#1
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Dark matter is:
As I read in the press, we have found a great percentage of dark matter.
Astronomers have suceeded in seeing the shadows of filaments in the light of the CMB. https://www.sciencealert.com/astrono...visible-matter quote So both teams of researchers relied on something called the Sunyaev-Zel'dovich effect, a phenomenon that causes photons left over from the glow of the Big Bang to scatter into slightly higher energies as they pass through the electrons in the gases surrounding galaxy clusters end quote This cosmic web becomes thicker. That is good news, maybe all of it is just that: "Dark matter" that we just doesn't seem able to see easily. But not anything exotic. Just that: normal matter. There are also filaments between the stars, this time detected by gravitational effects in the light of background stars. The whole thing looks like a connected web. And that web could be very massive. jacob |
#2
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Dark matter is:
In article , jacobnavia
writes: As I read in the press, we have found a great percentage of dark matter. Yes, as in matter which is dark. Not in the sense in which "dark matter" is most often used, namely as shorthand for "non-luminous and transparent non-baryonic matter other than neutrinos". This cosmic web becomes thicker. That is good news, maybe all of it is just that: "Dark matter" that we just doesn't seem able to see easily. But not anything exotic. Just that: normal matter. There are many arguments against this hypothesis, the main ones being big-bang nucleosynthesis and CMB observations, which both agree that most of the "missing matter" (i.e. "dark matter" as the term is normally used) cannot be baryonic. The whole thing looks like a connected web. And that web could be very massive. It could be significantly massive in a cosmological sense only if non-baryonic matter is associated with it. (This might well be the case, but we have no evidence one way or the other.) |
#3
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Dark matter is:
On 10/25/17 1:06 AM, Phillip Helbig (undress to reply) wrote:
"Dark matter" that we just doesn't seem able to see easily. But not anything exotic. Just that: normal matter. There are many arguments against this hypothesis, the main ones being big-bang nucleosynthesis and CMB observations, which both agree that most of the "missing matter" (i.e. "dark matter" as the term is normally used) cannot be baryonic. With what certainty should the 'cannot be' assertion be made. In science, such absolute assertions are very rare. Current big-bang nucleosynthesis calculations and CMB observation dark matter correlations should not exclude a complementary dark matter contribution by some other mechanism. |
#4
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Dark matter is:
On Wednesday, October 25, 2017 at 2:06:07 AM UTC-4, Phillip Helbig (undress to reply) wrote:
In article , jacobnavia writes: As I read in the press, we have found a great percentage of dark matter. Yes, as in matter which is dark. Not in the sense in which "dark matter" is most often used, namely as shorthand for "non-luminous and transparent non-baryonic matter other than neutrinos". This cosmic web becomes thicker. That is good news, maybe all of it is just that: "Dark matter" that we just doesn't seem able to see easily. But not anything exotic. Just that: normal matter. There are many arguments against this hypothesis, the main ones being big-bang nucleosynthesis and CMB observations, which both agree that most of the "missing matter" (i.e. "dark matter" as the term is normally used) cannot be baryonic. The whole thing looks like a connected web. And that web could be very massive. It could be significantly massive in a cosmological sense only if non-baryonic matter is associated with it. (This might well be the case, but we have no evidence one way or the other.) The axion is a possibility that is being looked for. If this particle is found it could be a nice fit for dark matter. https://www.youtube.com/watch?v=nYAplw_VbnE |
#5
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Dark matter is:
In article , "Richard D.
Saam" writes: On 10/25/17 1:06 AM, Phillip Helbig (undress to reply) wrote: "Dark matter" that we just doesn't seem able to see easily. But not anything exotic. Just that: normal matter. There are many arguments against this hypothesis, the main ones being big-bang nucleosynthesis and CMB observations, which both agree that most of the "missing matter" (i.e. "dark matter" as the term is normally used) cannot be baryonic. With what certainty should the 'cannot be' assertion be made. Relatively high certainty. In science, such absolute assertions are very rare. True. Strictly speaking, there are no absolute certainties. However, this doesn't mean that anything goes: http://chem.tufts.edu/answersinscien...ityofwrong.htm Current big-bang nucleosynthesis calculations and CMB observation dark matter correlations should not exclude a complementary dark matter contribution by some other mechanism. They exclude, to a high degree of certainty, most of the missing matter being baryonic. Yes, that might be wrong, but one needs to show that it is wrong; one can't claim that since there is no absolute certainty, we might as well assume that an alternative claim---with zero evidence to support it---is just as good. |
#6
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Dark matter is:
On Wednesday, 25 October 2017 23:34:51 UTC+2, Richard D. Saam wrote:
On 10/25/17 1:06 AM, Phillip Helbig (undress to reply) wrote: "Dark matter" that we just doesn't seem able to see easily. But not anything exotic. Just that: normal matter. There are many arguments against this hypothesis, the main ones being big-bang nucleosynthesis and CMB observations, which both agree that most of the "missing matter" (i.e. "dark matter" as the term is normally used) cannot be baryonic. With what certainty should the 'cannot be' assertion be made. In science, such absolute assertions are very rare. Current big-bang nucleosynthesis calculations and CMB observation dark matter correlations should not exclude a complementary dark matter contribution by some other mechanism. The whole issue is not dark matter because what is the definition? The issue is the relation between baryonic versus nonbaryonic matter in the universe and in our galaxy. The Book the Big Bang by Joseph Silk defines the following events: 1) Big Bang 2) Particle Creation 3) Annihilation of proton-antiproton pairs 4) Annihilation of electron-positron pairs 5) Nucleosynthesis of helium and deuterium 6) (1 week) Radiation thermalizes prior to this epoch 7) (10 Years) Universe becomes matter dominated. 8) (300000 Y) Universe becomes transparant 9) (1-2 bil Y) Galaxy formation begins My question is what is the percentage of baryonic matter in each and which particular processes caused these changes. (roughly) Suppose that all nonbaryonic matter in the universe (in outer space and in our Galaxy Halo) are neutrino's when and how did they form? An interesting article is: https://arxiv.org/abs/astro-ph/9407006 1994 "Big-Bang Nucleosynthesis and the Baryon Density of the Universe" See also: https://arxiv.org/abs/1505.01076 "Big Bang Nucleosynthesis: 2015" In this article the word nonbaryonic is not mentioned. The word dark matter is mentioned at the pages 3 and 16. See also: https://en.wikipedia.org/wiki/Big_Ba...esis#Deuterium "This explanation is also consistent with calculations that show that a universe made mostly of protons and neutrons would be far more clumpy than is observed.[8]" This raises the question how important is nonbaryonic matter for the evolution of the Universe? Nicolaas Vroom |
#7
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Dark matter is:
On 10/26/17 2:36 AM, Phillip Helbig (undress to reply) wrote:
In article , "Richard D. Saam" writes: On 10/25/17 1:06 AM, Phillip Helbig (undress to reply) wrote: "Dark matter" that we just doesn't seem able to see easily. But not anything exotic. Just that: normal matter. There are many arguments against this hypothesis, the main ones being big-bang nucleosynthesis and CMB observations, which both agree that most of the "missing matter" (i.e. "dark matter" as the term is normally used) cannot be baryonic. With what certainty should the 'cannot be' assertion be made. Relatively high certainty. Current big-bang nucleosynthesis calculations and CMB observation dark matter correlations should not exclude a complementary dark matter contribution by some other mechanism. They exclude, to a high degree of certainty, most of the missing matter being baryonic. Yes, that might be wrong, but one needs to show that it is wrong; one can't claim that since there is no absolute certainty, we might as well assume that an alternative claim---with zero evidence to support it---is just as good. It is not a matter of being wrong but incomplete. For reference, CMB blackbody parameters with associated redshifts(1+z)^n a Temperature 2.729*(1+z)^1 kelvin Frequency 1.60x10^11*(1+z)^1 Hz Wave Length .106*(1+z)^-1 cm Mass Density 4.67x10^-34*(1+z)^4 g/cm^3 Energy Density 4.20x10^-13*(1+z)^4 erg/cm^3 Photon Density 412*(1+z)^3 #/cm^3 Small variation of these numbers as indicators of Dark Matter represent a small segment of the universe parameter space. Larger frequencies(energies) have been studied for the WIMP searches but lower frequencies(down to the microHz level) have not been adequately searched (mostly due to instrumentation measurement inadequacies) for other dark matter contributors. As for nucleosynthesis mechanisms, there is an ongoing LHC study of nuclear dynamics simulating The Big Bang that may bring more certainty in resolving incompleteness. [[Mod. note -- Experiments at Brookhaven's RHIC (Relativistic Heavy Ion Collider) are also relevant here. -- jt]] |
#8
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Dark matter is:
In article ,
Nicolaas Vroom writes: On Wednesday, 25 October 2017 23:34:51 UTC+2, Richard D. Saam wrote: On 10/25/17 1:06 AM, Phillip Helbig (undress to reply) wrote: "Dark matter" that we just doesn't seem able to see easily. But not anything exotic. Just that: normal matter. There are many arguments against this hypothesis, the main ones being big-bang nucleosynthesis and CMB observations, which both agree that most of the "missing matter" (i.e. "dark matter" as the term is normally used) cannot be baryonic. With what certainty should the 'cannot be' assertion be made. In science, such absolute assertions are very rare. Current big-bang nucleosynthesis calculations and CMB observation dark matter correlations should not exclude a complementary dark matter contribution by some other mechanism. The whole issue is not dark matter because what is the definition? The issue is the relation between baryonic versus nonbaryonic matter in the universe and in our galaxy. Right. The Book the Big Bang by Joseph Silk defines the following events: 1) Big Bang 2) Particle Creation 3) Annihilation of proton-antiproton pairs 4) Annihilation of electron-positron pairs 5) Nucleosynthesis of helium and deuterium 6) (1 week) Radiation thermalizes prior to this epoch 7) (10 Years) Universe becomes matter dominated. 8) (300000 Y) Universe becomes transparant 9) (1-2 bil Y) Galaxy formation begins My question is what is the percentage of baryonic matter in each and which particular processes caused these changes. (roughly) After 3) and 4) the ratio is fixed. (Strictly speaking electrons are not baryonic matter, but they are known matter and in any case, with equal numbers of protons and electrons, the mass of electrons is negligible.) Suppose that all nonbaryonic matter in the universe (in outer space and in our Galaxy Halo) are neutrino's Doesn't seem to be possible, because neutrinos can't be heavy enough to be cold dark matter, and warm dark matter is ruled out by structure formation. when and how did they form? Like all the other particles. (Some neutrinos formed later, in nucleosynthesis and so on, but, like photons, by far the most are from the cosmic background.) See also: https://arxiv.org/abs/1505.01076 "Big Bang Nucleosynthesis: 2015" In this article the word nonbaryonic is not mentioned. Non-baryonic matter is not really relevant for nucleosynthesis. The word dark matter is mentioned at the pages 3 and 16. These days, in a cosmological context, "dark matter" means "non-luminous, transparent, non-baryonic matter apart from neutrinos". https://en.wikipedia.org/wiki/Big_Ba...esis#Deuterium "This explanation is also consistent with calculations that show that a universe made mostly of protons and neutrons would be far more clumpy than is observed.[8]" Right. 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. Although the book is mainly about MOND, Bob Sanders's book DECONSTRUCTING COSMOLOGY gives a good, unbiased overview of standard structure formation. (Bob is a MOND enthusiast, but the evidence for MOND comes from galaxy-scale physics. Even he admits that structure formation without the standard dark-matter scenario doesn't seem to work.) Also, since most of the matter is non-baryonic, without it the universe would not be nearly flat (assuming that everything else stays the same). |
#9
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Dark matter is:
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. Sadly, our ideas about a big bang and the resulting explanations make this hypothesis not so attractive for many people. 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. 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. Ambient light. |
#10
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Dark matter is:
In article , jacobnavia
writes: No physical counterpart of the supposed "dark matter" has been found in any lab. The same was true for neutrinos for a couple of decades, and we even knew the sources and how many were produced. Not all experiments are easy. 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. It is a possibility. But absence of evidence is not evidence of absence. Yes, there are other possibilities for dark matter, but particle dark matter is not completely ruled out yet. 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 The filamentary structure is produced in numerical simulations, even those which use only gravity. This is not a puzzle. Sadly, our ideas about a big bang and the resulting explanations make this hypothesis not so attractive for many people. There is no need for another hypothesis since the filamentary structure falls naturally out of numerical simulations. 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. Behind the galaxies is the CMB. We can't see any galaxies beyond the CMB. Even if the universe is infinite, we can't see beyond the CMB, and even if we could, we would see at best precursors of galaxies, since we are seeing things far away as they were long ago. 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. |
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