Modified Newtonian Dynamics (MoND)

As comic book guy might say, "Worst. Acronym. Ever."

MoND refers to a theory in physics, especially cosmology and astrophysics, that suggests that there is no real need to posit "dark matter". The case for dark matter has always been that the amount of observable matter in galaxies is not enough to understand how fast galaxies rotate. Either our views of gravity or our views of mass must change to cover these rotations. MoND opts for changing the view of gravity, rather than postulating vast quantities of mass.

Here is Sabine Hossenfelder's explanation of the point.

https://backreaction.blogspot.com/?fbclid=IwAR0Eild3WJDSYbL1NjgSjMsmenRUf6wbPy9HQE7DEkIrfLnlxHbvzp0g9Xc

Advocates of Modified Newtonian Dynamics propose changes of the Newtonian theory of gravity. Of course, the Einstein revolution did already modify Newton. The point though was that another differently-motivated modification will be necessary, and that scientists from six score years after the major Einsteinian theories have some work to do.

What is fascinating to me is the notion that Ockham's razor cuts both ways. Is MoND simpler than acknowledging the existence of all that "dark matter"? Does it get points for not multiplying entities?

Well, Newtonian mechanics is marvellously simple once grasped. That is precisely how it swept the intellectual world so quickly and devastatingly when it was announced. The desired modification of those dynamics adds complexity, at least from an important PoV.

Ockham may have stated his demand for simplicity in terms of the number of entities, but surely the straightforward character of the law by which objects attract one another should also not be modified "without necessity"?

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