The Physical Essence of Neutrons and the Inevitability of Cosmic Material Composition

According to the Unified Theory of Three Fundamental Forces, the basic interactions in nature that can be expressed by mechanical formulas are universal gravitation, electromagnetic force and strong interaction. The traditionally defined weak interaction is essentially the phenomenon of neutron decay. It only contains fixed observed values such as energy and particle quantity, without dedicated mechanical formulas or independent action mechanisms, so it does not fall into the category of fundamental forces. The strong interaction is a short-range mass coupling force with an exponential attenuation term, while the Coulomb electromagnetic force is a long-range charge coupling force. The inherent conflicts between their operating laws make it impossible for pure proton clusters to form stable atomic nuclei. As electrically neutral nucleons, neutrons undertake critical functions including buffering, connecting and spacing limitation. They first bind with protons via the strong nuclear force to form basic units, and then gradually draw other protons into the effective range of the strong force. Adjacent protons inside atomic nuclei are also subjected to the strong nuclear force, whose magnitude is far greater than the Coulomb repulsion between protons. The combined effect of multiple forces guarantees the stability of nuclear structures. Based on the formulas and calibrated parameters in Unified Theory of Three Fundamental Forces, this paper carries out quantitative comparative calculations of the two types of forces. The research results show that if neutrons did not exist in the universe, only hydrogen atoms would remain. Heavy elements and complex substances could not be produced, and core cosmic nuclear reactions including nuclear fusion and nuclear fission would disappear completely. Neutrons are essential for the existence of microscopic nuclear structures, macroscopic material worlds and cosmic energy evolution.