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#21
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Gravitational Scalar & Redshift Distortion
On Thu, 20 Feb 14, Steve Willner wrote:
_Probably_ more significant, different planets should give different values for "solar mass" (technically the Gaussian gravitational constant) because larger orbits would enclose more mass. Perhaps the OP or someone else could calculate the magnitude of these effects... Can't be much, because of the exquisite trajectory of Voyager 2 which must have confirmed the true distance of the giant planets to a very small delta. Eric |
#22
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Gravitational Scalar & Redshift Distortion
Op zondag 16 februari 2014 08:58:26 UTC+1 schreef Phillip Helbig
In article , Nicolaas Vroom writes: IMO the evidence only comes from WMAP data ie CMB radiation. When you study the literature for our "local" universe almost no one discusses the issue of non baryonic matter. Look up "baryon fraction in clusters". There is a regime between the local environment (Local Group, say) and the observable universe. There is evidence from galaxy clusters, for example, that there is non-baryonic matter. An interesting article to read is: http://arxiv.org/abs/1402.1764 "Cold dark matter heats up." The sentence near the beginning reads: "The remaining 95% consists of dark energy and dark matter (DM). LambdaCDM is being challenged by its apparent inability to explain the low density of DM measured at the centre of cosmological systems, ranging from faint dwarf galaxies to massive clusters containing tens of galaxies the size of the Milky Way." However there exists also an article in nature. See: http://www.nature.com/nature/journal...ture12953.html The sentence near the beginning reads: "In the LambdaCDM paradigm, the remaining 95 per cent consists of dark energy Lambda and cold dark matter." IMO meaning non-baryonic matter. The problem with the article is that they often mention the words baryons and dark matter, but almost never cold dark matter or non-baryonic matter. (I wished they did not use the word dark matter at all but only baryonic cold- or warm- and non-baryonic matter) Roughly speaking the current assumption is that 20% of matter in the universe is baryonic and 80% is non-baryonic. The picture that emerges from this article is that in our local universe (in the galaxies) this is more 80% baryonic and 20% non-baryonic (but most probably this last number is much too high). The reason is because in many cases IMO when they use the word dark matter they mean cold baryonic matter (gas) Of course this raises serious issues. Nicolaas Vroom |
#23
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Gravitational Scalar & Redshift Distortion
Op zondag 16 februari 2014 08:58:26 UTC+1 schreef Phillip Helbig
In article , Nicolaas Vroom Look up "baryon fraction in clusters". There is a regime between the local environment (Local Group, say) and the observable universe. There is evidence from galaxy clusters, for example, that there is non-baryonic matter. I have performed a second literature study 1) http://news.brown.edu/pressreleases/2013/10/lux First results from LUX dark matter detector At the beginning of this document we read: "Though dm has not yet been detected directly, scientists are fairly certain that it exists. Without its gravitational influence, galaxies and galaxy clusters would simply fly apart into the vastness of space." This line of reasoning only shows that there is a missing matter problem. 2) http://mnrasl.oxfordjournals.org/con...09/1/L128.full "Nearly 80 per cent of the mass density in the Universe cannot be explained with ordinary baryonic matter and requires an additional non- baryonic component aptly named dark matter to reconcile the inferred mass budget The next best targets may be hiding among the recently discovered population of ultrafaint dwarf galaxies around the Milky Way" 3a) http://arxiv.org/pdf/1402.2301v1.pdf DETECTION OF AN UNIDENTIFIED EMISSION LINE IN THE STACKED X-RAY SPECTRUM OF GALAXY CLUSTERS At page 11 we read (slightly modified): Mdm = Mtot - Mgas - Mstar The article in table 4 only shows Mdm but not Mtot. This article discusses galaxy clusters. 3b) http://arxiv.org/pdf/1402.4119v1.pdf An unidentified line in X-ray spectra of the Andromeda galaxy and Perseus galaxy cluster Same subject as 3a The problem with the articles is the total mass, the baryonic mass and the predicted nonbaryonic mass involved in the different galaxies (and clusters) discussed. In order to calculate the projected dm masses the NFW profile is used. IMO this assumes that the missing matter is in the halo. A different scenario is to assume that the missing matter is in the disc which could lead to much lower estimates. The big question is that if baryonic matter is discovered for example in the Milky Way this can be used (extrapolated) as a solution for the missing matter problem in the universe at large. Nicolaas Vroom. |
#24
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Gravitational Scalar & Redshift Distortion
[dark matter in solar system]
In article , Eric Flesch writes: Can't be much, because of the exquisite trajectory of Voyager 2 which must have confirmed the true distance of the giant planets to a very small delta. I agree the various spacecraft results will give the most sensitive limits, but "much" has to be made quantitative and compared with expected values to be of any use. If I'm doing this right, the critical density is about 0.9E-29 g/cm^3. Inside a 1 AU sphere, that's about 1E11 g and inside Jupiter's 5.2 AU orbit about 1.8E13 g or about 9E-21 solar masses. (Feel free to check my work!) I think Gaussian gravitational constants are known to 12 or so significant digits but not 20, so at first glance it looks as though the upper limit is far from significant. But I'd really like to see someone do the calculation correctly. -- Help keep our newsgroup healthy; please don't feed the trolls. Steve Willner Phone 617-495-7123 Cambridge, MA 02138 USA |
#25
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Gravitational Scalar & Redshift Distortion
On Tue, 25 Feb 14, Steve Willner wrote:
[dark matter in solar system] If I'm doing this right, the critical density is about 0.9E-29 g/cm^3. Inside a 1 AU sphere, that's about 1E11 g and inside Jupiter's 5.2 AU orbit about 1.8E13 g or about 9E-21 solar masses. Taking the term "dark matter" to mean the source of the extra gravity, because we can't see it, the working assumption of your calculation is that it is smeared out into a uniform distribution -- I think that's the unspoken assumption behind most current work on dark matter. My OP puts forth the alternative that its distribution is instead quite structural, and includes spherical asymptotes to large matter distributions. That's why I wouldn't pursue your calculation -- also because Voyager 2's trajectory would have been exceedingly sensitive to any variations from the inverse square rule. Still wondering if the Galactic halo has a well-defined outer perimeter. Imaging seems to show it, but my search for any literature on that has turned up nothing. |
#26
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Gravitational Scalar & Redshift Distortion
In article ,
Eric Flesch writes: ... the alternative that [dark matter] distribution is instead quite structural, and includes spherical asymptotes to large matter distributions. Any hypothesis needs a _quantitative_ test. At first glance, the numbers suggest solar system tests won't be significant, Voyager or no. (I'd actually expect Galileo and Cassini to give more significant tests than Voyager.) Still wondering if the Galactic halo has a well-defined outer perimeter. Imaging seems to show it, What observations are those? As a practical matter, signal to noise limits the detectability of faint haloes. I'd not expect a sharp boundary but something like an exponential density dropoff, but I'm certainly no expert. The Milky Way has high-velocity stars that will leave the Galaxy, so the intergalactic stellar abundance cannot be identically zero. Whether to count those stars as part of the halo can, of course, be debated. -- Help keep our newsgroup healthy; please don't feed the trolls. Steve Willner Phone 617-495-7123 Cambridge, MA 02138 USA |
#27
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Gravitational Scalar & Redshift Distortion
On Fri, 28 Feb 14, Steve Willner wrote:
Eric Flesch writes: ... the alternative that [dark matter] distribution is instead quite Still wondering if the Galactic halo has a well-defined outer perimeter. Imaging seems to show it, What observations are those? As a practical matter, signal to noise limits the detectability of faint haloes. Oops, the imaging that I had in mind was of the bulge, not the halo. So maybe I shouldn't have extended the topic to include the halo. Sorry for the confusion. Eric |
#28
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Gravitational Scalar & Redshift Distortion
In article , Nicolaas Vroom
writes: Op zondag 16 februari 2014 08:58:26 UTC+1 schreef Phillip Helbig In article , Nicolaas Vroom Look up "baryon fraction in clusters". There is a regime between the local environment (Local Group, say) and the observable universe. There is evidence from galaxy clusters, for example, that there is non-baryonic matter. I have performed a second literature study Right, but did you look up "baryon fraction in clusters"? This is the main argument for a large fraction of dark matter or missing matter being non-baryonic. |
#29
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Gravitational Scalar & Redshift Distortion
On 2/25/14, 12:56 AM, Steve Willner wrote:
[dark matter in solar system] If I'm doing this right, the critical density is about 0.9E-29 g/cm^3. Inside a 1 AU sphere, that's about 1E11 g and inside Jupiter's 5.2 AU orbit about 1.8E13 g or about 9E-21 solar masses. (Feel free to check my work!) I think Gaussian gravitational constants are known to 12 or so significant digits but not 20, so at first glance it looks as though the upper limit is far from significant. But I'd really like to see someone do the calculation correctly. Look at: http://arxiv.org/abs/gr-qc/0103044 It should help. RDS |
#30
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Gravitational Scalar & Redshift Distortion
On 3/12/14, 5:00 PM, Phillip Helbig---undress to reply wrote:
In article , Nicolaas Vroom writes: Op zondag 16 februari 2014 08:58:26 UTC+1 schreef Phillip Helbig In article , Nicolaas Vroom Look up "baryon fraction in clusters". There is a regime between the local environment (Local Group, say) and the observable universe. There is evidence from galaxy clusters, for example, that there is non-baryonic matter. I have performed a second literature study Right, but did you look up "baryon fraction in clusters"? This is the main argument for a large fraction of dark matter or missing matter being non-baryonic. It generally accepted that there are many more baryons observed in clusters than allowed by nucleosynthesis. But nucleosynthesis calculations could be wrong. All seems to be based on 1991 ref: http://ned.ipac.caltech.edu/cgi-bin/...pJ...376...51W that may require updating based on the National Ignition Facility experimental data. RDS |
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