Symmetry and quantum effects of extra dimension of space

It is supposed that the physical space has extra dimension. Possible effects of this innovation are investigated on the example of the simplest mathematical space - the four-dimensional Euclidean space. It is demonstrated that the origin and the nature of a rotational motion are clearly visible in four dimensions only. A pair of the Dirac equations associated with the natural tetrads on the four-dimensional Euclidean space is considered. Comparing these equations with the original Dirac equation in the Minkowski space-time, we show that there are two causal structures on the four-dimensional Euclidean space. With this, the rational proof of the existence of leptons and quarks, lepton-quark symmetry and confinement is obtained. To illustrate some questions connected with the so-called hidden symmetry and hidden dimensions, natural mappings of the four-dimensional Euclidean space onto the three-dimensional one are considered.