As mentioned before, gravity was excluded from the Special Theory of Relativity, due to the lack of matter in Minkowski spacetime. For Einstein this has been the main reason for formulating a separate theory of gravity.

The problem of course was, that Einstein now had to inconspicuously include his bizarre discovery in his theory. Maybe this has been the reason  that it lasted until November 1915, before he published his theory of gravity. At first he did so in four lectures on the "General Theory of Relativity". He thereby indicated that he regarded this theory as a generalization of the part described above, which he only then started calling the "Special Theory of Relativity". Six months later, he published his theory in five chapters in "Annalen der Physik".

 
The first chapter mainly deals with thought experiments, pilosophical and psychological contemplations aimed at clarifying the existence of a relation between the relativity of space and time of his Special Theory of Relativity, and the theory of gravity he contemplated. In the second chapter, Einstein makes clear first, that a great amount of very complicated mathematics is required in order to convert the 'relativity of space and time' into usable equations for gravity, and then gives an exposition. He considers the Special Theory of Relativity as special case (limit) because of the absence of gravity (De Vlieger §3). The field equations for his theory of gravity emerge only in the third chapter with a lot of mathematical juggling. So much in fact, that even mathematicians can hardly comprehend it because of the large jumps and intuitive preferences that Einstein sometimes exhibits. Two items that I will deal with later, are important:
  1. Einstein's field equations are explicitly based on (interstellaire) spaces where normally gravity prevails, but which themselves are completely empty. There is no form of energy present (De Vlieger §14 en §16).
  2. All laws of physics have to be expressed in the field equations in such a way, that they are valid in all relevant coordinate systems having a single time coordinate. All laws of physics must therefore be covariant, as it is called in physical lingo.
The fourth chapter serves to generalize the other disciplines of physics, such as those of liquids and electrodynamics, for his theory of gravity. Finally, in the fifth chapter, the perihelion precession of Mercury and the deflection of light near heavy celestial bodies are discussed, in order to prove the correctness of his theory. Einstein also emphasizes in this chapter, that Newtons theory of gravity is consistent with his theory, and is still accurate enough for general use in everyday situations.
 
 
In the scope of my book, mainly the third and fifth chapters are important. Firstly, because they most clearly represent the role of the abstract underlying tissue, or the earlier world of the galaxies, and secondly, to see how much effort Einstein had to make to conceal that earlier world.
 
In the third chapter of his theory, therefore, I am mainly concerned with the two above-mentioned items.

Ad 1 In formulating his field equations for gravity, Einstein explicitly starts with (interstellar) spaces in which normally gravity exists, but now contain absolutely no matter or energy and no electromagnetic fields and the like (De Vlieger §14). Although Einstein notes that  some intuitive arbitrariness is involved, he defends the situation qualitatively with good arguments. The intuitive element in his starting point, however, is not scientific from a western point of view, and therefore I will return to it in section 5.4.2.
 
Because these "empty" spaces are interstellar, they are principal based on an underlying spacetime that is more or less curved. I will call this spacetime 'timelike gravity spacetime (2 + 2)' to distinguish it from the spacelike Minkowski spacetime (3 + 1).
 
Note 39 For the sake of clarity, I restate that Western physics suggests that flat (= not curved) Minkowski spacetime (3 + 1) can be regarded as space  as we humans know it. That is why it is also called Minkowski space. In fact, however, it is an abstract underlying spacetime of the intergalactic space. It is therefore confusing that '3 + 1' in Western physics can be both the intergalactic part of the earlier world and the total later world on the condition that time is a dimension.
 
In Einstein's field equations, gravitational spacetime is not curved and is called the metric field. The field equations subsequently describe in what way the presence of, for example, a planet (matter / energy) curves this metric field. (The following section describes how this process is carried out in the field equations.) By starting with (interstellar) spaces, Einstein and his equations initially ended up with movements like those of the moons, the planets and the Sun.
 
Ad 2 Making the laws of physics covariant is actually a mathematical trick, by which these laws are formulated in such a way, that they are valid in both coordinate systems of spacetime: So both in Minkowski's '3 + 1' and the '2 + 2' of gravity (see also §5.3.2). With the covariance of the laws of physics, the earlier world of the galaxies (2 + 2) was therefore automatically treated as '3 + 1', which makes it conceivable as consistent with (classical) Western physics (see note 39). The only restriction was that the constant time should be interpreted as a fourth dimension.
 
In the fifth chapter of his theory, Einstein makes it clear that calculations of the planetary orbits prove to be much more accurate with his formula of gravity, which is only described in the next section, than when made with the gravitational formula of Newton: Remember the disappearance of the problems concerning the perihelion precession of the planet Mercury. But, he says; "calculations with his formula are extremely complicated and that it is therefore often better to use the Newton formula". Western physics now has two theories of gravity: a classic one for everyday usage - and a modern one for precision work.
This way Einstein makes sure that these theories are consistent with each other. In fact, he even regards the deflection of light by heavy celestial bodies, the so-called gravity lens, as a convincing proof of his theory of gravity. With that he actually says that gravity, as we humans experience it, no longer has to be seen as a physical trial. The question now is, of course, to what extent this can be reconciled with his allegedly bizarre discovery, which is based on the existence of a gravitational potential? In section 5.4.2 I hope to answer this question adequately. 
 
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