4 ms·

>"They are mentioned" No, they were not mentioned. If they were, you would be quoting it. >'"2013: ΛCDM provides an excellent fit to the improved CMB data" A

by nonbel 8y ago

>"They are mentioned" No, they were not mentioned. If they were, you would be quoting it. >'"2013: ΛCDM provides an excellent fit to the improved CMB data" As I've said, that's the "item 3" from the 5 item list, and it's ultimately confirmed by ESA's Planck satellite results in 2013. That is a strong confirmation.' You have to read the entire quote. This "fit" was a post-diction, not a pre-diction: "in order to obtain a fit, we have had to nearly double the baryon density over what it was so confidently known to be before it wasn't." Post-dictions can be interesting as part of model development but are unable to confirm a model. The new, (possibly adjusted) model then need to be checked against new data.

acqq 8y ago
What is your support for that claim? Can you quote other sources? I can quote my sources: Here are documented two independent approaches in estimating baryonic density: one is calculations based on the Big Bang Nucleosynthesis D/H ratio and another one is the values measured by the satellites observing the SMB. Note the two decades of similar values using both approaches: https://lambda.gsfc.nasa.gov/education/graphic_history/baryonicd.cfm https://lambda.gsfc.nasa.gov/education/graphic_history/baryo... "There is general good agreement between the recent CMB and D/H+BBN determinations shown in the figure." I don't see the "double" anywhere there. And the values could be traced to all the sources mentioned there.
- nonbel 8y ago
  My source is Stacy McGaugh (the guy who wrote that page). On the same page as the original link I found this: http://www.astro.umd.edu/~ssm/mond/BBNLCDMMOND.jpg http://www.astro.umd.edu/~ssm/mond/BBNLCDMMOND.jpg He is currently active at this blog: https://tritonstation.wordpress.com/ https://tritonstation.wordpress.com/ It looks like this doubling happened in ~2000 so it wouldnt show up in your chart.
  - acqq 8y ago
    > It looks like this doubling happened in ~2000 so it wouldnt show up in your chart. Since 2000 many new satellite measurements were done and the values improved. As I've quoted your page Planck in 2013 ultimately made the most precise CMB measurements that most conclusively fit the "dark matter" model and provably don't fit the "MOND" model. And for that proof there were no "factor 2" corrections, as you also confirm, at least since 2000. The way you wanted to believe, and how you quoted some other parts of the same document, was that that had to be done for that 2013 proof, and it obviously haven't had. BTW the nature of the measurements, especially those made decades ago, is such that when we started with some value and then later measured something only 2 times smaller or bigger (but then all repeated measurements remain closer to one another), it's still OK. It's not the absolute values that prove this or that, it's the measured shapes that match or not the very complex calculations. And that's what happened in 2013 with Planck: what was measured for more than a decade with other satellites, and finally most precisely with Planck, shows the shape that in practice can't match the MOND predictions but nicely matches what the "dark matter" model predicts.
    - nonbel 8y ago
      >"Since 2000 many new satellite measurements were done and the values improved." The point is that "suddenly" people started measuring a higher baryon density to make it fit what was required for lambda-CDM model to fit the CMB measurements. Ie, the lambda-CDM model did not pre-dict the spectrum beforehand, they had to tune it to match the data. And see how the squares and triangles start moving upwards once the blue circles appear: http://www.astro.umd.edu/~ssm/mond/BBNLCDMMOND.jpg http://www.astro.umd.edu/~ssm/mond/BBNLCDMMOND.jpg Remember the oil drop experiment mentioned by Feynman in his cargo cult science talk? That is what this looks like to Mcgaugh: http://calteches.library.caltech.edu/51/2/CargoCult.htm http://calteches.library.caltech.edu/51/2/CargoCult.htm I have to say, it is very frustrating to discuss this since you seem to misunderstand every simple point being made, and before that has been corrected you have gone on to miss another point that needs to be addressed. We are not discussing this at a very deep level... Perhaps English is not your native language, but I am just letting you know. I hope no offense is taken.
      - 8y ago
- nonbel 8y ago
  >"I do disagree with the assertion that I often see, and remains a widespread misconception among scientists, that MOND does not do a good job of explaining cosmic phenomena. I’ve been through all that, and it is simply incorrect to say dark matter is always better outside of galaxies. Sure, it has shortcomings, but often dark matter only appears to be better because it declines to make a comparably testable prediction. Clusters of galaxies are a great example: MOND is off by a factor of 2 in mass (20% in velocity). Dark matter makes no prediction. Anything over the luminous mass is OK. The rest is dark. It doesn’t matter if that’s a factor of 2 or 5 (the modern value) or 6 (the cosmic value) or ~100 (Zwicky’s value). Being a factor of 2 off only sounds bad because there is a definite prediction! With dark matter we don’t care what that factor is because we have no prediction – at least, not one that can not be fudged." Here in a recent comment he addresses the "galaxy cluster" issue: https://tritonstation.wordpress.com/2018/11/21/hypothesis-testing-with-gas-rich-galaxies/ https://tritonstation.wordpress.com/2018/11/21/hypothesis-te...

by nonbel 8y ago

acqq 8y ago

What is your support for that claim? Can you quote other sources? I can quote my sources: Here are documented two independent approaches in estimating baryonic density: one is calculations based on the Big Bang Nucleosynthesis D/H ratio and another one is the values measured by the satellites observing the SMB. Note the two decades of similar values using both approaches: https://lambda.gsfc.nasa.gov/education/graphic_history/baryonicd.cfm https://lambda.gsfc.nasa.gov/education/graphic_history/baryo... "There is general good agreement between the recent CMB and D/H+BBN determinations shown in the figure." I don't see the "double" anywhere there. And the values could be traced to all the sources mentioned there.

nonbel 8y ago
My source is Stacy McGaugh (the guy who wrote that page). On the same page as the original link I found this: http://www.astro.umd.edu/~ssm/mond/BBNLCDMMOND.jpg http://www.astro.umd.edu/~ssm/mond/BBNLCDMMOND.jpg He is currently active at this blog: https://tritonstation.wordpress.com/ https://tritonstation.wordpress.com/ It looks like this doubling happened in ~2000 so it wouldnt show up in your chart.
- acqq 8y ago
  > It looks like this doubling happened in ~2000 so it wouldnt show up in your chart. Since 2000 many new satellite measurements were done and the values improved. As I've quoted your page Planck in 2013 ultimately made the most precise CMB measurements that most conclusively fit the "dark matter" model and provably don't fit the "MOND" model. And for that proof there were no "factor 2" corrections, as you also confirm, at least since 2000. The way you wanted to believe, and how you quoted some other parts of the same document, was that that had to be done for that 2013 proof, and it obviously haven't had. BTW the nature of the measurements, especially those made decades ago, is such that when we started with some value and then later measured something only 2 times smaller or bigger (but then all repeated measurements remain closer to one another), it's still OK. It's not the absolute values that prove this or that, it's the measured shapes that match or not the very complex calculations. And that's what happened in 2013 with Planck: what was measured for more than a decade with other satellites, and finally most precisely with Planck, shows the shape that in practice can't match the MOND predictions but nicely matches what the "dark matter" model predicts.
  - nonbel 8y ago
    >"Since 2000 many new satellite measurements were done and the values improved." The point is that "suddenly" people started measuring a higher baryon density to make it fit what was required for lambda-CDM model to fit the CMB measurements. Ie, the lambda-CDM model did not pre-dict the spectrum beforehand, they had to tune it to match the data. And see how the squares and triangles start moving upwards once the blue circles appear: http://www.astro.umd.edu/~ssm/mond/BBNLCDMMOND.jpg http://www.astro.umd.edu/~ssm/mond/BBNLCDMMOND.jpg Remember the oil drop experiment mentioned by Feynman in his cargo cult science talk? That is what this looks like to Mcgaugh: http://calteches.library.caltech.edu/51/2/CargoCult.htm http://calteches.library.caltech.edu/51/2/CargoCult.htm I have to say, it is very frustrating to discuss this since you seem to misunderstand every simple point being made, and before that has been corrected you have gone on to miss another point that needs to be addressed. We are not discussing this at a very deep level... Perhaps English is not your native language, but I am just letting you know. I hope no offense is taken.
    - 8y ago
nonbel 8y ago
>"I do disagree with the assertion that I often see, and remains a widespread misconception among scientists, that MOND does not do a good job of explaining cosmic phenomena. I’ve been through all that, and it is simply incorrect to say dark matter is always better outside of galaxies. Sure, it has shortcomings, but often dark matter only appears to be better because it declines to make a comparably testable prediction. Clusters of galaxies are a great example: MOND is off by a factor of 2 in mass (20% in velocity). Dark matter makes no prediction. Anything over the luminous mass is OK. The rest is dark. It doesn’t matter if that’s a factor of 2 or 5 (the modern value) or 6 (the cosmic value) or ~100 (Zwicky’s value). Being a factor of 2 off only sounds bad because there is a definite prediction! With dark matter we don’t care what that factor is because we have no prediction – at least, not one that can not be fudged." Here in a recent comment he addresses the "galaxy cluster" issue: https://tritonstation.wordpress.com/2018/11/21/hypothesis-testing-with-gas-rich-galaxies/ https://tritonstation.wordpress.com/2018/11/21/hypothesis-te...