tag:blogger.com,1999:blog-7315236707728759521.post1938100085394704381..comments2024-03-27T22:28:06.861-06:00Comments on Dispatches From Turtle Island: Gravitation Wave Telescopes Strongly Disfavor Primordial Black Hole Dark MatterAndrew Oh-Willekehttp://www.blogger.com/profile/02537151821869153861noreply@blogger.comBlogger2125tag:blogger.com,1999:blog-7315236707728759521.post-87256489485763349272020-05-15T12:53:22.105-06:002020-05-15T12:53:22.105-06:00'I don't dispute the conclusion of this pa...'I don't dispute the conclusion of this paper, but do you think the 2 papers I linked on MOND " is pretty much the nail in the coffin " of MOND and therefore Deur by extension?"<br /><br />Definitely not.<br /><br />I don't have the time or space in a comment to spell it out the issues with each of those papers here, but one of the articles cited is doing bad statistical analysis, which has been addressed in responses to it. <br /><br />MOND is a toy model relative to Newtonian physics that isn't supposed to be valid outside its domain of applicability. GR is probably almost perfect in strong fields and, at least as conventionally applied and implemented, materially wrong in very weak fields. So, there should be some contradiction of GR. The weak equivalence principle is probably wrong. Deur's approach, which is a ground up quantum gravity approach (but can also be done classically) focusing on self-interaction of gravitational fields does escape a lot of the technical flaws in MOND that Sabine identifies.<br /><br />Dark matter predicts nothing in advance, which is a serious flaw. It is an incomplete theory since you need both a particle description and a model to explain how it ends up arranged in the universe for it to be complete and neither has been accomplished. LambdaCDM has multiple fatal flaws. No competitor dark matter theory works yet either. Clearly, there is beyond GR + Standard Model physics at work in dark matter/dark energy observations. But, no dark matter theory adequately explains it.<br /><br />But, it is reasonable to hope (although it is hard to test explicitly in non-linear models) that any theory which reproduces the galactic scale phenomena attributable to dark matter is also likely to reproduce the cosmology scales attributed to dark matter.<br /><br />The existence of a universal constant a0 is one respect in which Deur and MOND differ. Deur has no separate a0 constant as a fundamental constant (having only Newton's constant G as fundamental, it also lacks a cosmological constant lambda). But, the shape of a matter distribution plays a role in whether apparent dark matter phenomena kick in. In perfectly spherically symmetric systems there is no effect. The closer you get to a disk-shaped system, the stronger the effect gets. The closer you get to isolated two point source systems you get, it gets even stronger. That is how it can solve the cluster scale difficulties of MOND. andrewhttps://www.blogger.com/profile/08172964121659914379noreply@blogger.comtag:blogger.com,1999:blog-7315236707728759521.post-1949506303534772212020-05-15T00:03:06.528-06:002020-05-15T00:03:06.528-06:00I don't dispute the conclusion of this paper, ...I don't dispute the conclusion of this paper, but do you think the 2 papers I linked on MOND " is pretty much the nail in the coffin " of MOND and therefore Deur by extension?<br /><br />there are papers that show problems with various dark matter proposals, and papers that seemingly refute MOND<br /><br />Sabine had a post on the philosophy of MOND, and she argues MOND is in contradiction to GR/Newton, so it's hard to see how Deur can escape these issues.<br /><br />The MOND expert of that book acknowledges that while MOND can explain the second peak of the CMB, it cannot explain the third peak, and that the third peak remains best explained by dark matter, which can also explain everything MOND purports to explain.<br /><br />I wonder if MOND claim of ao is wrong, that it is something else going on with gravity or inertia, but not ao which Milgrom has claimed. neohttps://www.blogger.com/profile/16769182614452171312noreply@blogger.com