Gaia satellite may have validated Mond, an alternative theory of gravity that avoids dark matter

Sejong University in Seoul, South Korea recently posted a statement on its website about recent work that appeared in an article.Astrophysical Journal by Kyu-Hyun Chae, professor of physics and astronomy at this university. Its readings sound like bombs, at least for those who are not researchers in this field. And we still don’t know very well what the scientific community will say about it, nor whether the thesis expounded there will withstand far more intense scrutiny than what has already authorized publication, On which we can consult in free access. arXiv,

Let’s not go around anymore. If the researcher is right, we are on the verge of a revolution in fundamental physics, which has nothing less than evidence that both Newtonian and Einsteinian theories of gravitation must be revised, and put into a compatible form. should be kept. The equations, proposed by the famous Israelis Mordhai Milgrom and Jacob Bekenstein in 1984, were inspired by equations that Milgrom had already advanced within his own framework in 1982. Modified Newtonian DynamicsWhich is today known by the abbreviated name of Mond.

Second, the theory proposed by Milgrom and Bekenstein makes it possible, up to a certain point, to avoid assuming the existence of dark matter particles, particles that have never been observed before, either in accelerators or in buried detectors, and most of which are physical particles. Astronomers and astrophysicists expected the discovery before the end of 2010.

Dark matter, the key to the formation of galaxies?

Remember that these particles are the current state of knowledge needed to explain some features of fossil radiation and galaxies, if we consider no other theory of gravity than Einstein’s.

It is dark matter, which has been rapidly collapsing due to gravity since the Big Bang, which has caused and continues to collapse into galaxies and then clusters of galaxies, which have been coming together over the eons. It has taken billions of years to form the large-scale filamentous structure that we see in the universe. Without dark matter, galaxies would not exist today, in any case according to our knowledge of physics and if we did not modify the laws of gravity.

The universe has continued to grow for 13.8 billion years. Contrary to what our eyes tell us when we contemplate the sky, what composes it is far from static. Physicists make observations of the universe at different ages and perform simulations in which they replay its formation and its evolution. Dark matter appears to have played a large role from the beginning of the universe to the formation of the large structures seen today. © CEA Research

At the level of galaxies and clusters of galaxies, a theory respecting Mond’s formal framework predicts that the gravitational force decreases less rapidly with distance from an attractive source than Newton’s equations predict. from a strong Einstein. Thus it is observed that clouds of gas and stars under the influence of gravitational force undergo more rapid acceleration over long distances than or above what Newton’s theory predicts for acceleration below a finite acceleration. At the core of Mond is the assumption that the force due to gravity behaves according to the equation F=ma, rather than obeying Newton’s second law, F=ma.² / A₀ within the range of very low acceleration (a ≪ a₀ ∼ 1,2 × 10⁻¹⁰ M / s²,

But almost everything is also as if a galaxy actually contained more material in the form of stars than could be inferred from its brightness. So, if we don’t want to change the laws of gravity, there will be a distribution of mass that doesn’t radiate or radiates very little. We know that it cannot be normal matter in the form of cold gas because the amount of mass is so great that it would have modified the ratio between the abundances of the isotopes of hydrogen and d. helium at the end of the Big Bang. during the famous primordial nucleosynthesis.

AquaL, an incarnation of Mond based on the legendary Lagrange equations

We know that the Standard Model in cosmology postulates the existence of this exotic dark matter, but in fact, even assuming that it does not exist and should be called the Mond, the Big Bang theory would still be largely valid. Nevertheless, according to Kyu-Hyun Chae, we should now adopt instead of Einstein’s theory of gravity, a theory propounded by Milgrom and Bekenstein, called aqueous Lagrangian theory (equal).

There is a variant of the AquaL Mond that does not have the three major drawbacks. Indeed, despite solving some problems, Mond’s initial version violated three fundamental laws of physics, conservation of energy, momentum, and angular momentum. This is not automatically the case in the case of a theory based on the Lagrangian. Lagrangians appear in theories inspired by Lagrange’s analytical mechanics and they are the basis of all known fundamental theories of forces and matter. It is no coincidence that many of the famous treatises on theoretical physics by the famous Russian physicist Lev Landau begin with the Lagrangian hypothesis.

Although EQUAL is still not satisfactory in its current form (although it is compatible with the well-known weak equivalence principle) because it needs to be made compatible with special relativity and has problems in this regard, a relativistic version called RAQUAL is actually compatible. Not for example with observations related to clusters of galaxies.

But, how does Kyu-Hyun Chae suggest today that we should follow the path shown by Aqual in modifying the equations of general relativity?

Abnormal motion of stars in binary systems

The researchers relied on astrometric data on the movements of more than 26,000 double stars observed by the European Space Agency’s Gaia space telescope within a radius of about 650 light-years around the Sun. The stars in these binary systems orbit each other at such large distances that they can enter a regime of weak Maund acceleration, while being sufficiently isolated from many influences, so that one can measure gravitationally Couldn’t specify the acceleration (this game would be more difficult to play in the Solar System or specifically on Earth). Nor can we deduce the effects of dark matter on a scale that relates only to two stars, not to the motion of a star in a galaxy’s gravitational field.

The data from Gaia show that the motion of these stars does not respect Newton’s laws and yet according to Kyu-Hyun Chae, the observed violations reach the famous 5 sigma which authorizes to speak of the discovery because About one in a million this will not happen. The chance that only a chance effect is observed.

Let’s keep a cool head and wait for many more independent verifications before claiming the death of the theory of dark matter and the theory of general relativity.

However, we already know what Milgrom thinks: Chai’s discovery is the result of a very complex analysis of advanced data, which, as far as I can tell, he did very carefully and meticulously. But for such a far-reaching finding – and it is far-reaching indeed – we need confirmation by independent analyses, preferably with better future data. If this anomaly is confirmed as a violation of Newtonian dynamics, and especially if it is indeed consistent with Mond’s simplest predictions, it will have huge implications for astrophysics, cosmology and fundamental physics in general. . ,

We also know what Professor Javier Hernandez of Mexico’s National Autonomous University thinks about it (in Spanish: National Autonomous University of MexicoUNAM), who first suggested testing the laws of gravity with widely separated binary stars ten years ago: It is exciting that the divergence from Newtonian gravity, which my group has been claiming for some time, has now been independently confirmed… The unprecedented accuracy of the Gaia satellite, the carefully selected large samples used by Chai, and its detailed analysis, making their results quite robust. A search will be called. ,

Let’s wait a little longer to really think about it, as Milgrom himself suggests.

In 2016, Stacey McGaugh gave this lecture on the reasons why researchers like her turned to the Mond theory proposed by Israeli physicist Mordechai Milgrom in the early 1980s. Stacey McGaugh early in her career was a strong supporter of the existence of dark matter particles and therefore it is backwards, noting the contradiction between the predictions of dark matter theory in the world of galaxies and, conversely, the successes found naturally by the general framework Are. was determined by Milgrom’s modification of Newton’s laws of celestial mechanics, which Stacey McGaugh, like Planck, was resigned to accepting when he discovered quantum mechanics, that changing the fundamental laws of gravitation And it was necessary not to introduce new particles into astrophysics. To get a fairly accurate French translation, click on the white rectangle at the bottom right. Then the English subtitles should appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Select “French”. © Ted