the CMB frame of reference; basically it just says this stuff isn't zipping round the universe nearly at the speed of light, unlike cosmic rays and neutrinos (the former is an example of 'hot matter', the latter 'hot dark matter').

'Dark' refers to transparency to all forms of electromagnetic radiation; DM and photons are like two ships in the night, they pass each other by without either noticing the other. In practical, astronomical, terms this simply means DM does not emit light (or gamma rays, or x-rays, or ... or radio), nor does it absorb it.

'non-baryonic' means the CDM is made up of stuff other than the molecules, atoms, nuclei, and electrons we are made up of (and the Sun, and cosmic rays, and neutron stars, and dust, and gas, and ...). Neutrinos are 'non-baryonic'; however, they are not 'cold'. The question of whether black holes get counted as non-baryonic or not will be covered in the cases where it is necessary to eliminate them as a possible explanation for the various observations.

OK, time to start.

Is there a vague chance that proof or really good evidence is going to pop up somewhere here? I ask only because real astronomers/astrophysists seem to be unsure at this time and I would rather wait to read stuff until the people who have the equiptment and expertise have it really well mapped out. Conjecture can be entertaining but fact is the real thing.

 

[Dancing David]

The observations are facts?

Stars rotate around galaxies as though there is more matter than we can see.

 

[Wangler]

DRD, this is going to be another good thread, IMO. Thanks for starting, sorry to have bogged down the other.

 

[BenBurch]

Basically, the evidence for CDM is just as good or better than the evidence for many other things we see out in the cosmos.

 

[DeiRenDopa]

observations concerning CDM in our Milky Way galaxy, and other galaxies

The main technique used to estimate the distribution of mass in spiral galaxies, as a function of radius from the centre (nucleus) is to derive a rotation curve from observations of the light (radio, etc; electromagnetic radiation - I'll use 'light' as a synonym) emitted by such galaxies.

One technique involves observing how the line of sight velocity changes with position; here is a concise but accurate summary of how it's done, using a 'long slit' spectrum, and emission lines in the visual waveband.

There are many other ways to obtain a spiral galaxy rotation curve, using different wavebands, different lines; integrated light from sizable chunks of the target galaxy, individual sources (e.g. HII regions, bright stars); and so on.

The results are the same: the curves either keep rising or flatten out, right out (radially) to where no more light seems to be coming from the galaxy.

Using textbook physics, these curves can be interpreted to mean that the mass 'closer in' to the centre of the galaxy (than at any radius) keeps increasing as the radius increases. In fact, no other standard physics textbook interpretation has been proposed, that is also consistent with all the relevant observations.

However, adding up all the mass in these galaxies, estimated from the light emitted (by stars, dust, and gas/plasma) or light absorbed (by dust and gas), gives totals that are just too small ... and the difference (between 'rotation curve mass' and 'stars/dust/gas mass') gets larger as the radius increases.

In addition to spiral galaxy rotation curves, the mass of galaxies can be estimated by several other techniques.

Beyond the faintest (integrated light) edges of galaxies are objects which are moving within the gravitational well of the galaxies. These objects include planetary nebulae, globular clusters, and satellite (dwarf) galaxies. Just as the rotation curves can be interpreted to estimate the total mass 'closer in' (using physics which Newton pioneered), the motions of these more distant objects can also be interpreted, using the same physics, to estimate the total mass 'closer in'. This work is much, much more challenging than rotation curves! However, it probes the mass of galaxies at considerably greater distances than rotation curves can reach, and also gives estimates of the mass of elliptical galaxies, which do not have rotation curves.

These observations can be interpreted as being consistent with the rotation curve observations - galaxies seem to have 'halos' of mass that extend way beyond their 'visible' edges. The density of this (dark) halo mass decreases with radial distance from the nucleus.

Some elliptical galaxies, typically the giants found near the centres of clusters, emit x-rays. The physics of such emission is easily understood from a different part of the standard physics textbook, and the x-ray emission can be interpreted as tracing the (radial) mass distribution in these ellipticals - basically, for the hot plasma that emits the x-rays to be 'trapped' in the giant elliptical galaxy, the galaxy must have a mass that lies between two robust limits. Again, galaxy masses estimated using this technique are consistent with those estimated from motions of globular clusters and planetary nebulae ... and again, the total mass is considerably greater than that estimated from all the light emitted or absorbed by the stars and gas/plasma (ellipticals have essentially no dust).

Some dwarf galaxies, in our Local Group, are close enough that the line of sight velocities of individual stars can be measured, and the distribution of stars within the galaxies accurately measured. Assuming these dwarf galaxies are gravitationally bound, these observations can be interpreted, using standard textbook (Newtonian) physics to give estimates of the total mass of these dwarf galaxies. The results are both astonishing and unambiguous: these galaxies contain far, far more mass than is in the stars whose light we can detect (it's much the same with regard to gas/plasma; note that these galaxies have little dust).

Somewhat in contrast to rotation curves of spiral galaxies, interpretation of the observations using the other techniques I've briefly mentioned does not have to lead to firm conclusions about mass differences ... however, as far as I know, no alternative explanations (based on standard, textbook physics) have been proposed that are also consistent with the 'lensing' observations I will cover next.

So far, the parts of the standard physics textbooks used to interpret the millions of astronomical observations have been many, but have not included General Relativity (GR).

One last technique (two actually) involves estimating mass using GR, and is completely independent of all the techniques briefly described above. It is, to me at least, truly marvelous that 'GR observations' can be interpreted to arrive at conclusions that are completely consistent with the various other observations I've briefly described ... and this consistency across different techniques using different physics is surely one of the strongest indicators that 'unseen mass' is the right interpretation.

(to be continued)

 

[DeiRenDopa]

Is there a vague chance that proof or really good evidence is going to pop up somewhere here? I ask only because real astronomers/astrophysists seem to be unsure at this time and I would rather wait to read stuff until the people who have the equiptment and expertise have it really well mapped out. Conjecture can be entertaining but fact is the real thing.

.
As I said in the other thread (see the OP), to do justice to the vast amount of observational material relevant to the existence of CDM, even just within the three regions I intend to briefly touch, would take several months (or so I estimate).

I should also have added that the audience I am aiming at is not those with BSc (or higher) degrees in physics or astronomy; for such people, there are dozens of excellent textbooks, and hundreds of landmark papers.

Finally, do not expect a nice, simple, 'try this at home' explanation; just like the observational basis for SgrA* (the nucleus of the Milky Way) being a super-massive black hole, the observational basis for CDM is a rich, intricately-connected web of millions of observations and very large parts of standard physics textbooks. Depending on what you consider 'really good evidence' to be, you might have to convince yourself of almost all of standard astronomy and astrophysics first, before you could even begin to appreciate the evidence for CDM.

 

[Wangler]

The main technique used to estimate the distribution of mass in spiral galaxies, as a function of radius from the centre (nucleus) is to derive a rotation curve from observations of the light (radio, etc; electromagnetic radiation - I'll use 'light' as a synonym) emitted by such galaxies.

One technique involves observing how the line of sight velocity changes with position; here is a concise but accurate summary of how it's done, using a 'long slit' spectrum, and emission lines in the visual waveband.

There are many other ways to obtain a spiral galaxy rotation curve, using different wavebands, different lines; integrated light from sizable chunks of the target galaxy, individual sources (e.g. HII regions, bright stars); and so on.

The results are the same: the curves either keep rising or flatten out, right out (radially) to where no more light seems to be coming from the galaxy.

Using textbook physics, these curves can be interpreted to mean that the mass 'closer in' to the centre of the galaxy (than at any radius) keeps increasing as the radius increases. In fact, no other standard physics textbook interpretation has been proposed, that is also consistent with all the relevant observations.

However, adding up all the mass in these galaxies, estimated from the light emitted (by stars, dust, and gas/plasma) or light absorbed (by dust and gas), gives totals that are just too small ... and the difference (between 'rotation curve mass' and 'stars/dust/gas mass') gets larger as the radius increases.

In addition to spiral galaxy rotation curves, the mass of galaxies can be estimated by several other techniques.

Beyond the faintest (integrated light) edges of galaxies are objects which are moving within the gravitational well of the galaxies. These objects include planetary nebulae, globular clusters, and satellite (dwarf) galaxies. Just as the rotation curves can be interpreted to estimate the total mass 'closer in' (using physics which Newton pioneered), the motions of these more distant objects can also be interpreted, using the same physics, to estimate the total mass 'closer in'. This work is much, much more challenging than rotation curves! However, it probes the mass of galaxies at considerably greater distances than rotation curves can reach, and also gives estimates of the mass of elliptical galaxies, which do not have rotation curves.

These observations can be interpreted as being consistent with the rotation curve observations - galaxies seem to have 'halos' of mass that extend way beyond their 'visible' edges. The density of this (dark) halo mass decreases with radial distance from the nucleus.

Some elliptical galaxies, typically the giants found near the centres of clusters, emit x-rays. The physics of such emission is easily understood from a different part of the standard physics textbook, and the x-ray emission can be interpreted as tracing the (radial) mass distribution in these ellipticals - basically, for the hot plasma that emits the x-rays to be 'trapped' in the giant elliptical galaxy, the galaxy must have a mass that lies between two robust limits. Again, galaxy masses estimated using this technique are consistent with those estimated from motions of globular clusters and planetary nebulae ... and again, the total mass is considerably greater than that estimated from all the light emitted or absorbed by the stars and gas/plasma (ellipticals have essentially no dust).

Some dwarf galaxies, in our Local Group, are close enough that the line of sight velocities of individual stars can be measured, and the distribution of stars within the galaxies accurately measured. Assuming these dwarf galaxies are gravitationally bound, these observations can be interpreted, using standard textbook (Newtonian) physics to give estimates of the total mass of these dwarf galaxies. The results are both astonishing and unambiguous: these galaxies contain far, far more mass than is in the stars whose light we can detect (it's much the same with regard to gas/plasma; note that these galaxies have little dust).

Somewhat in contrast to rotation curves of spiral galaxies, interpretation of the observations using the other techniques I've briefly mentioned does not have to lead to firm conclusions about mass differences ... however, as far as I know, no alternative explanations (based on standard, textbook physics) have been proposed that are also consistent with the 'lensing' observations I will cover next.

So far, the parts of the standard physics textbooks used to interpret the millions of astronomical observations have been many, but have not included General Relativity (GR).

One last technique (two actually) involves estimating mass using GR, and is completely independent of all the techniques briefly described above. It is, to me at least, truly marvelous that 'GR observations' can be interpreted to arrive at conclusions that are completely consistent with the various other observations I've briefly described ... and this consistency across different techniques using different physics is surely one of the strongest indicators that 'unseen mass' is the right interpretation.

(to be continued)

Good post, DRD.

I hope to be able, in the next couple of days, post a discussion about this line of evidence, from this layman's perspective.

I hope to get this posted before you move much further along.

 

[DeiRenDopa]

Good post, DRD.

I hope to be able, in the next couple of days, post a discussion about this line of evidence, from this layman's perspective.

I hope to get this posted before you move much further along.

Thanks.

Note that this is only part of the observational evidence; for example, how various classes of dark baryonic matter can be ruled out - in spiral galaxies, ellipticals, and dwarf galaxies - is the subject of a later post (or several posts) ...

 

[Wangler]

Note that this is only part of the observational evidence; for example, how various classes of dark baryonic matter can be ruled out - in spiral galaxies, ellipticals, and dwarf galaxies - is the subject of a later post (or several posts) ...

I'm sure I'll have many opportunities to learn a great deal.

 

[Dancing David]

Thanks DRD, I appreciate your time and effort.

Wangler, you didn't bog the other thread, It has it's own momentum and pattern. Now is the quiet before the spam bomb.

 

[Zeuzzz]

The observations are facts?

Stars rotate around galaxies as though there is more matter than we can see.

That is all assuming that the only force at work is gravity, and it also assumes that gravity remains the dominant force when you scale up above the planetary/stellar level. We know that as you assend up scales other forces change their dominance, ie, EM forces usually far dominate gravity at smaller scales, so it is fully possible that as you scale up gravity starts to become secondary to other various forces and instabilities in plasma.

I see the problems with CDM and other similar cosmologies as follows:

• Like geology and unlike particle physics, cosmology is intrinsically an historical science and lacks direct experimental testing for many key hypotheses.

• Data in cosmology are limited to remotely sensed photons; there is no direct, in situ measurement as in space physics or planetary science.

• Most existing cosmology models focus on only one long-range force field (gravity) and ignore potential long-range effects of electromagnetism and plasmas.


On this last point, it is well known that electromagnetism is very effectively shielded out, which allows gravity to generally dominate over long scale lengths. Nevertheless, electromagnetism and plasmas can still be significant because:


“By definition, plasmas are an interactive mix of charged particles, neutrals, and fields that exhibits collective effects. In plasmas, charged particles are subject to long-range, collective Coulomb interactions with many distant encounters. Although the electrostatic force drops with distance (~1/r²), the combined effect of all charged particles might not decay because the interacting volume increases as r³. Magnetic field effects are often global with their connections reaching to galactic scales and beyond” (Goedbloed and Poedts, 2004) (Also see; B. Coppi, Attilio Ferrari, 2000 [full text])


Of course, this will be hotly contested by Big Bang advocates that require gravity being the only force at work, but is none-the-less a valid point that we have no real reason to discount at the moment.

The potential importance of electromagnetism and plasmas is indicated by the rapidly growing field of plasma astrophysics (see links and references at plasmas.org/). As one example of its significance for altering conventional assumptions, (Astrophysics: A New Approach, Kundt 2005) shows in detail how observed signatures of existing “black-hole” candidates can be more effectively interpreted as neutron star magnetospheres with accretion disks or neutron star binaries. Efforts to assess the potential impact of the new plasma astrophysics on cosmology issues are just beginning. Hopefully due to this we will not need to fill our universe up with CDM or other dubious metaphysical constructs, the vast and varied properties of plasma should be able to account for many of cosmologies unsolved mysteries in the near future.

 

[Reality Check]

That is all assuming that the only force at work is gravity, and it also assumes that gravity remains the dominant force when you scale up above the planetary/stellar level. We know that as you assend up scales other forces change their dominance, ie, EM forces usually far dominate gravity at smaller scales, so it is fully possible that as you scale up gravity starts to become secondary to other various forces and instabilities in plasma.

I see the problems with CDM and other similar cosmologies as follows:

• Like geology and unlike particle physics, cosmology is intrinsically an historical science and lacks direct experimental testing for many key hypotheses.

• Data in cosmology are limited to remotely sensed photons; there is no direct, in situ measurement as in space physics or planetary science.

• Most existing cosmology models focus on only one long-range force field (gravity) and ignore potential long-range effects of electromagnetism and plasmas.


On this last point, it is well known that electromagnetism is very effectively shielded out, which allows gravity to generally dominate over long scale lengths. Nevertheless, electromagnetism and plasmas can still be significant because:


“By definition, plasmas are an interactive mix of charged particles, neutrals, and fields that exhibits collective effects. In plasmas, charged particles are subject to long-range, collective Coulomb interactions with many distant encounters. Although the electrostatic force drops with distance (~1/r²), the combined effect of all charged particles might not decay because the interacting volume increases as r³. Magnetic field effects are often global with their connections reaching to galactic scales and beyond” (Goedbloed and Poedts, 2004) (Also see; B. Coppi, Attilio Ferrari, 2000 [full text])


Of course, this will be hotly contested by Big Bang advocates that require gravity being the only force at work, but is none-the-less a valid point that we have no real reason to discount at the moment.

The potential importance of electromagnetism and plasmas is indicated by the rapidly growing field of plasma astrophysics (see links and references at plasmas.org/). As one example of its significance for altering conventional assumptions, (Astrophysics: A New Approach, Kundt 2005) shows in detail how observed signatures of existing “black-hole” candidates can be more effectively interpreted as neutron star magnetospheres with accretion disks or neutron star binaries. Efforts to assess the potential impact of the new plasma astrophysics on cosmology issues are just beginning. Hopefully due to this we will not need to fill our universe up with CDM or other dubious metaphysical constructs, the vast and varied properties of plasma should be able to account for many of cosmologies unsolved mysteries in the near future in my opinion.

Hi Zeuzzz: Did you not read the posts on other threads that you were particpating in that refute Plasma Cosmology?

There is no evidence that electromagnetic forces are more important than gravitational forces on a cosmological scale.

In any case your posting is off topic. If you want to discuss Plasma Cosmology and its explanation for non-existance of the observed dark matter then start a new thread.

 

[sol invictus]

Now is the quiet before the spam bomb.

<nonsense>

BOOM!!

 

[Zeuzzz]

Hi Zeuzzz: Did you not read the posts on other threads that you were particpating in that refute Plasma Cosmology?

There is no evidence that electromagnetic forces are more important than gravitational forces on a cosmological scale.

In any case your posting is off topic. If you want to discuss Plasma Cosmology and its explanation for non-existance of the observed dark matter then start a new thread.

"There is no evidence that electromagnetic forces are more important than gravitational forces on a cosmological scale." Can you see my post? or is your mind still blocking out anything that does not adhere to your personal views? I stated why this could be the case, quite clearly and openly.

We'll just have to see about these *cough* 'refutations of plasma cosmology' in the near future when I have time to respond to them. So far i have not seen any, but will be happy to discuss them if you think they exist. I only briefly visit here each day at the mo, and will start a thread all about PC when I have more time. I didn't even mention plasma cosmology anyway in that post. You seem to have inferred this yourself from just reading some standard plasma astrophysics material, which is very telling.

I am giving my opinion (and many other astronomers) on CDM, and whether it is needed or not. Which, if you hadn't noticed, is exactly what this thread is about.

And, I am curious why you (as usual) chose to ignore the material in my previous post and just write about your personal opinion? Are all the links in my post 'woo' in your opinion? because by my standards, it looks like quite established scientific literature all published in respected science journals. If you can refute it, then please, be my guest.

 

[DeiRenDopa]

Now is the quiet before the spam bomb.

How prescient!

That is all assuming that the only force at work is gravity, and it also assumes that gravity remains the dominant force when you scale up above the planetary/stellar level. We know that as you assend up scales other forces change their dominance, ie, EM forces usually far dominate gravity at smaller scales, so it is fully possible that as you scale up gravity starts to become secondary to other various forces and instabilities in plasma. After all, 99% of the observable universe is in the plasma state, and this was not known when current theories were fomulated, so it is highly likely this will change many things about the way we view space.

I see the problems with CDM and other similar cosmologies as follows:

• Like geology and unlike particle physics, cosmology is intrinsically an historical science and lacks direct experimental testing for many key hypotheses.

• Data in cosmology are limited to remotely sensed photons; there is no direct, in situ measurement as in space physics or planetary science.

• Most existing cosmology models focus on only one long-range force field (gravity) and ignore potential long-range effects of electromagnetism and plasmas.


On this last point, it is well known that electromagnetism is very effectively shielded out, which allows gravity to generally dominate over long scale lengths. Nevertheless, electromagnetism and plasmas can still be significant because:


“By definition, plasmas are an interactive mix of charged particles, neutrals, and fields that exhibits collective effects. In plasmas, charged particles are subject to long-range, collective Coulomb interactions with many distant encounters. Although the electrostatic force drops with distance (~1/r²), the combined effect of all charged particles might not decay because the interacting volume increases as r³. Magnetic field effects are often global with their connections reaching to galactic scales and beyond” (Goedbloed and Poedts, 2004) (Also see; B. Coppi, Attilio Ferrari, 2000 [full text])


Of course, this will be hotly contested by Big Bang advocates that require gravity being the only force at work, but is none-the-less a valid point that we have no real reason to discount at the moment.

The potential importance of electromagnetism and plasmas is indicated by the rapidly growing field of plasma astrophysics (see links and references at plasmas.org/). As one example of its significance for altering conventional assumptions, (Astrophysics: A New Approach, Kundt 2005) shows in detail how observed signatures of existing “black-hole” candidates can be more effectively interpreted as neutron star magnetospheres with accretion disks or neutron star binaries. Efforts to assess the potential impact of the new plasma astrophysics on cosmology issues are just beginning. Hopefully due to this we will not need to fill our universe up with CDM or other dubious metaphysical constructs, the vast and varied properties of plasma should be able to account for many of cosmologies unsolved mysteries in the near future.

Zeuzzz, did you read the OP?

Would you mind, terribly, if I asked you to not spam this thread with your PC woo?

In case you missed it, here are a couple of things I said, in my first post which presented substantive content relevant to the thread (per the OP; emphasis added):

Using textbook physics, these [spiral galaxy rotation] curves can be interpreted to mean that the mass 'closer in' to the centre of the galaxy (than at any radius) keeps increasing as the radius increases. In fact, no other standard physics textbook interpretation has been proposed, that is also consistent with all the relevant observations.

Somewhat in contrast to rotation curves of spiral galaxies, interpretation of the observations using the other techniques I've briefly mentioned does not have to lead to firm conclusions about mass differences ... however, as far as I know, no alternative explanations (based on standard, textbook physics) have been proposed that are also consistent with the 'lensing' observations I will cover next.

And a point of clarification shortly afterwards:

Note that this is only part of the observational evidence; for example, how various classes of dark baryonic matter can be ruled out - in spiral galaxies, ellipticals, and dwarf galaxies - is the subject of a later post (or several posts) ...

.

If you would like to ask questions about specific alternative explanations of spiral galaxy rotation curves, involving only standard textbook physics, which are also consistent with all the relevant observations, please do so.

Ditto with respect to the other, non-GR, observations of galaxies (not clusters of galaxies, not cosmology).

For cosmology, why not wait until I get to that?

Oh, and I'd like to second RC's point: if you want to present more 'plasma cosmology' woo, then please either continue in the thread you dropped out of (and start by answering the many questions you so conveniently walked away from), or start a new thread.

 

[DeiRenDopa]

We'll just have to see about these *cough* 'refutations of plasma cosmology' in the near future when I have time to respond to them. So far i have not seen any, but will be happy to discuss them if you think they exist. I only briefly visit here each day at the mo, and will start a thread all about PC when I have more time. I didn't even mention plasma cosmology anyway in that post. You seem to have inferred this yourself from just reading some standard plasma astrophysics material, which is very telling.

I am giving my opinion (and many other astronomers) on CDM, and whether it is needed or not. Which, if you hadn't noticed, is exactly what this thread is about.

And, I am curious why you (as usual) chose to ignore the material in my previous post and just write about your personal opinion? Are all the links in my post 'woo' in your opinion? because by my standards, it looks like quite established scientific literature all published in respected science journals. If you can refute it, then please, be my guest.

Oh Zeuzzz, are you so deluded? Have you learned so little in the physics classes you have been taking?

Here's what you just wrote (excerpt):

EM forces usually far dominate gravity at smaller scales, so it is fully possible that as you scale up gravity starts to become secondary to other various forces and instabilities in plasma. After all, 99% of the observable universe is in the plasma state, and this was not known when current theories were fomulated, so it is highly likely this will change many things about the way we view space.

[...]

Most existing cosmology models focus on only one long-range force field (gravity) and ignore potential long-range effects of electromagnetism and plasmas.

.

Though I must say your seagull appearances, to drop woo, are getting more sophisticated; it seems you have taken lessons from the IDers, and have begun a new career as a quote miner ...

 

[Zeuzzz]

Oh, and i forgot to add a link to the (Goedbloed and Poedts, 2004) reference where I got the quote from. Here it is; http://www.lavoisier.fr/notice/gb405993.html or here http://www.astro.uu.nl/siu/res-hg.html

 

[DeiRenDopa]

Though I must say your seagull appearances, to drop woo, are getting more sophisticated; it seems you have taken lessons from the IDers, and have begun a new career as a quote miner ...

Oh, and i forgot to add a link to the (Goedbloed and Poedts, 2004) reference where I got the quote from. Here it is; http://www.lavoisier.fr/notice/gb405993.html or here http://www.astro.uu.nl/siu/res-hg.html

...

right on cue ...

Don't you mean 'mined the quote'?