The Medium for Motion: A Critical Clue to Understand Spacetime

Spacetime and motion are interconnected concepts. A better understanding of motion leads to a better understanding of spacetime. We use the historical critical analysis of the various theoretical proposals on motion in search of clues ignored. The prediction of the general relativity that the motion occurs in the static gravitational field is not valid because the motion always occurs in a given medium as vacuum, atmosphere, water, etc. The concept of motion and the equations of the special and general relativity, as the theory of Galilee-Newton reduce motion elements to particle and spacetime. In this paper, we present the medium (in special, the quantum vacuum), as the third essential element of motion, inseparable of spacetime since it is its material support of which the spacetime is its structural form, and we analyse its consequences in the theories of spacetime. Our contribution is declare, that the spacetime itself does not exist, or is a relational property of matter, but a structural property of matter.