Dark matter: our review suggests it's time to ditch it in favor of a new theory of gravity
We can model the motion of the planets in the Solar System quite accurately using Newton’s laws of physics. But in the early 1970s, scientists noticed that this didn’t work for disk galaxies — the stars on their outer edges, away from the gravitational force of all matter at their center — moving much faster than Newton’s theory predicted. This led physicists to propose that an invisible substance called “dark matter” exerts an extra gravitational pull, causing the stars to accelerate – a theory that has become very popular. However, in a recent review, my colleagues and I suggested that observations at multiple scales are much better explained in an alternative theory of gravity proposed by Israeli physicist Mordehai Milgrom in 1982 called Milgromian or Mond dynamics – requiring no material not visible. 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 possibl