The debate still goes on about the substances that permeates space, whether it is called space medium, eather, or whatever else that gives an undeniable character to space.
If we don't understand space we will never understand PHYSICS.
Formulating a rather questionable GR theory, Einstein finally realized, that if space is an empty thing- i.e. noting exist in it, being a total void, one cannot bend the "nothing" (only physical thing can be bent)
Please, read his own words about his undeniable mistake he made in his SR theory:
Albert Einstein, an address delivered on May 5th, 1920, in the University of Leyden.
The original version is available in the Collected Papers of Albert Einstein.
AGAINST HIS SUPPORTERS WARNING HE ADMITTED THAT THE SPACE IS NOT EMPTY IT HAS SOME EATHER LIKE SUBSTANCES FOR YOU CANNOT BEND A THING THAT ARE NOT EXISTS. (Anyway, the space appears to be flat.)
"More careful reflection teaches us, however, that the special theory of relativity does not compel us to deny ether. We may assume the existence of an ether,; only we must give up ascribing a definite state of motion to it, i.e. we must by abstraction take from it the last mechanical characteristic which Lorentz had still left it. We shall see later that this point of view, the conceivability of which shall at once endeavour to make more intelligible by a somewhat halting comparison, is justified by the results of the general theory of relativity."
And he went on:
"Think of waves on the surface of water. Here we can describe two entirely different things. Either we may observe how the undulatory surface forming the boundary between water and air alters in the course of time; or else with the help of small floats, for instance we can observe how the position of the separate particles of water alters in the course of time. If the existence of such floats for tracking the motion of the particles of a fluid were a fundamental impossibility in physics if, in fact, nothing else whatever were observable than the shape of the space occupied by the water as it varies in time, we should have no ground for the assumption that water consists of inovable particles. But all the same we could characterize it as a medium.
We have something like this in the electromagnetic field. For we may picture the field to ourselves as consisting of lines of force. If we wish to interpret these lines of force to ourselves as something inaterial in the ordinary sense, we are tempted to interpret the dynamic processes as motions of these lines of force, such that each separate line of force is tracked through the course of time. It is well known, however, that this way of regarding the electromagnetic field leads to contradictions.
Generalising we must say this: There inay be supposed to be extended physical objects to which the idea of motion cannot be applied. They may not be thought of as consisting of particles which allow themselves to be separately tracked through time. In Minkowski's idiom this is expressed as follows: Not every extended conformation in the four-dimensional world can be regarded as composed of world threads. The special theory of relativity forbids us to assume the ether to consist of particles observable through time, but the hypothesis of ether in itself is not in conflict with the special theory of relativity. Only we must be on our guard against ascribing a state of motion to the ether."
I have left the translator's mistakes unchanged.
The interesting thing is he recognized that GR theory cannot stand up in EMPTY space, although the reasoning above sounds like he just tried to explain away the contradictions. [kk]
