Using Newton’s laws of physics, we can model the motions of the planets in the solar system with complete precision. But in the early 1970s, scientists discovered that it did not work for him disk galaxies The stars at their outer edges, away from the gravity of all matter at their center, moved much faster than Newton’s theory predicted.
As a result, physicists have suggested that an invisible substance called “dark matter” provides additional gravity, causing stars to accelerate – a theory that has been widely accepted. But in a final statement, my colleagues and I suggest that observations across a wide range of scales are much better explained in an alternative theory of gravity called Milgromian Dynamics or Monday – Requires No Invisible Material. It was first proposed by the Israeli physicist Mordechai Milgrom in 1982.
Mond’s basic assumption is that when gravity becomes too weak, as it does near the edge of galaxies, it begins to behave differently from Newtonian physics. In this way, it is possible to explain why the stars, planets and gas at the edge of more than 150 galaxies spin faster than expected based solely on their visible mass. Mond, however, is not only Explain Like rotation curves, in many cases, Expecting they or they.
Philosophers of science claim that this power of prediction makes Mond superior to the standard cosmological model, which suggests that there is more dark matter in the universe than visible matter. In fact, according to this model, galaxies contain an extremely uncertain amount of dark matter that depends on the details of galaxy formation – which we do not always know. This makes it impossible to predict the rotational speed of galaxies. But such predictions are made regularly with Mond, and it has been confirmed so far.
Imagine that we know the distribution of visible mass in a galaxy, but do not yet know its rotational speed. In the standard cosmological model, it would only be possible to say with some certainty that the rotational speed would be between 100 km / s and 300 km / s in the suburbs. Mond gives a more accurate prediction that the rotation speed should be between 180 and 190 km / s.
If later observations reveal a rotational speed of 188 km / s, it agrees with both theories – but Mond is the clear favorite. This is a newer version of Occam’s razor – that the simplest solution is better than more complex solutions, in which case the notes should be explained with as few “free parameters” as possible. Free parameters are constants – certain numbers that we have to enter into equations to make them work. But the theory itself has not given them – there is no reason why any particular value exists – so we have to measure it by observation. An example is the gravitational constant, G, in Newton’s theory or the gravitational magnitude of dark matter in galaxies in the standard cosmological model.
We introduced a concept known as “theoretical elasticity” to capture the idea behind Occam’s code that a theory with the most free parameters agrees with a wider range of data, making it more complex. In our review, we used this concept when testing the Standard and Mond cosmological model against various astronomical observations, such as the rotation of galaxies and movements in galaxy clusters.
Each time, we gave a theoretical elastic score between -2 and +2. A score of -2 indicates that the model is making a clear and accurate prediction without looking at the data. Conversely, +2 means “everything is fine” – theorists could have room for almost any reasonable observation result (since there are so many free parameters). We also assessed how well each model fits the observations, with +2 indicating an excellent fit and -2 being reserved for observations that clearly show that the theory is incorrect. Then we subtract the degree of theoretical flexibility from the degree of agreement with observations, because it is good to match the data – but to be able to adjust everything is bad.
A good theory would give clear predictions, which were confirmed later, and an overall score of +4 on many different tests would be better (+2 – (-2) = +4). A bad theory will get a score between 0 and -4 (-2 – (+ 2) = -4). Accurate predictions can fail in this case – and they are unlikely to work with the wrong physique.
We found an average score for the Standard Cosmological Model of -0.25 across 32 tests, while Mond got an average score of +1.69 across 29 tests. The scores for each theory on many different tests are shown in Figures 1 and 2 below for Standard and Mond cosmological models, respectively.
It is immediately clear that no significant problems were identified for Mond, which is at least reasonably consistent with all data (note that the two bottom rows indicating forgery are empty in Figure 2).
problems with dark matter
One of the most striking flaws in the standard cosmic model involves “rod galaxies” – bright rod-shaped regions composed of stars – where spiral galaxies are often found in their central regions (see main image). The rods rotate in time. If galaxies were shrouded in huge halos of dark matter, their rods would slow down. However, most, if not all, of the observed galactic bands are moving rapidly. it is false standard cosmological model with a high degree of trust.
Another problem is that original models that the proposed galaxies have dark matter halos made a big mistake – they assumed that dark matter particles give gravity to the matter around them, but are unaffected by gravity’s attraction of ordinary matter. This simplifies the calculations, but does not reflect reality. When this was taken into account in subsequent simulations, it was clear that dark matter halos around galaxies do not reliably explain their properties.
There are many other flaws in the standard cosmological model that we looked at in our review, and Mond was often able to explain naturally enough. But the reason why the standard cosmological model is so popular may be due to miscalculations or limited knowledge of its faults, some of which have recently been discovered. It may also be due to people’s reluctance to change the theory of gravity, which has been so successful in many other areas of physics.
Mond’s large lead over the standard cosmological model in our study led us to conclude that the available observations strongly favor Mond. Although we do not claim that Mond is perfect, we still believe that it fixes the big picture – galaxies seriously lack dark matter.
Written by Indranil Banik, Postdoctoral Fellow in Astrophysics, University of St. Andrews.
This article first appeared in Conversation.
Reference: “From Galactic Sticks to Hubble Tension: Weighing Astrophysical Evidence for Melgromian Gravity
By Indranil Banik and Hongsheng Zhao, June 27, 2022 Available here symmetry.
DOI: 10.3390 / sym14071331