Unfortunately, in 1977, astronomers discovered that the visible mass of galaxies varies with the fourth power of the rotation speed of stars. This relation between the speed of stars and the mass of their galaxy is enforcing a direct link between the visible mass and the black mass of galaxies. This result was named after the astronomer who has highlighted the most numerous and the most significant cases. It is the law of Stacy McGaugh, indeed already noticed by Tully and Fisher in 1977. This link between dark matter and visible mass is entirely contrary to the theory of General Relativity. The tragedy is that many experiments designed to highlight the famous black mass since the middle of last century have failed.