#11
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Dark matter is:
On 10/28/17 1:36 AM, jacobnavia wrote:
Yes, but after years of searches I think that is useless to go on denying that we just have no idea how the universe works. No physical counterpart of the supposed "dark matter" has been found in any lab. There is no dark matter particle and hence exotic dark matter doesn't exist. Normal matter could have unknown behaviour however, at big scales. That is the logical conclusion. Just one thing. Matter could be organized at big scales by forces that at our level of being (1.8 meters, 5 watts brain freshly evolved from some primate) are undetectable by our labs and particle accelerators. Those forces acting at galactic or cluster scales could be determinant for our understanding of the cosmic web. Matter seems to be connected everywhere, and the size and forces that make those connections and filaments are unknown to us but they exist, since those filaments exist. There are filaments between the stars, and filaments between the galaxies, and filaments between the clusters of galaxies. Rivers of galaxies can be figured out, and astronomers have followed those filaments to figure out the biggest being they have ever seen, an incredible structure that you can see he http://www.dailymail.co.uk/sciencete...Milky-Way.html Its filamentary structure is evident in this drawing. As also envisioned by your adopted countryman Vincent Van Gogh's 1889 painting The Starry Night https://www.google.com/culturalinsti...bgEuwDxel93-Pg The Fluid sky is connected to the rolling hills and even the man made structures conform to this universal fluid. Ernst Mach developed this universe connectivity in the early 20th century Sadly, our ideas about a big bang and the resulting explanations make this hypothesis not so attractive for many people. Your idea does not have to contradict the big bang idea. Since observations indicate that a sea of galaxies extends away and away from us in all directions, I consider that the CMB doesn't really imply a big bang. Although there is variation, the individual galaxies within the sea have generally common rotational structure as well as the star planetary systems within. That has to be accounted for. It is just that: Cosmic Background. The sea of galaxies is bathed in the relic light from all uncountable galaxies extending till who knows where. This explains why is so uniform. But a common origin is needed to explain the uniformity. Ambient light. But adjacent to all of this universe matter(including us within it) is the vacuum at Heisenberg uncertainty. It is generally described as a chaotic random foam. Your structured bathing environment would required a coherent vacuum going back to the big bang that goes against current thinking. [[Mod. note -- Three points: 1. Yes, gravitomagnetism exists (experimental check: Gravity Probe B). But the *magnitude* of that "connection" is really, really small! 2. The Galaxy Zoo project's analysis (arXiv:0803.3247 = https://doi.org/10.1111/j.1365-2966.2008.13490.x) finds that galaxy rotation directions are statistically random. 3. From CMBR anisotropy measurements, we know that the universe isn't rotating to any significant extent. See, e.g., Collins and Hawkings (1973) and Bunn, Ferreira, and Silk, Physical Review Letters 77, 2883 (1996) (https://doi.org/10.1103/PhysRevLett.77.2883). -- jt]] |
#12
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Dark matter is:
On Saturday, 28 October 2017 06:24:42 UTC+2, Phillip Helbig wrote:
In article , Nicolaas Vroom writes: This raises the question how important is nonbaryonic matter for the evolution of the Universe? Very. Without dark matter, the fluctuations observed in the CMB would not have had time to form the structure we see today. As far as I understand the fluctuations in the CMB we see to day are caused by matter fluctuations of the Universe 300000 years after the BB. To be more specific in the outer layer of the Universe. (It is not the CMB that caused these fluctuations) During that period apperently there was already a division between baryonic versus non-baryonic matter which we can observe in the second and third peak CMB power spectrum. See: https://en.wikipedia.org/wiki/Cosmic...ary_anisotropy The question is how exactly do we know that these peaks are caused by baryonic and non baryonic matter, of which the last physical is an almost bare landscape. For more detail see ref 52 and 53 (Wayne Hu). Specific what is IMO the most tricky is the relation between the two. Nicolaas Vroom |
#13
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Dark matter is:
In article ,
Nicolaas Vroom writes: As far as I understand the fluctuations in the CMB we see to day are caused by matter fluctuations of the Universe 300000 years after the BB. Right. To be more specific in the outer layer of the Universe. Relative to us. (It is not the CMB that caused these fluctuations) Right; the anisotropies in the CMB are due to the fluctuations. We know the magnitude of the fluctuations of baryonic matter, since that is what we see. If there were no dark matter, there would not have been time for these to have evolved to the structures we see today. The idea is that dark matter can collapse sooner, since it is not stopped by radiation pressure. The baryonic matter then falls into the dark-matter potential wells. During that period apperently there was already a division between baryonic versus non-baryonic matter which we can observe in the second and third peak CMB power spectrum. See: https://en.wikipedia.org/wiki/Cosmic...ary_anisotropy Right. The question is how exactly do we know that these peaks are caused by baryonic and non baryonic matter, of which the last physical is an almost bare landscape. I'm not sure what the last clause means. How do we know? Calculate the power spectrum for various amounts of baryonic and non-baryonic matter and compare to observations. |
#14
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Dark matter is:
Le 29/10/2017 =C3=A0 07:24, Richard D. Saam a =C3=A9crit=C2=A0:
As also envisioned by your adopted countryman Vincent Van Gogh's 1889 painting The Starry Night https://www.google.com/culturalinsti...ry-night/bgEu= wDxel93-Pg The Fluid sky is connected to the rolling hills and even the man made structures conform to this universal fluid. Mmmm. Vincent had problems... Was he seeing dark matter? Maybe. Maybe he could see what we can't. In any case I am not mystic when science is involved and I do not see any "fluids" anywhere. My point is that a massive web of connections could explain a lot of things. Galaxies feed on dark gas, and the mass of that gas outside the galaxies could be considerable. Its movements could determine the shape of the visible part. Is that all powered by gravity? Gravity decreases as the square of distance, so at big scales is not so important like other (possible) forces that could decrease much more slowly and take over at big scales. |
#15
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Dark matter is:
In article ,
"Phillip Helbig (undress to reply)" writes: It is just that: Cosmic Background. The sea of galaxies is bathed in the relic light from all uncountable galaxies extending till who knows where. This explains why is so uniform. Your hypothesis cannot explain the power spectrum of the CMB. That would be the power spectrum of the fluctuations. Perhaps even more fundamentally, the "sea of light" cannot explain why the spectral energy distribution of the CMBR is a perfect blackbody with unit emissivity. This has been known since COBE. Posters to this thread should watch and understand the Dan Hooper colloquium I mentioned on Oct 20: https://youtu.be/pPs_tvDYAl4 There are still many unknowns, but the unconventional suggestions posted here are not new and are contrary to observations. -- Help keep our newsgroup healthy; please don't feed the trolls. Steve Willner Phone 617-495-7123 Cambridge, MA 02138 USA |
#16
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Dark matter is:
Le 30/10/2017 =C3=A0 19:51, Steve Willner a =C3=A9crit=C2=A0:
Perhaps even more fundamentally, the "sea of light" cannot explain why the spectral energy distribution of the CMBR is a perfect blackbody with unit emissivity. This has been known since COBE. Why shouldn't be a black body spectrum? A black body spectrum is the one of a body at thermal equilibrium, and the sea of galaxies apparently is at thermal equilibrium... Why not? And if the CMB was just a PERFECT black body spectrum and all "wrinkles in the face of god", as someone said, were just objects (or holes) of incredible size? Foreground objects or holes. Now, you can take a spectrum of it and add whatever theories come to mind but the physical reality must be taken into account... Hubble observations point to a huge number of galaxies just beyond its reach to detect. The sea of galaxies is not some invention I have figured out. [[Mod. note -- There are (at least) two problems with this "sea of light/galaxies" explanation for the CMB: 1. Viewing a body at thermal equilibrium isn't enough to get a black-body spectrum -- the body-being-viewd also has to be *optically thick*. The set of galaxies is not optically thick at most CMB wavelengths (we can see through it to see those more distant objects you just mentioned). 2. Any viable explanation for the CMB needs to be able to *quantitatively* match the CMB-anisotropy power spectrum, including the positions, heights, and widths of the 5-or-so peaks visible in the observed data. See, e.g., the nice graph in https://en.wikipedia.org/wiki/Cosmic...ary_anisotropy The fact that the hot big bang model *can* quantitatively match this spectrum is a powerful argument in its favor. I've never seen a similar match from a sea-of-light/galaxies model. Is there one? -- jt]] This observation (NASA) is one year old: quote Astronomers came to the surprising conclusion that there are at least 10 times more galaxies in the observable universe than previously thought. end quote See article at https://www.nasa.gov/feature/goddard...vable-univers= e-contains-10-times-more-galaxies-than-previously-thought AT LEAST, they said carefully... And all those galaxies are VERY far away. The Universe goes on and on and on. We see no limit. |
#17
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There is nothing there (Xenon Collaboration)
First Dark Matter Search Results from the XENON1T Experiment:
quote from the abstract A profile likelihood analysis shows that the data are consistent with the background-only hypothesis. end quote There is it. One Ton of Xenon liquid/gas and years of effort show us that there is nothing there. The detector doesn't detect anything but background noise. This means that since there is nothing exotic, matter has behaviours that we do not understand at all. WIMPS were tied to CDM cosmology and their absence means that many theories are just wrong. The logical conclusion (from a layman viewpoint) is that normal matter has attractive forces that hold the galaxy together as a spinning disk. Not gravity, since gravity decreases as the square of distance: it doesn't go very far... Like all forces actually. Nuclear force doesn't reach beyond 2.5 10E-15 meters. Each force has a range of masses and scales where it is active. At each scale then, we can discover new forces that attract matter to itself. At galactic scales this attractive force holds the disk spinning like a rigid whole. And no, I can't calculate that. Astronomers can, doesn't look (to me) a very difficult undertaking. They have the mass distribution of the galaxy, what can be accounted by gravity, and the rest. This rest is the effects of that force. But maybe things aren't so simple and that force could be very complicated to figure out, like the nuclear force, that actually is a derivative of other, stronger forces between the quarks, etc. Only one thing is certain: All cosmologies have failed but we always had one, since we left our caves and started looking at the sky. |
#18
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Dark matter is:
In article , jacobnavia
writes: Hubble observations point to a huge number of galaxies just beyond its reach to detect. The sea of galaxies is not some invention I have figured out. But you seem to think that this idea is somehow ignored by the community. We know that the universe is approximately flat. Assuming a simple topology, that means that it is either infinite or very much larger than the particle horizon (the theoretical limit of how far we can see; in practice that limit is essentially the last scattering surface [which is operationally defined as the surface at which the universe becomes optically thick]). So, essentially all astronomers in the world agree that there are more galaxies than we can see, even more than we could see with arbitrarily powerful instruments. The moderator commented: # 1. Viewing a body at thermal equilibrium isn't enough to get a black-body # spectrum -- the body-being-viewd also has to be *optically thick*. # The set of galaxies is not optically thick at most CMB wavelengths # (we can see through it to see those more distant objects you just # mentioned). Right. I think that it was Hoyle or Burbidge---before the measurement of the black-body spectrum---who pointed out that the energy in the CMB is approximately the same as that which has been radiated by stars, so in terms of order-of-magnitude back-of-the-envelope calculations, the recycled starlight idea was valid. It appears to be just a coincidence, though, and fails several predictions (black-body spectrum, power spectrum of observed anisotropies, etc). # 2. Any viable explanation for the CMB needs to be able to *quantitatively* # match the CMB-anisotropy power spectrum, including the positions, # heights, and widths of the 5-or-so peaks visible in the observed data. # See, e.g., the nice graph in # https://en.wikipedia.org/wiki/Cosmic...ary_anisotropy # The fact that the hot big bang model *can* quantitatively match # this spectrum is a powerful argument in its favor. I've never seen # a similar match from a sea-of-light/galaxies model. Is there one? Note that the CMB power spectrum was a robust prediction long before any peaks were observed. Yes, it depends on various parameters, but a) one cannot just fit anything and b) the parameters which produce the best fit have values which jibe well with other measurements. quote Astronomers came to the surprising conclusion that there are at least 10 times more galaxies in the observable universe than previously thought. end quote In the OBSERVABLE universe. They are talking about faint dwarf galaxies here. Even in the intermediate neighbourhood of the Milky Way these are hard to observe. And all those galaxies are VERY far away. The Universe goes on and on and on. We see no limit. Yes, it might very well go on without limit, but a) this has nothing to do with the number of galaxies in the OBSERVABLE universe and b) is completely compatible with the big bang. |
#19
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There is nothing there (Xenon Collaboration)
In article , jacobnavia
writes: First Dark Matter Search Results from the XENON1T Experiment: quote from the abstract A profile likelihood analysis shows that the data are consistent with the background-only hypothesis. end quote There is it. One Ton of Xenon liquid/gas and years of effort show us that there is nothing there. The detector doesn't detect anything but background noise. This means that since there is nothing exotic, matter has behaviours that we do not understand at all. No. It means that this detector didn't detect what it could have detected. It doesn't mean that dark matter is ruled out. It doesn't even mean that WIMPs are ruled out. WIMPS were tied to CDM cosmology and their absence means that many theories are just wrong. Where are WIMPs tied to CDM cosmology? Dark matter, yes, but dark matter doesn't have to be WIMPs. In particular, it could be self-interacting and form objects the size of a baseball, or a house, or a mountain. Or it could be in primordial black holes of 100 solar masses or so (smaller ones are ruled out by microlensing). At each scale then, we can discover new forces that attract matter to itself. At galactic scales this attractive force holds the disk spinning like a rigid whole. No. You are referring to flat rotation curves of galaxies. This doesn't mean that the angular speed is constant with radius (approximately, and above some minimum radius), but rather the actual physical speed. Rigid rotation would imply that the speed of rotation increases with distance. And no, I can't calculate that. Astronomers can, doesn't look (to me) a very difficult undertaking. They have the mass distribution of the galaxy, what can be accounted by gravity, and the rest. This rest is the effects of that force. Yes, this is MOND, essentially. |
#20
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Dark matter is:
On Thursday, 2 November 2017 03:39:27 UTC+1, Phillip Helbig wrote:
We know that the universe is approximately flat. Assuming a simple topology, that means that it is either infinite or very much larger than the particle horizon (the theoretical limit of how far we can see; in practice that limit is essentially the last scattering surface [which is operationally defined as the surface at which the universe becomes optically thick]). So, essentially all astronomers in the world agree that there are more galaxies than we can see, even more than we could see with arbitrarily powerful instruments. I do not fully agree with your argumentation. When you want to understand what we can observe you have to use the friedmann equations. To see the results select: http://users.telenet.be/nicvroom/friedmann's%20equation%20L=0.01155.htm In Figure 1B it is the blue line what we can see/observe. The black line is the maximum distance of the Universe as the result of the Big Bang. I expect this is the particle/radiation limit. At present the size of the Universe is roughly 35 bly. From this simulation the claim that the expansion of the universe undergoes acceleration is arbitrary. The blue line (of what we can see at present) starts approx 300000 y after the BB (See Figure 1C) and reaches it furtest distance 5 by after the BB. The blue line shows what we see of the Universe in the past i.e. in some sense all the present day galaxies in the past. This also means that if you have a more powerfull instrument you can not see more galaxies but only the same galaxies (in the past) more accurate. With a more powerfull instrument you can see younger galaxies. They are not further away (at that time) but at closer distance. Nicolaas Vroom [[Mod. note -- If you have a more sensitive instrument you can see *fainter* galaxies at any given distance. Since there are a lot more faint galaxies than bright galaxies in any given volume of space, this means that you overall see more galaxies even within the same volume of space. -- jt]] |
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