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This theory, however, is still regarded skeptically [8], p. 43:
“It remains to be seen if these observations can withstand more exact investigations; for now, the VSL theory poses big challenges to the theorists, as it shakes the basics of physics much more than the inflation model. It is still far from belonging to the established physics. It is mere speculation.”
But according to the CTH, a light speed decreasing with time as per (3) is, however, no speculation, but a consequence that coercively follows from the GTR. Observations also show, the universe expands at the speed of light: The farthest objects we can observe with our telescopes, have a red shift of  z » 5.5, meaning they move away from us at more than
95% of the light speed.

3.2 The cosmic (absolute?) time
 

                              (5)

As the following quotations show, Ernst Mach was the first and later other scientists, as well, to take an “absolute” time into consideration whose existence is defined by cosmic processes [1], p. 21 ff:
“If, by natural laws, one process would be especially distinguished, then one could use this for the definition of an “absolute” time measure….. Mach had assumed that the “entropy of the universe” could be used as a value for the absolute time.”
J. Barrow also expresses doubts towards the conventional time term [9], p. 481:
"How can we know that there is not a basic time measure which is linked to the total universe?”
Paul Davies is even more explicit [2], p. 212:
"Cannot one use the expansion of the universe itself as a clock?”
It is interesting, Henning Genz even takes the same solution as (1) into consideration, by questioning but, however, not giving a founded reason for this  [6], p. 229:
“Why then not go all the way and use the radius of the universe as time parameter?”
According to (5), those basic values representing our physical reality, time (t), space (R), and matter(M) are linked to the cosmic evolution in a surprising way.
The discomfort towards the abstract Newton time expressed in the above quotations obviously rests on the fact, it escapes any attempt to interpret it as an empirically verifyable term.
An impressive feature of the CTH is, it demands a time metric which is linked to cosmic processes we can observe, and it can, strictly logically, be deduced from the GTR  [4].
 
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