  The difference between Lorentz invariance and Lorentz covariance is discussed
in detail. A covariant formalism is developed for the internal space-time
symmetry of extended particles, especially in connection with the insightful
observations Feynman made during the period 1969-72. A Lorentz-group formalism
is presented for the harmonic oscillator model of Feynman, Kislinger and
Ravndal, which was originally based on hadronic mass spectra. This covariant
version allows us to construct a parton distribution function by
Lorentz-boosting the oscillator wave function of a hadron at rest. The role of
the time-separation variable is discussed in detail. It is shown that, due to
our inability to make measurements on this variable, it belongs to Feynman's
rest of the universe. Our failure to observe the rest of the universe leads to
an increase in entropy.
