Does Dark Matter exist?

Does Dark Matter exist?

Is it possible that what we have invented as dark matter to explain the motion of stars in galaxies and clusters is a figment of our imagination? Could it be that Einstein’s General Relativity has a flaw? Does dark matter exist?

Vera Rubin verified that stars in the outer edges galaxies are moving around the galactic center at about the same speed as those closer to the center. This cannot be explained by all the visible matter. This faster than predicted motion it was theorized is due to extra unseen matter, or Dark Matter that surrounds all galaxies.

But could this motion be equally well explained by a modification of Einstein’s General Relativity, just like Newton’s equations were modified by Einstein’s General Relativity?

GR has been shown to be highly accurate for massive objects up to several light years apart. Is it possible that gravity behaves very differently, at larger distances? In 1983, Israeli physicist Mordehai Milgrom published a hypothesis showing that a modification of Newtonian mechanics could almost perfectly explain our observations.

Milgrom found that if you calculate using just the laws of Newton, the acceleration due to gravity at the point where you need dark matter to explain the velocity of stars, this acceleration was the same for every galaxy. There was some critical value of acceleration, such that if the acceleration was larger than that value you didn’t need dark matter, but when the acceleration was smaller, you needed dark matter.

So what Milgrom said is that maybe we just need to modify the theory of gravity such that at high acceleration, it falls off by one over radius squared, as in Newton’s equation But at smaller accelerations, gravity falls off at one over the radius, instead of radius squared.

If you invoke Milgrom’s hypothesized modification of gravity, it fits the data almost perfectly. It fits our observations of the motions of stars not just in our own galaxy, but dozens of other galaxies.