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  1. #21
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    My vote goes to the former..... Excellent post...

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  3. #22
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    Thanks! Trying to look at all angles, I should say, that if "Dim Matter" was too numerous -- lots & lots of dim brown dwarfs -- then perhaps our solar system statistically 'should' have had a catastrophic, planetary-system-disrupting, near-approach encounter, with such purportedly-omni-present bodies ? Perhaps planet-finder missions might see non-planetary perturbations, of visible star motions, caused, not by their own planets, but by brown dwarfs ??

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  5. #23
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    One would think that brown dwarfs should be spotted by a heat signature? they are after all rather massive and would be radiating large amounts of energy...

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    The give aways in the title "theoretical" mathmatics
    We are using theorys which work on top of the maths of uncertainty
    So before we start the basis of all work done isnt 100% accurate by nature
    These methods have brought up great advances and for our uses predict all symptoms we need to know, without us knowing the cause
    Even with Einsteins great insight and his following theorys, we seem to me to be following like sheep up a blind alley
    Somewhere with all modern computing power science has lost its way, not relying on observation and fact
    Instead chasing models that dont exist beyond a simulation program or a blackboard

    Great thread
    That hubble deep field image has always nagged at me
    Photons dont lie, we just need the right tools to collect them

    Sorry if these next few questions are a bit lame, but my brains been learning telescope stuff lately and its wiped a lot of the physics stuff lol
    If gravity is a symptom of mass disturbing a brain, then there is no such thing as gravity?
    Just the disturbance caused by a mass in a brain?
    Objects pull together in space because their masses bend space/time, and they roll "downhill" toward each other?
    If this is true, why do we still use the term gravity?
    Im not talking amongst the masses, just people like us who know different?

    If brown dwarfs (and other dim bodies) account for the missing mass that explains the spin of galaxies, how come theres so much dead wood on galactic rims?
    It would make more sense for the earliest objects to be created closer to the blackhole?
    Or would galactic drift since the beginning of the universe, allow for enough accretion of roaming stars?

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  9. #25
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    "dim matter" -- Brown Dwarfs "fit the bill" for "dark matter"

    Looking at a [spiral] galaxy from the outside, one sees first a large, spherical halo of stars, that surrounds the flat disk... This halo is made up of smaller, long-lived stars, which were made many billions of years ago. Their motion seems to be random [i.e., fully 'virialized' or 'thermalized'], so that there is no apparent overall rotation. And, although it is the dimmest component of the galaxy, it is believed that the halo contains most of the matter of the galaxy... Typically, between 80-90% of the matter of a [spiral] galaxy is found to be spread out beyond the disk, it is not in the form of visible stars & gas. All we know about this matter is that it does not give off or reflect a great deal of light. The dark matter, as it is called, may be old burned-out stars, or black holes, or very cold dust, or some combination of all of these (Smolin. Life of the Cosmos, p.121-122).
    the galactic halo...has a luminous inner component defined by globular
    star clusters and other easily observable stars (with coronae of hot gas possibly expelled by supernovae and of high-velocity neutron stars) and an outer dark-matter component inferred from its gravitational impact on the Milky Way's spiral disk... these "halo stars" were born when the Milky Way was young
    The discovery of HE 0107-5240 in the Milky Way's halo demonstrated that stars that are less massive than Sol can form from very metal-poor gas... even relatively low-mass Population III [i.e., first] stars could have formed and survived until today, still shining faintly below easy detectability as main sequence dwarf stars in distant reaches of the galactic halo.
    Note, too, that a sizable population of Brown Dwarfs, whose close encounters with our star system would dramatically disrupt the same, could account for the famous "Nemesis" theory, re-interpreting the same, only to the degree, that our star system has interacted, not with some single Brown Dwarf dim companion, but dozens of different such substars, over the past 4.5 Gyr.

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  11. #26
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    Local Inter-stellar Cloud filters out low luminosity objects, from human space telescopes??

    Our star system currently resides in a vast inter-stellar dust cloud. Could that be blocking our observations, of dim objects ?


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    According to the June 2010 AD issue of Astronomy magazine, an amateur astronomer, doing a longer, deeper exposure, of the Cygnus X-1 black-hole, observed a previously-unseen bow-shock. Thus, once again, every time human observers do a longer, deeper, more sensitive exposure, they see more than they had before.

    Please ponder, that whenever you see such "easy returns", where every effort is immediately rewarded by improvements, that that is a sure sign you are part of a "primitive", "Wright-brothers-at-Kitty-Hawk" stage of technological development. For, once a technology or technique "matures", by definition, you've hit the point of diminishing returns. So, that every single extra effort immediately pays dividends, is a case-closed-cold proof positive, that human observations of space, are exceedingly primitive, basic & myopic. The only logical inference, then, is that "there's LOTS left to observe".

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    Quote Originally Posted by Gandalf223 View Post
    Could not agree more. Physicists hate constants in their equations. Dark matter (so called) is a theoretical construct designed to duplicate Einstein's Cosmological Constant.
    You are confusing dark matter and dark energy.


    Quote Originally Posted by Gandalf223 View Post
    I'd be happier with the whole dark matter thing, if the physicists who promote it would preface their ideas with, "WTF?????"
    There is more to dark matter and dark energy than "wtf?". Furthermore, I'll note that the whole point of science is to investigate things that are not well understood, so by definition, scientists are always working on something that is not well understood. If scientists had to prefix everything that is poorly understood with "WTF" then most scientific papers would have that prefix.
    Astronomer. Lund Observatory

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    Quote Originally Posted by Space Jockey View Post
    Wouldn't that be something a universal version on Einstien's original concept applied and reworked to explain this. Now that I could see. It really does not make sense-the static universe and we now know why. But It is easily imaginable the invisible force he tried to find working as a law just as gravity does. maybe it is an unknown component of gravity itself ?.
    But that is precisely what "dark energy" is, by another name. The reason why the modern term is "dark energy" is that modern astronomers prefer to think of it as a real component of the universe that is caused by something physical that can in principle be observed and studied, rather than being just an unexplained constant. But that's basically where the difference is. We even use the same symbol (Greek lambda) that Einstein used to refer to the cosmological constant.
    Astronomer. Lund Observatory

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  19. #30
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    Quote Originally Posted by Widdekind View Post
    There are two distinct concepts here:

    "Dim Matter" -- Vera Rubin, looking through her telescope, infers that there must be more mass, not visible with her instrument, to account for the motions of the matter that is visible, in her instrument

    "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'
    These are two separately-motivated tacks, on the "missing mass" problem in Cosmology. The former is observational, the latter theoretical. I am arguing, that the former is true ("lots of dim brown dwarfs, as yet unobserved"), whilst the latter is false ("something subtle, about fusion, on ultra-large scales, in a rapidly expanding spacetime, introduce errors into current theoretical models").

    This is not true. I know, because my current research work is on Dark Matter, not "Dim" matter. I am making computer simulations to explore how WIMPs (the most popular candidate for dark matter) would be absorbed by a star and how they might affect the star's evolution. The ultimate goal is to come up with a test that can tell us whether WIMPs exist or not.

    Anyway, dark matter refers to the fact that galaxies and galaxy clusters clearly have more matter than we can observe. Note that what we can observe includes not only stars, but interstellar gas, intergalactic gas, and we can even estimate the density of black holes and brown dwarfs by counting the frequency of microlensing events. We can add up all of this and find that galaxies and clusters have much more gravity than can be accounted with these known objects. Dark matter is whatever is responsible for the additional mass. The point is that this is entirely observational, and not at all based on cosmology, or theoretical scribbles on a white board.

    When you say "lots of dim dwarfs, as yet unobserved" you are basically talking about "MACHOs", one of the candidates for *DARK* matter which has fallen out of favour because the predicted microlensing events where not observed.

    The evidence for dark matter is strong. It is not only the fact that galaxies rotate too fast, it is not only that galaxy clusters rotate too fast. For example, when we make computer simulations of the formation of galaxies, they don't come out right unless you also have dark matter. If you insert WIMP-like dark matter, then galaxies form readily and they look just like the galaxies we observe in the universe.

    Notice that every argument I've given has been at the galaxy level, not cosmology, and every argument was based on observation, not theoretical scribbles on a white board.

    You might be confusing dark matter and dark energy. Only dark energy is based on cosmological arguments. In the case of dark energy, that's just a statement of the accelerated expansion of the universe.

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