  In 1905, Einstein discovered the famous equation: E=mc^2, which means that
the rest mass of a particle is some kind of energy. This energy is generally
referred to as "rest energy", since the particle is believed to be at rest.
This paper proposes a new interpretation to the term mc^2. Observing the
similarity between the term mc^2 and the kinetic energy term mv^2/2, we propose
to interpret mc^2 as being one term of kinetic energy. In other words we
propose that, in the called "rest frame", the massive particles are not really
at rest, but they are doing a special kind of motion at the light speed c. In
this interpretation the "mass" is not an intrinsic property of the particle.
The "mass" is simply the kinetic energy associated with this special kind of
motion. The more important consequence of this hypothesis is that the term
mc^2, present in the relativistic Hamiltonian, must be rewritten as: mc^2 =>
p_0 c, where p_0 = mc is the modulus of the instantaneous linear moment
\vec{p}_0 associated with the special motion. We analyse a physical scenario in
which this special motion is a Microscopic Orbital Circular Motion (MOCM). The
characteristic length scale of the MOCM is of the order of the Compton
wavelength of the particle.
