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Scientists: Dark matter exists
18 years 1 month ago #17481
by Gregg
Reply from Gregg Wilson was created by Gregg
Read the article. This is about as nutty as it gets. These "scientists" do not recognize the existence of a gravitational flux and a light carrying medium. They are 2/3rds blind.
Gregg Wilson
Gregg Wilson
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18 years 1 month ago #17356
by Thomas
Replied by Thomas on topic Reply from Thomas Smid
I think the dark matter astronomers are jumping to conclusions here: if the observations would indicate that the lensing is neither associated with the galaxy clusters themselves nor with the hot has, now <i>that</i> could be considered as proof of dark matter. I mention this because I have suggested on my webpage
Plasma Theory of 'Gravitational Lensing' of Light
that the lensing of light is actually due to the fact that stars (and galaxies) should be electrically charged. So the observed lensing might be due to ordinary matter after all.
Generally, I am actually somewhat puzzled why all astronomers are so confident that they know the mass of the ordinary matter (i.e. the mass of stars) in a galaxy so exactly. The 'known' figures are largely based on the apparent luminosity of stars and the (more or less empirical) mass-luminosity relationship. It is obvious that any errors in the latter will have a crucial influence: according to the mass-luminosity relationship, a star with half the mass has only 1/10 of the luminosity, so with 10 times as many stars of half the mass, one would have the same overall brightness but 5 times the overall mass. Looking at [url] planetquest.jpl.nasa.gov/SIM/science_henry.pdf [/url] , one finds indeed that the luminosities for stars less than 1 solar mass are uncertain by about 2-3 magnitudes (i.e. up to about a factor 10). It is quite remarkable that the mass luminosity relationship, which a) is quite uncertain for low mass stars, b) obtained only in the solar neighbourhood and c) obtained only from double stars, is applied to all stars in our or other galaxies regardless. I don't therefore think that the observations justify the conclusion of dark matter here. There might be much more mass in the form of ordinary stars than thought.
Thomas
www.physicsmyths.org.uk
www.plasmaphysics.org.uk
Generally, I am actually somewhat puzzled why all astronomers are so confident that they know the mass of the ordinary matter (i.e. the mass of stars) in a galaxy so exactly. The 'known' figures are largely based on the apparent luminosity of stars and the (more or less empirical) mass-luminosity relationship. It is obvious that any errors in the latter will have a crucial influence: according to the mass-luminosity relationship, a star with half the mass has only 1/10 of the luminosity, so with 10 times as many stars of half the mass, one would have the same overall brightness but 5 times the overall mass. Looking at [url] planetquest.jpl.nasa.gov/SIM/science_henry.pdf [/url] , one finds indeed that the luminosities for stars less than 1 solar mass are uncertain by about 2-3 magnitudes (i.e. up to about a factor 10). It is quite remarkable that the mass luminosity relationship, which a) is quite uncertain for low mass stars, b) obtained only in the solar neighbourhood and c) obtained only from double stars, is applied to all stars in our or other galaxies regardless. I don't therefore think that the observations justify the conclusion of dark matter here. There might be much more mass in the form of ordinary stars than thought.
Thomas
www.physicsmyths.org.uk
www.plasmaphysics.org.uk
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18 years 1 month ago #17401
by nemesis
Replied by nemesis on topic Reply from
There is a good summary of this observation in the August 26, 2006 issue of Science News, vol. 170, p. 131. I'd like to hear TVF weigh in on this since it is a direct challenge to the MM, which has no need of "dark matter".
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18 years 1 month ago #17433
by tvanflandern
Replied by tvanflandern on topic Reply from Tom Van Flandern
<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by nemesis</i>
<br />I'd like to hear TVF weigh in on this since it is a direct challenge to the MM, which has no need of "dark matter".<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">The arguments are rather technical, but I'll do my best to make it relatively non-technical.
First, ignore the cheer-leading quotes in Science News. They are from Big Bang proponents. Any competent reporter with an interest in the truth would have contacted Milgrom of anyone in the MOND (Modified Newtonian Dynamics) school for rebuttal quotes or a concession. That did not happen. If the reporter was put off until MOND proponents had studied the paper, he would be under obligation to report back what they have to say, because either way that would be news as interesting as the original story. But don't hold your breath waiting to see that reported.
Here is the summary of what the authors reported in their technical paper, which was impossible to get from the Sceince News article. Parenthetical remarks are mine.
Proof of existence of dark matter: ApJ 648:L109-L113 (2006). Gravitational potentials of galaxy clusters are too deep to be caused by the detected baryonic mass and a Newtonian gravitational force law. Proposed solutions invoke either dominant quantities of non-luminous "dark matter" or alterations to the particles' dynamical response to the gravitational force law (MOND). The actual existence of dark matter can only be confirmed either by laboratory detection or, in an astronomical context, by the discovery of a system in which the observed baryons and the inferred dark matter are spatially segregated. An ongoing galaxy cluster merger is such a system. We next assume that stars make up just 1-2% of the total mass (which assumes dark matter exists), and that plasma makes up 5-15% of the total mass (again assuming dark matter exists). But during a merger of two clusters, galaxies behave as collisionless particles, while the fluid-like X-ray–emitting intracluster plasma experiences ram pressure. Therefore, in the course of a cluster collision, galaxies spatially decouple from the plasma. Such an effect is clearly seen in the unique cluster 1E 0657-558. Two galaxy concentrations that correspond to the main cluster and the smaller sub-cluster have moved ahead of their respective plasma clouds that have been slowed by ram pressure. This phenomenon provides an excellent setup for our simple test. <i>In the absence of dark matter, the gravitational potential will trace the dominant visible matter component, which is the X-ray plasma.</i> [Emphasis added – see remarks below.] If, on the other hand, the mass is indeed dominated by collisionless dark matter, the potential will trace the distribution of that component, which is expected to be spatially coincident with the collisionless galaxies. Thus, by deriving a map of the gravitational potential, one can discriminate between these possibilities. Weak gravitational lensing of background galaxies shows an observed displacement between the bulk of the baryons and the gravitational potential, which proves the presence of dark matter for the most general assumptions regarding the behavior of gravity.
Now here are my comments. Restating the conclusion in its essence, if we assume the existence of dark matter and make inferences about the light distribution based on that assumption, we can verify our assumption. However, the converse is equally true. If we assume no dark matter, then light and gravity are expected to coincide, just as observed. The dominant visible matter component is the stars, not the plasma. See the italicized sentence above, where the opposite was assumed. So the conclusion of this paper is invalid because it uses interpretations valid only if dark matter exists to argue that dark matter exists. -|Tom|-
<br />I'd like to hear TVF weigh in on this since it is a direct challenge to the MM, which has no need of "dark matter".<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">The arguments are rather technical, but I'll do my best to make it relatively non-technical.
First, ignore the cheer-leading quotes in Science News. They are from Big Bang proponents. Any competent reporter with an interest in the truth would have contacted Milgrom of anyone in the MOND (Modified Newtonian Dynamics) school for rebuttal quotes or a concession. That did not happen. If the reporter was put off until MOND proponents had studied the paper, he would be under obligation to report back what they have to say, because either way that would be news as interesting as the original story. But don't hold your breath waiting to see that reported.
Here is the summary of what the authors reported in their technical paper, which was impossible to get from the Sceince News article. Parenthetical remarks are mine.
Proof of existence of dark matter: ApJ 648:L109-L113 (2006). Gravitational potentials of galaxy clusters are too deep to be caused by the detected baryonic mass and a Newtonian gravitational force law. Proposed solutions invoke either dominant quantities of non-luminous "dark matter" or alterations to the particles' dynamical response to the gravitational force law (MOND). The actual existence of dark matter can only be confirmed either by laboratory detection or, in an astronomical context, by the discovery of a system in which the observed baryons and the inferred dark matter are spatially segregated. An ongoing galaxy cluster merger is such a system. We next assume that stars make up just 1-2% of the total mass (which assumes dark matter exists), and that plasma makes up 5-15% of the total mass (again assuming dark matter exists). But during a merger of two clusters, galaxies behave as collisionless particles, while the fluid-like X-ray–emitting intracluster plasma experiences ram pressure. Therefore, in the course of a cluster collision, galaxies spatially decouple from the plasma. Such an effect is clearly seen in the unique cluster 1E 0657-558. Two galaxy concentrations that correspond to the main cluster and the smaller sub-cluster have moved ahead of their respective plasma clouds that have been slowed by ram pressure. This phenomenon provides an excellent setup for our simple test. <i>In the absence of dark matter, the gravitational potential will trace the dominant visible matter component, which is the X-ray plasma.</i> [Emphasis added – see remarks below.] If, on the other hand, the mass is indeed dominated by collisionless dark matter, the potential will trace the distribution of that component, which is expected to be spatially coincident with the collisionless galaxies. Thus, by deriving a map of the gravitational potential, one can discriminate between these possibilities. Weak gravitational lensing of background galaxies shows an observed displacement between the bulk of the baryons and the gravitational potential, which proves the presence of dark matter for the most general assumptions regarding the behavior of gravity.
Now here are my comments. Restating the conclusion in its essence, if we assume the existence of dark matter and make inferences about the light distribution based on that assumption, we can verify our assumption. However, the converse is equally true. If we assume no dark matter, then light and gravity are expected to coincide, just as observed. The dominant visible matter component is the stars, not the plasma. See the italicized sentence above, where the opposite was assumed. So the conclusion of this paper is invalid because it uses interpretations valid only if dark matter exists to argue that dark matter exists. -|Tom|-
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18 years 1 month ago #17404
by nemesis
Replied by nemesis on topic Reply from
So in a nutshell, they are assuming what they are trying to prove. I think Science News is really no better at science reporting than other mass media, such as big-city newspapers. Everything is distorted by the lens of simplification and popularization.
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18 years 1 month ago #17678
by JMB
Replied by JMB on topic Reply from Jacques Moret-Bailly
<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by nemesis</i>
<br />So in a nutshell, they are assuming what they are trying to prove. I think Science News is really no better at science reporting than other mass media, such as big-city newspapers. Everything is distorted by the lens of simplification and popularization.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Not only: All papers, including the papers published in the "good" reviews show this problem. Two points must be taken into account:
1) Very complicated systems are built by many specialists, and most of them are unable to distinguish between results which are proved independently from the hypothesis and results which contain the hypothesis that people intend to prove.
2) Old theories are sure and well verified (for instance thermodynamics, classical electromagnetism...). Their consequences are not completely developed and used first.
Two examples:
1) Quantum electrodynamics is "proved" using "Bell inequalities", but these inequalities are founded on the use of Lie algebra introduced by quantum electrodynamics !
2) In astrophysics, a lot of results are founded on an evaluation of the distances by the redshifts while ordinary optics, much developed using lasers, show that there are interactions between light beams refracted by matter: frequency combinations, frequency shifts, ...
Science is so wide now, and young people must produce results so quickly that they often do not understand well what they are doing; they have learnt a lot of courses which were not connected enough, and there is generally no check of a coherent, full understanding. Enough time should be left to learn much and think well.
<br />So in a nutshell, they are assuming what they are trying to prove. I think Science News is really no better at science reporting than other mass media, such as big-city newspapers. Everything is distorted by the lens of simplification and popularization.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Not only: All papers, including the papers published in the "good" reviews show this problem. Two points must be taken into account:
1) Very complicated systems are built by many specialists, and most of them are unable to distinguish between results which are proved independently from the hypothesis and results which contain the hypothesis that people intend to prove.
2) Old theories are sure and well verified (for instance thermodynamics, classical electromagnetism...). Their consequences are not completely developed and used first.
Two examples:
1) Quantum electrodynamics is "proved" using "Bell inequalities", but these inequalities are founded on the use of Lie algebra introduced by quantum electrodynamics !
2) In astrophysics, a lot of results are founded on an evaluation of the distances by the redshifts while ordinary optics, much developed using lasers, show that there are interactions between light beams refracted by matter: frequency combinations, frequency shifts, ...
Science is so wide now, and young people must produce results so quickly that they often do not understand well what they are doing; they have learnt a lot of courses which were not connected enough, and there is generally no check of a coherent, full understanding. Enough time should be left to learn much and think well.
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