Blog Ekkehard Friebe

Ich nehme Bezug auf meinen Blog-Eintrag: Nikolai Rudakov: „Establishment”. Aus dem dort genannten Buch (1981): „Fiction stranger than truth – In the metaphysical labyrinth of relativity” von Nikolai Rudakov bringe ich nachstehend eine weitere Leseprobe:

Zitat:

5 Inertial Systems

One of the fundamental concepts of special relativity is that of the inertial reference frame, also referred to as inertial reference System or just inertial system. The terms „frame“ and „system“ are synonymous in the context of the theory and are not to be primarily thought of as something structurally complex. The two essential characteristics of an inertial system in the Einsteinian scheme are its ability to serve as a point of origin for Cartesian co-ordinates and its inertiality. Other characteristics are of lesser importance. The reference point function is undoubtedly the principal feature of the Einsteinian inertial system, and it places the system more in the realm of analytical geometry than in the realm of physics. This is quite in accordance with the Einsteinian principle of mathematical pre-eminence which leads to inflated significance being attached to features of mathematical nature. The second attribute, inertiality, is a basic property ascribed to all physical bodies in Newtonian dynamics and associated with their mass.

Einstein’s initial ideas of what was later called the special theory were contained in the kinematical part of his 1905 paper. Kinematics is a branch of mechanics which deals with the geometrical description of mechanical motion. It examines the configuration of motion, and this includes rectilinear as well as circular motion, but it disregards causes. Kinematics is based on geometrical points, which symbolise mechanical bodies, velocities and accelerations. It deals with space and time, but not with mass and its associated concepts, such as inertia, momentum and force. In the kinematical part of the 1905 paper Einstein, starting from two postulates and using kinematical arguments, attempted to demonstrate the untenability of the Newtonian concept of absolute time as a consequence of relative motion. But he did not elaborate or analyse the wider implications arising from his Interpretation of relative motion. These implications became clear after the publication of his 1905 paper, and as a result the kinematics of Einstein’s theory had to be restricted to uniform and non-accelerated motion and the corresponding dynamics to strictly inertial phenomena.

One of the difficulties of Einstein’s kinematics is that its relationship with dynamics, and that means Newtonian dynamics, has never been elucidated. Although there is an important difference between dealing with geometrical points in kinematical terms and the material points of dynamics with their involvement of inertia, momentum and force, Einstein never acknowledged this difference and never made any effort to explain how bis kinematical theory and Newtonian dynamics fit together. He saw no reason to distinguish kinematical and dynamical Statements. For instance, when Einstein says: Lei us take a System of co-ordinates in which the equations of Newtonian mechanics hold good, he must be criticised. Newtonian mechanics does not hold good in Systems of co-ordinates, but in Systems based on mass-points. Co-ordinate Systems are secondary and theoretical structures erected on mass-points. For some people the Einsteinian shift of emphasis may not appear significant, but in fact the quoted phrase is placed at the beginning of the kinematical part of the 1905 paper and determines the subsequent direction of the discussion.

Einstein prefers to talk in terms of reference frames and co-ordinate Systems, and even attaches observers, rigid rods and clocks to them, but we are never told in what way or to what extent these frames and Systems are similar to material points or to physical bodies with a substantial volume of mass. It appears that sometimes geometrical points and mass-points are equivalent and sometimes they are not. This produces an undercurrent of imprecision and ambivalence in relativistic arguments. The plain fact is that we do not encounter Cartesian co-ordinate Systems in the physical world and even less observers mounted on the intersections of co-ordinates. The question as to how the point of origin of co-ordinates is to be determined in concrete physical situations as well as in Einsteinian imaginary trains and lifts has no simple answer and is by no means unimportant. A conventionally chosen reference point, the geometrical centre of a body chosen as a reference frame, the centre of mass of a body and the centre of a gravitational System do not necessarily coincide. Some points are difficult to establish, some are subject to change. Reference points are selected because they are physically easy to determine and not because they are centres of inertial Systems. Mass and gravitational centres are hidden and subject to fluctuations and intrinsic uncertainties. Einstein disregards the fact that a terrestrial observer, for instance, is 6300 km away from the point of origin of the co-ordinates of his „inertial“ System and that his line of vision is not identical with the geometrical line originating from the centre of his reference frame.

Relativists refer to the mathematical formalism of the theory as a guarantee of rigorous exactitude, but they do not worry about the uncertainties in the physical basis of their formalism. Has Einstein ever tried to consider real physical bodies in his theory? His preoccupation with the geometrical formalism of a restricted kinematical problem hides the unpleasant fact that any motion, and this includes relative motion, is meaningless without the concept of mass and aggregates of mass, and in particular without Newtonian absolute space and time. Inertial Systems in relative motion cannot be thought of without real bodies, rigid space and constant time-flow. These three are absolutely necessary prerequisites.

(Zitatende)

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Beste Grüße Ekkehard Friebe