A Physical Explanation on Why Our Space Is Three Dimensional

It is a basic, ancient and mysterious issue: why our space is three dimensional? This issue is related to philosophy, mathematics, physics and even religion, and thus aroused great research interests. The author makes an in-depth analysis of the problem, and finally comes to a conclusion: For any vector space with symmetry, orthogonality, homogeneity and completeness, the space dimension must be three on condition that: the energy obeys the law of conservation, the dynamics law is governed by the covariance principle, and thus the cross-product must can be defined in the space. Our space just meets and requires the above constraints, so its dimension is three.