The Origin of Gravitation and Electromagnetism Zhong-Cheng Liang School of Electronic and Optical Engineering, Nanjing University of Posts and Telecommunications, Nanjing, China Email: zcliang@njupt.edu.cn Abstract. Assuming that protons and electrons are three-dimensional body particles that have only mass and volume, the volume repulsion can ensure the finiteness of particle density. A scalar potential and a vector potential are constructed respectively with the mass density and the momentum density. A set of particle field equations is derived from the scalar and vector potentials with the help of vector calculus. The equation set is general field equations in three-dimensional flat space, instead of that in four-dimensional curved spacetime. It is shown that the particle field includes gradient field, divergence field and curl field. The gradient field predicts both attraction and repulsion between particles, the divergence field represents the undulation of particles, and the curl field describes the vortex motion of the particles. It is proven that gravitation and electromagnetism both originate from the interaction of body particles. The undulation of pure electronic system represents both gravitational waves and electromagnetic waves. If graviton and photon are regarded as body particles identical to electron, the electrons are the dark matter in the background of the universe. Keywords: Particle, field, interaction, gravitation, electromagnetism 1 Introduction In 1687, Newton put forward the laws of motion and the law of universal gravitation, laid the foundation of classical mechanics [1]. The gravitational force is directly proportional to the mass of object, and is inversely proportional to the square of the distance between objects. In 1865, Maxwell proposed the electromagnetic field equations on the basis of his predecessors' work, which laid the foundation of classical electrodynamics [2]. The electric (magnetic) force is directly proportional to the charge (current) and inversely proportional to the square of the distance between charges (current elements). Despite of this similarity, gravitation and electromagnetism are regarded as different fundamental interactions because of the particularity of magnetic force. In classical physics, the gravitational force is thought to be transmitting through vacuum instantaneously, while the electromagnetic force is considered to be transmitting through electromagnetic field at a limited speed of light. In order to maintain the motion invariance of electromagnetic laws, Einstein put forward the special theory of relativity in 1905 and established the conception that electromagnetism is related to the nature of time and space [3]. In his general theory of relativity, he further interpreted the origin of gravitation as the bending of space-time [4]. On the other hand, quantum field theory treats particles as excited states of their underlying fields. The origin of electromagnetic force is attributed to the exchange of photons. As messenger particles, photons are point particles that have no mass and volume. The background of quantum field theory is Minkowski's flat spacetime, the final outcome is that tens of fundamental particles are needed to explain the electromagnetic, strong and weak interactions in the Standard Model of particle physics [5]. A number of quantum gravity theories are proposed to deal with the problem of gravitation, which explain the origin of gravity by the exchange of gravitons between objects [6]. One of them is the string theory developed from quantum field theory. The unusual aspect of string theory is to expand particles from zero-dimensional points to one-dimensional strings [7]. The success of string theory is in that one mode will always correspond to a graviton. However, the price of this success are unusual features such as six extra dimensions of space in addition to the usual three for space and one for time. Currently, there is still no complete and consistent quantum theory of gravity. Apart from the major formal and conceptual problems that need to be overcome, the common problem they encounter is that so far there is no way to put quantum gravity predictions to experimental verification. Theoretical physics is logic formal system based on the core concepts of space, time, particle, field and interactions. According to the set theory [8], logic formal systems based on different conceptual sets are not Theoretical Physics, Vol. 4, No. 2, June 2019 https://dx.doi.org/10.22606/tp.2019.42004 85 Copyright © 2019 Isaac Scientific Publishing TP