The Story of Dark Matter

Several astronomical observations concerning the structure of galaxies, the rotation of stars in spiral galaxies, the motions of galaxies within a cluster of galaxies, and so on, cannot be understood in terms of Newton’s universal law of gravitation and the visible atomic matter within the galactic systems. This chapter reviews the progress made over many decades in the understanding of these cosmological observations that indicate a serious breakdown of Newton’s universal law of gravitation unless there exists additional unseen matter, named “dark matter.” The only alternative to “dark matter” is to modify Newtonian gravity. The chapter presents a critical review of the two main approaches to providing the additional gravity required to understand the puzzling astronomical observations: (1) the “dark matter” hypothesis providing additional unseen mass and (2) modification of Newton’s universal law of gravity such that there is a stronger gravitational field at larger distances. Both Milgrom’s modified Newtonian dynamics (MOND) theory and Robson’s recent quantum theory of gravity provided by the generation model (GM) of particle physics are discussed.