If we assume that: (a) The four fundamental forces of nature are independent waves without rest mass, and their speeds are constant in a vacuum, just like light. (b) Light or electromagnetic waves and gravity are comparable in structure. The weak and strong interials are similar in structure. (c) Light and the weak interaction have the same speed c_L with spin number +1 or -1. (d) Gravity and the strong interaction have the same speed c_G without spin. (e) The primary particles, namely electrons (or positrons), electron neutrinos, and dark neutrinos in this paper, are made of the above four waves. We can find and describe some fundamental characteristics of the primary particles (e.g., their sizes, energies, and interactions) and introduce new attractive results from them (e.g., the source of the Pauli exclusion principle, the solution of the Einstein-Podolsky-Rosen paradox, and c_G slightly faster than c_L).