**Page No:**5359-5366

Wenzhong David Zhang

**Keywords:**Dynamic elementary dipole, fine structure constant, the least action, uncertainty principle, spin energy, quantum entanglement, vacuum polarization

**Abstract:** A dynamic elementary dipole model, with a spinning twin elementary unit charge particles having opposite signs of the
charges, is proposed to explain the internal structure and the mutually induced oscillating electric and magnetic fields of
a propagating photon. The twin elementary unit charge particles under electric attraction force form a dynamic
elementary dipole and achieve a relatively stable orbital motion with a constant drifting speed of its mass centre. From a
combined mechanical and electromagnetic analysing, the widely accepted formula for the fine structure constant is
derived. It is revealed that the fine structure constant is the ratio of the radius of the dynamic elementary dipole to the
corresponding radius of its photon. The fine structure constant is also derived as the ratio of the spinning angular
frequency inside the dynamic elementary dipole to the corresponding angular frequency of its photon. In the effect of the
spin, the drift movement of the mass centre of the dynamic elementary dipole, accomplished in the joined action of the
electric and the magnetic fields, is derived as the light speed in the free space. Base on the derivation of the least action
of the spinning elementary unit charge particle, a modified uncertainty principle is proposed. The modified uncertainty
principle permits dramatically increased levels of precision for scientific measurements and engineering design in
comparison with the Heisenberg Uncertainty Principle. The spin energy of the elementary unit charge particle inside the
dynamic elementary dipole is derived as just half of the energy of its photon. The quantum number of half for the
spinning elementary unit charge particle is deduced. The free space is revealed as a dielectric medium full of dynamic
elementary dipoles, having electric and magnetic polarizability naturally.

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