Science is our human understanding of the world, but this understanding is not real at once, and it needs a development process of scientific understanding, which is gradually close to truth and truth; Sometimes it is impossible to reach the truth for quite a while, just close to the truth; This is an objective secret, and its complexity cannot be separated from the limited understanding of human beings. Especially our understanding of space, especially our deep understanding of matter. Classical physics is the foundation of all natural sciences. In fact, classical physics has nothing to do with space at all, and there is no need to discuss what space is. Without the connection with the essence of space, classical physics can reflect the objective world well and serve technology well. However, when human beings don't know what space is, linking classical physics with space will inevitably lead to contradictions and confusion. Classical physics is not a theory derived from the most basic principle of particle motion, but from observation, experiment and production technology. It is a macro theory summed up from experience. Mathematical equations and formulas are empirical equations and empirical formulas. So classical physics is an objective and real phenomenon, but it is not a real description. Because vacuum is not empty, vacuum will inevitably interact with macro objects, which will inevitably lead to slight deviation between macro empirical equation and empirical formula, which is imperceptible in classical theory and general production and construction. Classical physics is more like a technical specification when it understands and describes objective and real movements. Therefore, when classical physics is promoted to the height of space and goes deep into the micro-depth, it will inevitably make the theory rigid and absurd. So I can boldly say: "classical physics is an approximate description of the objective and a summary of experience;" It is not an objective and true description, nor is it a mathematical description of objective movement.