It is shown that in the standard Maxwell electrodynamics the class of gauge fields is much larger than it is usually stated. The possible significance of the new unexploited gauge fields is discussed.
A new form of the generally convariant Maxwell electrodynamics is considered. The theory may be applied to arbitrary media without explicit knowledge of the constitutive relations of the media. This opens new possibilities for the description of electromagnetism in the Universe as a whole.
An interference experiment with incoming and refracted light rays is described which distinguishes between the Einstein and Poincare-Lorentz views on the nature of relativistic effects. The Lorentz transformation rule with a delayed clock cynchronization is checked experimentally.
The general convariance of the new form of Maxwell electrodynamics is established. The physical meaning of the new source term present in field equations is clarified. The Faraday induction law in arbitrary media is discussed.
One of the most fundamental properties of both Newton's mechanics and Maxwell electrodynamics is the absence of any physical constants in their basic equations. All necessary constants appear only at the stage of applications of these theories to specific phenomena. This is one of the reasons of universality and generality of these theories since physical constants always reflect our ignorance in formulation of physical laws. Therefore primary equations of physics should not contain physical constants at all, including the fundamental ones.
Quantum mechanics and general relativity seem to be counterexamples of the above requirement since Schroedinger equation contains both the fundamental Planck constant and the mass of the particle and Einstein equation contains the gravitational constant. It is however possible to suspect that both these great theories may be in some sense secondary and their basic equations may be derived from more fundamental formulations in which all physical constants do not appear.
An equivalence principle valid not only for gravitation, but also for all fundamental interactions is proposed. It is shown that the new equivalence principle does not always coincide with the well-known Einstein equivalence principle.