There is evidence of the existence of dark matter for quite some time now. The first time we had an idea that there was something else that we did not see was in the twenties and thirties of the last century. But the clearest evidence came with the studies of American astrophysicist Vera Rubin on the movements of spiral galaxies, which are the basis for us to think that there is dark matter. To understand what Vera Rubin's work means, you must know that we know the relationship between the mass contained in galaxies and the light they produce. This means that we can calculate how much mass a galaxy contains thanks to the light that reaches us from it. At the same time, we can also estimate the mass of a galaxy by studying its rotation speed. What Vera Rubin observed is that the data she obtained thanks to that relationship did not add up. Much more mass than what was visible was needed to justify the speed at which galaxies rotated. This is considered the most classic evidence for the existence of dark matter, but there are many more.
