In the last batch of simulations, we dropped a long gas stream into the gravitational potential of a cluster to see if it would get torn apart and produce features resembling those seen in reality : small, optically dark hydrogen clouds without stars. It didn't. But it did turn the stream into some remarkably snake-like structures, which was nice.
An obvious and (relatively) easy to fix problem with this is that we just ignored the parent galaxy where the gas came from in the first place. We showed that this probably wouldn't make any difference, but of course it's better to test this. This way we can model not only what happens to the gas streams but how they form in the first place, as well as what happens to the galaxy.
It's just possible that if the initial structure of the streams produced is very different to what we assumed in the previous model, we might get a very different outcome. Also, if this does produce the dark hydrogen clouds we're after, we need to know if the galaxy still looks like a galaxy - if it gets smashed into something unlike anything observed, that would falsify the model. And probably the most important feature is the stars : with stars included in the galaxy we can now test if the clouds produced would really be optically dark or not. Previously we could only measure the properties of the gas and just assumed there wouldn't be any stars present.
A preliminary analysis shows that, as predicted, including the galaxy makes no difference for the dark clouds : they still form but they're still very, very rare - and that's without checking if they'd be optically dark or not, so I expect them to be even rarer in this model. The galaxies get bashed around a bit, but about half of them suffer no noticeable effects at all. The other half have some nice structures induced in them for a while, but nothing outlandish. They don't even lose a measurable amount of gas. And, alas, there are no more snakes...
People have been suggesting that dark clouds are some form of "tidal debris" for years, but there are only two other papers explicitly showing this is a possibility. Unfortunately those results have been over-interpreted. While large dark gas streams can be produced, small ones with properties like some of those observed are almost impossible to produce in this way.
There's still a fair bit of work left to do with these purely gravitational models. This model uses a galaxy with properties typical of a spiral galaxy, whereas the previous claims were based on one using a less massive spiral with a more gas that was more extended. So we need to do run a direct comparison to see if and how that influences the results. We also need to measure the stellar content of the stripped gas. Previous models said this was very low, I suspect ours will show it to be a bit higher. Still, it's very clear that the pure tidal debris scenario just doesn't work.
What is very much harder to predict is what would happen if we included the hot gas in the intracluster medium. In principle this is easy to do, in practise not so much. More physics, more computationally expensive. The original "flying snakes" took just a few days of computation time. These galaxies - which have more components and more stars - took about three weeks. Adding in the surrounding gas could make things take several times longer again. We'll get there eventually, but not today.
Peratt uses this approach to create a model which treats the galaxy fundamentally as a plasma phenomenon. And this makes sense, because people have been creating galaxy-like structures within the laboratory using plasmas since Bostick (50's!). There's no need for dark matter with this approach, as Peratt demonstrated in the early 80's on government supercomputers.
ReplyDeleteSee here:
http://www.plasma-universe.com/Galaxy_formation
The problem with modeling today is that the modelers are all looking at each others' work as a guide for what work they should do. If you want to create historical work in this area, you must extract yourself, foremost, from the social dynamics which are at play in these fields. The stench of politics is thick in these domains. To become a part of history here, a person has to learn to appreciate successful-but-underappreciated work, and they must give up any hope of being celebrated for their successes within their own lifetimes.
It is the choice which everybody in these fields today must make:
Do I create papers which the community will find acceptable, but which will in due time be disregarded since the community has worked itself into a theoretical dead end?
Or do I create papers which are truly groundbreaking and historical and which are in service to where the data is plainly taking us?
We need more people today opting B. A willingness to take risks and attempt "new" approaches is the only way we'll get out of the current mess.
In fact the intergalactic structures I'm studying are hundreds to thousands of times larger than the Herschel galactic filaments, and we can be confident that they are transient. Indeed, it's a mystery why they aren't stable ! In the Virgo cluster (and others) galaxies have significantly less HI than galaxies in the field and smaller HI discs, so they appear to have lost much of their original gas content. The above simulations show that this cannot be due to harassment by the other galaxies. Other simulations have demonstrated that ram pressure stripping by the ICM could easily be responsible. The problem is that those simulations predict detectable HI emission on scales >100 kpc. Only four such features are known in the entire cluster, despite there being >300 late-type galaxies which are losing gas (quantifying how many streams we expect to detect is a work in progress, I suspect it will turn out to be around a factor of ten more than are actually detected). So there must be some mechanism which rapidly destroys most of the streams but not all.
ReplyDeleteAs to the galactic-scale filaments, I'm no expert in this, however many of my colleagues are.
What Herschel has shown us is that the filamentary structures are, without a doubt, not circumstantial or due to chance observation: They are in fact a fundamental aspect of star formation. What we see is that transient events can produce many stars at once like pearls on a necklace.
Many in the star formation community are in full agreement, this is a regular topic of discussion whenever a star formation workshop rolls into town. I know quite a few people involved in simulating such filaments and they look reasonably convincing to me as a layman. Not sure about forming stars along a line though, as the people I know are mainly interested in forming clusters.
Verschuur is one of the few astronomers in the world who is analyzing the HI hydrogen all-sky surveys by hand.... Herd mentality has led the radio astronomy community towards more of an algorithmic WMAP approach
Not true at all ! I for one spent several years writing a code to let me and others analyse HI data by hand more efficiently (http://astrorhysy.blogspot.cz/2014/08/hydrogen-dinosaurs-and-user-support.html). The ALFALFA team use a combination of visual and automatic extraction. I know some of the GALFA-HI team personally and know for a fact they look at their data, not three days ago I made a movie for someone overlaying the HI and CO data. Actually I've never heard of anyone who relied entirely on automated source extraction for an HI survey, it would be a very silly thing to do since no automated extractor is good enough. I wrote an automatic extractor, but I would never pretend it's anything more than an aid - even for unresolved extragalactic sources, which are much the easiest things to analyse.
As new telescopes begin to increase the data rate, we will inevitably (given the small size of the community) need to rely more on automated techniques. But I very much doubt this will mean we never look at data - instead, it should tell use which parts are likely to be worth looking at in detail. Don't know about WMAP, though I do know a lot of people in the optical surveys rely much more heavily on automatic techniques. Too heavily, perhaps - but then that doesn't mean that no-one is doing more detailed analysis on smaller data sets. Far from it.
The stench of politics is thick in these domains.
No it isn't. You may like to think so for some reason, but it isn't. If anything the opposite is true : people are actively competing to disprove each other. I have witnessed this many, many, many times. It varies from mild rivalry to (quite literally) death threats. If someone could come up with a rival model that would do a better job, no matter how crazy it might at first appear I have absolutely no doubt whatsoever they would do so and shout about it very loudly, regardless of their career prospects.
ReplyDeleteRhys Taylor Re: "If someone could come up with a rival model that would do a better job, no matter how crazy it might at first appear I have absolutely no doubt whatsoever they would do so and shout about it very loudly, regardless of their career prospects."
ReplyDeleteBut, Peratt already did this on government supercomputers. He has shown that dark matter is not necessary; we can explain galactic rotation curves. We simply have to alter the way in which astrophysicists model cosmic plasmas.
You seem to think that the scientific community can have it both ways: The powerful knowledge that is gained from the focus of specialization on one hand ...
... yet also the wisdom and power to properly self-correct which only a broad view can provide.
You cannot have both without extreme effort to do so. The scientific community has chosen the former, and it is at the expense of the latter.
If you'd like to see an example of how this works, see Tim Thompson's rebuttal to Peratt's galactic simulations, where he freely admits that galactic researchers have never taken the time to actually learn the research supporting this alternative approach (which Tim blames Peratt for!) ...
http://www.internationalskeptics.com/forums/showpost.php?s=808a20363648151505620e5b174cdc4c&p=4782369&postcount=8%EF%BB%BF
Tim wants us to believe that the Astrophysical Journal would treat Peratt's approach fairly, but IEEE and the AJ operate from two competing sets of assumptions.
What we end up with is specialist scientists critiquing ideas from other specialists, even though they freely admit that they cannot take the time to actually learn that which they are critiquing. Yet, they still assert that they are experts over the domain (the territory). But, what they are critiquing is a competing worldview which they admit they do not understand. The domain and worldview are conflated by mainstream thinkers and science journalists, as if there are no competing worldviews.
What we have here is a tower of babel. Nobody is taking the time to formulate a broad view, and the end result is typically confusion.
Chris Reeve
ReplyDeleteYou cannot have both without extreme effort to do so.
Of course you can, that's why we have conferences ! Specialists in different areas meet and interact all the time. And people do do background reading in areas outside their own specialist field. Individuals may be specialists (not everyone is), the community is general by definition. Self-correction happens constantly (this very post is an example of that !!), and people regularly publish radical alternative ideas. I don't know why you want to think it doesn't.
http://astrorhysy.blogspot.cz/2015/10/false-consensus.html
I agree with Tim. It's obvious that if you report your ideas in an obscure journal then no-one will read it. I see a search for "Peratt" returns zero results on arXiv, which is basically a declaration of obscurity. It's really not that hard to publish in the standard journals, let alone upload to arXiv. If you don't put your work where people will read it, then no-one will read it.
In any case, testing alternative fringe ideas isn't the goal of these (current) simulations. They only show that one popular model doesn't work. The idea of testing this with MOND has been raised, which might be feasible but it's some way down the line. As I said, increasing the complexity of the physics - even when adding in something simple like external gas pressure - greatly increases the computational cost. Practical limitations cannot be ignored.
Truth be told I'm not really much of theorist anyway, just an observer. I'd rather be publishing papers on a bunch of observational data that's being lying fallow for quite a while now. If someone else wants to try and simulate these objects using an alternative method, I will be more than happy to consult with them to compare their results with the observations. But I have neither the time, inclination, and certainly nothing remotely like the expertise required to do this myself. I gave up a good chunk of the last ~18 months or so just learning how to do these simulations, I doubt very much I'd be able to handle magnetohydrodynamics at all.
In any case, so far it looks like the dark galaxy hypothesis works pretty well. Therefore any alternative model must do at least as well as that, so it makes little sense to say that we have to change the way we model plasmas. That looks to me to be unnecessary at this stage. Which is not to say it isn't something that shouldn't be done for the sake of testing an alternative, only that it would be extremely foolhardy to assume that current physics is definitely wrong.
Rhys Taylor IEEE is not an obscure journal. It's the world's largest technical organization. It's also the only place in the world currently where scientists can publish papers which explain astronomical observations using laboratory plasma observations, because they do not reject papers there which model cosmic plasmas as having non-zero E-fields.
ReplyDeleteThese are hardly fringe ideas. Kristian Birkeland successfully explained the aurora using this approach. Anthony Peratt has advised the Department of Energy on the Nuclear Non-Proliferation Treaty. He works on the z-machine, one of the world's largest plasma laboratories. You're not going to find a more qualified critic of astrophysical theory.
MOND is simply math in need of a physical basis. The theorists I am pointing you to are approaching the problem from the other side: start w a physical basis and work towards a math solution. That is the approach which Birkeland used to such effect.
Astronomers read papers in ApJ, A&A, MNRAS, etc. If you want astronomers to read a paper, publish in one of those. If they're publishing papers on galaxies full of Dyson spheres to explain outliers from the Tully Fisher relation, then I don't accept that they'll reject plasma cosmology if it's got anything sensible to say. And stick it on arXiv like everyone else does, that is pretty much where everyone in the astronomy community finds out about papers these days. Regardless of the size of the IEEE, Transactions on Plasma Science is a total non-entity as far the astronomy community are concerned.
ReplyDeleteAnd yes, they are fringe ideas. Plasma cosmology / electric universe is not a thing in mainstream astronomy, it exists only on the internet. If you want it to transition to having a wider audience, it must publish in typical journals.
Rhys Taylor All of those journals rely upon fluids-based MHD models. They assume that cosmic plasmas, unlike the plasmas we observe in the lab, exhibit zero electrical resistance. They assume that E-fields play no important role in cosmic plasmas. They also assume that large-scale magnetic fields are frozen-in rather than simply electrodynamic.
ReplyDeleteThis approach was invented by Hannes Alfven, who of course published in IEEE. Alfven was awarded the Nobel for this invention and used the occasion of his 1970 acceptance speech to distance himself from this approach.
He never intended this technique to be applied throughout the discipline. And he considered his own invention of MHD to be his biggest mistake.
Graduate students who learn the MHD equations are not taught any of this history today.
Rhys Taylor The situation is in fact quite remarkable. I know of no other situation in any scientific discipline where the insistence that we should be looking to the laboratory to understand something is treated as "fringe" or "pseudoscientific".
ReplyDeleteThat is the premise of all of the works published in IEEE's Transactions of Plasma Science. The heresy, simply put, is that ...
We can understand cosmic plasmas by studying laboratory plasmas.
It's apparently absurd, but it seems that the reason why can only be explained through the history of the domain. The mistake which people make is in relying upon science journalists to convey that history.
They don't.
That's only true of Ideal MHD. Resistive (Ohmic) MHD has been the norm in astrophysical simulations for many years, ever since it became computationally practical.
ReplyDeleteAnd it's not true that they ignore lab studies, rather that most are performed under conditions that are nothing like those found in space. They have to use the universe as our lab because there isn't anyone doing super low density cold plasmas on earth.
Catherine Braiding Whatever change you are speaking of has definitively left us with the situation where magnetic fields are still not associated with electric currents -- as occurs in every plasma laboratory here on Earth every single day.
ReplyDeleteMy first question is does Resistive MHD permit E-fields? Does it suddenly force astrophysicists to consider the role of electric currents in large-scale magnetic fields?
Adding the resistance back in only solves one of the three areas of difference between fluids and plasmas.
The standard here should be: Are the cosmic plasmas permitted to behave as laboratory plasmas?
The induction equation generally includes terms for the current, yes.
ReplyDeleteI would suggest you look into the work of Mark Wardle and BP Pandey (Pandey came from a plasma physics background), Mouschovias, T Ch, and Inutsuka, S. - They all specialise in molecular clouds and star formation, which was my area of research for a long time.
And you haven't really answered my question: How much should we depend upon lab plasmas when the conditions in the lab are nothing like those in space?
Catherine Braiding Re: "How much should we depend upon lab plasmas when the conditions in the lab are nothing like those in space?"
ReplyDeleteVerschuur observed redshifts which correspond with the CIV's of common elements. That indicates ongoing ionization.
The ionosphere is layered. Have you ever charge-loaded a metal sphere in a bell jar? It is very easy to create layered plasmas. Those are of course in the lab called double layers. They are electrodynamic phenomena.
Double layers have been observed recently by instrumentation in space ...
http://physics.aps.org/articles/v6/131
"The remarkable result reported by Mozer et al. is that streams of 7000 double layers were observed in one minute: it was like ascending a stairway of 7000 steps very quickly. Each double layer is detected as an electric field spike of a typical duration of 0.45 milliseconds and a potential step of about 30 volts. The train of double layers propagates along the magnetic field lines at 3100 kilometers per second, which is the speed of an unusual mode called electron acoustic waves that can exist in a plasma containing both hot and cold electron populations [8]"
The presence of DL's indicates that astrophysicists are using the wrong set of assumptions in particular, common situations.
There has been a push at the IEEE to classify DL's as astrophysical phenomena. The idea that they can be observed, yet not officially acknowledged, is really a throwback for me to the Renaissance. How exactly does one seal the deal on that?
As you of course know, synchrotron radio is very common. That is electrons spiraling in a magnetic field.
Yet, when the specialists and science journalists talk about radio waves, they seem to gloss over that fact -- as well as many other facts which would seem to make the case for a more electrical situation in space.
That doesn't actually answer the question - how similar are the conditions (not the results of the experiment) to those in space ? It is entirely possible to get a result in excellent good agreement with observations - right down to the small details - by a completely wrong method.
ReplyDeletehttp://astrorhysy.blogspot.cz/2016/04/perfectly-wrong-or-necessary-but-not.html
Again, publish the results in an actual astronomy journal, not somewhere else. None of the main astronomy journals are beholden to any particular model. Doesn't matter how good the reputation of the other journals are or how good the science is, if you publish somewhere that astronomers don't read, then astronomers won't read it so of course it will be regarded as fringe. That's self-evident. Knowing which journal to publish in can hardly be as complicated as understanding MHD itself, which leaves me extremely skeptical of the EU claims to put it mildly.
Rhys Taylor Re: "That doesn't actually answer the question - how similar are the conditions (not the results of the experiment) to those in space ?"
ReplyDeleteThe issue is that one of the claims which has been made is that plasmas scale. The very reason why Kristian Birkeland is called by some the first laboratory astrophysicist is that it is possible to do laboratory verification of the claims being made. He built a terrella and replicated many planetary sciences phenomena such as the aurora.
Why is it that Bostick was able to create galactic morphologies in a small plasma lab experiment with nothing but an electrodynamic plasma? That was in the 50's.
In principle, it is conceivable that some solar phenomena which have to-date been attributed to large-scale processes will in fact be reproduced within the laboratory through electrical experiments.
That even well-informed experts consistently ignore this situation is maybe short-sighted.
Further, there's really no reason at this point to assume homogeneity of charge. The presence of DL's can cause large charge differentials.
What I am saying is that your simple narrative that all space has similar charge is certainly not based upon anything we've observed within the laboratory. In the lab, there are DL's. DL's create discontinuities in charge density.
So conditions are not similar, and the justification is that the results look similar to the observations. See link above for why one has to be very careful about that line of reasoning.
ReplyDeleteI never said anything about all of space having a similar charge.
Rhys Taylor At certain charge densities, gravity stops being the dominant force. This charge density is far lower than most people acknowledge. We observe the transition to occur below 1% for the ionosphere.
ReplyDeleteIt was Alfven's observations of the ionosphere which led him to realize his mistake.
"Verschuur is one of the few astronomers in the world who is analyzing the HI hydrogen all-sky surveys by hand. He does this because the HI hydrogen features must be picked apart in order to meaningfully analyze their structure and behavior. Herd mentality has led the radio astronomy community towards more of an algorithmic WMAP approach. When the data is analyzed by hand, evidence for ongoing ionization reveals itself. You will start to see redshifts which occur at specific critical ionization velocity values. Mainstream astronomers try to explain this away, but this sort of thing is to be expected in the electrodynamic plasma approach because the filaments will be rotating, at times generating synchrotron. That rotation, by itself, can induce an electromagnetic pull of ions from the surrounding space. And we can expect to see a fairly well-structured layering within the filament itself."
ReplyDeleteUnfortunately Gerrit has a cold today, so I can't ask him about this, but I've never heard him talking about 'redshifts which occur at specific critical ionization velocity values'. I think you may be misunderstanding his work on Galactic hydrogen. Also, as Rhys pointed out, we've been analysing our (extragalactic) hydrogen data by hand all the way through.
Also, with Gerrit having published three papers in ApJ in the last three years, I don't think you can argue both that (a) he agrees with you and (b) mainstream astronomy journals refuse to accept your work because they are biased. At least one (and I suspect both) of these must be false.
Incidentally, there's a whole division of the American Astronomical Society devoted to Laboratory Astrophysics and a European Task Force on Laboratory Astrophysics. The idea that astronomy ignores what happens in laboratories is patently false, when those results are actually useful in an astrophysical context.
Robert Minchin Re: "Unfortunately Gerrit has a cold today, so I can't ask him about this, but I've never heard him talking about 'redshifts which occur at specific critical ionization velocity values'. I think you may be misunderstanding his work on Galactic hydrogen."
ReplyDeleteI find it telling that we are having this conversation at all.
We've already seen in this thread a failure by one person (who was apparently called here to correct the record) to understand that double layers -- one of the most important features of electrodynamic laboratory plasmas -- are apparently observed in space.
It seems that we are now adding CIV's to the list.
See Verschuur's paper at https://arxiv.org/ftp/arxiv/papers/0704/0704.3021.pdf
"In a simple model for the Galaxy, nearby gas shares a motion not very different from that of the sun, and hence there would only be a small Doppler shift of order 10 to 20 km/s due to random bulk motions known to be typical of interstellar space to produce the observed emission profiles. What is observed is far more complicated, however. Local HI with velocities around zero km/s with respect to the local standard of rest (l.s.r. - the standard defined by radio astronomers, who display HI emission profiles as a function of this velocity) usually dominates the high galactic latitude profiles but there is also a great deal of emission around –50 km/s, produced in a population of so-called intermediate velocity clouds, as well as about –125 km /s for so-called high-velocity clouds. An unambiguous estimate for the distance to these HI features has not yet been agreed upon although there is little doubt that they are galactic.
Verschuur & Peratt [1] have described the Gaussian decomposition of interstellar HI emission profile shapes and find that at least three families of linewidths of order 34, 13 and 6 km/s characterize the profiles. If the linewidths are taken to indicate kinetic temperature these would imply that the HI along a given line of sight manifests temperatures of order 24,000, 3,500 & 750 K. However, at the former value the hydrogen atoms should be ionized and hence not observable at 21-cm wavelength.
Recently published results of a more extensive study [2] confirm the existence of these linewidth families"
_We've already seen in this thread a failure by one person (who was apparently called here to correct the record) _
ReplyDeleteNo-one was called here.
Chris Reeve There is nothing there about redshifts, Gerrit is talking about linewidths in the paper you linked to. The combination of your apparent inability to distinguish between completely separate concepts and your rude dismissal of those who disagree with you in any way as being unable to understand concepts is pretty persuasive evidence that you are actually a crackpot pseudo-scientist and it isn't worth my time engaging with you. I'm not surprised you haven't been able to get your papers published if this is the attitude you show generally.
ReplyDeleteRobert Minchin If I've personally erred in calling them redshifts, it does not at all change the reason for this discussion.
ReplyDeleteThe fact of the matter is that neither CIV's nor double layers are currently considered to be astrophysical phenomena in the mainstream -- even though they've both apparently been observed in space.
Both concepts point to a fundamental mistake in the way in which cosmic plasmas are being modeled.
CIV's indicate ongoing ionization on a significant scale.
A double layer is the sandwiching of plus and minus charge next to each other, without combining. It only makes sense in an electrodynamic context; without an ongoing electrical current, it would disappear.
Why would such observations be ignored? Rhys seems to think that there are no politics in this domain, but both of these observations happen to undermine conventional theory.
Starting from the premise of a gravity-dominated universe, there's no reason to consider either.
That's fine. But, that also explains why researchers choose to publish in particular journals. The point of peer review is not to judge scientific frameworks. To claim that findings which support a more electrical view of the universe should be published in a journal which favors a more gravitational perspective is not a process for facilitating innovation in this domain.
Robert Minchin Here's an excerpt from Verschuur's The Invisible Sky on the controversy over HI hydrogen ...
ReplyDelete"Anomalous Velocity Hydrogen
Not all is understood about the distribution of HI in the Milky Way. For example, large areas of sky are found to contain HI moving at velocities that are not expected if the gas is confined to the plane of the Galaxy. In particular, when a radio telescope is pointed above or below the galactic plane, only relatively local gas traveling at velocities between ±20 km/s with respect to zero, defined in terms of the average random motion of stars near the sun, should be observed. However, HI at very high negative velocities, which indicates motion toward us, is found at high galactic latitudes. These structures are known as high-velocity clouds, although detailed maps of such features show them to be filamentary instead of cloud-like. Their distance and origin continue to be the subject of controversy."
The filamentary nature of these structures is very significant, insofar as laboratory plasmas conduct electricity over filaments.
The CIV's are observed to be associated with these filaments. Correct me if I'm wrong, but if they truly exist in space, CIV's are being misinterpreted as velocities. In IEEE, theorists leave the door open to a rotational explanation.
When Verschuur raised this problem, he was dismissed by the WMAP group. And everybody continued on, as if the claim was never aired. But, why is the WMAP group even qualified to react to this claim? It's not clear that their own approach to this analysis could even identify CIV's, much less disprove them.
It is a disgraceful and dangerous thing for an infidel to hear a Christian [theologian]... talking nonsense on these [scientific] topics, and we should take all means to prevent such an embarrassing situation, in which people show up vast ignorance in a Christian and laugh it to scorn.
ReplyDeleteOr in other words... comments closed !