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    Default Dark Matter - don't we see all we need? Part 2



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    as-yet-un-human-un-observed "Dim Matter"

    (0) Before Galileo, humans were limited to direct visual detection, of astronomical objects. How many stars are there, listed, in Ptolemy's Almagest -- hundreds ?

    Even +300 years later, humans still believed, that their galaxy, containing hundreds of billions of stars, was an 'island universe'. Today, humans know, that 'the Universe' stretches across a colossal cosmos, encompassing hundreds of billions of galaxies.

    Every time, that humans have developed & deployed more sensitive space 'eyes', they have seen huge amounts of more material, previously unsuspected of even existing. Thus, space observation is no where near a 'mature' science, like modern propeller aircraft, or internal combustion engines, where eking out additional performance is a costly & time-consuming art. Instead, space observation is more like the human aircraft industry, in the 1920s, with the 'bare bones basics' understood, but rapid improvements in performance still patently possible.

    As the following examples show, as a general rule, one can seemingly always postulate the presence, of lower luminosity examples, of known-and-observed higher luminosity objects. To wit, one can always extend the 'luminosity function', of astronomical objects, to lower luminosities, and infer the existence of m-o-r-e (not necessarily 10x more) normal-but-as-yet-human-un-detected "dim matter". Now is no-where near time to 'call it quits' on 'space eyes', and pushing for fainter, lower-luminosity detections, of "dim matter".



    (1) Gamma-Ray-Bursts (GRBs) are high-energy Super-Novae (SN), caused by the core collapse, of super-massive stars. Such 'Hyper-Novae' (HN), then, should reflect the local, there-and-then Star Formation Rate (SFR). And, such is completely consistent with current human observations, if one infers the existence, of an as-yet-human-un-observed population, of low luminosity host galaxies:

    Correcting for this, we find that the implied SFR to beyond z = 8 is consistent with measurements based on Lyman-break galaxies after accounting for unseen galaxies at the faint end of the UV luminosity function (kistler).


    (2) Metals, observed in the absorption spectra of distant Quasars, suggest the inferable existence, of as yet-human-un-observed, low luminosity galaxies:

    There is now clear evidence, for the presence of massive winds, from Lyman-break galaxies (LBGs). The spectra of LBGs often show strong absorption lines, e.g. of CIV, which are blue-shifted relative to the velocity of the emission lines in the galaxy... Such absorption can be produced, by a wind, moving out from the star-forming regions of the galaxy, so that is red-shift is smaller than that of the emission regions. Characteristic velocities are ~200 km/s...

    Whenever the sight-line to a QSO passes within ~40 kpc of an LBG, very strong absorption lines (w/ column density exceeding 1e14 cm-2) are produced, and that the corresponding absorbing material spans a velocity range of dv > 250 km/s; for about half of the cases, strong CIV absorption is even produced, for impact parameters within 80 kpc. This frequency implies, that about 1/3 of all CIV metal absorption lines, with N>1e14 cm-2 in QSO spectra, are due to gas within ~80 kpc from those LBGs, which are bright enough to be included in current surveys. It is plausible, that the remaining 2/3, are due to fainter LBGs (Schneider. Extragalactic Astronomy and Cosmology, p.378-9).


    (3) Half of all human-observed baryons, detected in the old-and-far-away universe (z>2), 'go missing' from the young-and-near-by universe (z<2):

    At 4 > z < 2, the majority (~85%) of baryonic matter is contained in the Ly-a forest, mainly in systems of column density 1e14 cm-2 < N(HI) < 3e15 cm-2. Thus, at these high red-shifts, we observe nearly the full inventory of baryons. At lower red-shift, this is no longer the case. Indeed, only a fraction of the baryons can be observed in the local Universe, for instance in stars, or in the inter-galactic gas, in clusters of galaxies.

    From theoretical arguments, we expect that the majority of baryons today should be found in the form of intergalactic gas, for example in galaxy groups & large-scale filaments, that are seen in simulations of structure formation. This gas is expected to have a temperature between 1e5 and 1e7 K, and is therefore very difficult to detect; it is called the 'warm-hot inter-galactic medium'. At these temperatures, the gas is essentially fully ionized, so that it cannot be detected in absorption line spectra. However, the temperature and density are too low to expect significant x-ray emission from the gas (Schneider. Extragalactic Astronomy and Cosmology, p.334-5).
    If you add up all the visible matter in galaxies today, you get only about a tenth of the total endowment created by the big bang. Where is the rest, and why did it not end up in galaxies? ... The current best guess is that the bulk of the normal matter is trapped in giant gaseous filaments. This so-called warm-hot intergalactic medium, or WHIM, is hard to detect directly (Geach 2011).


    (4) More sensitive sky surveys always have detected dimmer, more distant, ever fainter and far-away, galaxies:


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    Back again? I'm sorry, but I'm quite concerned about all the misinformation you try to spread. This particular post is innocent enough, as you merely say that better telescopes show more stuff, but I know that this is just the start of your claim that:

    Quote Originally Posted by Widdekind
    Yet, with 'dark matter' & 'dark energy', "Magick & Mystery" are again entering (human) Science.
    I know that you are not shy about mischarcterizing science, as in:

    Quote Originally Posted by Widdekind
    "Dark Matter" -- 'Theoreticians', scrawling symbols on blackboards, claiming that their formulas, for fusion physics, are an accurate mathematical model, of the ultra-early universe -- and then claiming that those models are incompatible, with much 'normal matter'
    I wouldn't care so much if it weren't for the fact that you try so hard to spread pseudoscience and other posters start believing you, thinking that you have done impartial research. We all generally assume that other posters are acting in good faith and that if contrary evidence was presented to them, they would change their mind. In turn, spreading speudosciece it tends to create an undeserved distrust and disdain for real science. In your last post you accused me of mis-represeting you. I think that my reply to your post showed evidence that I didn't.

    If you want me to think more highly of you and your intentions, you will probably have to correct some of your false statements (e.g. description of dark matter) or show that explanations and evidence can sway your opinion. But so far what I have seen from you is that when counter all your points, you just go quiet for a few days, and then come back and continue posting the same ideas as before like nothing happened.
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    It is common knowledge, that popular science presentations, about "dark matter" & "dark energy", tend to trumpet the "mysteriousness" of the mass-energies, that they represent.

    It is exactly true, that theoretical physicists claim, that their mathematical formulas, "scrawlable on blackboards", accurately model the ultra-early universe -- and that those mathematical models claim, that our space-time "cannot" contain much "normal" matter. Now, it may also be true... that those claims... are also... themselves... true. To wit, if those theoretical physicists' mathematical models are, actually, correct... then, even so, this writer did not misspeak.

    I am deeply suspicious, of non-baryonic 'dark matter' (except for neutrinos), and 'dark energy'. My being suspicious, neither makes me correct, nor incorrect. My being suspicious, neither makes other physicists correct, nor incorrect. My asking questions, arising from my skepticisms, does not impede the progress of scientific inquiry.

    I would like to point out, with appropriate politeness, that the same human physicists, who claim to comprehend fusion physics, in the ultra-hot, ultra-dense, ultra-early universe... cannot themselves manage to manufacture so much as a single working fusion reactor -- at far more 'mundane', 'mere star core' temperatures & densities. For example, a question from me to you -- how do Primordial Nucleo-Synthesis physicists 'know' what the appropriate capture cross-sections are? How do humans 'know' how matter behaves, at 500 mega-kelvin, at ultra-densities & pressures?

    And more, if I may -- the current-conventional cosmology accepts that space-time has a slight positive (closed) curvature. Er go, our space-time is closed, and was so, in the ultra-early universe. Er go, Primordial Nucleo-Synthesis did not occur in flat space-time, but in a potentially highly-curved 'hyper-spherical' space-time. How would a closed space-time curvature affect the fusion physics, of the 'ultra-plasmas' present, at that ultra-early epoch?

    Interlude -- if the CMBR, today, is a few kelvin; and if that same radiation, during PNS, was a few hundred mega-kelvin; and if radiation temperature scales with redshift (1+z); then PNS occurred at a redshift of z ~ 1e8. And then, if the current 'cosmic curvature radius' is ~100 billion light-years, then the 'cosmic curvature radius', during PNS, was smaller by the factor of 1e8 -- to wit, ~1000 light-years. Given that fusion is a micro-scopic phenomenon, I suppose that a ~1000 ly Rcurv would make space-time still seem fairly flat. So, perhaps, though I know not, assuming a flat space-time 'backdrop', for the fusion physics, is not inaccurate.
    I neither know the answers to any of these questions, nor currently comprehend, why they would be non-relevant, to the relevant 'ultra-fusion' physics.

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    Quote Originally Posted by Widdekind View Post
    It is common knowledge, that popular science presentations, about "dark matter" & "dark energy", tend to trumpet the "mysteriousness" of the mass-energies, that they represent.
    Popular science presentations are driven by what people want to hear. In any case, I don't think it is wrong to say that dark matter and dark energy are mysterious. We don't know what they are. That does't excuse you from calling them magic. In science there is always something we don't understand. That is the whole point of science, to look at things that are currently a mystery and learn how they work.


    It is exactly true, that theoretical physicists claim, that their mathematical formulas, "scrawlable on blackboards", accurately model the ultra-early universe -- and that those mathematical models claim, that our space-time "cannot" contain much "normal" matter.
    Theories about the early universe is only one of several lines of work that point in the direction of dark matter. I have listed a number of other lines of work which you seem to just ignore:

    - Galaxy rotation curves.
    - Cluster dyamics.
    - The bullet cluster.
    - Lack of microlensing events (point against Machos).
    - Galaxy simulations that fail to form galaxies without dark matter.
    - Extensions to the standard model predict heavy neutral particles.
    - Type Ia Supernovae / acceleration of the universe.

    Dark matter is by no means proven, but your characterization of it as nothing more than scribbles about the early universe is simply false. Furthermore, I should note that those "scribbles on a black board" are actually sound science based on experiments (e.g. in particle accelerators) that tell us how physics behave at high energies. To suppose, as you do, that this is wrong and that the laws of the universe used to be different, without any shred of evidence, is akin to believing in magic.

    I am deeply suspicious, of non-baryonic 'dark matter' (except for neutrinos), and 'dark energy'. My being suspicious, neither makes me correct, nor incorrect. My being suspicious, neither makes other physicists correct, nor incorrect.
    There is a line between healthy skepticism and unwarranted mistrust of scientists. Where is the line between a skeptic and a conspiracy theorist? Where is the line between a doubt and magical thinking?

    A scientist is a human being, who is not stupid, and is deeply curious about how the world works. The scientist has no interest in creating magical hypotheses without any basis in real evidence. Rather than assume that scientists are just making up bullsh*t and reaming up a make-belief world, or that they are universally delirious, you should consider the possibility that you might not know the subject well enough and need to learn a little more.

    In the course of my conversations with you I have pointed out a good number of fundamental flaws in your thinking and your guesses of how evidence is conducted. You have repeatedly said that dark matter is scribbles on the black board about the early universe even though I have extensively shown otherwise (e.g. my list above). You have insisted that the mass of the universe is measured by looking at the HDF and HUDF and counting the number of galaxies there, even though I have explained that this is false and absurd. At which point does one cross the line from healthy skepticism and legitimate scientific inquiry and move into the realm of conspiracy theory and pseudoscience?


    My asking questions, arising from my skepticisms, does not impede the progress of scientific inquiry.
    As I said in this post, which you seem to have ignored, you do not merely raise questions, you make assertions and claims which are false, and insist on them regardless of the evidence or arguments presented to you.

    Asking questions = Good.

    Curiosity = Good.

    Spreading misinformation= Bad.

    Ignoring explanations = Bad.


    I would like to point out, with appropriate politeness, that the same human physicists, who claim to comprehend fusion physics, in the ultra-hot, ultra-dense, ultra-early universe... cannot themselves manage to manufacture so much as a single working fusion reactor -- at far more 'mundane', 'mere star core' temperatures & densities.
    I'm sorry, but this is a load of crap. Please excuse my non-politeness, but I cannot believe that you are saying this with a straight face. Making a fusion reaction has absolutely nothing to do with understanding how fusion works. It is an engineering problem, and a difficult one. The problem is not that we cannot make it work (Hydrogen Bombs work very well) the problem is making a machine that is a heck of a lot smaller than a star and still manages to produce the same temperature and pressure of a stellar core and can extract energy in order to run an electric generator in a way that is safe, reliable, economical and financially practical. Next you'll say that we don't understand antimatter because you cannot buy antimatter at a pharmacy.

    For example, a question from me to you -- how do Primordial Nucleo-Synthesis physicists 'know' what the appropriate capture cross-sections are? How do humans 'know' how matter behaves, at 500 mega-kelvin, at ultra-densities & pressures?
    The first question is like asking "how planets know about gravity". For the second question I would direct your attention at a machine known as a particle accelerator. Our understanding of the early universe is limited by our experimental ability to recreate conditions with particle accelerators. That's why there are some parts of the early universe that are well understood and other parts that are not understood at all. We know how hadrons behave at high energy, we have been studying them in particle accelerators for ages.

    And more, if I may -- the current-conventional cosmology accepts that space-time has a slight positive (closed) curvature. Er go, our space-time is closed, and was so, in the ultra-early universe. Er go, Primordial Nucleo-Synthesis did not occur in flat space-time, but in a potentially highly-curved 'hyper-spherical' space-time.
    The first thing you've shown here is that you don't know how to read scientific quantities. This is the figure you quote:

    Omega_tot = 1.0023 +0.0056/-0.0054

    This value cannot be distinguished from zero based on those error bars. The measurement and the 1-sigma error bars include both zero ad negative Omega_tot. The correct statement is that we do not the sign of Omega_tot.

    The second thing you've shown is that you'll happily make guesses about the implications of Omega_tot > 0 and simply assume that your guesses are true. Here you have assumed that Omega_tot > 0 would be a problem. Please read the Wikipedia page on the Flatness Problem. Let me quote just a bit:

    Quote Originally Posted by Wikipedia
    The current density of the universe is observed to be very close to this critical value. Since the total density departs rapidly from the critical value over cosmic time,[1] the early universe must have had a density even closer to the critical density, departing from it by one part in 1062 or less. This leads cosmologists to question how the initial density came to be so closely fine-tuned to this 'special' value.
    If the universe today is very close to Omega_tot = 0, the early universe would have been even closer. I understand that this sounds counter-intuitive, but you should have made an attempt to check your assumptions before using them as evidence against the modern cosmological model.

    Anyway, the Planck epoch is the epoch of the universe where gravity should play a role in quantum mechanics and vice versa. This period is entirely unknown because we lack a theory of quantum gravity. But this period also happens well before the nucleosynthesis period of the early universe.
    Last edited by DanielC; 07-14-2011 at 01:17 PM.
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    Every month, every issue, of every pop-sci magazine (Discover, Science News, Science Illustrated, Popular Science, Astronomy, Sci-Am) typically trumpets the "mysterious non-common-sensical-ness" of Cosmology ('dark-this-and-that-and-the-other'), and Quantum Mechanics ('QM-is-so-counter-intuitive'). Such statements stimulate a strong sense of skepticism, in me.

    That said, I see no need to argue, over science. If 'dark energy' -- alias, 'cosmic anti-pressure', which words I find less averse -- turns out to be true, I simply want to know what it is, and what can be done with it. I don't have a vested interest, in the non-existence, of cosmic anti-pressure, etc. Maybe the hype helps sell the science, at least a little, to a wider audience, which would be welcome.

    I do press the point, that "Dim Matter" does exist -- half of all baryons, even 'by the books', exists in an as-yet-human-non-detected state. That's a few trillion solar masses, between here & Andromeda ('more than less'). Now, presumably, those particular baryons are ultra-diffuse, warm inter-galactic HII gas. But, there is a general principal, which point I politely press:

    Dim Matter -- everything astronomical has a lower-luminosity 'cousin', somewhere in this cosmos
    For 2000 years, since Ptolemy, humans have detected more & fainter stars, that they never saw before; more & fainter galaxies; more & fainter inter-galactic gas; and so on. You can (almost) always assume the existence, of the 'lower-luminosity limit', of whatever you're currently contemplating cosmologically.

    That's all the point I want to press.

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    Quote Originally Posted by Widdekind View Post
    Every month, every issue, of every pop-sci magazine (Discover, Science News, Science Illustrated, Popular Science, Astronomy, Sci-Am) typically trumpets the "mysterious non-common-sensical-ness" of Cosmology ('dark-this-and-that-and-the-other'), and Quantum Mechanics ('QM-is-so-counter-intuitive'). Such statements stimulate a strong sense of skepticism, in me.
    I can't blame you. But please remember that those magazines are not written by scientists, they are not scientific journals, and they write whatever sells. I have noticed a similar pattern in "science" magazines. Instead of explaining something interesting, they focus on "mystery". But I understand that people are more likely to pay for a magazine saying "mystery mystery" than a magazine explaining how (say) supernovas require convection to work or how they involve neutrinos. Personally I find the "how it works" far more interesting, but I understand that many consumers are not like me.

    But in brief: Please remember that those magazines are not "science". Those magazines are to science what Taco Bell is to Mexican food (i.e. processed and wrapped for mass consumption by non-Mexicans).
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    Quote Originally Posted by DanielC View Post

    Omega_tot = 1.0023 +0.0056/-0.0054

    This value cannot be distinguished from zero based on those error bars.
    The moderators, on Science Forums, who seem to be 'in the loop', seemingly said, that the current preference 'in the field' is for a closed cosmology. Is that not true?





    If the universe today is very close to Omega_tot = 0, the early universe would have been even closer.
    Yes. But, if this space-time fabric, is topologically 'closed' today, then it was 'way back when', as well (yes??). To wit, the 'qualitative topological structure', of our space-time, is unchanging. Numbers aside, if our cosmos is closed today; then so it was, as well, during PNS; and, since PNS occurred at a redshift of z = millions-to-hundreds-of-millions (yes??), the cosmological Rcurv would have been that much smaller. But, again, our space-time is ~10 Gyr old; so its radius-of-curvature is probably of order 10s of G-ly; and so, again, it still would have been 'big', by micro-scopic standards, during PNS.

    You're saying, that non-sustained fusion reactions, in fusion bombs, accurately picture the PNS epoch?

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    Quote Originally Posted by Widdekind View Post
    The moderators, on Science Forums, who seem to be 'in the loop', seemingly said, that the current preference 'in the field' is for a closed cosmology. Is that not true?
    That is not true at all. At least, in my GR class I had this question in the final oral exam and if I had said what you said I would have had the question wrong.

    Yes. But, if this space-time fabric, is topologically 'closed' today, then it was 'way back when', as well (yes??).
    To my knowledge, yes, but you've jumped the gun to assume that the curvature would have been greater back then and made that a central part of your argument. I don't think that that is correct at all. The Flatness problem is that if the universe looks close to flat today (it does) then it must have been much much closer to flat earlier on. The value of Omega_tot tends to diverge as the universe expands.

    You're saying, that non-sustained fusion reactions, in fusion bombs, accurately picture the PNS epoch?
    No. I said that experiments (e.g. particle accelerators) have taught us how fusion works. Fusion is actually a very well understood subject. A bomb is a bit of a brute force application with only a scrap of science mixed in.
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    Quote Originally Posted by DanielC View Post
    To my knowledge, yes, but you've jumped the gun to assume that the curvature would have been greater back then and made that a central part of your argument. I don't think that that is correct at all. The Flatness problem is that if the universe looks close to flat today (it does) then it must have been much much closer to flat earlier on. The value of Omega_tot tends to diverge as the universe expands.
    If our space-time fabric is topologically 'closed' -- to wit, hyper-spherical -- then, to my understanding, the Radius of Curvature (Rcurv) is the 'hyper-spatial radius', of the 'hyper-sphere', whose 3D 'hyper-surface', is our space, at any given time. And, so, when Rcurv was allot less, 'way back when', our space-time was much more curved. Put another way, although you are correct, that our space-time would have been 'ultra-close to critical density', 'way back when'... even so, 'way back when', ultra-small deviations still amounted, to huge curvatures, b/c of the 'ultra-conditions'.



    No. I said that experiments (e.g. particle accelerators) have taught us how fusion works. Fusion is actually a very well understood subject. A bomb is a bit of a brute force application with only a scrap of science mixed in.
    OK. If you make me, I can show you, that the original Alpher-Bethe-Gamow 1948 paper assumed PNS in a matter-dominated epoch. But, they predicted the CMBR, and I doubt that they didn't realize PNS would have happened, under radiation-domination. So, I accept the basics of their argument.

    However, I have one point I would want yet to push -- neutrinos. Our cosmos is submerged in a sea of cold neutrinos, a 'neutrino CMB' as it were. Please ponder this point -- 'way back when', there was an ultra-relativistic, ultra-dense 'neutrino fog', through which all the then-fusing baryons were obliged to propagate. Can I not claim, that modern human particle-accelerator experiments do not mimic such 'neutrino-dense' conditions? And, if not, how would such a 'neutrino soup' backdrop, or stage, have affected the physics??

    I notice that that cited article does say, that the ultra-relativistic, primordial, neutrinos would have cooled out of matter-interactiveness, after two seconds -- several minutes before even PNS. Yet, those same neutrinos, after a further ~400 kyr of cooling, interacted strongly enough with matter, to smooth out fluctuations, ultimately imprinted in the CMBR. I don't understand, how, if neutrinos were matter-interactive, at 400 kyr, why they weren't, at 4 minutes.

 

 
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