The Story of Dark Matter began when scientists observed that planets such as Mercury and Uranus did not seem to follow the Newtonian physics law for the planets. Some unseen force seemed to be blocking their trajectory. While Fritz Zwicky was observing galaxies outside the Milky Way, he made the hypothesis that the galaxies were attracting one another through gravity. He came up with a complex formula which he thought could tell him three things: “1) the radial extent of a system, 2) the mean square of the velocities of a system, (or) 3) the total mass of the system.” Just as when a bunch of marbles which are dropped into a solid well could eventually tell us how deep it is, Mr. Zwicky figured a similar idea for galaxies when they first fell
