  The Dirac equation describes the motion of electrons in electromagnetic
field, but it considers spin as intrinsic property without any real motion. We
postulate spin as the intrinsic feature of vacuum, in which the incident
electromagnetic radiation can create vortices with well defined spinning
frequency and completely undefined axis of rotation. The vortices have finite
surface determined by the spinning frequency that makes the peripheral speed
equal to the velocity of light. According to the Lorentz equations of special
relativity, the product of radius and mass of rotating objects is independent
of the frequency of rotation and it is equal to 3/4h/2pic for all fermions.
This invariance explains how the light with infinite spatial dimension and zero
mass can produce finite mass and size for the particles in the pair-creation
processes. The vortex model interprets the rest energy as the kinetic energy of
spinning motion. The isotropic character of spinning can be represented by
helical motion with right or left-handed chirality corresponding to the duality
of matter and anti-matter. Conservation rule is proposed for the chirality
explaining the electron-positron annihilation and the pair-creation processes.
The vortex induced field rotation around the particle can reproduce the
gravitational formula if the curvature of field is derived from the Lorentz
contraction on the surface of rotating sphere. Generalized Hamiltonian is
suggested for the fermions describing the spinning motion in the internal frame
of particles, it reproduces the Dirac equation, when the rest energy is
predominant.
