(ORDO NEWS) — We can model the motion of the planets in the solar system quite accurately using the Newtonian laws of physics.
But in the early 1970s scientists noticed that these laws do not work well for disk galaxies – stars located on the periphery of such galaxies, far from a powerful source of gravity, which is matter lying in the center of the galaxy, moved much faster than Newtonian physics predicted.
This led scientists to believe that the extra gravitational force is caused by an invisible substance known as dark matter, which causes the stars to accelerate, a hypothesis that has become very popular today and is known as the dark matter hypothesis.
However, in a new study, scientists led by Indranil Banik show that the results of observations of the universe are better described by an alternative hypothesis, first proposed by the Israeli physicist Mordechai Milgrom in 1982 and called the Modified Newtonian Dynamics, or MOND theory. This theory does not require the presence of invisible matter.
The main postulate of the MOND theory is that in cases where gravity becomes very weak, for example, at the periphery of galaxies, the laws of gravity change, in comparison with normal conditions.
This explains the fact that the stars, planets and gas located at the periphery, in the case of more than 150 galaxies well known to science, rotate faster than expected, based on their apparent mass.
Moreover, the MOND hypothesis has a higher predictive power in relation to the rotation curves of galaxies than the standard cosmological model, the authors believe, since in the dark matter hypothesis.
The kinematic properties of galaxies strongly depend on the amount of dark matter in them, and this, in turn, is determined by the details formation of the galaxy, the elucidation of which is sometimes difficult or even impossible.
According to the authors, the MOND hypothesis makes it possible to more accurately predict the rotation of galaxies, and due to this, it received a higher score on the rating scale developed by the authors.
The essence of the scale is as follows – first, the flexibility of the theory is separately assessed on a scale from -2 points (clear forecast) to +2 points (the model explains any available data), and then – the correspondence of the theory to observations, from -2 points (poor fit) to + 2 points (perfect match).
The authors then subtracted the theory’s flexibility score from the observational fit score, since a good fit to observational data is welcome but the theory’s ability to explain any kind of data is definitely not its virtue.
An ideal theory should get 2+2 = 4 points on this scale, and a bad theory should get from -4 to 0 points. According to the authors, the standard cosmological model scored -0.25 on 32 tests, while the MOND hypothesis scored +1.69 on 29 tests.
According to the authors, the data obtained as a result of this analysis indicate the need to abandon the dark matter hypothesis in favor of an alternative theory of gravity.
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