Far out cosmology: Does dark matter exist? MOND supported (Introduction)

by David Turell @, Monday, July 19, 2021, 20:02 (10 days ago) @ David Turell

Another essay on why MOND may be the answer:

https://aeon.co/essays/we-should-explore-alternatives-to-the-standard-model-of-physics?...

"There is one problem, however. For four decades and counting, scientists have failed to detect the dark matter particles in terrestrial laboratories. You might think this would have generated some doubts about the standard cosmological model, but all indications are to the contrary. According to the 2014 edition of the prestigious Review of Particle Physics: ‘The concordance model [of cosmology] is now well established, and there seems little room left for any dramatic revision of this paradigm.’ Still, shouldn’t the lack of experimental confirmation at least give us pause?

"In fact, there are competing cosmological theories, and not all of them contain dark matter. The most successful competitor is called modified Newtonian dynamics (MOND). Observations that are explained under the Standard Model by invoking dark matter are explained under MOND by postulating a modification to the theory of gravity. If scientists had confirmed the existence of the dark particles, there would be little motivation to explore such theories as MOND. But given the absence of any detections, the existence of a viable alternative theory that lacks dark matter invites us to ask: does dark matter really exist?

***

"In three papers published in 1983, Milgrom proposed a simple modification to Isaac Newton’s laws that relate gravitational force to acceleration. (Albert Einstein’s theory reduces to Newton’s simpler theory in the regime of galaxies.) He showed that his modification correctly predicts the asymptotic flatness of orbital rotation curves.

***

"Milgrom’s hypothesis correctly predicts the rotation curve of every galaxy that has been tested in this way. And it does so without postulating the presence of dark matter.

"Note the stark difference between the way in which the two theories explain the anomalous rotation-curve data. The standard cosmological model executes an ad-hoc manoeuvre: it simply postulates the existence of whatever amount and distribution of dark matter are required to reconcile the observed stellar motions with Newton’s laws. Whereas Milgrom’s hypothesis correctly predicts orbital speeds given the observed distribution of normal matter alone. No Standard Model theorist has ever come up with an algorithm that is capable of doing anything as impressive as that.

***

"Just last year, two theorists in the Czech Republic, Constantinos Skordis and Tom Złośnik, showed that there exist fully relativistic versions of Milgrom’s hypothesis that are perfectly capable of reproducing the CMB data without dark matter. This relativistic version of MOND, which they call RMOND, incorporates an additional field that mimics the behaviour of particle dark matter on the largest cosmological scales, and yields Milgromian dynamics on the scale of galaxies.

***

"I honestly don’t know whether this troubling state of affairs reflects a general ignorance about MOND, or whether some darker psychological mechanism is at work. But I hope that scientists and educators can begin creating an environment in which the next generation of cosmologists will feel comfortable exploring alternative theories of cosmology."

Comment: It seems like we need a new paradigm about dark matter. I am no judge as to which theory might be correct. The last article prior to this one was from a group trying to study MOND, and they seemed to have trouble getting grants.


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