The general space-time composition was analyzed starting in ancient times. During the previous three millenniums, to explain elementary physical phenomena, the world was twice admitted to be immersed into an "aether". Presently the "aether" is assumed to be asymptotically close to the vacuum. This approximation is included in the foundation of the special theory of relativity.
The analysis is based on the Galileo's postulate that all inertial reference frames are equal. The postulate results immediately in the absolute speed limit, which is identical for all bodies in all reference frames. Two kinds of elementary particles are admitted: unhurried and restless ones (exemplified, accordingly, with electrons and photons). Any particle may be treated as wave packet, the particle mass and momentum depending on the reference frame. Thus, space-time-symmetry is the natural background for the relativistic and quantum theories.
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