Current mainstream galactic dynamics theories introduce the unproven hypothetical concept of dark matter to explain the anomalous rotational speeds of stars in the outer regions of galaxies, claiming that it provides additional gravitational force to bind outer stars and prevent galactic disintegration. Strictly following the core law of universal gravitation—inverse square of the distance—and based on observed rotational speed data of the Milky Way and external galaxies, combined with the nature of gravitational interactions between celestial bodies, this paper clarifies the core logic of forces acting on celestial bodies in galaxies: the motion of stars is dominated by the gravitational pull of nearby, close-range stars; the gravitational effect of distant stars is extremely small in magnitude compared to that of nearby stars, acting as a weak secondary influence, but is by no means negligible. Hundreds of billions of stars, interstellar matter, and other visible celestial bodies inside a galaxy form a natural constraint mechanism through omnidirectional mutual gravitational pull and balance. This mechanism sufficiently explains the rotational speed characteristics of outer stars and spiral arm structures without invoking the dark matter hypothesis. Through detailed arguments from the core gravitational law, observational facts, and dynamic modeling, this paper reconstructs a galactic dynamics system based on real mutual gravitation between celestial bodies, offering a new approach that aligns with the physical essence of galactic motion.
Jiaqing Yan (Fri,) studied this question.