Part 3. What is the gravity.

Reconsidering the basics of the physic.

Part 3. What is the space-time.

In order to answer the question of why there has to be a medium for electromagnetic waves, besides, such a medium is not the stationary Aether, as Michelson-Morley experiment showed, but has to go together with the planet itself, we have to start from the very beginning, to reconsider what is the gravity as a such.