Let’s talk about Dark Matter (no, we don’t mean the PD): does it exist or not?

One of the mysteries of the cosmos is Dark Matter, not the one that makes up the PD, but the one that conditions the movement and shape of the galaxies. Today, indeed for centuries, we have been able to model the motions of the planets of the Solar System quite accurately using Newton's laws of physics. But in the early 1970s, scientists noticed that this law didn't work for disk galaxies: the stars at their outer edges, away from the gravitational pull of all matter at their center, were moving much faster than expected. from Newton's theory.

This led physicists to propose that an invisible substance, called " dark matter ", provided additional gravitational attraction, causing the stars to accelerate – a theory that has become very popular. However, many physicists now believe that this accelerated motion is much better explained by an alternative theory of gravity proposed by the Israeli physicist Mordehai Milgrom in 1982, called milgrosian dynamics or Mond, which does not require any invisible matter.

Mond's main postulate is that when gravity becomes very weak, as it does at the edges of galaxies, it begins to behave differently from Newtonian physics . In this way, it is possible to explain why the stars, planets and gas found at the edges of more than 150 galaxies rotate faster than expected based only on their visible mass, but Mond does not just explain these curves of rotation; in many cases, he predicts them.

Philosophers of science have argued that this predictive power makes Mond superior to the standard cosmological model, which proposes that there is more dark matter than visible matter in the universe. According to this model, in fact, galaxies have a highly uncertain amount of dark matter, which depends on the details of how the galaxy was formed, which we do not always know. This makes it impossible to predict the rotation speed of galaxies. Instead such predictions are made for control with Mond's rule and have so far been confirmed.

Let's imagine we know the distribution of visible mass in a galaxy, but don't yet know its rotation speed. In the standard cosmological model, it would be possible to say with some certainty that the rotation speed is between 100 and 300 km / s in the periphery. Mond manages to make a more precise prediction, namely that the rotation speed must be between 180 and 190 km / s.

Here we come to apply a sort of modern version of Occam's Razor, which states that it is useless to create entities when the explanation can come from simpler solutions. What good is a mysterious "Dark Matter" when a variation in the standard theory, which includes only a simple variation in the Force of Gravity, explains the universe much better

In practice, Mond's theory better predicts the velocity of galaxies, so it's better because it doesn't require the creation of unnecessary entities to explain physics and predict events. If we applied the same principle to politics we would have a few organizations and parties to dissolve …


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The article Let's talk about Dark Matter (no, we don't mean the PD): does it exist or not? comes from ScenariEconomici.it .


This is a machine translation of a post published on Scenari Economici at the URL https://scenarieconomici.it/parliamo-di-materia-oscura-no-non-intendiamo-il-pd-esiste-o-no/ on Fri, 05 Aug 2022 15:27:23 +0000.