It has been shown that the very general symmetries of space-time do not necessarily lead to the special theory of relativity (STR). In this connection the general form of space-time kinematics has been developed. It includes three physical versions. One of them coincides with the STR, the second version comes to the Lorentz ether theory, the third version is not analysed in the present paper. It has been proved that the experimental data gathered up to now are not able to definitely choose one of these versions. Such a choice could be made in the modified Champeney experiment looking for the third order term in (1/c), where c stands for the speed of light.

On "general kinematics" in an empty space

It has been shown that the existence of nonrelativistic terms proportional to c−2 (c is the light speed) in any electromagnetic experiment is forbidden by the general properties of admissible space-time transformations. Therefore, the validity of Einstein's postulates properly could be checked only in experiments looking for the terms proportional to c−3 The scheme of a Mossbauer experiment which would be able to reveal the third order terms is suggested. It repeats the scheme of the Champeney experiment with application of a resonance method of registration for recoil-free radiation.

Proposal for a new Mössbauer experimental test of special relativity

The paper deals with the effect of energy absorption by a moving resistive sheet whose speed is parallel to the normal vector of the plane. The heating effect becomes significantly large when the speed approaches the velocity of a plane electromagnetic wave in vacuum, independently of the sense of movement (sheet moving ‘away’ from the beam or ‘meeting’ the beam). Significant graphical results are presented

Electromagnetic energy absorption by a moving conductor plane

Equation of the ray surface and Fermat's principle in moving anisotropic media

This essay describes the life of the outstanding Soviet scientist A. A. Fridman (1888–1925), known in the western literature as Friedmann, in connection with the centenary of his birth. The main stages in the life of Fridman are discussed in chronological order, beginning with his years at high school and university. Archive files are used in an account of the first steps of Fridman's scientific activity dealing with the problems in mathematical physics and aerodynamics. His participation in the First World War (1914–1917) is then described, followed by his professorship in Perm' University (1818–1920) and finally by the last very fruitful part of his life in Petrograd (1920–1925) where he taught at leading higher educational establishments and worked at the Main Geophysical Laboratory of which he became Director during the last year of his life. Particular attention is given to Fridman's work on relativistic cosmology (1922–1925) and dispute on the subject between Fridman and Einstein in connection with Fridman's theory of an expanding universe. The full bibliography of Fridman's work (73 items) is included.

V. L. Ginzburg

Papers

Einstein collection 1973