The mass of an electron is crucial in various equations and applications within quantum physics, particularly in the design of electron guns, cathode ray tubes (CRTs), and magnetrons. It plays a significant role in understanding transit time effects in vacuum tubes and magneto ionic resonance in the ionosphere. The discussion raises the question of whether electron mass can be considered an essential quantity in quantum physics and how to rank physical quantities by their importance. While some view the ranking of physical quantities as pseudo-science, the mass of an electron is undeniably foundational in many scientific equations and technologies. Overall, the significance of electron mass in quantum physics and its applications is widely acknowledged.