Introduction :

The nature of light being a subject of intensive research and speculation over the centuries still remains a "dark" issue of modern physics. It has been established that light transfers energy from the source to the receiver by discrete portions, the quanta. However, there is no unified point of view on the nature of the material carrier of the light quantum, that is, the photon. There are several types of photon used in descriptions of the experiments that demonstrate quantum optical effects. The difference in usage of the term "photon" reflects the difference in interpretation of the results of such experiments.

Among quantum optical effects the so-called "essentially quantum effects" that have no classical analogues are worth special mentioning. Such effects cannot be described in the framework of the semiclassical model based on the Maxwell equations, and quantum models are used to describe the effects.

Although the quantum formalism provides a good description of the essentially quantum optical effects, there are great difficulties in its interpretation. In this work it will be shown that any of the well-known interpretations of the quantum formalism for the case of the "non-classical" light is inconsistent with the main concepts of the special theory of relativity. The main disagreement between special relativity and quantum theory is in the attitude towards measurement. While measurement is of primary importance in quantum mechanics, special relativity asserts that all the detected characteristics of light exist a priori (before the measurement). All implications of special relativity are postulated for any inertial frame of reference, not for physical frames (in the sense of actually existing laboratories) as it must be in the study of a quantum object. In this connection, the derivation of the formulas for the Doppler effect for light and those for the Fizeau experiment are especially remarkable. In special relativity they are derived on the basis of the four-dimensional kinematics. At the same time it is the interaction of light with the measurement systems or fields that matters in the experiments substantiating the formulas; that is, dynamics is essential in these cases.

However, it should be recognized that, while ignoring the role of measurement, the relativistic kinematics describes properly the results of some optical experiments. From this fact we have concluded that in the four-dimensional kinematics formalism there is dynamics "hidden" in the geometry of space. In other words, if the interaction between light (photons) and the fields or matter is taken into account, the experimentally proven equations of special relativity kinematics can be derived in the framework of the model of the three-dimensional Euclidean space and the time independent of the spatial coordinates.

It would be more correct to say that the phenomena of starlight aberration does not contradict special relativity kinematics, because the formula for the angle of aberration deduced from the classical law of addition of velocities coincides with the corresponding formula of special relativity with good accuracy.

It will be shown using the Fizeau and Doppler effects that by detailing the "hidden" dynamics of special relativity it is possible to obtain the same formulas as in relativistic kinematics, but in the framework of the three-dimensional Euclidean space and time independent of the spatial coordinates. The derivation of the formula the for the Doppler effect is performed from the photon point of view for the circularly polarized photon in the pure state. In our argument we use the Ritz hypothesis that the fundamental constant C is the speed of light with respect to the source of light. W. von Ritz put forward an emission theory (1908) that is in accord with the observations for the aberration of star positions, the Fizeau experiments, the original Michelson-Morley experiment, and also most of other experiments carried out for determining the "ether wind". In this work we provide an analysis of the main critique of the Ritz theory that prevented it from being accepted in physics. From the model of the three-dimensional Euclidean space and time independence of the spatial coordinates it follows that the speed of light in various geometric frames of reference may have any value. However, this conclusion needs to be detailed when the real physical frames of reference where the experiments are conducted are discussed, specifically, those that demonstrate the invariance of the speed of light.

In this work we derive a formula for the transformation of the energy of photon from one inertial (in the sense of Galileo) frame to another one. According to the formula, the energy of a circularly polarized photon is transformed in accordance with the same equations with respect to the center of mass. In other words, in this work we prove that the "elementary" particle of light, that is, the photon, appears to be like, from the point of view of energy, a complex material object with intrinsic rotational degrees of freedom.

Assuming that the intrinsic rotations in the photon about the center of mass can manifest themselves externally as electric and magnetic fields, the wave characteristics of the photon as a particle may be identical to its wave properties as a quantum of electromagnetic field.

A deeper understanding of the nature of photon requires further investigation into the properties of physical vacuum. From our point of view, rejecting the four-dimensional formalism of special relativity and assuming the model of the three-dimensional space and time independent of the spatial coordinates allows us to return to the ideas of "luminiferous" ether and introduce a medium where light propagates as a process. We consider that the photon is a vortex process in the medium that can be modeled by a superfluid consisting of pairs of oppositely charged particles having respective equal charges and spins. (In the ground state the total spin of the pair is equal to zero.) Actually, the vortices in such a superfluid would be electric dipoles and possess quantum properties. Moreover, due to the generation of a considerable inertial mass in the vortex core, such vortices would demonstrate corpuscular properties.

Assigning the properties of superfluid to the physical vacuum allows us to provide a physical model of the interaction of the photon with the measurement system (to make more concrete, the physical meaning of the dynamics "hidden" in the four-dimensional kinematics of special relativity). Namely, at the interaction between the photon and the measurement system a precession of the spins of the micro-particles constituting the superfluid physical vacuum is generated in the vacuum (the so-called uniformly precessing domain is created). The frequency of the precession is the frequency of the photon detected by the measurement system.

As it is known, besides relativistic kinematics, relativistic dynamics and the theory of electromagnetism are also constituent parts of special relativity. The following two formulas refer to the photon in relativistic dynamics: E = mc² for energy and p = mc for the momentum. The applicability of the formulas is discussed in this work. As far as electromagnetism is concerned, according to what was said above, there exist the quantum optical effects that have no classical analogues, that is, cannot be described in the framework of classical electrodynamics based on the Maxwell equations. From this point of view, the mandatory requirement of the invariance with respect to the Lorentz symmetry group of the Maxwell equations for all the laws of light, even yet undiscovered, if to follow the first postulate of special relativity, is logically groundless.