can be made to vanish.
FIG. 1.
[9]That material velocities exceeding that of light are not possible, follows from the appearance of the radical
in the special Lorentz transformation (29).
By the introduction of the imaginary time variable,
, Minkowski has made the theory of invariants for the four-dimensional continuum of physical phenomena fully analogous to the theory of invariants for the three-dimensional continuum of Euclidean space. The theory of four-dimensional tensors of special relativity differs from the theory of tensors in three-dimensional space, therefore, only in the number of dimensions and the relations of reality.